Kerry Dee Walton, Ph.D.

Imaging of thalamocortical dysrhythmia in neuropsychiatry
Schulman, Joshua J; Cancro, Robert; Lowe, Sandlin; Lu, Feng; Walton, Kerry D; Llinas, Rodolfo R
2011 ;5:69-69, Frontiers in Human Neuroscience
Abnormal brain activity dynamics, in the sense of a thalamocortical dysrhythmia (TCD), has been proposed as the underlying mechanism for a subset of disorders that bridge the traditional delineations of neurology and neuropsychiatry. In order to test this proposal from a psychiatric perspective, a study using magnetoencephalography (MEG) was implemented in subjects with schizophrenic spectrum disorder (n = 14), obsessive-compulsive disorder (n = 10), or depressive disorder (n = 5) and in control individuals (n = 18). Detailed CNS electrophysiological analysis of these patients, using MEG, revealed the presence of abnormal theta range spectral power with typical TCD characteristics, in all cases. The use of independent component analysis and minimum-norm-based methods localized such TCD to ventromedial prefrontal and temporal cortices. The observed mode of oscillation was spectrally equivalent but spatially distinct from that of TCD observed in other related disorders, including Parkinson's disease, central tinnitus, neuropathic pain, and autism. The present results indicate that the functional basis for much of these pathologies may relate most fundamentally to the category of calcium channelopathies and serve as a model for the cellular substrate for low-frequency oscillations present in these psychiatric disorders, providing a basis for therapeutic strategies
— id: 136950, year: 2011, vol: 5, page: 69, stat: Journal Article,

Abnormal thalamocortical activity in patients with Complex Regional Pain Syndrome (CRPS) type I
Walton, K D; Dubois, M; Llinas, R R
2010 Jul;150(1):41-51, Pain
Complex Regional Pain Syndrome (CRPS) is a neuropathic disease that presents a continuing challenge in terms of pathophysiology, diagnosis, and treatment. Recent studies of neuropathic pain, in both animals and patients, have established a direct relationship between abnormal thalamic rhythmicity related to Thalamo-cortical Dysrhythmia (TCD) and the occurrence of central pain. Here, this relationship has been examined using magneto-encephalographic (MEG) imaging in CRPS Type I, characterized by the absence of nerve lesions. The study addresses spontaneous MEG activity from 13 awake, adult patients (2 men, 11 women; age 15-62), with CRPS Type I of one extremity (duration range: 3months to 10years) and from 13 control subjects. All CRPS I patients demonstrated peaks in power spectrum in the delta (<4Hz) and/or theta (4-9Hz) frequency ranges resulting in a characteristically increased spectral power in those ranges when compared to control subjects. The localization of such abnormal activity, implemented using independent component analysis (ICA) of the sensor data, showed delta and/or theta range activity localized to the somatosensory cortex corresponding to the pain localization, and to orbitofrontal-temporal cortices related to the affective pain perception. Indeed, CRPS Type I patients presented abnormal brain activity typical of TCD, which has both diagnostic value indicating a central origin for this ailment and a potential treatment interest involving pharmacological and electrical stimulation therapies
— id: 111814, year: 2010, vol: 150, page: 41, stat: Journal Article,

Oral administration of pharmacologically active substances to squid: a methodological description
Berk, William; Teperman, Jake; Walton, Kerry D; Hirata, Kazunari; Sugimori, Mutsuyuki; Llinas, Rodolfo R
2009 Feb;216(1):1-6, Biological bulletin
The squid giant synapse is a well-defined experimental preparation for the study of ligand-dependant synaptic transmission. Its large size gives direct experimental access to both presynaptic and postsynaptic junctional elements, allowing direct optical, biophysical, and electrophysiological analysis of depolarization-release coupling. However, this important model has not been utilized in pharmacological studies, other than those implementable acutely in the in vitro condition. A method is presented for oral administration of bioactive substances to living squid. Electrophysiological characterization and direct determination of drug absorption into the nervous system demonstrate the administration method described here to be appropriate for pharmacological research
— id: 94219, year: 2009, vol: 216, page: 1, stat: Journal Article,

Central pain as a thalamocortical dysrhythmia
Walton KD; Llinas RR
Translational pain research : from mouse to man Boca Raton FL : CRC, 2009,
— id: 5253, year: 2009, vol: , page: 301, stat: Chapter,

Intravascular Neural Interface with Nanowire Electrode
Watanabe H; Takahashi H; Nakao M; Walton K; Llinas RR
2009 Jul;92(7):29-37, Electronics & communications in Japan = Denki Gakkai ronbunshi
A minimally invasive electrical recording and stimulating technique capable of simultaneously monitoring the activity of a significant number (e.g., 10(3) to 10(4)) of neurons is an absolute prerequisite in developing an effective brain-machine interface. Although there are many excellent methodologies for recording single or multiple neurons, there has been no methodology for accessing large numbers of cells in a behaving experimental animal or human individual. Brain vascular parenchyma is a promising candidate for addressing this problem. It has been proposed [1, 2] that a multitude of nanowire electrodes introduced into the central nervous system through the vascular system to address any brain area may be a possible solution. In this study we implement a design for such microcatheter for ex vivo experiments. Using Wollaston platinum wire, we design a submicron-scale electrode and develop a fabrication method. We then evaluate the mechanical properties of the electrode in a flow when passing through the intricacies of the capillary bed in ex vivo Xenopus laevis experiments. Furthermore, we demonstrate the feasibility of intravascular recording in the spinal cord of Xenopus laevis
— id: 141092, year: 2009, vol: 92, page: 29, stat: Journal Article,

Magnetic sources of the M50 response are localized to frontal cortex
Garcia-Rill, E; Moran, K; Garcia, J; Findley, W M; Walton, K; Strotman, B; Llinas, R R
2008 Feb;119(2):388-398, Clinical neurophysiology
OBJECTIVE: To determine the source localization(s) of the midlatency auditory magnetic response M50, the equivalent of the P50 potential, a sleep state-dependent waveform known to habituate to repetitive stimulation. METHODS: We used a paired stimulus paradigm at interstimulus intervals of 250, 500 and 1000 ms, and magnetoencephalographic (MEG) recordings were subjected to computational methods for current density reconstruction, blind source separation, time-frequency analysis, and data visualization to characterize evoked dynamics. RESULTS: Each subject showed localization of a source for primary auditory evoked responses in the region of the auditory cortex, usually at a 20-30 ms latency. However, responses at 40-70 ms latency that also decreased following the second stimulus of a pair were not localizable to the auditory cortex, rather showing multiple sources usually including the frontal lobes. CONCLUSIONS: The M50 response, which shows habituation to repetitive stimulation, was not localized to the auditory cortex, but showed multiple sources including frontal lobes. SIGNIFICANCE: These MEG results suggest that sources for the M50 response may represent non-auditory, perhaps arousal-related, diffuse projections to the cortex
— id: 78727, year: 2008, vol: 119, page: 388, stat: Journal Article,

CNS recording and stimulation using intravascular submicron-scale probes
Watanabe H; Walton K; Llinas R
2007 ;33:?-?, Society for Neuroscience Abstract Viewer & Itinerary Planner
— id: 75349, year: 2007, vol: 33, page: ?, stat: Journal Article,

Non-auditory localization of midlatency auditory evoked activity (P50): a MEG study
Garcia-Rill E; Garcia J; Moran KA; Findley WM; Walton KD; Llinas R
2006 ;32:?-?, Society for Neuroscience Abstract Viewer & Itinerary Planner
— id: 75345, year: 2006, vol: 32, page: ?, stat: Journal Article,

