Esther P Gardner, Ph.D.

Spike trains in posterior parietal and premotor cortex encode trained and natural grasping behaviors
Gardner E.P.; Putrino D.; Chen J.
2011 ;12:?-?, BMC Neuroscience
To investigate the role of somatosensory and motor information during grasping behaviors, we used digital video and burst analysis of simultaneously recorded spike trains to define burst epochs when neuronal firing rates exceeded 1 SD above the mean. We reconstructed the trajectory of hand movements during each burst from successive digital video images as three macaques grasped and manipulated objects in a trained prehension task, and when engaged in natural grasping behaviors to acquire pieces of fruit. In the task, neurons in posterior parietal areas 5 and 7b/AIP and in ventral premotor cortex responded more vigorously during object acquisition than to manipulation. Firing rates rose 250-500 ms before touch, and peaked as the hand was preshaped during reach, or at initial contact with the object. Firing rates declined as grasp was secured, and returned to baseline or were inhibited during subsequent actions. Some neurons responded to grasping actions of the right and left hands (bilateral neurons), suggesting that their firing patterns reflect grasp intentions, or the internal motor commands for execution of these behaviors. Acquisition-sensitive firing patterns were also observed when the animal grasped food morsels at various workspace locations. Firing began as the animal projected the hand towards the food, and continued as the hand tracked it. Figure 1. Firing peaked as the fingertips contacted the food, and ended when it was secured in the hand. High firing was elicited when food morsels were plucked from a tray, with the fingers preshaped for precision grip, or during tracking actions when the fingers were spread apart to maximize surface area. As in the task, bilateral neurons responded to prehensile actions performed unilaterally by either hand. A second, weaker burst often occurred when food was placed in the mouth. Other neurons responded vigorously to acquisition by the contralateral hand, but fired at highest rates when bilateral actions were coordinated between the left and right hands, as when food morsels were transferred between them. These intrapersonalcoordinated neurons did not just encode equivalent tactile information from either side, but preferentially signaled coincident somatosensory data shared between hemispheres during synergistic hand actions. The two classes of bilateral neurons thus provide somesthetic feedback from both limbs, and encode whether they are acting independently or in concert. Our findings support hypotheses that firing patterns in posterior parietal and premotor cortex reflect the animal's intentions to accomplish task goals in motor coordinates. They suggest that actions preceding contact reinforce subsequent neural responses, allowing subjects to acquire and manipulate objects in a continuous, smooth sequence. (Figure presented)
— id: 146283, year: 2011, vol: 12, page: ?, stat: Journal Article,

Tangential torque tunes touch
Gardner, Esther P
2010 Apr 1;588(Pt 7):1035-1035, Journal of physiology
— id: 109057, year: 2010, vol: 588, page: 1035, stat: Journal Article,

Neural representation of hand kinematics during prehension in posterior parietal cortex of the macaque monkey
Chen, Jessie; Reitzen, Shari D; Kohlenstein, Jane B; Gardner, Esther P
2009 Dec;102(6):3310-3328, Journal of neurophysiology
Studies of hand manipulation neurons in posterior parietal cortex of monkeys suggest that their spike trains represent objects by the hand postures needed for grasping or by the underlying patterns of muscle activation. To analyze the role of hand kinematics and object properties in a trained prehension task, we correlated the firing rates of neurons in anterior area 5 with hand behaviors as monkeys grasped and lifted knobs of different shapes and locations in the workspace. Trials were divided into four classes depending on the approach trajectory: forward, lateral, and local approaches, and regrasps. The task factors controlled by the animal-how and when he used the hand-appeared to play the principal roles in modulating firing rates of area 5 neurons. In all, 77% of neurons studied (58/75) showed significant effects of approach style on firing rates; 80% of the population responded at higher rates and for longer durations on forward or lateral approaches that included reaching, wrist rotation, and hand preshaping prior to contact, but only 13% distinguished the direction of reach. The higher firing rates in reach trials reflected not only the arm movements needed to direct the hand to the target before contact, but persisted through the contact, grasp, and lift stages. Moreover, the approach style exerted a stronger effect on firing rates than object features, such as shape and location, which were distinguished by half of the population. Forty-three percent of the neurons signaled both the object properties and the hand actions used to acquire them. However, the spread in firing rates evoked by each knob on reach and no-reach trials was greater than distinctions between different objects grasped with the same approach style. Our data provide clear evidence for synergies between reaching and grasping that may facilitate smooth, coordinated actions of the arm and hand
— id: 105646, year: 2009, vol: 102, page: 3310, stat: Journal Article,

Spike train analysis toolkit: enabling wider application of information-theoretic techniques to neurophysiology
Goldberg, David H; Victor, Jonathan D; Gardner, Esther P; Gardner, Daniel
2009 Sep;7(3):165-178, Neuroinformatics
Conventional methods widely available for the analysis of spike trains and related neural data include various time- and frequency-domain analyses, such as peri-event and interspike interval histograms, spectral measures, and probability distributions. Information theoretic methods are increasingly recognized as significant tools for the analysis of spike train data. However, developing robust implementations of these methods can be time-consuming, and determining applicability to neural recordings can require expertise. In order to facilitate more widespread adoption of these informative methods by the neuroscience community, we have developed the Spike Train Analysis Toolkit. STAToolkit is a software package which implements, documents, and guides application of several information-theoretic spike train analysis techniques, thus minimizing the effort needed to adopt and use them. This implementation behaves like a typical Matlab toolbox, but the underlying computations are coded in C for portability, optimized for efficiency, and interfaced with Matlab via the MEX framework. STAToolkit runs on any of three major platforms: Windows, Mac OS, and Linux. The toolkit reads input from files with an easy-to-generate text-based, platform-independent format. STAToolkit, including full documentation and test cases, is freely available open source via http://neuroanalysis.org , maintained as a resource for the computational neuroscience and neuroinformatics communities. Use cases drawn from somatosensory and gustatory neurophysiology, and community use of STAToolkit, demonstrate its utility and scope
— id: 138477, year: 2009, vol: 7, page: 165, stat: Journal Article,

Petilla terminology: nomenclature of features of GABAergic interneurons of the cerebral cortex
Ascoli, Giorgio A; Alonso-Nanclares, Lidia; Anderson, Stewart A; Barrionuevo, German; Benavides-Piccione, Ruth; Burkhalter, Andreas; Buzsaki, Gyorgy; Cauli, Bruno; Defelipe, Javier; Fairen, Alfonso; Feldmeyer, Dirk; Fishell, Gord; Fregnac, Yves; Freund, Tamas F; Gardner, Daniel; Gardner, Esther P; Goldberg, Jesse H; Helmstaedter, Moritz; Hestrin, Shaul; Karube, Fuyuki; Kisvarday, Zoltan F; Lambolez, Bertrand; Lewis, David A; Marin, Oscar; Markram, Henry; Munoz, Alberto; Packer, Adam; Petersen, Carl C H; Rockland, Kathleen S; Rossier, Jean; Rudy, Bernardo; Somogyi, Peter; Staiger, Jochen F; Tamas, Gabor; Thomson, Alex M; Toledo-Rodriguez, Maria; Wang, Yun; West, David C; Yuste, Rafael
2008 Jul;9(7):557-568, Nature reviews. Neuroscience
Neuroscience produces a vast amount of data from an enormous diversity of neurons. A neuronal classification system is essential to organize such data and the knowledge that is derived from them. Classification depends on the unequivocal identification of the features that distinguish one type of neuron from another. The problems inherent in this are particularly acute when studying cortical interneurons. To tackle this, we convened a representative group of researchers to agree on a set of terms to describe the anatomical, physiological and molecular features of GABAergic interneurons of the cerebral cortex. The resulting terminology might provide a stepping stone towards a future classification of these complex and heterogeneous cells. Consistent adoption will be important for the success of such an initiative, and we also encourage the active involvement of the broader scientific community in the dynamic evolution of this project
— id: 94591, year: 2008, vol: 9, page: 557, stat: Journal Article,

