Ponto-geniculo-occipital-wave suppression amplifies lateral geniculate nucleus cell-size changes in monocularly deprived kittens

We have previously shown that during the post-natal critical period of deve lopment of the cat visual system, 1 week of instrumental rapid eye movement (REM) sleep deprivation (IRSD) during 2 weeks of monocular deprivation (MD ) results in significant amplification of the effects of solely the 2-week MD on cell-size in the binocular segment of the lateral geniculate nucleus (LGN) [36,40]. In this study, we examined whether elimination of ponto-geni culo-occipital (PGO)-wave phasic activity in the LGN during REM sleep (REMS ), rather than suppression of all REMS state-related activity, would simila rly yield enhanced plasticity effects on cell-size in LGN. PGO-activity was eliminated in LGN by bilateral pontomesencephalic lesions [8,32]. This met hod of removing phasic activation at the level of the LGN preserved sleep a nd wake proportions as well as the tonic activities (low voltage, fast freq uency ECoG and low amplitude EMG) that characterize REM sleep. The lesions were performed in kittens on post-natal day 42, at the end of the first wee k of the 2-week period of MD, the same age when IRSD was started in the ear lier study. LGN interlaminar cell-size disparity increased in the PGO-wave- suppressed animals as it had in behaviorally REM sleep-deprived animals. Sm aller A1/A-interlaminar ratios reflect the increased disparity effect in bo th the REM sleep- and PGO-suppressed groups compared to animals subjected t o MD-alone. With IRSD, the effect was achieved because the occluded eye-rel ated, LGN Al-lamina cells tended to be smaller relative to their size after MD-alone, whereas after PGO-suppressing lesions, the Al-lamina cells retai ned their size and the non-occluded eye-related, A-lamina cells tended to b e larger than after MD-alone. Despite this difference, for which several po ssible explanations are offered, these A1/A-interlaminar ratio data indicat e that in conjunction either with suppression of the whole of the REMS stat e or selective removal of REM sleep phasic activity at the LGN, altered vis ual input evokes more LGN cell plasticity during the developmental period t han it would otherwise. These data further support involvement of the REM s leep state in reducing susceptibility to plasticity changes and undesirable variability in the course of normative CNS growth and maturation. (C) 1999 Elsevier Science B.V. All rights reserved.