Unihemispheric REM Sleep as a Contralateral Side-Effect of Unihemispheric Slow-Wave Sleep
Abstract
Rapid eye movement sleep (REMS), discovered in 1953, remains functionally enigmatic despite its near-universal presence in terrestrial mammals and birds, even under high predation risk during muscle atonia. REMS deprivation leads to lethality in weeks, underscoring its essential role.Cetaceans exhibit only unihemispheric slow-wave sleep (USWS), with no detectable REMS, while fur seals show cetacean-like USWS dominance and near-absence of REMS at sea, reverting to typical bihemispheric REMS on land.
In the published hypothesis of sleep as Hebbian reinforcement of local inhibitory synapses eroded during wakefulness, SWS restores inhibitory efficacy via local synchronization, but at the cost of weakening long-distance excitatory connections and REMS compensates by disordered replay of prior activity patterns. In USWS, this mechanism generates a contralateral side-effectunihemispheric REM sleep (UREMS)-manifesting as rehearsal in the "awake" hemisphere without full EEG REMS signatures. UREMS is less efficient (~84% of bilateral REMS, estimated under constant REMS/SWS ratio) but preserves essential motor coordination for breathing and buoyancy.
Simultaneous USWS and UREMS reduce total sleep time requirement, potentially lowering predation risk. This framework explains REMS suppression in aquatic mammals and suggests UREMS-like phenomena may occur in terrestrial species via regional sleep variations. Future EEG analyses could identify UREMS signatures, with implications for sleep research across taxa.
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BibTeX
@misc{touzet2026unihemispheric,
title = {{Unihemispheric REM Sleep as a Contralateral Side-Effect of Unihemispheric Slow-Wave Sleep}},
author = {Claude Touzet},
howpublished = {HAL},
year = {2026},
month = sep,
url = {https://hal.science/hal-05715865v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Unihemispheric REM Sleep as a Contralateral Side-Effect of Unihemispheric Slow-Wave Sleep
AU - Claude Touzet
PY - 2026
DA - 2026/09/07
PB - HAL
UR - https://hal.science/hal-05715865v1
AB - Rapid eye movement sleep (REMS), discovered in 1953, remains functionally enigmatic despite its near-universal presence in terrestrial mammals and birds, even under high predation risk during muscle atonia. REMS deprivation leads to lethality in weeks, underscoring its essential role.Cetaceans exhibit only unihemispheric slow-wave sleep (USWS), with no detectable REMS, while fur seals show cetacean-like USWS dominance and near-absence of REMS at sea, reverting to typical bihemispheric REMS on land. In the published hypothesis of sleep as Hebbian reinforcement of local inhibitory synapses eroded during wakefulness, SWS restores inhibitory efficacy via local synchronization, but at the cost of weakening long-distance excitatory connections and REMS compensates by disordered replay of prior activity patterns. In USWS, this mechanism generates a contralateral side-effectunihemispheric REM sleep (UREMS)-manifesting as rehearsal in the "awake" hemisphere without full EEG REMS signatures. UREMS is less efficient (~84% of bilateral REMS, estimated under constant REMS/SWS ratio) but preserves essential motor coordination for breathing and buoyancy. Simultaneous USWS and UREMS reduce total sleep time requirement, potentially lowering predation risk. This framework explains REMS suppression in aquatic mammals and suggests UREMS-like phenomena may occur in terrestrial species via regional sleep variations. Future EEG analyses could identify UREMS signatures, with implications for sleep research across taxa.
ER -