Terminology for neuroscience data discovery: multi-tree syntax and investigator-derived semantics
Gardner, Daniel; Goldberg, David H; Grafstein, Bernice; Robert, Adrian; Gardner, Esther P
2008 Sep;6(3):161-174, Neuroinformatics
The Neuroscience Information Framework (NIF), developed for the NIH Blueprint for Neuroscience Research and available at http://nif.nih.gov and http://neurogateway.org , is built upon a set of coordinated terminology components enabling data and web-resource description and selection. Core NIF terminologies use a straightforward syntax designed for ease of use and for navigation by familiar web interfaces, and readily exportable to aid development of relational-model databases for neuroscience data sharing. Datasets, data analysis tools, web resources, and other entities are characterized by multiple descriptors, each addressing core concepts, including data type, acquisition technique, neuroanatomy, and cell class. Terms for each concept are organized in a tree structure, providing is-a and has-a relations. Broad general terms near each root span the category or concept and spawn more detailed entries for specificity. Related but distinct concepts (e.g., brain area and depth) are specified by separate trees, for easier navigation than would be required by graph representation. Semantics enabling NIF data discovery were selected at one or more workshops by investigators expert in particular systems (vision, olfaction, behavioral neuroscience, neurodevelopment), brain areas (cerebellum, thalamus, hippocampus), preparations (molluscs, fly), diseases (neurodegenerative disease), or techniques (microscopy, computation and modeling, neurogenetics). Workshop-derived integrated term lists are available Open Source at http://brainml.org ; a complete list of participants is at http://brainml.org/workshops
— id: 138478, year: 2008, vol: 6, page: 161, stat: Journal Article,

Neurophysiology of prehension. III. Representation of object features in posterior parietal cortex of the macaque monkey
Gardner, Esther P; Babu, K Srinivasa; Ghosh, Soumya; Sherwood, Adam; Chen, Jessie
2007 Dec;98(6):3708-3730, Journal of neurophysiology
Neurons in posterior parietal cortex (PPC) may serve both proprioceptive and exteroceptive functions during prehension, signaling hand actions and object properties. To assess these roles, we used digital video recordings to analyze responses of 83 hand-manipulation neurons in area 5 as monkeys grasped and lifted objects that differed in shape (round and rectangular), size (large and small spheres), and location (identical rectangular blocks placed lateral and medial to the shoulder). The task contained seven stages -- approach, contact, grasp, lift, hold, lower, relax -- plus a pretrial interval. The four test objects evoked similar spike trains and mean rate profiles that rose significantly above baseline from approach through lift, with peak activity at contact. Although representation by the spike train of specific hand actions was stronger than distinctions between grasped objects, 34% of these neurons showed statistically significant effects of object properties or hand postures on firing rates. Somatosensory input from the hand played an important role as firing rates diverged most prominently on contact as grasp was secured. The small sphere -- grasped with the most flexed hand posture -- evoked the highest firing rates in 43% of the population. Twenty-one percent distinguished spheres that differed in size and weight, and 14% discriminated spheres from rectangular blocks. Location in the workspace modulated response amplitude as objects placed across the midline evoked higher firing rates than positions lateral to the shoulder. We conclude that area 5 neurons, like those in area AIP, integrate object features, hand actions, and grasp postures during prehension
— id: 76140, year: 2007, vol: 98, page: 3708, stat: Journal Article,

Neurophysiology of prehension. I. Posterior parietal cortex and object-oriented hand behaviors
Gardner, Esther P; Babu, K Srinivasa; Reitzen, Shari D; Ghosh, Soumya; Brown, Alice S; Chen, Jessie; Hall, Anastasia L; Herzlinger, Michael D; Kohlenstein, Jane B; Ro, Jin Y
2007 Jan;97(1):387-406, Journal of neurophysiology
Hand manipulation neurons in areas 5 and 7b/anterior intraparietal area (AIP) of posterior parietal cortex were analyzed in three macaque monkeys during a trained prehension task. Digital video recordings of hand kinematics synchronized to neuronal spike trains were used to correlate firing rates of 128 neurons with hand actions as the animals grasped and lifted rectangular and round objects. We distinguished seven task stages: approach, contact, grasp, lift, hold, lower, and relax. Posterior parietal cortex (PPC) firing rates were highest during object acquisition; 88% of task-related area 5 neurons and 77% in AIP/7b fired maximally during stages 1, 2, or 3. Firing rates rose 200-500 ms before contact, peaked at contact, and declined after grasp was secured. 83% of area 5 neurons and 72% in AIP/7b showed significant increases in mean rates during approach as the fingers were preshaped for grasp. Somatosensory signals at contact provided feedback concerning the accuracy of reach and helped guide the hand to grasp sites. In error trials, tactile information was used to abort grasp, or to initiate corrective actions to achieve task goals. Firing rates declined as lift began. 41% of area 5 neurons and 38% in AIP/7b were inhibited during holding, and returned to baseline when grasp was relaxed. Anatomical connections suggest that area 5 provides somesthetic information to circuits linking AIP/7b to frontal motor areas involved in grasping. Area 5 may also participate in sensorimotor transformations coordinating reach and grasp behaviors and provide on-line feedback needed for goal-directed hand movements
— id: 111675, year: 2007, vol: 97, page: 387, stat: Journal Article,

Neurophysiology of prehension. II. Response diversity in primary somatosensory (S-I) and motor (M-I) cortices
Gardner, Esther P; Ro, Jin Y; Babu, K Srinivasa; Ghosh, Soumya
2007 Feb;97(2):1656-1670, Journal of neurophysiology
Prehension responses of 76 neurons in primary somatosensory (S-I) and motor (M-I) cortices were analyzed in three macaques during performance of a grasp and lift task. Digital video recordings of hand kinematics synchronized to neuronal spike trains were compared with responses in posterior parietal areas 5 and AIP/7b (PPC) of the same monkeys during seven task stages: 1) approach, 2) contact, 3) grasp, 4) lift, 5) hold, 6) lower, and 7) relax. S-I and M-I firing patterns signaled particular hand actions, rather than overall task goals. S-I responses were more diverse than those in PPC, occurred later in time, and focused primarily on grasping. Sixty-three percent of S-I neurons fired at peak rates during contact and/or grasping. Lift, hold, and lowering excited fewer S-I cells. Only 8% of S-I cells fired at peak rates before contact, compared with 27% in PPC. M-I responses were also diverse, forming functional groups for hand preshaping, object acquisition, and grip force application. M-I activity began < or =500 ms before contact, coinciding with the earliest activity in PPC. Activation of specific muscle groups in the hand was paralleled by matching patterns of somatosensory feedback from S-I needed for efficient performance. These findings support hypotheses that predictive and planning components of prehension are represented in PPC and premotor cortex, whereas performance and feedback circuits dominate activity in M-I and S-I. Somatosensory feedback from the hand to S-I enables real-time adjustments of grasping by connections to M-I and updates future prehension plans through projections to PPC
— id: 71334, year: 2007, vol: 97, page: 1656, stat: Journal Article,

Towards effective and rewarding data sharing
Gardner, Daniel; Toga, Arthur W; Ascoli, Giorgio A; Beatty, Jackson T; Brinkley, James F; Dale, Anders M; Fox, Peter T; Gardner, Esther P; George, John S; Goddard, Nigel; Harris, Kristen M; Herskovits, Edward H; Hines, Michael L; Jacobs, Gwen A; Jacobs, Russell E; Jones, Edward G; Kennedy, David N; Kimberg, Daniel Y; Mazziotta, John C; Miller, Perry L; Mori, Susumu; Mountain, David C; Reiss, Allan L; Rosen, Glenn D; Rottenberg, David A; Shepherd, Gordon M; Smalheiser, Neil R; Smith, Kenneth P; Strachan, Tom; Van Essen, David C; Williams, Robert W; Wong, Stephen T C
2003 ;1(3):289-295, Neuroinformatics
— id: 138479, year: 2003, vol: 1, page: 289, stat: Journal Article,

Sensory monitoring of prehension in the parietal lobe: a study using digital video
Gardner, Esther P; Debowy, Daniel J; Ro, Jin Y; Ghosh, Soumya; Babu, K Srinivasa
2002 Sep 20;135(1-2):213-224, Behavioural brain research
Digital video provides technological tools for monitoring hand kinematics during prehension, and for correlating motor behavior with the simultaneously recorded firing patterns of neurons in parietal cortex of monkeys. The constancy of the hand action in the task allowed us to derive population responses of neurons in both S-I and posterior parietal cortex (PPC) from serial single unit recordings. Activity of PPC neurons preceded that in S-I, and was often shape-selective for particular objects, suggesting that they play an important role in motor planning of prehension. Detailed sensory monitoring of hand-object interactions occurred in S-I, where distinct groups of neurons responded to specific behaviors such as grasping, lifting, holding or releasing objects
— id: 39582, year: 2002, vol: 135, page: 213, stat: Journal Article,

