TMS-induced cortical potentiation during wakefulness locally increases slow wave activity during sleep.
BACKGROUND
Sleep slow wave activity (SWA) is thought to reflect sleep need, increasing in proportion to the length of prior wakefulness and decreasing during sleep. However, the process responsible for SWA regulation is not known. We showed recently that SWA increases locally after a learning task involving a circumscribed brain region, suggesting that SWA may reflect plastic changes triggered by learning.


RESULTS
To test this hypothesis directly, we used transcranial magnetic stimulation (TMS) in conjunction with high-density EEG in humans. We show that 5-Hz TMS applied to motor cortex induces a localized potentiation of TMS-evoked cortical EEG responses. We then show that, in the sleep episode following 5-Hz TMS, SWA increases markedly (+39.1+/-17.4%, p<0.01, n = 10). Electrode coregistration with magnetic resonance images localized the increase in SWA to the same premotor site as the maximum TMS-induced potentiation during wakefulness. Moreover, the magnitude of potentiation during wakefulness predicts the local increase in SWA during sleep.


CONCLUSIONS
These results provide direct evidence for a link between plastic changes and the local regulation of sleep need.
Huber
Reto
R
Department of Psychiatry, University of Wisconsin, Madison, Madison, Wisconsin, United States of America.
Esser
Steve K
SK
Ferrarelli
Fabio
F
Massimini
Marcello
M
Peterson
Michael J
MJ
Tononi
Giulio
G
D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000502:physiology; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology; D006801:Humans; D017774:Long-Term Potentiation / Q000502:physiology; D009044:Motor Cortex / Q000502:physiology; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation; D014851:Wakefulness / Q000502:physiology*