Experimental Brain Research

, Volume 176, Issue 1, pp 70–84 | Cite as

Monocular-unihemispheric sleep and visual discrimination learning in the domestic chick

  • Gian G. MascettiEmail author
  • Marina Rugger
  • Giorgio Vallortigara
  • Daniela Bobbo
Research Article


During sleep, domestic chicks (Gallus gallus) show brief and transient periods during which one eye is open while the other remains shut. Electrophysiological recordings showed that the hemisphere contra-lateral to the open eye exhibited an EEG with fast waves typical of wakefulness, whereas the hemisphere contra-lateral to the closed eye exhibited an EEG typical of slow wave sleep. We investigated the pattern of monocular-unihemispheric sleep (Mo-Un sleep; i.e. selective preferential closure/opening of the left or right eye during sleep) following three types of visual learning tasks. The first group of chicks was submitted to a colour discrimination task (1), the second group to a spatial discrimination task with colour as a conspicuous, but irrelevant, cue (2), the third group to a spatial task without colour cue. After learning, the amount of binocular sleep and Mo-Un sleep patterns were recorded. The first and the second group of chicks exhibited more right Mo-Un sleep (right eye-closure/left unihemispheric sleep), suggesting that this pattern may be connected with prevalent engagement of left hemisphere during training trials. The third group showed a significant more left Mo-Un sleep (left eye-closure/right unihemispheric sleep) which would be associated with a prevalent engagement of right hemisphere during trials. Chicks of the control groups, did not learn the task, but were submitted to an equal number of trials. Controls of tasks 1 and 2 showed more left Mo-Un sleep suggesting a dominance of right hemisphere during exposure trials. Instead there was no eye-closure bias in controls of task 3, suggesting an absence of hemispheric dominance during trials. It is suggested that the Mo-Un sleep pattern may be a type of local sleep associated with a process of functional recovery in the hemisphere which was mainly engaged during training trials.


Sleep Unihemispheric sleep Chick Visual learning Lateralization 



This research was supported by Grant COFIN-PRIN n. 2004113175_004 from the Italian Ministry of University Education and Research (MIUR). The authors wish to thank Prof. Chiara Cirelli of the University of Wisconsin, for a critical reading and helpful comments on an earlier version of the manuscript. The authors also wish to thank Prof. Nicolette Whitteridge for the revision of the manuscript.


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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Gian G. Mascetti
    • 1
    Email author
  • Marina Rugger
    • 1
  • Giorgio Vallortigara
    • 2
  • Daniela Bobbo
    • 1
  1. 1.Department of General PsychologyUniversity of PadovaPadovaItaly
  2. 2.Department of Psychology & B.R.A.I.N Centre for NeuroscienceUniversity of TriesteTriesteItaly

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