Comparison of neuronal firing rates in somatosensory and posterior parietal cortex during prehension
Debowy DJ; Ghosh S; Ro JY; Gardner EP
2001 Apr;137(3-4):269-291, Experimental brain research
To evaluate their functional roles during prehension, single-unit recordings were made in the hand area of primary somatosensory areas 3b, 1 and 2 (S-I) and posterior parietal areas 5 and 7 (PPC) of the same animal. Response profiles of mean firing rate during performance of a multistage reach, grasp, and lift task were analyzed to determine the period(s) of peak firing and to measure statistically significant rises or falls in rate compared with baseline. We used the peak firing stage(s) to subdivide the population into classes tuned to single actions or two successive stages, or into multiaction groups that had sustained facilitation (BT) or inhibition (GI) during hand-object interactions. Four times as many neurons fired at peak rates during acquisition stages (approach, contact, grasp) than upon release, and their firing rates were higher. Grasping evoked the strongest responses, as grasp-tuned neurons had the highest peak rates in the population; BT, contact-grasp, and grasp-lift cells also fired maximally in the grasp stage. Grasping also coincided with maximal inhibition of GI cells, as well as of neurons tuned to approach or relaxation of grasp. Holding evoked the lowest mean rates, and had the fewest tuned cells. S-I and PPC showed significant differences in behaviors evoking peak firing as well as facilitation and inhibition; these correlated with input modalities in each area. Hand contact with the object and positioning of the fingers for grasp was the most strongly represented behavior in anterior S-I, where 61% received tactile inputs from glabrous skin. Nearly 60% were facilitated at contact, 38% fired at peak rates, and 10% were inhibited; release of grasp evoked peak firing in only 5% of 3b-1 neurons. In posterior S-I, where proportions of tactile and deep inputs were similar, positioning and grasping elicited peak responses in 38% and 31%, respectively; 80% were facilitated or inhibited during grasping. During lift and hold, inhibition rose to 43%, while excitation declined under 10%. PPC had the highest proportions firing at peak rates during hand preshaping before contact (28%) and had the most facilitated responses (38%) in this stage. Only 10% fired at peak rates during grasping. During later manipulatory actions, proportions of facilitated and inhibited responses in PPC were similar to those in posterior S-I. The data support models in which PPC plans hand movements during prehension rather than guiding their execution. Sensory monitoring of hand-object interaction occurs in S-I, where cells sense specific hand behaviors, signal stage completion, enable error correction, and may update grasp programs formulated in PPC. The results are discussed in relation to those obtained from lesion studies in humans
— id: 20663, year: 2001, vol: 137, page: 269, stat: Journal Article,

Common data model for neuroscience data and data model exchange
Gardner D; Knuth KH; Abato M; Erde SM; White T; DeBellis R; Gardner EP
2001 Jan-Feb;8(1):17-33, Journal of the American Medical Informatics Association
OBJECTIVE: Generalizing the data models underlying two prototype neurophysiology databases, the authors describe and propose the Common Data Model (CDM) as a framework for federating a broad spectrum of disparate neuroscience information resources. DESIGN: Each component of the CDM derives from one of five superclasses-data, site, method, model, and reference-or from relations defined between them. A hierarchic attribute-value scheme for metadata enables interoperability with variable tree depth to serve specific intra- or broad inter-domain queries. To mediate data exchange between disparate systems, the authors propose a set of XML-derived schema for describing not only data sets but data models. These include biophysical description markup language (BDML), which mediates interoperability between data resources by providing a meta-description for the CDM. RESULTS: The set of superclasses potentially spans data needs of contemporary neuroscience. Data elements abstracted from neurophysiology time series and histogram data represent data sets that differ in dimension and concordance. Site elements transcend neurons to describe subcellular compartments, circuits, regions, or slices; non-neuroanatomic sites include sequences to patients. Methods and models are highly domain-dependent. CONCLUSIONS: True federation of data resources requires explicit public description, in a metalanguage, of the contents, query methods, data formats, and data models of each data resource. Any data model that can be derived from the defined superclasses is potentially conformant and interoperability can be enabled by recognition of BDML-described compatibilities. Such metadescriptions can buffer technologic changes
— id: 26821, year: 2001, vol: 8, page: 17, stat: Journal Article,

Depression of neuronal firing rates in somatosensory and posterior parietal cortex during object acquisition in a prehension task
Ro JY; Debowy D; Ghosh S; Gardner EP
2000 Nov;135(1):1-11, Experimental brain research
Prehension is an object-oriented behavior consisting of four components: reach, grasp, manipulation, and release. To determine how such actions are represented in primary somatosensory (S-I) and posterior parietal cortex (PPC), we used digital video to synchronize spike trains of neurons recorded in Brodmann's areas 3b, 1, 2, 5, and 7 with the hand kinematics as monkeys performed a prehension task. Statistical analyses indicated that one-third of task-modulated neurons showed significantly depressed firing rates during object acquisition and/or manipulation. This population was dominated by neurons innervated by deep receptors that sensed extension movements of the fingers, or by tactile receptors in hairy skin sensing stretch. Grasp-inhibited responses were the most common type. Tonic firing rates of these cells dropped significantly during approach as the hand was preshaped for grasping, or at contact when grasp was initiated, and persisted until hand motion ceased or as the grip relaxed. Maximum suppression of firing occurred at grasp completion. Their lack of specificity for particular hand behaviors formed the inhibitory counterpart of broadly tuned cells that fired prolonged bursts during grasp and manipulatory stages of prehension. The remainder of the task-inhibited population showed biphasic responses. Firing rates were significantly depressed during grasping and manipulation when the hand interacted directly with the object, but were enhanced prior to contact, when the hand was preshaped (approach-tuned), or upon relaxation of grasp and release of the object from the hand (loweror relax-tuned). Grasp-inhibited responses occurred primarily in S-I, whereas biphasic inhibitory activity was recorded mainly in PPC. Suppression of activity within these populations may thereby increase the saliency of excitatory responses to acquisition and manipulation of objects. Reduction of firing during prehension might also signal the flexed postures used to retain objects in the hand, rather than a generalized gating of sensory information. The similarity of responses to active and passive extension movements suggests that the inhibitory responses may provide important postural and motor information about the hand kinematics when performing skilled tasks
— id: 39506, year: 2000, vol: 135, page: 1, stat: Journal Article,

S-I and posterior parietal cortical neurons are sensitive to object size and shape during prehension
Debowy, D; Ro, J Y; Ghosh, S; Gardner, E P
1999 Oct 23-28;25(1-2):2195-2195, Abstracts (Society for Neuroscience)
— id: 15837, year: 1999, vol: 25, page: 2195, stat: Journal Article,

Facilitation of neuronal activity in somatosensory and posterior parietal cortex during prehension
Gardner EP; Ro JY; Debowy D; Ghosh S
1999 Aug;127(4):329-354, Experimental brain research
In order to study prehension in a reproducible manner, we trained monkeys to perform a task in which rectangular, spherical, and cylindrical objects were grasped, lifted, held, and lowered in response to visual cues. The animal's hand movements were monitored using digital video, together with simultaneously recorded spike trains of neurons in primary somatosensory cortex (S-I) and posterior parietal cortex (PPC). Statistically significant task-related modulation of activity occurred in 78% of neurons tested in the hand area; twice as many cells were facilitated during object acquisition as were depressed. Cortical neurons receiving inputs from tactile receptors in glabrous skin of the fingers and palm, hairy skin of the hand dorsum, or deep receptors in muscles and joints of the hand modulated their firing rates during prehension in consistent and reproducible patterns. Spike trains of individual neurons differed in duration and amplitude of firing, the particular hand behavior(s) monitored, and their sensitivity to the shape of the grasped object. Neurons were classified by statistical analysis into groups whose spike trains were tuned to single task stages, spanned two successive stages, or were multiaction. The classes were not uniformly distributed in specific cytoarchitectonic fields, nor among particular somatosensory modalities. Sequential deformation of parts of the hand as the task progressed was reflected in successive responses of different members of this population. The earliest activity occurred in PPC, where 28% of neurons increased firing prior to hand contact with objects; such neurons may participate in anticipatory motor control programs. Activity shifted rostrally to S-I as the hand contacted the object and manipulated it. The shape of the grasped object had the strongest influence on PPC cells. The results suggest that parietal neurons monitor hand actions during prehension, as well as the physical properties of the grasped object, by shifting activity between populations responsive to hand shaping, grasping, and manipulatory behaviors
— id: 6198, year: 1999, vol: 127, page: 329, stat: Journal Article,

