A study of sleep in the European blackbird

Author(s): Kaiser, W., Helb, H. W., Beszczynska, B.

Journal/Book: Physiol Behav. 1996; 60: The Boulevard, Langford Lane, Kidlington, Oxford, England OX5 1GB. Pergamon-Elsevier Science Ltd. 1115-1120.

Abstract: Sleep states in the blackbird, Turdus merula, were determined by recording the electroencephalogram (EEG), electrooculogram (EOG), electromyogram (EMG), and heart rate (HR), and from behavioral observations and responses to auditory stimulation by natural calls. The presence of changes in slow wave activity was determined from the power spectra of the EEG. