Intracellular recordings from the lateral geniculate neurons of cats

Abstract

(1) Intracellular recordings were made in 41 neurons in the lateral geniculate nucleus (LGN) of cats anesthetized with Nembutal. (2) The LGN neurons showed either the EPSP's fluctuating in two or three steps (37 neurons) or those with a large amplitude and an all-ornothing character (4 neurons). The time course and the amplitude of the EPSP's differed from unit to unit. The amplitude of the large EPSP's was near the firing threshold (3.1-11.5 mV). (3) The IPSP's recorded from the LGN neurons were classified into two groups: 1) short-term small IPSP's and 2) long-term large IPSP's. There were intermediate ones too. The small ones were 8-50 msec in duration and 3-8 mV in amplitude and the large ones, 50-170 msec in duration and 6-22 mV in amplitude. (4) A sequence of the IPSP's occurred spontaneously and was elicited by electrical stimulation of the optic nerve (ON), visual cortex, superior colliculus and by light illumination of the retina. (5) The LGN neurons were classified into three groups according to their first response to electrical stimulation of the ON. The Type 1 neuron responded with EPSP's to stimulation of one side of the ON. The Type 2 neuron responded with EPSP's to the stimulation of both sides of the ON. The Type 3 neuron responded with an EPSP to the stimulation of one side of the ON, and with an IPSP to the stimulation of the other side. Among a total of 12 units, 4 belonged to Type 1, 2 to Type 2, and 6 to Type 3. The latency of the IPSP's produced by stimulation of the dominant and nondominant ON's ranged 2.7-5.0 msec and 2.5-6.0 msec, respectively. (6) By stimulation of the ipsilateral visual cortex, the antidromic spike discharge and an IPSP (latency 1.8-7.0 msec) were elicited. Stimulation of Area 18 sometimes produced IPSP's. (7) In the on-response neuron, the response to diffuse light illumination consisted of a high frequency burst of 3-4 spikes followed by an IPSP and then by spike discharges maintained during the light-“on.” A. recurrence of the IPSP's occurred during the light-“off.” In the offresponse neuron, the IPSP was induced by light-“on,” and a succession of burst responses and the IPSP by light-“off.” (8) The networks for the functionally reciprocal (the on-response and the off-response fibers) and also the networks for the inhibitory binocular interactions were discussed. © 1971, PHYSIOLOGICAL SOCIETY OF JAPAN. All rights reserved.