Posterior parietal cortex (PPC) may initiate goal-directed actions of the hand
Gardner, E P; Debowy, D; Ro, J Y; Ghosh, S
1999 Oct 23-28;25(1-2):2196-2196, Abstracts (Society for Neuroscience)
— id: 15836, year: 1999, vol: 25, page: 2196, stat: Journal Article,

Area 3B-1 neurons monitor specific task stages during prehension
Debowy, D; Ghosh, S; Ro, J Y; Gardner, E P
1998 Nov 7-12;24(1-2):1127-1127, Abstracts (Society for Neuroscience)
— id: 15925, year: 1998, vol: 24, page: 1127, stat: Journal Article,

Facilitation of neuronal activity in sensorimotor cortex during prehension
Gardner, E P; Ro, J Y; Debowy, D; Ghosh, S
1998 Nov 7-12;24(1-2):1127-1127, Abstracts (Society for Neuroscience)
— id: 15927, year: 1998, vol: 24, page: 1127, stat: Journal Article,

Digital video: a tool for correlating neuronal firing patterns with hand motor behavior
Ro JY; Debowy D; Lu S; Ghosh S; Gardner EP
1998 Aug 1;82(2):215-231, Journal of neuroscience methods
This report describes the use of multimedia technology for simultaneous recording of single unit responses in cerebral cortex, and imaging of hand kinematics as monkeys grasp and manipulate objects. These imaging methods allow direct correlation of full-frame, full-field video images with the actual spike trains recorded with microelectrodes. Our implementation of digital video provides high-resolution snapshots of the hand motor behavior every 33.3 ms, and a precise calibration and display of the synchronously recorded electrophysiological activity digitized at rates up to 44.5 kHz on the same platform. These imaging methods permit non-invasive, non-traumatic monitoring of both trained and spontaneous activity in experimental animals, while providing synchronized digitized records of neuronal spike trains. We also describe software instruments that quantify and analyze the digitized spike trains. One instrument employs user-selectable objective criteria for distinguishing spikes from noise, separates individual action potential waveforms by their amplitude and duration, and compiles time stamps for each spike train. A second instrument constructs rasters and histograms of repeated behavioral trials using the timing of the corresponding video frame for alignment. These analyses reveal functional classes of cortical neurons signaling specific stages of prehension
— id: 57233, year: 1998, vol: 82, page: 215, stat: Journal Article,

Suppression of neuronal activity in sensorimotor cortex during prehension
Ro, J Y; Debowy, D; Ghosh, S; Gardner, E P
1998 Nov 7-12;24(1-2):1127-1127, Abstracts (Society for Neuroscience)
— id: 15926, year: 1998, vol: 24, page: 1127, stat: Journal Article,

Discrimination of simulated texture patterns on the human hand
Kops CE; Gardner EP
1996 Aug;76(2):1145-1165, Journal of neurophysiology
1. Textures formed by periodic dot arrays are defined by the dot density, spacing, and angular orientation with respect to the direction of motion. In this report we evaluate the effects of the dot density (intensive cues) and arrangement (spatial cues) on the ability of human subjects to discriminate texture patterns scanned across an OPTACON tactile stimulator that selective stimulates rapidly adapting cutaneous mechanoreceptors. We compared dot arrays arranged on the index finger in specific patterns (horizontal, vertical, diamond, up diagonal, or down diagonal orientation) and spaced 4.8, 7.2, or 9.6 mm apart (high, medium, and low density) with the use of a two-alternative forced-choice protocol. 2. Textures are well discriminated when their elements are tightly spaced along one axis and widely spaced on all other axes. Humans distinguish textures that differ only in orientation with mean accuracy of 75% at low density and 65% at medium density, but discriminate high-density textures poorly (mean accuracy = 48%). Accuracy is related to the angular disparity between patterns, and to similarity of spacing and orientation along major and minor axes of the arrays. Vertical and horizontal patterns are more accurately distinguished than the oblique ones, and diamond arrays are the least well discriminated. Diagonal and diamond textures are often confounded, and the up and down diagonal patterns are confused with each other particularly as the texture density rises. The preference for the vertical and horizontal patterns may relate to an interaction between the orientation axis of the texture and its direction of motion across the skin. 3. Intensive cues provided by the total number of applied stimuli supplement the spatial cues inherent to the pattern orientation, because textures that differ in both spacing and orientation are discriminated better than those that differ only in orientation or spacing. Mean accuracy ranges from 96% for comparisons of high- and low-density textures, which differ in the total number of dots by a factor of 2, to 80% when medium-density patterns are compared with high- or low-density textures. 4. Textures that differ in density but not in orientation are less well discriminated than those of different orientation. For example, 82% of patterns that differ in both density and orientation are distinguished correctly in pairings of low- and medium-density textures, whereas those that differ only in density are discriminated correctly on 45% of trials. Subjects seem to use spatial rather than intensive cues when discriminating patterns of similar density, suggesting that the similarity of form (the spatial arrangement of the closely spaced dots) is more readily apparent than small differences in spacing along the axis of motion. 5. Subjects are most most successful in differentiating texture patterns when they are able to mentally picture the orientation and spacing of the pattern. We found a strong correlation between the subjects' ability to discriminate textures of a given spacing and their ability to identify the specific texture by matching it to the appropriate visual representation. Subjects are able to identify correctly all five orientations at low and medium densities, with mean accuracy of 76%, but recognize only the vertical arrays when high-density patterns are presented. The ability to image the textures is noteworthy, because subjects received no feedback about performance. 6. Spatial imaging of textures appears limited by the diameter of cutaneous receptive fields on the hand. We propose that the structural axis of a regular texture array results from perceptual linkage of adjacent elements along one principal axis by continuous bands of neural activity when their spacing is smaller than the receptive field diameter.(ABSTRACT TRUNCATED)
— id: 57366, year: 1996, vol: 76, page: 1145, stat: Journal Article,

Discrimination of the direction of motion on the human hand: a psychophysical study of stimulation parameters
Gardner EP; Sklar BF
1994 Jun;71(6):2414-2429, Journal of neurophysiology
1. In these experiments we assess the relative importance of the spatial and temporal properties of a moving tactile stimulus in determining the ability of humans to discriminate its direction of motion. Movement along the finger was simulated by applying a series of pulses to adjacent locations on the skin using the tactile array of an OPTACON stimulator. Simulated motion permitted us to vary independently the overall distance moved as well as the spacing, timing, and number of sequential stimuli. Different combinations of spatiotemporal parameters allowed us to further examine the relationship of apparent velocity of motion and sweep duration to behavioral performance. Discrimination accuracy was measured using signal detection techniques to calculate the discrimination parameter d' and PCmax, a bias-free measure of the percent correct identification of the direction of motion. 2. In experiments where the path length was constant, discriminability of the direction of motion increased as the spacing between successive pulses narrowed. Similarly, for a given interpulse spacing, the accuracy of discrimination increased linearly with distance, saturating at perfect performance. These apparent spatial effects on performance actually reflect the total number of stimuli presented to the skin rather than their proximity. Sweeps containing the same number of pulses are equally discriminable regardless of either their spacing or the total distance crossed on the skin. d' values obtained at 1.2-, 2.4-, and 4.8-mm spacings appear indistinguishable when plotted as a function of the total number of pulses in a sweep. 3. Experiments in which both the distance moved and the spacing between pulses was varied randomly confirmed that discrimination accuracy depends on the total number of pulses in a sweep rather than the spatial dimensions of the path traversed. Stimulation of only two points that mark the start and stop locations on the skin appears insufficient to enable subjects to discriminate correctly the direction of motion. Two-point stimulation elicits random performance whether the points lie 1.2 or 4.8 mm apart. Discriminability rises linearly to near-perfect performance when eight or more pulses are delivered sequentially. Extrapolation of the d' and PCmax curves suggests a mean threshold of approximately three points for 75% correct discrimination of the direction of motion across the skin. 4. The relationship of stimulus spacing to discriminability over a fixed path suggests that direction discrimination does not simply involve computation of the location of the start and stop points on the skin or their spatial disparity.(ABSTRACT TRUNCATED AT 400 WORDS)
— id: 56529, year: 1994, vol: 71, page: 2414, stat: Journal Article,