Modeling study of the relationship between spinal motorneuron pool firing rate and hindlimb posture duirng locomotion: consideration of the effects of altering gravity during development
Laczko J; Walton KD; Llinas R
2006 ;32:?-?, Society for Neuroscience Abstract Viewer & Itinerary Planner
— id: 75346, year: 2006, vol: 32, page: ?, stat: Journal Article,

A neuro-mechanical transducer model for controlling joint rotations and limb movements
Laczko, Jozsef; Kerry, Walton; Rodolfo, Llinas
2006 Jan 20;59(1-2):32-43, Ideggyogyaszati szemle
Here we report on the development of an integrated general model for the control of limb movements. The model computes muscle forces and joint rotations as functions of activation signals from motoneuron pools. It models the relationship between neural signals, muscle forces and movement kinematics by taking into account how the discharge rates of motoneuron pools and the biomechanical characteristics of the musculoskeletal system affect the movement pattern that is produced. The lengths and inertial properties of limb segments, muscle attachment sites, the muscles' force-length, force-frequency and force-velocity (of contraction) relationships, as well as a load parameter that simulates the effect of body weight are considered. There are a large number of possible ways to generate a planned joint rotation with muscle activation. We approach this 'overcompleteness problem' by considering each joint to be controlled by a single flexor/extensor muscle pair and that only one of the two muscles is activated at a given time. Using this assumption, we have developed an inverse model that provides discharge rates of motoneuron pools that can produce an intended angular change in each joint. We studied the sensitivity of this inverse model to the muscle force-length relationship and to limb posture. The model could compute possible firing rates of motoneuron pools that would produce joint angle changes observed in rats during walking. It could also compare motoneuron activity patterns received for two different hypothetical force-length relations and show how the motoneuron pool activity would change if joints would be more flexed or extended during the entire movement
— id: 63608, year: 2006, vol: 59, page: 32, stat: Journal Article,

CNS recording and stiumulation using intravascular submicron-scale probes
Watanabe H; Ruddy B; Aquetil PA; Walton KD; Hunter I; Llinas R
2006 ;32:?-?, Society for Neuroscience Abstract Viewer & Itinerary Planner
— id: 75342, year: 2006, vol: 32, page: ?, stat: Journal Article,

Neuro-vascular central nervous recording/stimulting system: using nanotechnology probes
Llinas RR; Walton KD; Nakao M; Hunter L; Anqueth PA
2005 ;7:111-127, Journal of nanoparticle research
— id: 75330, year: 2005, vol: 7, page: 111, stat: Journal Article,

Neuromagnetic correlates of Gilles de la Tourette Syndrome
Moran KA; Leckman JF; Vaccarino FM; Walton KD; Llinas RR
2005 ;31:-, Society for Neuroscience Abstract Viewer & Itinerary Planner
— id: 75337, year: 2005, vol: 31, page: , stat: Journal Article,

Somatotopic dynamics revealed during simple audio-motor reaction time tasks
Sekar K; Moran KA; Ramirez RR; Walton KD; Llinas R
2005 ;31:-, Society for Neuroscience Abstract Viewer & Itinerary Planner
— id: 75336, year: 2005, vol: 31, page: , stat: Journal Article,

Long-term effects of microgravity on the swimming behaviour of young rats
Walton, Kerry D; Benavides, Louis; Singh, Neeraj; Hatoum, Nagi
2005 Jun 1;565(Pt 2):609-626, Journal of physiology
The postnatal development of sensory systems has been shown in studies over the last four decades to be influenced by experience during critical periods of development. We report here that similar experience-dependent development can be observed in the swimming behaviour of young rats reared from postnatal day 14 (P14) to P30 in the reduced gravitational field of low earth orbit. Animals flown in space when placed in the water on the day of landing maintained their head and forelimbs in a balanced posture. However, until the animals began to swim, their hindquarters showed little lateral postural control resulting in rotation about the longitudinal axis (60 degrees+/-4 deg). Such results suggest an 'unlinking' of postural control of the forequarters from the hindquarters in the early hours after landing. Similar instability seen in animals age-matched to the day of launch (97+/-7 deg) and in ground control animals (9+/-3 deg) was corrected within one or two rotations, even in the absence of swimming. Animals flown in space began to swim sooner after being placed in the water, and the duration of swimming strokes was shorter than in control animals. Motion analysis revealed a difference in the swimming style on landing day. In flight animals, the knee joint was more flexed throughout the stroke, there was a narrower range of movement, and the linear velocity of the tip of the foot was faster throughout most of the stroke than in age-matched control animals. Thus, posture in the water as well as swimming speed and style were altered in the animals flown in space. Some of these characteristics persisted for as long as the animals were followed (30 days). These included the short pre-swimming interval and short stroke duration in flight animals. These findings clearly show that an altered gravitational field influences the postnatal development of motor function. The nature of the differences between animals reared in space for 16 days and those remaining on the ground reflects an adaptation of the flight animals to the microgravity environment. The data suggest that the most fundamental of these adaptations is a resetting of the basic motor rhythm to a higher frequency
— id: 56183, year: 2005, vol: 565, page: 609, stat: Journal Article,

The effects of microgravity on the development of surface righting in rats
Walton, Kerry D; Harding, Shannon; Anschel, David; Harris, Ya'el Tobi; Llinas, Rodolfo
2005 Jun 1;565(Pt 2):593-608, Journal of physiology
The active interaction of neonatal animals with their environment has been shown to be a decisive factor in the postnatal development of sensory systems, which demonstrates a critical period in their maturation. The direct demonstration of such a dependence on the rearing environment has not been demonstrated for motor system function. Nor has the role of gravity in mammalian motor system development been investigated. Here we report the results of two space flight missions examining the effect of removing gravity on the development of surface righting. Since the essential stimulus that drives this synergy, gravitation, was missing, righting did not occur while the animals were in the microgravity environment. We hypothesize that this absence of contextual motor experience arrested the maturation of the motor tactics for surface righting. Such effects were permanent in rats spending 16 days (from postnatal day (P), P14 to P30), but were transient in animals spending nine days (from P15 to P24) in microgravity. Thus, active, contextual interaction with the environment during a critical period of development is necessary for the postnatal maturation of motor tactics as exemplified by surface righting, and such events must occur within a particular time period. Further, Earth's gravitational field is not assumed by the developing motor system. Rather, postnatal motor system development is appropriate to the gravitational field in which the animal is reared
— id: 56102, year: 2005, vol: 565, page: 593, stat: Journal Article,

Cerebellum
Llinas R; Walton K; Lang EJ
The synaptic organization of the brain New York : Oxford University Press, 2004,
— id: 3487, year: 2004, vol: , page: 271, stat: Chapter,

Cerebellum
Llinas, Rodolfo R; Walton, Kerry D; Lang, Eric J
The synaptic organization of the brain (5th ed) New York, NY, US: Oxford University Press, 2004,
The cerebellum, a very distinct region of the brain, derives its name as a diminutive of the word 'cerebrum.' To the ancient anatomists, this was a second, smaller brain in its own right. This is particularly explicit in the German language, where Kleinhirn ('cerebellum') translates literally into 'small brain.' It occupies, in all vertebrates, a position immediately behind the tectal plate and straddles the midline as a bridge over the fourth ventricle. In addition, it is the only region of the nervous system to span the midline without interruption. In this chapter, we show how the role of the cerebellum in motor coordination arises from an interplay between the intrinsic excitability of the Purkinje and cerebellar nuclear cell membranes and from the crystal-like organization of the synaptic connectivity in the cerebellar cortex
— id: 4728, year: 2004, vol: , page: 271, stat: Chapter,

