Identification of neurons producing long-term potentiation in the cat motor cortex: intracellular recordings and labeling.
Intracellular, in vivo recordings were used to identify and subsequently to label neurons in the cat motor cortex in which long-term potentiation (LTP) was induced. Thirty-nine motor cortical neurons that produced excitatory postsynaptic potentials (EPSPs) in response to microstimulation in areas 1-2 (SI) or in area 5a (SIII) were studied. Amplitudes of EPSPs produced in response to test stimulation (1 Hz) were recorded before and after tetanic stimulation (200 Hz, 20 seconds). In 25/39 cells (64%), EPSP amplitudes were significantly increased following the tetanic stimulation (65 +/- 51% average increase), and remained at the potentiated level as long as stable recordings could be maintained (20 +/- 18 minutes, maximum = 90 minutes). LTP was induced exclusively in cells that produced monosynaptic EPSPs in response to area 1-2 or area 5a stimulation. Of the 39 analyzed cells, 13 were labeled by intracellular injections of 5% biocytin. Neurons in which LTP was induced included both pyramidal and nonpyramidal cells and were located exclusively in layers II or III of the motor cortex; cells in deeper cortical layers were not potentiated. These findings indicate that various corticocortical inputs can increase the efficacy of synaptic transmission in a subset of motor cortical neurons. We propose that this plasticity in synaptic transmission constitutes one of the bases of motor learning and memory.
Keller
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A
Rockefeller University, New York, New York 10021.
Iriki
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A
Asanuma
H
H
D000818:Animals; D002415:Cats; D005260:Female; D008239:Lysine / Q000031:analogs & derivatives; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009044:Motor Cortex / Q000166:cytology / Q000502:physiology*; D009473:Neuronal Plasticity; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D011930:Reaction Time; D013570:Synaptic Membranes / Q000502:physiology
C013411:biocytin; D008239:Lysine