REM sleep deprivation in monocularly occluded kittens reduces the size of cells in LGN monocular segment

Study Objectives: In this study, we test the hypothesis that when REM-state activation (which impinges upon all lateral geniculate nucleus laminae irr espective of stimulating eye) is deprived, the monocular segment (MS) that is cut off from visual input and also deprived of REM-state activation will exhibit smaller cells, owing to the loss of extrinsic as well as intrinsic activation. Design: We carried out a study comparing soma sizes in the MSs of kittens s ubjected to monocular deprivation (MD) + REM deprivation (RD) to two age-ma tched nonRD groups, MD ONLYs and MD MOMS (MD kittens living in their home c ages). Measurements and Results: Perikaryal outlines of 100 cells in each of the b ilateral MSs were measured. As predicted, mean cell size in the MS connecte d to the patched eye of MD+RD kittens, but in neither of the control groups , was significantly smaller than in the MS afferented by the nonpatched eye . One-way ANOVAs comparing MS cell-size means from the same sides across gr oups were also significant, but the two MSs showed different results on pos t hoc tests. The ordering of MS cell-size means correlated significantly wi th a measure that aggregates the sources of activation reaching a particula r MS and their durations. Conclusions: These results reveal that removal of REM-state activation duri ng CNS development amplifies the plasticity processes generated when normal Visual afferentation to central visual areas is interrupted. Our findings in the MS of the LGN indicate that during the usual operation of REM sleep, central visual-sensory sites receive intrinsic activation that, in the vis ual system, is additive and complementary to the stimulation obtained from extrinsic sources. In the course of early development, normative symmetrica l activation of central visual areas during REM sleep may counterbalance pl asticity changes caused either by absent or aberrant sensory stimulation.