A model for swimming motor control in rats reared from P14 to P30 in microgravity
Laczko, J.; Walton, K.; Llinas, R.
2003 ;2003:?-?, Society for Neuroscience Abstract Viewer & Itinerary Planner
Coordinated limb movements require the proper interaction between neuronal, muscular, and skeletal systems. The link between such systems may be addressed using mathematical models that simulate muscle contraction and that resulting joint rotations. A computer model for limb movement is presented that mimics muscle contraction and joint rotations as a function of motor neuron firing frequencies. The model generates angular changes in each joint with activation of a flexor-extensor muscle pair. The issue is that there are a large number of possible solutions to the generation of angular changes in a joint with muscle activation. This known as the over completeness problem We address it by proposing that in each joint only one of the muscles (the flexor or the extensor) is activated at a certain moment. The model considers the intersegmental joint angles, the lengths and masses of limb segments, the sites of muscle attachments, the force-length and force-frequency relationships of the muscles. The motor command for each muscle in each time interval is the firing rate of the muscle's motoneuron pool. This command generates angular motions in the joint. We apply the model to ankle muscle activities in two groups of swimming rats. One group spend 16 days in microgravity (flight) while the second group remained in the terrestrial environment. For both groups swimming was recorded on land. We computed firing rates of motoneuron pools to mimic joint angle changes that were recorded experimentally. The model predicts an increased firing rate for the muscles of the flight group. We propose that this is the result of the differences in motor control developed under different environmental conditions. The predicted higher firing rate is compatible with the observed higher flexions in the joints of the rats of the flight group
— id: 92289, year: 2003, vol: 2003, page: ?, stat: Journal Article,

Spaceflight induces changes in the synaptic circuitry of the postnatal developing neocortex
DeFelipe, J; Arellano, J I; Merchan-Perez, A; Gonzalez-Albo, M C; Walton, K; Llinas, R
2002 Aug;12(8):883-891, Cerebral cortex
The establishment of the adult pattern of neocortical circuitry depends on various intrinsic and extrinsic factors, whose modification during development can lead to alterations in cortical organization and function. We report the effect of 16 days of spaceflight [Neurolab mission; from postnatal day 14 (P14) to P30] on the neocortical representation of the hindlimb synaptic circuitry in rats. As a result, we show, for the first time, that development in microgravity leads to changes in the number and morphology of cortical synapses in a laminar-specific manner. In the layers II/III and Va, the synaptic cross-sectional lengths were significantly larger in flight animals than in ground control animals. Flight animals also showed significantly lower synaptic densities in layers II/III, IV and Va. The greatest difference was found in layer II/III, where there was a difference of 344 million synapses per mm(3) (15.6% decrease). Furthermore, after a 4 month period of re-adaptation to terrestrial gravity, some changes disappeared (i.e. the alterations were transient), while conversely, some new differences also appeared. For example, significant differences in synaptic density in layers II/III and Va after re-adaptation were no longer observed, whereas in layer IV the density of synapses increased notably in flight animals (a difference of 185 million synapses per mm(3) or 13.4%). In addition, all the changes observed only affected asymmetrical synapses, which are known to be excitatory. These results indicates that terrestrial gravity is a necessary environmental parameter for normal cortical synaptogenesis. These findings are fundamental in planning future long-term spaceflights
— id: 42311, year: 2002, vol: 12, page: 883, stat: Journal Article,

Space flight affects magnocellular supraoptic neurons of young prepuberal rats: transient and permanent effects
Garcia-Ovejero, D; Trejo, JL; Ciriza, I; Walton, KD; Garcia-Segura, LM
2001 OCT 24 ;130(2):191-205, Brain research. Developmental brain research
Effects of microgravity on postural control and volume of extracellular fluids as well as stress associated with space flight may affect the function of hypothalamic neurosecretory neurons. Since environmental modifications in young animals may result in permanent alterations in neuroendocrine function, the present study was designed to determine the effect of a space flight on oxytocinergic and vasopressinergic magnocellular hypothalamic neurons of prepuberal rats. Fifteen-day-old Sprague-Dawley female rats were flown aboard the Space Shuttle Columbia (STS-90, Neurolab mission, experiment 150) for 16 days. Age-matched litters remained on the ground in cages similiar to those of the flight animals. Six animals from each group were killed on the day of landing and eight animals from each croup were maintained under standard vivarium conditions and killed 18 weeks after landing. Several signs of enhanced transcriptional and biosynthetic activity were observed in magnocellular supraoptic neurons of flight animals on the day of landing compared to control animals. These include increased c-Fos expression, larger nucleoli and cytoplasm, and higher volume occupied in the neuronal perikaryon by mitochondriae, endoplasmic reticulum, Golgi apparatus, lysosomes and cytoplasmic inclusions known as nematosomes. In contrast, the volume occupied by neurosecretory vesicles in the supraoptic neuronal perikarya was significantly decreased in flight rats. This decrease was associated with a significant decrease in oxytocin and vasopressin immunoreactive levels, suggestive of an increased hormonal release. Vasopressin levels, cytoplasmic volume and c-Fos expression returned to control levels by 18 weeks after landing. These reversible effects were probably associated to osmotic stimuli resulting from modifications in the volume and distribution of extracellular fluids and plasma during flight and landing. However, oxytocin levels were still reduced at 18 weeks after landing in flight animals compared to controls. This indicates that space flight during prepuberal age may induce irreversible modifications in the regulation of oxytocinergic neurons, which in turn may result in permanent endocrine and behavioral impairments. (C) 2001 Elsevier Science B.V. All rights reserved
— id: 105132, year: 2001, vol: 130, page: 191, stat: Journal Article,

Functional analysis of the human alpha7 neuronal nicotinic receptor gene promoter from normal and schizophrenic individuals
Short, M.; Gault, J.; Vianzon, R.; Logel, J.; Hopkins, J.; Robinson, M.; Drebing, C.; Berger, R.; Walton, K.; Sullivan, B.; Freedman, R.; Leonard, S.
2001 ;27(2):2626-2626, Abstracts (Society for Neuroscience)
Biological and genetic evidence supports the hypothesis that the alpha7 neuronal nicotinic receptor subunit (CHRNA7) has an important role in a sensory processing deficit found in many schizophrenics. Sequence and SSCP analysis have identified 13 single bp variants, 11 double bp variants and 2 individuals with multiple base insertions in a 231bp promoter region upstream of the ATG translation start site. Functional analysis of these polymorphisms in the 231bp promoter using a luciferase reporter gene transcription assay has been done. Additional functional assays have been run for fragments of 1kb and 2.6kb of upstream promoter sequence. Analysis of polymorphisms at -86 C to T, -178 delG, -194 G to C, and -241 A to G, using this reporter assay, shows a statistically significant drop in the transcription activity in transfected SHSY-5Y neuroblastoma cells. The polymorphism -86 C to T, found more frequently in schizophrenic subjects, decreases promoter activity by 18% (P<0.0001). Functional analysis of the 2.6kb fragment of the promoter reveals a statistically significant decrease in activity, suggesting the presence of a repressor element. The putative promoter mutations may reduce transcriptional activity in the in vivo alpha7 subunit and potentially contribute to the decrease in alpha7 expression, seen in postmortem brain of schizophrenics
— id: 92450, year: 2001, vol: 27, page: 2626, stat: Journal Article,

