Abstract
The effects of monocular deprivation on excitatory post-synaptic activity in the lateral geniculate nucleus and on the afferent activity to the geniculate in the cat were examined. Field potentials elicited by electrical stimulation of the optic nerves were recorded and analysed. This approach revealed that the most severe effects of deprivation originate at the input stage to the lateral geniculate nucleus. 1. The membrane currents resulting from excitatory post-synaptic activity in the geniculate are at least a factor of two smaller in amplitude in the deprived than in the non-deprived laminae, indicating a severe reduction of synaptic strength. This effect is equally pronounced for activity mediated by the X- and the Y-system and has to be considered as the major origin of the imbalance of activity from the deprived and non-deprived eye apparent in cortex. 2. Judged from amplitudes and latencies of compound action potentials in the optic tract, afferent Y-activity is not affected by deprivation. This indicates that the number of afferents from the retina of the deprived eye to the geniculates is not significantly reduced by deprivation. 3. During several periods of recording conduction block in the afferents from both eyes was observed.