Simulation of motion on the skin. V. Effect of stimulus temporal frequency on the representation of moving bar patterns in primary somatosensory cortex of monkeys
Gardner EP; Palmer CI; Hamalainen HA; Warren S
1992 Jan;67(1):37-63, Journal of neurophysiology
1. To assess the mechanisms used by cortical neurons to sense motion across the skin, we applied pulsatile stimuli to a series of adjacent positions on the glabrous skin of the hand using a computer-controlled OPTACON stimulator. We describe responses of 129 single neurons in primary somatosensory cortex of alert monkeys to a horizontal bar pattern that was displaced proximally or distally in 1.2-mm steps at 10-, 20-, and 40-ms intervals (100, 50, and 25 Hz, respectively). These frequencies span the range in which apparent motion is transformed perceptually in humans from a smooth uninterrupted sweep into a series of distinct pulses that are resolved as separate events. The experiments are thus designed to decipher the neural correlates distinguishing continuous motion from discrete taps. 2. Cortical receptive fields mapped with moving bar patterns spanned 5-24 rows on the tactile array (16.2 +/- 5.4, mean +/- SD). Over 40% of the fields encompassed 18 or more rows (greater than or equal to 21.6 mm), allowing these neurons to integrate spatial information from an entire image displayed on the OPTACON. Cortical receptive fields are considerably larger than those of mechanoreceptors mapped with the same moving bar patterns (4.2 +/- 2.3 rows, mean +/- SD), reflecting convergent inputs in subcortical and cortical relays. Responses were either relatively uniform across the field or strongest at the initial point of entry, depending on the frequency of stimulation. A sharply defined field center was absent from most of the cells recorded in this study. 3. Temporal frequency of stimulation appears to be a major determinant of cortical firing patterns. Low-frequency stimuli are more effective in activating cortical neurons, producing more spikes per sweep and greater phase-locking to individual stimuli than do high frequencies. The total spike output of cortical neurons is proportional to the pulse interval over the range 10-40 ms, increasing linearly by an average of 5.9 spikes/10-ms increase in pulse period. Peak firing rates and modulation amplitude are also highest when pulses are presented at long intervals, falling significantly as the stimulation frequency rises. The reduction in firing at high pulse rates is apparently due to central mechanisms, as both rapidly adapting and Pacinian corpuscle afferents display nearly constant spike outputs and uniform sensitivity within the field when tested with identical bar patterns. Central networks thus behave as low-pass filters, reducing cortical responses to rapidly applied sequential stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)
— id: 13752, year: 1992, vol: 67, page: 37, stat: Journal Article,

Simulation of motion on the skin. III. Mechanisms used by rapidly adapting cutaneous mechanoreceptors in the primate hand for spatiotemporal resolution and two-point discrimination
Gardner EP; Palmer CI
1990 Apr;63(4):841-859, Journal of neurophysiology
1. The contribution of rapidly adapting (RA) mechanoreceptors to two-point discrimination has been evaluated by examining their ability to resolve the spacing of grating patterns shifted across the skin. The experiments test two different neural coding mechanisms that have been proposed to underlie resolution of spatial detail on the hand: 1) a rate-intensity code in which the spacing of surface features is encoded by the average frequency of firing of individual sensory afferents, and 2) an isomorphic representation of shape in which variations in the firing patterns of individual afferents reflect the spatiotemporal profile of skin indentation. 2. To measure the spatial acuity of RA mechanoreceptors innervating the hands of macaque monkeys, we displayed pairs of horizontal bars spaced 1-13 mm apart on a computer-controlled OPTACON stimulator placed over glabrous skin. Two-point resolution was measured by simultaneously pulsing pairs of rows at rates of 100, 50 and 25 Hz; each pair was shifted in tandem across the hand to simulate lateral motion. Single-fiber recordings were made from physiologically identified RA afferents in anesthetized monkeys. 3. Receptive field diameter appears to be the critical determinant of spatial resolution of gaps between two bars. RAs fire continuously if bar spacing is less than the field diameter but do not summate inputs when both active rows are contained within the field. Response profiles evoked by two bars spaced less than 4.8 mm apart can be predicted from the single-bar profiles, assuming occlusion between overlapping inputs with the strongest member dominating axonal output. Two-thirds of the RAs tested discharge 1 spike/pulse as bar patterns cross the field, yielding a uniform spike train whose frequency reflects stimulus pulse rates but fails to indicate gaps between bars. An additional 17% fire 2 spikes/pulse when the bars contact or straddle the field center, but also fail to differentiate individual stripes spaced less than 3.6 mm apart. 4. Only 17% of RAs represent gaps narrower than the field diameter. These fibers show double-peaked response profiles to bar patterns spaced at least 2.4 mm apart, firing 2 spikes/pulse as first one, and then the second stripe crosses the field center. Timing between peaks corresponds to bar spacing. Responses are reduced in amplitude when adjacent bars straddle the field center, as occlusion between simultaneous inputs prevents summation of inputs from the two stimuli. Fifteen of 16 RAs failed to resolve bars spaced 1.2 mm apart, as double-spike responses were evoked only by the leading stripe.(ABSTRACT TRUNCATED AT 400 WORDS)
— id: 57416, year: 1990, vol: 63, page: 841, stat: Journal Article,

Simulation of motion on the skin. IV. Responses of Pacinian corpuscle afferents innervating the primate hand to stripe patterns on the OPTACON
Palmer CI; Gardner EP
1990 Jul;64(1):236-247, Journal of neurophysiology
1. To measure spatial acuity of Pacinian corpuscle (PC) afferents in the median and ulnar nerves of macaque monkeys, we displayed horizontal bar patterns spaced 1-13 mm apart on a computer-controlled OPTACON stimulator contacting the hand. Two-point resolution was measured by simultaneously pulsing pairs of rows at rates of 100, 50, and 25 Hz; each pair was shifted in tandem across the skin in 1.2-mm steps to simulate tangential motion at speeds of 30-120 mm/s. Single-fiber responses are reported from eight physiologically identified PC afferents innervating the fingers and palm in anesthetized monkeys. 2. Pacinian afferents differ in their sensitivity to stripe patterns moved across the hand. Bursting PCs fire bursts of two or three spikes/pulse when one of the bars is close to the field center and one spike/pulse when adjacent bars straddle the center. These bursts result in double-peaked response profiles at stripe spacings greater than or equal to 2.4 mm. The passage of individual stripes over the field center is therefore represented by bursts of impulses superimposed on a continuous spike train. Unfortunately, many of these fibers also demonstrate fluctuations in firing that appear unrelated to the stripe pattern and therefore obscure its clear representation. 3. The remainder of the PC population displays uniform-sensitivity responses that resemble those previously reported for rapidly adapting (RA) afferents. They fire one spike/pulse as long as at least one of the bars is contained within the field. They merge individual stripes spaced less than one field diameter apart and show a pause in firing at wider spacing. Spatial resolution of gaps in the stripe pattern is therefore determined by receptive-field diameters, which extend up to 9.6 mm when tested with the OPTACON. 4. PCs display poorer spatial resolution than RAs, because of their larger receptive fields and less regular firing patterns. Only two of eight PCs tested demonstrated a pause in activity representing the gap between bars spaced 4.8 mm apart, whereas 11 of 14 RAs ceased firing briefly between stripes. Resolution of the individual stripes by all of the PCs tested was observed only at bar spacings of 1 cm (8 rows) or more. Spatial resolution of stripes is further impeded by the tendency of PC afferents to summate inputs from stripes spaced less than 2.4 mm apart; this results in response profiles with a single, large-amplitude broad peak.(ABSTRACT TRUNCATED AT 400 WORDS)
— id: 65748, year: 1990, vol: 64, page: 236, stat: Journal Article,