Isolation of a human alpha10 nicotinic receptor cDNA and expression studies in human brain, thymus and lymphocytes
Drebing, C. J.; Mihovilovic, M.; Logel, J.; Hickman, C. D.; Short, M.; Walton, K.; Gault, J.; Freedman, R.; Leonard, S.
2000 ;26(1-2):?-?, Abstracts (Society for Neuroscience)
Rat alpha 10 (GenBank AF196344) was recently cloned by Boulter, et al. Chicken alpha 9 (AF082192) and human alpha 9 (HSA243342) have also been cloned. A partial clone for human alpha 10 has been sequenced in our laboratory. The coding sequence of human alpha 10 has 82% homology to the rat sequence at the nucleotide level and 91% homology in amino acid sequence. Alpha 10 message was detectable by PCR in thymocytes, myasthenia gravis thymus, immortalized peripheral B-cells, Ramos cell line (RA-1) and cell lines from thymic epithelia (TE) and thymic fibroblasts (TF). The alpha 10 transcript was also seen in human postmortem cingulate, lung and pituitary. The human alpha 10 clone has 56% homology in amino acid sequence with human alpha 9. Alpha 9 message was detectable in thymic fibroblasts (TF) but was only visible by Southern hybridization in thymus, thymocytes and Ramos cells, and therefore appears less abundant than alpha 10 message. Human alpha 9 maps to chromosome 6; alpha 10 maps to chromosome 11. Linkage to p50 sensory gating has been found at 11p15.5 and at 6q25-27 (Coon, et al., 1993), therefore these receptors may be of interest in the study of schizophrenia. The presence of alpha 10 message in thymic tissue suggests these receptors may also be of interest in the study of myasthenia gravis
— id: 92451, year: 2000, vol: 26, page: ?, stat: Journal Article,

Mutation screen of the promoter region of the human alpha7 neuronal nicotinic receptor subunit in normal and schizophrenic individuals
Logel, J.; Gault, J.; Vianzon, R.; Hopkins, J.; Short, M.; Robinson, M.; Drebing, C.; Berger, R.; Walton, K.; Sullivan, B.; Freedman, R.; Leonard, S.
2000 ;26(1-2):?-?, Abstracts (Society for Neuroscience)
Biological and genetic evidence supports the hypothesis that the alpha7 neuronal nicotinic receptor subunit (CHRNA7) has an important role in a sensory processing deficit found in many schizophrenics. Our laboratory is completing a mutation screen of the alpha7 transcribed sequence, intronic splice junctions and the promoter. Mutation results on the 248 bp promoter region upstream of the ATG translation start site will be reported. Single strand conformation polymorphism (SSCP) analysis of the proximal alpha7 promoter region identified 27 distinct patterns, 12 of which were unique to schizophrenics. Twenty-one schizophrenic individuals appear to have one of these 12 patterns, not found in controls. Sequence analysis of some of the 27 patterns show polymorphisms at position -194GfwdarwC, -191GfwdarwA, -190insG, -178delG and -166CfwdarwT, which are located in or near consensus sequences for transcription factor binding sites for Sp-1, AP-2, Egr-1 and CREB. Other polymorphisms have been identified at -86CfwdarwT, -84AfwdarwG and -46GfwdarwT. Functional analysis of polymorphisms at -191A, -178delG, -86T and -84G, using a luciferase reporter gene transcription assay, shows a statistically significant drop in the transcription activity in transfected SHSY-5Y neuroblastoma cells. The putative promoter mutations may reduce transcriptional activity for the in vivo alpha7 subunit and potentially contribute to the decrease in alpha7 expression, seen in postmortem brain of schizophrenics
— id: 92452, year: 2000, vol: 26, page: ?, stat: Journal Article,

Identification of a critical period for the development of righting strategy
Harding, S.; Anschel, D.; Walton, K. D.
1999 ;25(1-2):227-227, Abstracts (Society for Neuroscience)
— id: 92453, year: 1999, vol: 25, page: 227, stat: Journal Article,

Locomotion in neonatal rats during and after space flight
Sulica, D.; Laczko, J.; Walton, K. D.
1999 ;25(1-2):226-226, Abstracts (Society for Neuroscience)
— id: 92454, year: 1999, vol: 25, page: 226, stat: Journal Article,

Expression of the human alpha7 neuronal nicotinic acetylcholine receptor and a partial gene duplication
Drebing, C.; Logel, J.; Benhammou, K.; Robinson, M.; Gault, J.; Walton, K.; Meriwether, J.; Short, M.; Hopkins, J.; Berger, R.; Maslak, M.; Breese, C.; Freedman, R.; Leonard, S.
1998 ;24(1-2):832-832, Abstracts (Society for Neuroscience)
— id: 92455, year: 1998, vol: 24, page: 832, stat: Journal Article,

Genomic organization and partial duplication of the human alpha7 neuronal nicotinic acetylcholine receptor subunit gene
Leonard, S.; Gault, J.; Robinson, M.; Berger, R.; Drebing, C.; Logel, J.; Hopkins, J.; Moore, T.; Meriwether, J.; Jacobs, S.; Kim, E. J.; Choi, M. J.; Walton, K.; Breese, C.; Freedman, R.
1998 ;24(1-2):832-832, Abstracts (Society for Neuroscience)
— id: 92456, year: 1998, vol: 24, page: 832, stat: Journal Article,

Cerebellum
Llinas R; Walton K
The synaptic organization of the brain New York : Oxford Univ. Press, 1998,
— id: 3259, year: 1998, vol: , page: 255, stat: Chapter,

Postnatal development under conditions of simulated weightlessness and space flight
Walton K
1998 Nov;28(1-2):25-34, Brain research. Brain research reviews
The adaptability of the developing nervous system to environmental influences and the mechanisms underlying this plasticity has recently become a subject of interest in space neuroscience. Ground studies on neonatal rats using the tail suspension model of weightlessness have shown that the force of gravity clearly influences the events underlying the postnatal development of motor function. These effects depend on the age of the animal, duration of the perturbation and the motor function studied. A nine-day flight study has shown that a dam and neonates can develop under conditions of space flight. The motor function of the flight animals after landing was consistent with that seen in the tail suspension studies, being marked by limb joint extension. However, there were expected differences due to: (1) the unloading of the vestibular system in flight, which did not occur in the ground-based experiments; (2) differences between flight and suspension durations; and (3) the inability to evaluate motor function during the flight. The next step is to conduct experiments in space with the flexibility and rigor that is now limited to ground studies: an opportunity offered by the International Space Station.
— id: 7464, year: 1998, vol: 28, page: 25, stat: Journal Article,

Effects of space flight on righting reflexes and swimming in neonatal rats
Hefferman, C.; Benavides, L.; Walton, K.
1997 ;23(1-2):637-637, Abstracts (Society for Neuroscience)
— id: 92457, year: 1997, vol: 23, page: 637, stat: Journal Article,

Walking in neonatal rats exposed to microgravity or hypergravity during postnatal development
Sulica, D.; Walton, K.
1997 ;23(1-2):637-637, Abstracts (Society for Neuroscience)
— id: 92458, year: 1997, vol: 23, page: 637, stat: Journal Article,

Motoneurons undergoing apoptosis have increased JNK (SAPK) activity but not ERK1 activity
Glicksman, M. A.; Walton, K.; Basma, A.; Neff, N. T.; Dionne, C. A.; Maroney, A. C.
1996 ;22(1-3):564-564, Abstracts (Society for Neuroscience)
— id: 92459, year: 1996, vol: 22, page: 564, stat: Journal Article,

Oxidation in ALS
Donaldson, D. H.; Rahmani, Z.; Berger, R.; Walton, K.; Bleskan, J.; Mezey, E.; Usdin, T. B.; Groner, Y.; Rosen, D. R.
1993 ;19(1-3):195-195, Abstracts (Society for Neuroscience)
— id: 92461, year: 1993, vol: 19, page: 195, stat: Journal Article,

