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Human cortical excitability depends on time awake and circadian phase

Julien Q. Ly1, 2*, Sarah L. Chellappa1*, Giulia Gaggioni1*, Soterios Papachilleos1, Alexandre Brzozowski1, Chloé Borsu1, Mario Rosanova3, Simone Sarasso3, Simon Archer4, Derk-Jan Dijk4, Christophe Phillips1, Pierre Maquet1, 2, Marcello Massimini3 and Gilles Vandewalle1
  • 1 Cyclotron research Centre, Neurology, Belgium
  • 2 CHU of Liège, Neurology, Belgium
  • 3 Università degli Studi di Milano, Department of Clinical Sciences, Italy
  • 4 Surrey Sleep Research Centre , United Kingdom

Objectives: The dynamics of neuronal excitability is considered to be mainly driven by sleep homeostasis directly depending on time spent awake. However, no study has been properly designed to investigate a putative circadian timing system influence on human cortical excitability. Here we assessed this circadian modulation using transcranial magnetic stimulation coupled with electroencephalography (TMS/EEG). Methods: Twenty-two healthy young men (18-30 years) underwent 8 TMS/EEG sessions during a 28h sustained wakefulness under stringent constant routine conditions. Participants were stratified in two groups according to a polymorphism in PERIOD3 (PER3), known to affect sleep-wake regulation (15 PER3 4/4; 7 PER3 5/5). Cortical excitability was inferred from the normalized amplitude of the first component of TMS-evoked EEG potentials over the prefrontal cortex, a brain region highly sensitive to sleep deprivation. Results: Cortical excitability significantly increased with time spent awake. However, the dynamics of this change was not linear and presented a pronounced local decrease around the so-called evening wake-maintenance zone. Conversely, a marked local amplification was found at the end of biological night when the circadian system maximally promotes sleep . This time-course was best predicted by the interaction of linear (sleep homeostasis) and sine-wave (circadian) functions. Interestingly, analyses by genotypes showed that the overnight difference in cortical excitability between sleep and wake maintenance zones was more pronounced in PER3 5/5. Conclusions: These results demonstrate that temporal changes in cortical excitability depend on the interplay between sleep homeostasis and circadian timing system, and differ with respect to the PER3 polymorphism.

Acknowledgements

This work was supported by grants from the Belgian National Funds for Scientific Research (FRS-FNRS), AXA, WBI and the University of Liège (ULg).

Keywords: TMS/EEG co-registration, Circadian Rhythm, Sleep Deprivation, sleep homeostasis, Per3 polymorphism

Conference: Belgian Brain Council 2014 MODULATING THE BRAIN: FACTS, FICTION, FUTURE, Ghent, Belgium, 4 Oct - 4 Oct, 2014.

Presentation Type: Oral Presentation

Topic: Clinical Neuroscience

Citation: Ly JQ, Chellappa SL, Gaggioni G, Papachilleos S, Brzozowski A, Borsu C, Rosanova M, Sarasso S, Archer S, Dijk D, Phillips C, Maquet P, Massimini M and Vandewalle G (2014). Human cortical excitability depends on time awake and circadian phase. Conference Abstract: Belgian Brain Council 2014 MODULATING THE BRAIN: FACTS, FICTION, FUTURE. doi: 10.3389/conf.fnhum.2014.214.00022

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Received: 27 Jun 2014; Published Online: 30 Jun 2014.

* Correspondence:
Dr. Julien Q Ly, Cyclotron research Centre, Neurology, Liège, Liège, 4000, Belgium, julienlycrc@gmail.com
Dr. Sarah L Chellappa, Cyclotron research Centre, Neurology, Liège, Liège, 4000, Belgium, schellappa@ulg.ac.be
Miss. Giulia Gaggioni, Cyclotron research Centre, Neurology, Liège, Liège, 4000, Belgium, giulia.gaggioni@doct.ulg.ac.be