Simulation of motion on the skin. I. Receptive fields and temporal frequency coding by cutaneous mechanoreceptors of OPTACON pulses delivered to the hand
Gardner EP; Palmer CI
1989 Dec;62(6):1410-1436, Journal of neurophysiology
1. Tactile discrimination of form requires motion of the hand across the object scanned. To dissociate lateral distortion of the skin from neuronal processing mechanisms involving multiple receptor classes and parallel central networks, we have simulated motion of bar patterns across the fingers and palm by the use of a computer-controlled grid of sequentially activated probes (OPTACON stimulator). Horizontal bar patterns have been swept across the hand at speeds of 30-120 mm/s to quantitatively characterize responses of cutaneous mechanoreceptive afferents recorded in the median and ulnar nerves. 2. Mechanoreceptors with phasic responses to pressure are activated by spatial patterns on the OPTACON, whereas those with tonic pressure responses are not; moving-bar patterns strongly excite both Meissner's afferents [rapidly adapting (RA) mechanoreceptors] and Pacinian corpuscles (PCs) but fail to excite slowly adapting (SA) afferents. OPTACON-type stimulators thus allow selective activation of phasic mechanoreceptor channels with spatially complex stimuli. 3. RA afferents respond in an all-or-none fashion to activation of two to five adjacent rows spanning 1-5 mm on the finger, with nearly identical latencies on all trials; response profiles are remarkable for their regularity and reproducibility. PCs have larger fields (4-13 rows) and stronger but more irregular responses than RAs. 4. Uniform sensitivity throughout the receptive field is a consistent feature of RA responses. Individual mechanoreceptor terminals appear to have equal access to the spike initiation zone and provide the same amplitude input as the fiber discharges 1 spike/pulse at each field location in 75% of the RAs tested. Uniform sensitivity allows each afferent to transmit a repetitive signal of the parameter of interest such as object speed, contour, or texture. 5. One-quarter of RAs fire two spikes to probe indentation and retraction at the field center. Such graded responses are usually observed in only one direction of motion, reflecting a preferred sequence of receptor activation rather than a specific location on the skin. PCs fire bursts of two to four spikes throughout most of their receptive fields; sensitivity is broadly distributed rather than peaked. Thus phasic mechanoreceptors fail to provide a precise signal of stimulus location; localization at the level of individual papillary ridges appears to be signaled by a population mechanism involving unique combinations of RA, SA, and PC afferents.(ABSTRACT TRUNCATED AT 250 WORDS)
— id: 10412, year: 1989, vol: 62, page: 1410, stat: Journal Article,

Simulation of motion on the skin. II. Cutaneous mechanoreceptor coding of the width and texture of bar patterns displaced across the OPTACON
Gardner EP; Palmer CI
1989 Dec;62(6):1437-1460, Journal of neurophysiology
1. These experiments assay the functional significance of receptive-field architecture for information processing. Rapidly adapting (RA) afferents have been previously shown to converge information from clusters of 14-25 Meissner's corpuscles, whereas afferents innervating Pacinian corpuscles (PCs) have only a single, large receptor terminal. We tested two opposing hypotheses of functional architecture: 1) summation models, in which an afferent integrates signals from all of its terminals, showing monotonic increases in activity as a function of contact area, and 2) winner-take-all models, in which the most strongly activated receptor in the cluster dominates axonal output by cancellation of signals from other branches. 2. Bar and stripe patterns have been swept across the finger or palm of the monkey's hand at speeds of 30-120 mm/s with the use of a computer-controlled grid of sequentially activated miniature probes (OPTACON stimulator). The dense packing of OPTACON probes permits placement of up to five groups of stimulators within an individual receptive field, allowing us to activate one or more clusters of Meissner's corpuscles simultaneously and to stimulate the bulbar corpuscle of PC afferents at different orientations through the skin. Integration of information from moving bar patterns has been tested with two protocols. In the variable width protocol, the total number of activated rows in the pattern is varied from one to five, with a constant spacing of 1.2 mm between pulsed rows. In the variable density protocol, the length of skin stimulated is held constant at 5 mm and the spacing of stimuli varied. 3. RA afferents show no evidence of summation of inputs within their receptive fields. Motion of wide bars across the field increases the duration of firing but not the total spikes evoked by each pulse. Responses to the leading edge of wide bars were found to be identical to those evoked by a single-row bar. Simultaneous activation of two to five rows evokes the same or fewer spikes per pulse than the most effective individual row tested alone. When broad-bar patterns are centered over the field, contacting the maximum number of receptors, RAs follow activity in the dominant branch or terminus, suppressing additional inputs. Lack of summation is observed at all pulse frequencies tested (25-100 Hz). 4. Moving bar patterns evoke responses as long as at least one row stimulates the receptive field; broader patterns evoke longer spike trains whose total number of impulses is proportional to bar width.(ABSTRACT TRUNCATED AT 400 WORDS)
— id: 10411, year: 1989, vol: 62, page: 1437, stat: Journal Article,

OAHC opposed
Gardner, E P
1989 May;10(5):237-237, Nursing & health care
— id: 145571, year: 1989, vol: 10, page: 237, stat: Journal Article,

Somatosensory cortical mechanisms of feature detection in tactile and kinesthetic discrimination
Gardner EP
1988 Apr;66(4):439-454, Canadian journal of physiology & pharmacology
Neurons in somatosensory cortex of primates process sensory information from the hand by integrating information from large populations of receptors to extract specific features. Tactile neurons in areas 1 and 2 are shown to select features such as contact area, edge orientation, motion across the skin, or direction of movement. Features coded by kinesthetic neurons in areas 3a and 2 relate to joint movement, the joint angle around which the movement occurs, or coordinated postures of the hand and arm. An even higher order cortical cell integrates tactile and kinesthetic information; these 'haptic neurons' respond optimally to contact of objects actively grasped in the hand. These global features are coded at the expense of loss of information concerning fine-grained spatial detail
— id: 11142, year: 1988, vol: 66, page: 439, stat: Journal Article,

High-dose naloxone in tardive dyskinesia
Lindenmayer JP; Gardner E; Goldberg E; Opler LA; Kay SR; van Praag HM; Weiner M; Zukin S
1988 Oct;26(1):19-28, Psychiatry research
Tardive dyskinesia (TD) is thought to result from nigrostriatal dopaminergic supersensitivity secondary to prolonged neuroleptic exposure. Preclinical studies have demonstrated that the opiate antagonist naloxone can acutely reverse a haloperidol-induced hyperdopaminergic state. In a trial of high-dose naloxone, 20 patients with TD received i.v. naloxone (20 mg, 40 mg, and placebo) under double-blind conditions. At baseline and at regular postdrug intervals, patients were evaluated using a battery of motor, clinical, and neuropsychological measures to study effects on neurological, behavioral, and cognitive functions. There was a significant improvement in involuntary movements at 30 min postnaloxone, together with improvement in clinical ratings at that time point, as well as some cognitive changes. The implications of these findings for the putative functional relationship between dopaminergic and enkephalinergic systems in the nigrostriatal area are discussed
— id: 32797, year: 1988, vol: 26, page: 19, stat: Journal Article,

Coding of the spatial period of gratings rolled across the receptive fields of somatosensory cortical neurons in awake monkeys
Warren S; Hamalainen HA; Gardner EP
1986 Sep;56(3):623-639, Journal of neurophysiology
In order to measure the texture coding capabilities of motion-, direction-, and orientation-sensitive neurons in SI cortex, we rolled wheels with surface milled gratings across their receptive fields. Gratings of spatial periods 0.8-9.6 mm were presented in pseudorandom order; each was tested 5-20 times in the distal, proximal, radial, and ulnar directions. Thirty eight cortical neurons were studied with three to eight different gratings in order to determine the effect of spatial period on neuronal firing rates. While all 38 cells had their firing rates modulated by motion of the gratings, only 11 neurons were able to distinguish changes in its spatial period. These cells had small receptive fields located on the hand. Most motion-sensitive neurons showed little effect of spatial period on firing rates and had relatively flat frequency response curves. One showed decreased firing to spatial periods over the range 0.8-6.4 mm; three others increased their firing rates over the range 0.8-3.2 mm, followed by a decline in activity to larger spatial periods. Direction- and orientation-sensitive neurons showed only minor changes in firing rates as a function of spatial period. Sixteen cells showed flat frequency response functions, three showed increased firing rates, and four decreased firing rates as spatial period of the grating increased. Direction and orientation preferences were maintained over the range 0.8-9.6 mm for all 23 neurons tested. Although four cells showed a drop in direction index (DI) as the spatial period was increased, none showed a loss of direction sensitivity, as DI was greater than 35 for all gratings tested. Two neurons showed increased firing to motion in the last-preferred direction and two others decreased firing in the best direction. The remaining 19 neurons showed parallel effects of texture in all directions. Some motion-sensitive neurons showed weak direction preferences when tested with fine gratings; these preferences disappeared with coarser gratings, due to increased responsiveness to motion in the least-preferred direction. These data demonstrate that movement-sensitive neurons do not require continuous trajectories across the skin but instead sequential activation of points aligned in a specific path. Cortical neurons appear capable of integrating information from points separated by up to 9 mm, as long as they are presented in the appropriate temporal sequence. Firing rates of direction- and orientation-sensitive neurons are more profoundly modified by changes in the direction of motion across the skin, and the temporal order of stimulation, than by alterations in the spatial characteristics of the moving stimulus.(ABSTRACT TRUNCATED AT 400 WORDS)
— id: 62225, year: 1986, vol: 56, page: 623, stat: Journal Article,