The isolated and perfused brain of the guinea-pig in vitro
Muhlethaler M; de Curtis M; Walton K; Llinas R
1993 Jul 1;5(7):915-926, European journal of neuroscience
We describe here an isolated and perfused in vitro adult guinea-pig whole brain preparation which is an extension of the previously described in vitro brainstem-cerebellum preparation. Viability was tested by the analysis of trans-synaptic responses along the visual pathways following the electrical stimulation of the optic nerve or the optic radiations. The evoked field potentials were recorded in the dorsal lateral geniculate, the superior colliculus and the visual cortex. The distribution of extracellular currents was studied using current source density analysis, in order to determine the amplitude, time course and spatial organization of the synaptic activity at these sites. The study indicates that field potentials were very similar to those described in vivo. These data demonstrate the survival of a complex adult sensory system in vitro and suggest that this preparation can be used for the analysis of multisynaptic circuits in the mammalian brain
— id: 8289, year: 1993, vol: 5, page: 915, stat: Journal Article,

Electroresponse and synaptic characteristics of neonatal rat lumbar motoneurons: A whole-cell recording study
Pickering, A. E.; Walton, Kerry D.
1993 ;19(1-3):617-617, Abstracts (Society for Neuroscience)
— id: 92460, year: 1993, vol: 19, page: 617, stat: Journal Article,

Hindlimb suspension in neonatal rats leads to permanent deficits in air righting reflexes
Skorina, Jane; Walton, Kerry D.; Hillman, Dean; Llinas, Rodolfo
1992 ;18(1-2):961-961, Abstracts (Society for Neuroscience)
— id: 92268, year: 1992, vol: 18, page: 961, stat: Journal Article,

Identification of a critical period for motor development in neonatal rats
Walton KD; Lieberman D; Llinas A; Begin M; Llinas RR
1992 Dec;51(4):763-767, Neuroscience
Manipulation of the developing nervous system has provided valuable insights into nervous system function. One important concept to arise from this type of study has been the identification of specific 'critical periods' for the development of various functions. A critical period has been most clearly shown for the visual system where monocular eye closure for a few weeks led to functionally significant changes in visually guided behaviors and the connectivity of the visual cortex. Critical periods have also been defined for other sensory systems. Although studies of the effect of manipulating sensory systems during development are sometimes difficult to interpret (e.g. Ref. 7), this difficulty is compounded in the case of the motor system. Problems arise because manipulations of the postnatal motor system are difficult to implement and usually require invasive procedures such as tenotomy, neurotomy, and nerve crush (for review, see Ref. 17). We have approached the problem of manipulating the motor environment by adapting a paradigm widely used to study the experimental effects of simulated weightlessness in adult rats: namely, tail suspension. This method has several advantages for manipulating the motor system: (i) because it is noninvasive, it is less discomforting than neurotomy, tenotomy or nerve crush; (ii) it does not immobilize the animals, they move about the cage and extend and flex their hindlimbs; and (iii) it specifically examines the importance of load-bearing on the development of antigravity muscles and their neuronal circuits.(ABSTRACT TRUNCATED AT 250 WORDS)
— id: 8288, year: 1992, vol: 51, page: 763, stat: Journal Article,

Changes in locomotion and neuromuscular development in the neonatal rat accompany simulated weightlessness
Walton, K. D.; Jacoby, J.; Ko, K.; Williams, S. A.; Linas, R.
1992 ;18(1-2):961-961, Abstracts (Society for Neuroscience)
— id: 92462, year: 1992, vol: 18, page: 961, stat: Journal Article,

INTEGRATING INTERACTIVE COMPUTER MODULES INTO THE NEUROSCIENCE CURRICULUM
WALTON K D
1991 ;17(1-2):519-519, Abstracts (Society for Neuroscience)
— id: 92463, year: 1991, vol: 17, page: 519, stat: Journal Article,

HINDLIMB SUSPENSION FOR SHORT PERIODS IMPAIRS MOTOR DEVELOPMENT IN NEONATAL RATS
WALTON K D; LIEBERMAN D; BEGIN M; LLINAS R R
1991 ;17(1-2):937-937, Abstracts (Society for Neuroscience)
— id: 92378, year: 1991, vol: 17, page: 937, stat: Journal Article,

Hindlimb suspension during a "criticalperiod" for motor development impairs locomotion and righting reflexes in neonatal rats
Walton K; Begin A; Llinas A; Lee S; Llinas R
Abstracts (Third IBRO World Congress of Neuroscience) Oxford UK : Pergamon Press, 1991,
— id: 3582, year: 1991, vol: , page: 309, stat: Chapter,

Hindlimb suspension impairs swimming in neonatal rats: identification of a "critical period" for motor development
Walton K; Lierberman D; Llinas R
Abstracts (Third IBRO World Congress of Neuroscience) Oxford UK : Pergamon Press, 1991,
— id: 3581, year: 1991, vol: , page: 309, stat: Chapter,

Postnatal changes in motoneurone electrotonic coupling studied in the in vitro rat lumbar spinal cord
Walton KD; Navarrete R
1991 Feb;433:283-305, Journal of physiology
1. Electrotonic coupling between motoneurones innervating ankle flexor and extensor muscles, as well as between unidentified lumbar motoneurones, was studied using intracellular recordings in an in vitro spinal cord-hindlimb preparation isolated from rats between birth (P0) and 13 days (P13). 2. Graded ventral root stimulation could elicit graded, short latency depolarizations (SLD) which preceded, coincided with, or followed the antidromic action potential. These SLDs were identified as electrotonic junctional potentials by their latency, relative insensitivity to changes in membrane potential and their resistance to one or more of the following: (1) high-frequency stimulation, (2) collision with a somatofugal action potential, (3) removal of Ca2+ from the bathing solution. 3. SLDs were studied in 162 neurones and were identified in 77.2% of the cells in preparations from P0 to P3 rats (n = 57), but only in 30.8% at P8 to P13 (n = 39). 4. SLDs were largest in the youngest animals (P0 to P3), decreasing from a mean of 1.31 mV (+/- 0.17, n = 34) to 0.56 mV (+/- 0.10, n = 7) at P8 to P13. The SLDs comprised two to eight (4.3 +/- 0.36) all-or-none components as determined from twenty collision experiments. 5. Electrotonic coupling between motoneurones was specific. SLDs could be elicited in given motoneurones by stimulation of their homonymous but never of their antagonistic muscle nerves. 6. These results indicate that electrotonic coupling between lumbar motoneurones in neonatal animals exhibits a high degree of specificity and that its significance, as judged by the amplitude and frequency of occurrence of SLDs, decreases postnatally at a rate that can be correlated with the functional maturity of the motoneurones and the muscular system
— id: 14152, year: 1991, vol: 433, page: 283, stat: Journal Article,

FUNCTIONAL EXPRESSION OF NATIVE AND MUTATED MURINE BOMBESIN-GASTRIN-RELEASING PEPTIDE RECEPTOR COMPLEMENTARY DNA IN MAMMALIAN AND AMPHIBIAN CELLS
SEGERSON T P; MONTGOMERY S; STORK P J S; WALTON K; GILADI E; GOODMAN R H; SPINDEL E R
1990 ;16(1):7-7, Abstracts (Society for Neuroscience)
— id: 92464, year: 1990, vol: 16, page: 7, stat: Journal Article,

INTRINSIC SUBTHRESHOLD 10-50 HZ MEMBRANE OSCILLATIONS IN INTERNEURONS IN THE FOURTH LAYER OF THE FRONTAL CORTEX
WALTON K D; YAROM Y; LLINAS R
1990 ;16(2):1134-1134, Abstracts (Society for Neuroscience)
— id: 92391, year: 1990, vol: 16, page: 1134, stat: Journal Article,

ELECTROPHYSIOLOGY OF THE ISOLATED ADULT GUINEA-PIG BRAIN INVITRO
Llinas, R; Muhlethaler, M; Walton, K
1989 Jul;414(2):P16-P16, Journal of physiology
— id: 31680, year: 1989, vol: 414, page: P16, stat: Journal Article,

