Directional information flows between brain hemispheres across waking, non-REM and REM sleep states: An EEG study

Mario Bertini, Michele Ferrara, Luigi De Gennaro, Giuseppe Curcio, Fabio Moroni, Claudio Babiloni, Francesco Infarinato, Paolo Maria Rossini, Fabrizio Vecchio PhD

Research output: Contribution to journalArticlepeer-review


The present electroencephalographic (EEG) study evaluated the hypothesis of a preferred directionality of communication flows between brain hemispheres across 24 h (i.e., during the whole daytime and nighttime), as an extension of a recent report showing changes in preferred directionality from pre-sleep wake to early sleep stages. Scalp EEGs were recorded in 10 normal volunteers during daytime wakefulness (eyes closed; first period: from 10:00 to 13:00 h; second period: from 14:00 to 18:00 h; third period: from 19:00 to 22:00 h) and nighttime sleep (four NREM-REM cycles). EEG rhythms of interest were delta (1-4 Hz), theta (5-7 Hz), alpha (8-11 Hz), sigma (12-15 Hz) and beta (16-28 Hz). The direction of the inter-hemispheric information flow was evaluated by computing the directed transfer function (DTF) from these EEG rhythms. Inter-hemispheric directional flows varied as a function of the state of consciousness (wake, NREM sleep, REM sleep) and in relation to different cerebral areas. During the daytime, alpha and beta rhythms conveyed inter-hemispheric signals with preferred Left-to-Right hemisphere direction in parietal and central areas, respectively. During the NREM sleep periods of nighttime, the direction of inter-hemispheric DTF information flows conveyed by central beta rhythms was again preponderant from Left-to-Right hemisphere in the stage 2, independent of cortical areas. No preferred direction emerged across the REM periods. These results support the hypothesis that specific directionality of communication flows between brain hemispheres is associated with wakefulness, NREM (particularly stage 2) and REM states during daytime and nighttime. They also reinforce the suggestive hypothesis of a relationship between inter-hemispheric directionality of EEG functional coupling and frequency of the EEG rhythms.

Original languageEnglish
Pages (from-to)270-275
Number of pages6
JournalBrain Research Bulletin
Issue number6
Publication statusPublished - Mar 30 2009


  • Consciousness
  • Corpus callosum
  • Directed transfer function (DTF)
  • Quantitative electroencephalography (qEEG)
  • Sleep mentation

ASJC Scopus subject areas

  • Neuroscience(all)


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