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.