CALCIUM CONDUCTANCES TRIGGER DOUBLET FIRING IN NEONATAL RAT MOTONEURONES INVITRO
Navarrete, R; Walton, KD
1989 Aug;415(5):P70-P70, Journal of physiology
— id: 31789, year: 1989, vol: 415, page: P70, stat: Journal Article,

POSTNATAL CHANGES IN ELECTROTONIC COUPLING BETWEEN RAT LUMBAR MOTO-NEURONES STUDIED IN AN INVITRO SPINAL CORD-HINDLIMB PREPARATION
Navarrete, R; Walton, KD
1989 Oct;417(20):P22-P22, Journal of physiology
— id: 31783, year: 1989, vol: 417, page: P22, stat: Journal Article,

The effectiveness of different isomers of octanol as blockers of harmaline-induced tremor
Sinton CM; Krosser BI; Walton KD; Llinas RR
1989 May;414(1):31-36, Pflugers archiv = European journal of physiology
Intracellular recording in the guinea-pig brainstem slice has demonstrated that high molecular weight alcohols block the low threshold calcium channel (LTCC) in the inferior olive (IO). These alcohols thus provide a tool for understanding the function of the pacemaking cellular networks of the olivo-cerebellar system, since the LTCC has been implicated in the oscillatory behavior of these neurons. Aspects of normal and pathological tremor are also believed to be mediated by these circuits, and thus development of effective ways of blocking the LTCC in vivo may eventually lead to novel treatments for essential tremor. The present experiments evaluated the effectiveness of the isomers of octanol in decreasing harmaline-induced tremor in vivo in the rat. Harmaline was used in this study because its tremorgenic action is mediated at the level of IO; octanol was found to be a potent antagonist of harmaline-induced tremor. Significant differences between the isomers further suggested conformational differences. This, taken in conjunction with the lack of effect of octanol in both IO lesioned rats and oxotremorine-induced tremor, implied that the action of the alcohol may be mediated at a specific binding site. These findings thus support the conclusions that the antagonism of harmaline-induced tremor by octanol occurs in the IO, and, in view of the previously reported in vitro data, that octanol may be an effective blocker of the LTCC in vivo
— id: 9928, year: 1989, vol: 414, page: 31, stat: Journal Article,

SPONTANEOUS ACTIVITY IN THE SPINAL CORD AND INFERIOR OLIVARY NUCLEUS OF NEONATAL RAT RECORDED IN-VITRO
WALTON K D
1989 ;15(1):504-504, Abstracts (Society for Neuroscience)
— id: 92466, year: 1989, vol: 15, page: 504, stat: Journal Article,

POSTNATAL-CHANGES IN THE ELECTRICAL PROPERTIES OF MUSCLE-IDENTIFIED RAT MOTONEURONS AN IN-VITRO STUDY
NAVARRETE R; WALTON K D; LLINAS R
1988 ;14(2):1060-1060, Abstracts (Society for Neuroscience)
— id: 92415, year: 1988, vol: 14, page: 1060, stat: Journal Article,

Activity-related extracellular potassium transients in the neonatal rat spinal cord: an in vitro study
Walton KD; Chesler M
1988 Jun;25(3):983-995, Neuroscience
Transient increases and decreases in extracellular potassium (delta[K+]o) were recorded from the gray matter of hemisected, neonatal rat spinal cords isolated from 3, 4, 9- and 10-day-old pups. delta[K+]o were evoked in both the ventral and dorsal regions of the gray matter by electrical stimulation. In the ventral horn, repetitive stimulation of the ventral root was required to elicit detectable delta[K+]o. By contrast, single dorsal root stimuli evoked clear delta[K+]o. In the dorsal horn, single orthodromic stimuli elicited delta[K+]o as large as 4-5 mM from a baseline of 4.5 mM. With repetitive stimulation the [K+]o reached, but never exceeded, a ceiling of 10-11 mM. Undershoots were seen only after repetitive stimulation. Spontaneous delta[K+]o were observed in the ventral horn and were well correlated with ventral root activity. Spontaneous delta[K+]o were rare in the dorsal cord, but were recorded after bath application of apamin or tetraethylammonium. The magnitude and distribution of evoked K+ transients and postsynaptic components of the evoked field potential were well correlated in both the dorsal and the ventral gray matter. delta[K+]o were reversibly blocked by 1 mM CdCl2 in the bath and diminished by 1 mM BaCl2. Bath application of mephenesin, apamin or tetraethylammonium diminished evoked delta[K+]o in a stimulus-dependent manner. In apamin and tetraethylammonium, decreases from control responses were largest with high intensity stimulation, the opposite was the case with mephenesin. These results are interpreted in terms of the spinal circuits activated by high- and low-intensity electrical stimulation. We conclude that activity-related delta[K+]o in neonatal spinal cord are large enough to modulate neuronal electrical activity and the [K+]o is well regulated compared to other immature CNS regions studied. Thus, local increases in [K+]o may, by modulating neuronal activity, play a role in neonatal spinal cord developmental processes
— id: 11086, year: 1988, vol: 25, page: 983, stat: Journal Article,

THE RELATIONSHIP OF HORMONAL AND IMMUNOLOGICAL RESPONSES TO STRESS IN TYPE A BEHAVIOR
BLASDELL K S; MILLS P; WALLACE R K; VANZANDT W L; SCHNEIDER R; WALTON K; HILL D
1987 ;13(2):1295-1295, Abstracts (Society for Neuroscience)
— id: 92467, year: 1987, vol: 13, page: 1295, stat: Journal Article,

EVOKED AND SPONTANEOUS [K+]O TRANSIENTS ARE LARGE IN NEONATAL RAT LUMBAR SPINAL-CORD - AN INVITRO STUDY
Chesler, M; Walton, K
1987 Sep;390(9):P46-P46, Journal of physiology
— id: 31355, year: 1987, vol: 390, page: P46, stat: Journal Article,

Further studies on depolarization release coupling in squid giant synapse
Llinas R; Sugimori M; Walton K
1987 ;221:1-17, Advances in experimental medicine & biology
— id: 9943, year: 1987, vol: 221, page: 1, stat: Journal Article,

SPINAL NETWORK DEVELOPMENT AND ITS RELATION TO HINDLIMB MOVEMENT AN IN-VITRO ELECTROPHYSIOLOGICAL STUDY IN NEONATAL RAT
NAVARRETE R; WALTON K; LLINAS R
1987 ;13(2):824-824, Abstracts (Society for Neuroscience)
— id: 92426, year: 1987, vol: 13, page: 824, stat: Journal Article,

BLOCKADE OF HARMALINE-INDUCED TREMORS BY ALCOHOLS MAY BE MEDIATED BY THE LOW THRESHOLD CALCIUM CHANNEL
SINTON C M; KROSSER B; WALTON K D; LLINAS R R
1987 ;13(1):228-228, Abstracts (Society for Neuroscience)
— id: 92429, year: 1987, vol: 13, page: 228, stat: Journal Article,

NEW DIRECTIONS IN MAMMALIAN CNS IN-VITRO BEYOND THE SLICE
WALTON K; FELDMAN J; GETTING P; RENAUD L; LLINAS R
1987 ;13(2):1430-1430, Abstracts (Society for Neuroscience)
— id: 92421, year: 1987, vol: 13, page: 1430, stat: Journal Article,

