Loss of temporal sensitivity in dorsal lateral geniculate nucleus and area 18 of the cat following monocular deprivation.

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Abstract
Evoked potentials generated by a temporally modulated, homogeneous visual stimulus were recorded from the optic tract, dorsal lateral geniculate nucleus (LGN), and cortical area 18 of both normal and monocularly deprived cats. At all 3 recording sites, the amplitude of the evoked response varied monotonically with the log of the modulation depth of the stimulus. This allowed the use of regression analysis to estimate a threshold modulation depth at each stimulation frequency. Plots of threshold modulation depth vs. modulation frequency yielded temporal sensitivity functions for each recording site. Peak sensitivity ranged between 30 and 40 Hz in LGN and cortex and near 50 Hz for optic tract. Sensitivity declined at both higher and lower frequencies in all areas. In normal cats, no significant differences were observed in the sensitivity functions derived from independent stimulation of the left and right eyes. In the monocularly deprived cats, sensitivity functions derived from stimulation of the experienced eye were essentially normal, but those derived from stimulation of the deprived eye were severely depressed in both the LGN and area 18. This reduction in temporal sensitivity was observed at all frequencies but was somewhat greater at higher temporal rates. Results are consistent with a loss in Y-cell function at the level of the LGN, probably at the retinogeniculate synapse, but do not preclude changes in temporal sensitivity among other components of the visual pathways following monocular deprivation.