Long-term potentiation of horizontal connections provides a mechanism to reorganize cortical motor maps.

1. Field potential recordings were used in rat motor cortex (MI) slice preparations to investigate the potential for activity-dependent modifications in the effectiveness of synaptic connections formed by layer II/III horizontal projections. 2. Long-term potentiation (LTP) of synaptic efficacy in MI horizontal pathways could be produced at short (0.5 mm) and long (1.0 mm) distances by theta burst stimulation (TBS), but only during local, transient application of the gamma-aminobutyric acid-A (GABAA) receptor antagonist, bicuculline methiodide (bic) immediately before TBS. Mean increase of the field potential amplitude measured 25-35 min after LTP induction ranged between 24 and 34%. Cooperative effects of conjoint TBS of two horizontal pathways on LTP induction were observed. 3. These results demonstrate that persistent changes in the functional interactions of cortical neurons can arise by activity-dependent mechanisms within the local horizontal connections and suggest a likely mechanism to recognize cortical representation patterns.

[1]  M. Descheˆnes,et al.  Intracortical distribution of axonal collaterals of pyramidal tract cells in the cat motor cortex , 1980, Brain Research.

[2]  R K Wong,et al.  Cellular factors influencing GABA response in hippocampal pyramidal cells. , 1982, Journal of neurophysiology.

[3]  B. Alger,et al.  Use-dependent depression of IPSPs in rat hippocampal pyramidal cells in vitro. , 1985, Journal of neurophysiology.

[4]  E. G. Jones,et al.  Reduction in number of immunostained GABAergic neurones in deprived-eye dominance columns of monkey area 17 , 1986, Nature.

[5]  S. Hendry,et al.  Activity-dependent regulation of GABA expression in the visual cortex of adult monkeys , 1988, Neuron.

[6]  Donald Robertson,et al.  Plasticity of frequency organization in auditory cortex of guinea pigs with partial unilateral deafness , 1989, The Journal of comparative neurology.

[7]  J. Kaas,et al.  Reorganization of retinotopic cortical maps in adult mammals after lesions of the retina. , 1990, Science.

[8]  M. Merzenich,et al.  Functional reorganization of primary somatosensory cortex in adult owl monkeys after behaviorally controlled tactile stimulation. , 1990, Journal of neurophysiology.

[9]  M. Merzenich,et al.  Repetitive microstimulation alters the cortical representation of movements in adult rats. , 1990, Somatosensory & motor research.

[10]  J. Kaas,et al.  Injury-induced reorganization of somatosensory cortex is accompanied by reductions in GABA staining. , 1991, Somatosensory & motor research.

[11]  P. Land,et al.  Activity‐dependent regulation of glutamic acid decarboxylase in the rat barrel cortex: Effects of neonatal versus adult sensory deprivation , 1991, The Journal of comparative neurology.

[12]  C. Gall,et al.  Differential effects of monocular deprivation on glutamic acid decarboxylase and type II calcium-calmodulin-dependent protein kinase gene expression in the adult monkey visual cortex [published erratum appears in J Neurosci 1991 May;11(5):following Table of Contents] , 1991, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[13]  KM Jacobs,et al.  Reshaping the cortical motor map by unmasking latent intracortical connections , 1991, Science.

[14]  M. Mishkin,et al.  Massive cortical reorganization after sensory deafferentation in adult macaques. , 1991, Science.

[15]  T. Wiesel,et al.  Targets of horizontal connections in macaque primary visual cortex , 1991, The Journal of comparative neurology.

[16]  R. Seitz,et al.  Learning of Sequential Finger Movements in Man: A Combined Kinematic and Positron Emission Tomography (PET) Study , 1992, The European journal of neuroscience.

[17]  Karl J. Friston,et al.  Functional anatomy of human procedural learning determined with regional cerebral blood flow and PET , 1992, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[18]  J. Donoghue,et al.  Organization and Adaptability of Muscle Representations in Primary Motor Cortex , 1992 .

[19]  T. Wiesel,et al.  Receptive field dynamics in adult primary visual cortex , 1992, Nature.

[20]  J P Donoghue,et al.  Immediate and delayed changes of rat motor cortical output representation with new forelimb configurations. , 1992, Cerebral cortex.

[21]  Mark F. Bear,et al.  Neocortical long-term potentiation , 1993, Current Opinion in Neurobiology.

[22]  A Keller,et al.  The patterns and synaptic properties of horizontal intracortical connections in the rat motor cortex. , 1993, Journal of neurophysiology.

[23]  B L McNaughton,et al.  Dynamics of the hippocampal ensemble code for space. , 1993, Science.

[24]  M. Bear,et al.  Common forms of synaptic plasticity in the hippocampus and neocortex in vitro. , 1993, Science.

[25]  C. Gilbert,et al.  Long‐term changes in synaptic strength along specific intrinsic pathways in the cat visual cortex. , 1993, The Journal of physiology.

[26]  J. Donoghue,et al.  N-methyl-d-aspartate receptor mediated component of field potentials evoked in horizontal pathways of rat motor cortex , 1994, Neuroscience.