Electrophysiological properties of neonatal rat motoneurones studied in vitro
Fulton BP; Walton K
1986 Jan;370(3):651-678, Journal of physiology
The electroresponsive properties of neonatal lumbar spinal motoneurones were studied using isolated, hemisected spinal cords from neonatal rats aged 3-12 days. The extracellular and intracellular responses to electrical stimulation of the ventral and dorsal root were studied as well as the intracellular response to current injection. Field potentials recorded in the lateral motor area following electrical stimulation of lumbar ventral roots had a triphasic positive-negative-positive wave form. The negative component did not return to the base line smoothly but exhibited a 'shoulder' where the negativity increased in duration. Following electrical stimulation of the dorsal root, presynaptic field potentials were recorded upon activation of the afferent axons as well as following synaptic activation of interneurones and motoneurones. The input resistances of neonatal motoneurones determined from the slope of current-voltage plots were high compared with the adult. The resistance decreased with age with a mean of 18.1 M omega for animals 3-5 days old, 8.8 M omega for animals 6-8 days old and 5.4 M omega for animals 9-11 days old. Values for the membrane time constant were similar to those in the adult with a mean of 4.5 ms. Action potentials elicited by ventral or dorsal root stimulation or by intracellular current injection were marked by a pronounced after-depolarization (a.d.p.) and an after-hyperpolarization (a.h.p.). The amplitude of the a.h.p. varied with that of the a.d.p. The amplitude of excitatory post-synaptic potentials (e.p.s.p.s) elicited by electrical stimulation of the dorsal root was affected by intracellular current injection. Two types of e.p.s.p.s were distinguished: those with a biphasic reversal (early phase first) and those in which the early phase was unaffected by inward current injection while the later phase was reversed. Unlike in the adult, the reversals could be achieved with low current levels and the amplitude of both types of e.p.s.p. was increased by inward current injection. Inhibitory post-synaptic potentials (i.p.s.p.s) were elicited by dorsal or ventral root stimulation. The amplitude of these i.p.s.p.s was diminished and reversed in sign with inward current injection and their amplitude was enhanced with outward current injection. Activation of neonatal motoneurones with long current pulses revealed that there is one steady-state firing range.(ABSTRACT TRUNCATED AT 400 WORDS)
— id: 18884, year: 1986, vol: 370, page: 651, stat: Journal Article,

Ionic mechanisms underlying the firing properties of rat neonatal motoneurons studied in vitro
Walton K; Fulton BP
1986 Nov;19(3):669-683, Neuroscience
Ionic mechanisms underlying the firing properties of spinal motoneurons of neonatal rats (postnatal days 3-10) have been investigated using a hemisected, in vitro spinal cord preparation. These results demonstrate the presence of a high-threshold voltage-dependent calcium response and partial sodium-dependent spikes. The calcium current is evident during the falling phase of the action potential and is the major component of the after-depolarizing potential. The subsequent increase in intracellular calcium concentration activates a calcium-dependent potassium conductance (gK-Ca), the major component of the after-hyperpolarizing potential. The gCa, by activating gK-Ca, is the primary determinant of firing rate in neonatal motoneurons. For, when gCa was blocked by Cd2+, the interspike interval decreased, the maximum firing rate and the slope of the firing frequency-injected current relation increased. The calcium current is particularly robust during the first few postnatal days; during this period, tetrodotoxin resistant action potentials can be elicited by direct stimulation under control conditions. In animals older than 5 days such calcium spikes could be elicited only after decreasing gK with intracellular Cs+ or extracellular tetraethylammonium. This was the case even when 1 mM of the bath CaCl2 was replaced with BaCl2. The rising phases of calcium spikes recorded from neurons in both age groups demonstrate several components suggesting the calcium spikes comprise several discrete events, which probably originate across the dendritic membrane. When gK was decreased by bath application of tetraethylammonium+ and Cs+, neonatal motoneurons generated prolonged Ca-dependent spikes lasting for up to 6 s. Repolarization of Ca spikes occurred in two stages, the first was rapid (-2.11 +/- 0.8 V/s, n = 6) but incomplete. The second, was slower (-0.01 +/- 0.003 V/s, n = 5) and returned the membrane potential to the resting level after about 1-2 s. It is suggested that accumulation of extracellular potassium may contribute to the slow phase of repolarization. Motoneurons from the younger age group (3-5 days old) demonstrate all-or-none partial spikes rising from the after-depolarization of directly elicited sodium-dependent action potentials. Similar partial spikes were elicited from neurons from older animals during intracellular Cs+ loading. The partial spikes had faster rates of rise than the tetrodotoxin-resistant spikes and were not seen after tetrodotoxin treatment, suggesting that they are sodium-dependent.(ABSTRACT TRUNCATED AT 400 WORDS)
— id: 18883, year: 1986, vol: 19, page: 669, stat: Journal Article,

CALCIUM-DEPENDENT LOW THRESHOLD REBOUND POTENTIALS AND OSCILLATORY POTENTIALS IN NEONATAL RAT SPINAL MOTONEURONS IN-VITRO
WALTON K; LLINAS R
1986 ;12(1):386-386, Abstracts (Society for Neuroscience)
— id: 92433, year: 1986, vol: 12, page: 386, stat: Journal Article,

Spontaneous oscillatory potentials in lumbar spinal cord of neonatal rat studied in vitro
Walton K; Llinas R
1986 ;16:118-118, Proceedings of the International Union of Physiological Sciences
— id: 55729, year: 1986, vol: 16, page: 118, stat: Journal Article,

AN ISOLATED IN-VITRO PREPARATION OF THE NEONATAL RAT BRAINSTEM AND SPINAL CORD
WALTON K; LLINAS R
1985 ;11(1):24-24, Abstracts (Society for Neuroscience)
— id: 92440, year: 1985, vol: 11, page: 24, stat: Journal Article,

Electrophysiological properties of neurons in the central nucleus of the
Llinas R; Walton K; Fernandez de Molina A
1984 ;75(Suppl):?-?, Trabajos del Instituto Cajal
— id: 55927, year: 1984, vol: 75, page: ?, stat: Journal Article,

REVERSAL PROPERTIES OF MONOSYNAPTIC EXCITATORY POSTSYNAPTIC POTENTIALS IN NEONATAL RAT MOTONEURONS STUDIED IN SPINAL CORD IN-VITRO
WALTON K
1984 ;10(1):4-4, Abstracts (Society for Neuroscience)
— id: 92468, year: 1984, vol: 10, page: 4, stat: Journal Article,

Hydrogen peroxide as a source of molecular oxygen for in vitro mammalian CNS preparations
Walton K; Fulton B
1983 Nov 14;278(1-2):387-393, Brain research
Using an isolated neonatal rat spinal cord preparation, we have studied the ability of hydrogen peroxide to act as a source of oxygen for mammalian central nervous system (CNS) maintained in vitro. We report here that hydrogen peroxide, in low concentrations (0.001-0.004%), can effectively provide the only source, or act as a supplementary source of oxygen. This is brought about via the intracellular enzyme catalase which catalyzes the conversion of H2O2 into molecular oxygen and water
— id: 18885, year: 1983, vol: 278, page: 387, stat: Journal Article,

3- and 4-Aminopyridine in synaptic transmission as the squid griant synapse
Llinas R; Walton K; Sugimori M; Simon S
1982 ;35:69-79, Advances in the biosciences
— id: 44348, year: 1982, vol: 35, page: 69, stat: Journal Article,

Electrophysiological activity recorded from the cerebral cortex of an isolated mammalian brain maintained in vitro
Walton K; Llinas R
1982 ;8:935-935, Abstracts (Society for Neuroscience)
— id: 44666, year: 1982, vol: 8, page: 935, stat: Journal Article,

CALCIUM DEPENDENT SPIKES IN NEONATAL RAT SPINAL-CORD INVITRO
FULTON, BP; WALTON, K
1981 JAN ;317(AUG):P25-P26, Journal of physiology
— id: 105133, year: 1981, vol: 317, page: P25, stat: Journal Article,