Objective classification of motion- and direction-sensitive neurons in primary somatosensory cortex of awake monkeys
Warren, S; Hamalainen, H A; Gardner, E P
1986 Sep;56(3):598-622, Journal of neurophysiology
In order to classify movement-sensitive neurons in SI cortex, and to estimate their relative distribution, we have developed a new simple method for controlled motion of textured surfaces across the skin, as well as a set of objective criteria for determining direction selectivity. Moving stimuli were generated using 5 mm thick precision gear wheels, whose teeth formed a grafting. They were mounted on the shafts of low-torque potentiometers (to measure the speed and direction of movement) and rolled manually across the skin using the potentiometer shaft as an axle. As the grafting wheel was advanced, its ridges sequentially contacted a specific set of points on the skin, leaving gaps of defined spacing that were unstimulated. This stimulus was reproducible from trial to trial and produced little distention of the skin. Three objective criteria were used to categorize responses: the ratio of responses to motion in the most and least preferred directions [direction index (DI)], the difference between mean firing rates in the two directions divided by the average standard deviation [index of discriminability (delta'e)], and statistical tests. Neurons were classified as direction sensitive if DI greater than 35, delta's greater than or equal to 1.35 (equivalent to 75% correct discrimination by an unbiased observer), and firing rates in most- and least-preferred directions were significantly different (P less than 0.05). Good agreement was found between the three classification schemes. Recordings were made from 1,020 cortical neurons in the hand and forearm regions of primary somatosensory cortex (areas 3b, 1 and 2) of five macaque monkeys. Tangential motion across the skin was found to be an extremely effective stimulus for SI cortical neurons. Two hundred eighty six of 757 tactile neurons (38%) responded more vigorously to moving stimuli than to pressure or tapping the skin. One hundred twenty-one cells were tested with moving gratings and were classified according to their ability to differentiate movement in longitudinal and transverse directions. Responses to the moving gratings resembled those observed when stroking the skin with brushed, edges, or blunt probes. Three major types of firing patterns were found: motion sensitive, direction sensitive, and orientation sensitive. Motion-sensitive neurons (37%) responded to movement in both longitudinal and transverse directions with only slight difference in firing rates and interval distributions. Responses throughout the field were fairly uniform, and no clear point of maximum sensitivity was apparent. Direction-sensitive neurons (60%) displayed clear preferences for movement in one or more directions.4
— id: 138481, year: 1986, vol: 56, page: 598, stat: Journal Article,

Differential sensitivity to airpuffs on human hairy and glabrous skin
Hamalainen, H A; Warren, S; Gardner, E P
1985 ;2(4):281-302, Somatosensory research
To compare the relative sensitivities of glabrous and hairy skin, we measured reaction times (RTs) and detectability (d') of airpuffs delivered to the hairy dorsum and glabrous thenar eminence of the hand of six human subjects. In contrast to previous studies with mechanical contact stimuli, airpuffs applied to hairy skin were detected with equal or greater fidelity than airpuffs tested on glabrous skin. Mean RTs to three simultaneously applied airpuffs were significantly shorter (p less than .005) on hairy skin in five of six subjects, and in 74% of paired sessions; no significant difference in mean RTs was observed in 16% of the sessions. The superiority of hairy skin was less evident, however, when single airpuffs were tested, as significantly shorter responses were observed on only 45% of the paired sessions, and nearly identical responses on 38% of the sessions. Detectability of airpuffs (d'), which is independent of the value of RTs, was identical on hairy and glabrous skin at high airpuff intensities (1,600 dyn), and superior (n = 4) or equal (n = 2) on hairy skin with low airpuff intensities (800 dyn). Spatial summation was more pronounced on hairy than on glabrous skin. Three simultaneously presented airpuffs produced significantly shorter RTs than one airpuff in 85% of the paired sessions on hairy skin, but on only half of the sessions on glabrous skin. The spatial distribution of stimulus force was less important on hairy skin, as three low-intensity airpuffs produced the same or shorter RTs than one high-intensity airpuff. By contrast, on glabrous skin, detectability was significantly better when force was concentrated at a single point (1 X 1,600 dyn) than when diffused over a wide skin area (3 X 800 dyn). The enhanced sensitivity of hairy skin to airpuffs appears partially attributable to hair motion in the airstream. After hair removal by chemical depilation, detectability of airpuffs was reduced on hairy skin to a level equal to or below that on glabrous skin. Spatial summation on the depilated skin corresponded to that observed on the intact hairy skin, indicating that depilation did not abolish intensity discrimination, but rather lowered the overall sensitivity of hairy skin. These results show that hair follicle units form a very sensitive detection mechanism on hairy skin of the human hand, similar to that provided by Meissner's and Pacinian afferents in glabrous skin. These findings with airpuffs provide the first example of a tactile stimulus that is less effective for mechanoreceptors in glabrous skin than in hairy skin.(ABSTRACT TRUNCATED AT 400 WORDS)
— id: 138482, year: 1985, vol: 2, page: 281, stat: Journal Article,

Somatosensory evoked potentials (SEPs) and cortical single unit responses elicited by mechanical tactile stimuli in awake monkeys
Gardner, E P; Hamalainen, H A; Warren, S; Davis, J; Young, W
1984 Dec;58(6):537-552, Electroencephalography & clinical neurophysiology
The origins of surface recorded evoked potentials have been investigated by combining recordings of single unit responses and somatosensory evoked potentials (SEPs) from the postcentral gyrus of 4 alert macaque monkeys. Responses were elicited by mechanical tactile stimuli (airpuffs) which selectively activate rapidly adapting cutaneous mechanoreceptors, and permit patterned stimulation of a restricted area of skin. Epidurally recorded SEPs consisted of an early positive complex, beginning 8-10 msec after airpuff onset, with two prominent positive peaks (P15 and P25), succeeded by a large negative potential (N43) lasting 30 msec, and a late slow positivity (P70). SEPs, while consistent in wave form, varied slightly between monkeys. The amplitude of the early positive complex was enhanced by increasing the number of stimulated points, or by placing the airpuffs in the receptive fields of cortical neurons located beneath the SEP recording electrode. SEP amplitude was depressed when preceded 20-40 msec earlier by a conditioning stimulus to the same skin area. Single unit responses in areas 3b and 1 of primary somatosensory (SI) cortex consisted of a burst of impulses, beginning 11-12 msec after the airpuff onset, and lasting another 15-20 msec. Peak unitary activity occurred at 12-15 msec, corresponding to the P15 wave in the SEP. No peak in SI unit responses occurred in conjunction with the P25 wave. Although SI neurons fired at lower rates during P25, the lack of any peak in SI unit responses suggests that activity in other cortical areas, such as SII cortex, contributes to this wave. Most unit activity in SI cortex ceased by the onset of N43, and was replaced by a period of profound response depression, in which unit responses to additional tactile stimuli were reduced. We propose that the N43 wave reflects IPSPs in cortical neurons previously depolarized and excited by the airpuff stimulus. Late positive potentials (P70) in the SEP had no apparent counterpart in SI unit activity, suggesting generation at other cortical loci
— id: 138483, year: 1984, vol: 58, page: 537, stat: Journal Article,