Presynaptic calcium currents in squid giant synapse
Llinas R; Steinberg IZ; Walton K
1981 Mar;33(3):289-321, Biophysical journal
A voltage clamp study has been performed in the presynaptic terminal of the squid stellate ganglion. After blockage of the voltage-dependent sodium and potassium conductances, an inward calcium current is demonstrated. Given a step-depolarization pulse, this voltage- and time-dependent conductance has an S-shaped onset. At the 'break' of the voltage step, a rapid tail current is observed. From these results a kinetic model is generated which accounts for the experimental results and predicts for the time course and amplitude a possible calcium entry during presynaptic action potentials.
— id: 9968, year: 1981, vol: 33, page: 289, stat: Journal Article,

Relationship between presynaptic calcium current and postsynaptic potential in squid giant synapse
Llinas R; Steinberg IZ; Walton K
1981 Mar;33(3):323-351, Biophysical journal
The relationship between calcium current and transmitter release was studied in squid giant synapse. It was found that the voltage-dependent calcium current triggers the release of synaptic transmitter in direct proportion to its magnitude and duration. Transmitter release occurs with a delay of approximately 200 mus after the influx of calcium. A model is presented which describes these relations formally.
— id: 9969, year: 1981, vol: 33, page: 323, stat: Journal Article,

A presynaptic voltage clamp study in the squid stellate ganglion
Llinas R; Walton K
Regulatory mechanisms of synaptic transmission New York : Plenum, 1981,
— id: 3280, year: 1981, vol: , page: 154, stat: Chapter,

Transmission in the squid giant synapse: a model based on voltage clamp studies
Llinas R; Steinberg IZ; Walton K
1980 Sep;76(5):413-418, Journal de physiologie
1. Voltage clamp studies were performed in squid giant synapse after blockage of the voltage-dependent sodium and potassium conductances. 2. Presynaptic depolarization under these conditions demonstrates the presence of voltage-dependent calcium conductance change for the duration of the voltage step, and a tail current at the break of the pulse. 2. This calcium current triggers a postsynaptic response which can be measured directly at the postsynaptic fiber. 4. These voltage clamp experiments have allowed the development of a mathematical model that describes the kinetics of the calcium current and the relationship between calcium current and transmitter release.
— id: 9970, year: 1980, vol: 76, page: 413, stat: Journal Article,

Voltage-dependent calcium conductances in neurons
Llinas R; Walton K
1980 ;6:87-118, Cell surface reviews
— id: 44350, year: 1980, vol: 6, page: 87, stat: Journal Article,

A model for synaptic transmission
Llinas R; Steinberg IZ; Walton K
1979 Jan-Feb;4(1):170-173, Brain research bulletin
— id: 9976, year: 1979, vol: 4, page: 170, stat: Journal Article,

Place of the cerebellum in motor learning
Llinas R; Walton K
Brain mechanisms in memory and learning New York, Raven Press, 1979,
— id: 2530, year: 1979, vol: , page: 17, stat: Chapter,

Vestibular compensation: a distributive property of the central nervous system
Llinas R; Walton K
Integration in the nervous system Tokyo : Igaku-Shoin, 1979,
— id: 3246, year: 1979, vol: , page: 145, stat: Chapter,

VOLTAGE-CLAMP STUDY OF EFFECTS OF TEMPERATURE ON SYNAPTIC TRANSMISSION IN SQUID
LLINAS, R; WALTON, K; SUGIMORI, M
1978 JAN ;155(2):454-454, Biological bulletin
— id: 105134, year: 1978, vol: 155, page: 454, stat: Journal Article,

The role of cerebellar and brain stem nuclei in vestibular compensation in rats: a 2-deoxy-D-glucose study
Walton K; Llinas R
1978 ;4:70-70, Abstracts (Society for Neuroscience)
— id: 44692, year: 1978, vol: 4, page: 70, stat: Journal Article,

Calcium dendritic spikes in the mammalian Purkinje cells
Llinas R; Sugimori M; Walton K
1977 ;3:58-58, Abstracts (Society for Neuroscience)
— id: 44693, year: 1977, vol: 3, page: 58, stat: Journal Article,

Significance of the olivo-cerebellar system in compensation of ocular position following unilateral labyrinthectomy
Llinas R; Walton K
Control of gaze by brain stem neurons Amseterdam : Elesevier, 1977,
— id: 3248, year: 1977, vol: , page: 399, stat: Chapter,

PRESYNAPTIC CALCIUM CURRENTS IN SQUID STELLATE GANGLION - VOLTAGE CLAMP STUDY USING TTX AND TEA
LLINAS, R; WALTON, K; SUGIMORI, M
1977 JAN ;153(2):436-437, Biological bulletin
— id: 105135, year: 1977, vol: 153, page: 436, stat: Journal Article,

Presynaptic calcium currents and their relation to synaptic transmission: voltage clamp study in squid giant synapse and theoretical model for the calcium gate
Llinas R; Steinberg IZ; Walton K
1976 Aug;73(8):2913-2922, Proceedings of the National Academy of Sciences of the United States of America
A voltage clamp study of the presynaptic terminal in squid stellate ganglion has given quantitative results relating inward Ca2+ current to presynaptic membrane potential and postsynaptic response to inward Ca2+ current. The results indicate an S-shaped curve for the relationship between presynaptic potential and Ca2+ current and a linear relationship between Ca2+ current and postsynaptic potential. A similar S-shaped curve was found for the time-dependent properties of the Ca2+ conductance. Based on these results a mathematical model was developed which accounts for the experimental results in this and previously published papers by other authors. The model suggests that five subunits are involved in the Ca2+ gate and that the subunits change noncooperatively from an inactive to an active form upon membrane depolarization.
— id: 9985, year: 1976, vol: 73, page: 2913, stat: Journal Article,

Neuronal systems in the cerebellum
Llinas R; Walton K
Simpler networks and behavior Sunderland MA : Sinauer Assoc., 1976,
— id: 3249, year: 1976, vol: , page: 274, stat: Chapter,

Synaptic transmission in squid giant synapse after potassium conductance blockage with external 3- and 4-aminopyridine
Llinas R; Walton K; Bohr V
1976 Jan;16(1):83-86, Biophysical journal
— id: 9988, year: 1976, vol: 16, page: 83, stat: Journal Article,

VOLTAGE CLAMP STUDY OF PRESYNAPTIC CALCIUM CURRENT IN SQUID GIANT SYNAPSE
LLINAS, R; WALTON, K; HESS, R
1976 JAN ;35(3):696-696, Federation Proceedings (Federation of American Societies for Experimental Biology)
— id: 105136, year: 1976, vol: 35, page: 696, stat: Journal Article,

Inferior olive: its role in motor learing
Llinas R; Walton K; Hillman DE; Sotelo C
1975 Dec 19;190(4220):1230-1231, Science
Specific chemical lesion of the rat inferior olive by intraperitoneal administration of 3-acetylpyridine prevents recuperation from motor abnormalities generated by unilateral labyrinthine lesion. Moreover, in animals that have recuperated from the balyrinthine lesion, 3-acetylpyridine produces a reversal of the symptoms within 2 hours of administration. These results indicate that the integrity of the olivo-cerebellar system is necessary for the acquisition and retention of this form of motor learning, but that the cerebellum itself is not the seat of such learning.
— id: 9990, year: 1975, vol: 190, page: 1230, stat: Journal Article,

Role of the inferior olive in vestibular compensation
Llinas R; Walton K; Hillman DE; Sotelo C
1975 ;1:213-213, Abstracts (Society for Neuroscience)
— id: 44697, year: 1975, vol: 1, page: 213, stat: Journal Article,

ACTION OF 3-AMINOPYRIDINE AND 4-AMINOPYRIDINE ON SYNAPTIC TRANSMISSION IN SQUID GIANT SYNAPSE
LLINAS, R; WALTON, K; BOHR, V
1975 JAN ;149(2):435-435, Biological bulletin
— id: 105137, year: 1975, vol: 149, page: 435, stat: Journal Article,