Two epizootics of lymphocytic choriomeningitis virus occurring in laboratory mice despite intensive monitoring programs
Smith, A L; Paturzo, F X; Gardner, E P; Morgenstern, S; Cameron, G; Wadley, H
1984 Jul;48(3):335-337, Canadian journal of comparative medicine = Revue canadienne de medecine comparee
Two epizootics of lymphocytic choriomeningitis virus in mice occurred within two months in one research facility consisting of several widely separated rooms. These outbreaks developed despite intensive institutional monitoring policies designed to prevent introduction and spread of lymphocytic choriomeningitis virus. Evidence derived from serological and virological assays and interviews with the concerned investigators suggested that a single transplantable tumor carried in mice may have been responsible for spread of the virus. However, the tumor was not contaminated with lymphocytic choriomeningitis virus at the time of its introduction into the mouse facility. The origin of the virus responsible for the outbreaks was not definitively established although data supported an hypothesis that the virus was introduced into the research facility by a wild or feral mouse. Virus spread from infected mice to humans did not occur, as measured by serological tests. However, a large and valuable animal facility was depopulated for safety reasons. Absorption of sera with lymphocytic choriomeningitis virus antigen proved a necessary and reliable method for confirming specificity of lymphocytic choriomeningitis virus fluorescence-positive reactions
— id: 145572, year: 1984, vol: 48, page: 335, stat: Journal Article,

Multiple-joint neurons in somatosensory cortex of awake monkeys
Costanzo, R M; Gardner, E P
1981 Jun 15;214(2):321-333, Brain research
(1) In the somatosensory cortex of alert monkeys, 55 neurons were found which receive convergent information from two or more adjacent joints. Most of these multiple-joint neurons were excited by postures of the hand, particularly those involved in grasping. (2) Three basic types of joint interactions were observed. The simplest neurons (occlusion neurons) responded to postures of several different joints, but combination of the preferred postures produced no further increase in firing. The more complex cells showed summated responses to combined postures of adjacent joints, or subliminal facilitation between joints. The responses of both summation neurons and subliminal facilitation neurons were graded with joint angle, and there was an optimum or preferred position for both joints which gave the strongest response. (3) Multiple-joint neurons may provide a neuronal substrate for extracting postural information from several different populations of kinesthetic neurons. They therefore act as feature-detecting neurons, abstracting information about specific body postures
— id: 138473, year: 1981, vol: 214, page: 321, stat: Journal Article,

Properties of kinesthetic neurons in somatosensory cortex of awake monkeys
Gardner, E P; Costanzo, R M
1981 Jun 15;214(2):301-319, Brain research
(1) To study neural mechanisms used to encode kinesthetic information in somatosensory cortex of awake monkeys, we recorded from 227 single neurons responsive to joint movement or specific postures of the forelimb or hand (kinesthetic neurons). Unit responses were characterized quantitatively with respect to: (a) firing patterns; (b) responses to ramp changes in joint position and joint velocity; and (c) responses to sinusoidal joint movements. (2) Kinesthetic neurons were divided into 3 groups. Rapidly-adapting neurons (44%) responded only to joint movement, giving a burst of impulses proportional to velocity. They showed no tonic responses to limb posture. Two populations of tonically active neurons were observed: slowly-adapting neurons (43%) and postural neurons (13%). Both types increased their firing rates with increasing degrees of flexion or extension, showing maximum excitation at the extremes of joint position in the preferred direction. They were distinguished by their sensitivity to the velocity of movement, the size of the angle over which they respond, and the phase relation of their responses to sinusoidal joint movement. (3) The firing rates of kinesthetic neurons in S-I cortex are functions of both joint angle and joint velocity. The importance of each component varies in the 3 classes: velocity of movement is the most important determinant of firing rates of rapidly-adapting and slowly-adapting kinesthetic neurons, and joint angle predominates the responses of postural neurons
— id: 138474, year: 1981, vol: 214, page: 301, stat: Journal Article,

Psychophysical measurements of perceived intensity of single-point and multiple-point cutaneous stimuli in humans and subhuman primates
Gardner, E P; Tast, J M
1981 Sep;46(3):479-495, Journal of neurophysiology
— id: 138480, year: 1981, vol: 46, page: 479, stat: Journal Article,

A quantitative analysis of responses of direction-sensitive neurons in somatosensory cortex of awake monkeys
Costanzo, R M; Gardner, E P
1980 May;43(5):1319-1341, Journal of neurophysiology
— id: 138476, year: 1980, vol: 43, page: 1319, stat: Journal Article,

Spatial integration of multiple-point stimuli in primary somatosensory cortical receptive fields of alert monkeys
Gardner EP; Costanzo RM
1980 Feb;43(2):420-443, Journal of neurophysiology
— id: 62223, year: 1980, vol: 43, page: 420, stat: Journal Article,

Temporal integration of multiple-point stimuli in primary somatosensory cortical receptive fields of alert monkeys
Gardner EP; Costanzo RM
1980 Feb;43(2):444-468, Journal of neurophysiology
— id: 62224, year: 1980, vol: 43, page: 444, stat: Journal Article,

Neuronal mechanisms underlying direction sensitivity of somatosensory cortical neurons in awake monkeys
Gardner, E P; Costanzo, R M
1980 May;43(5):1342-1354, Journal of neurophysiology
— id: 138475, year: 1980, vol: 43, page: 1342, stat: Journal Article,

Obituary: W Alden Spencer
Gardner, E P; Kandel, E R; Schwartz, J H
1978 ;3(9):771-772, Neuroscience
— id: 145573, year: 1978, vol: 3, page: 771, stat: Journal Article,

Single-unit responses to natural vestibular stimuli and eye movements in deep cerebellar nuclei of the alert rhesus monkey
Gardner, E P; Fuchs, A F
1975 May;38(3):627-649, Journal of neurophysiology
To study the possible role of the cerebellum in the vestibular-ocular reflex, extracellular responses of cerebellar nuclear neurons were recorded in awake monkeys during natural vestibular stimulation; 115 neurons in the fastigial nucleus responded to horizontal sinusoidal accelerations applied to the head by means of whole-body rotation. More than 75% of these cells were located in a distinct layer, 500 mum thick, in the rostral part of the fastigial nucleus; they were excited by contralateral horizontal angular acceleration and inhibited by ipsilateral rotation (type IIf neurons). The remaining 25% of the population were scattered more caudally in the nucleus, and were excited by ipsilateral rotation and inhibited by contralateral rotation (type If). All showed fairly high resting discharges, averaging 50 spikes/s. Sinusoidal horizontal rotation (0.2--4.8 HZ) produced clear periodic modulation of the firing rate of fastigial neurons, which was approximately sinusoidal about the resting rate at low frequencies. As the frequency of oscillation (and the applied acceleration) increased, the sinusoidal modulation of unit firing increased in amplitude; at high stimulus frequencies the firing rate was usually driven to zero during the inhibitory part of stimulus cycle, but did not saturate in the excitatory half leading to an increase in the mean firing rate. The maximum firing rates of fastigial neurons were related to the peak acceleration by a power function. At all stimulus frequencies, the peak firing frequency of fastigial neurons lagged the input angular acceleration. Maximum firing of most units occurred just prior to the maximum velocity of the head. The gain and phase lag of the averaged unit discharge relative to head acceleration were calculated by Fourier analysis, using the fundamental as a first approximation of the response. Over a 20-fold stimulus range (0.2--4.0 HZ), mean phage lags of type IIf unit responses with respect to the applied acceleration remained relatively constant; the phase lag at 0.9 HZ measured 62 plus or minus 13 degrees. This phase lag is very similar to that recorded from vestibular nerve fibers (15), suggesting that type IIf fastigial neurons provide an excitatory signal to the ipsilateral vestibular nuclei which is in phase with direct vestibular afferent input, although functionally opposite in sign. Over the same frequency range, the gain decreased at minus- 18 dB/decade. Our data suggests that the majority of fastigial neurons work in parallel with flocculus Purkinje cells to functionally inhibit type Iv neurons in the ipsilateral vestibular nuclei
— id: 145574, year: 1975, vol: 38, page: 627, stat: Journal Article,

Sensory funneling. I. Psychophysical observations of human subjects and responses of cutaneous mechanoreceptive afferents in the cat to patterned skin stimuli
Gardner, E P; Spencer, W A
1972 Nov;35(6):925-953, Journal of neurophysiology
— id: 145576, year: 1972, vol: 35, page: 925, stat: Journal Article,

Sensory funneling. II. Cortical neuronal representation of patterned cutaneous stimuli
Gardner, E P; Spencer, W A
1972 Nov;35(6):954-977, Journal of neurophysiology
— id: 145575, year: 1972, vol: 35, page: 954, stat: Journal Article,

Geometry of the ventrobasal complex: functional significance in skin sensation
Iwamura, Y; Gardner, E P; Spencer, W A
1972 ;6(1):185-202, Brain behavior & evolution
— id: 145577, year: 1972, vol: 6, page: 185, stat: Journal Article,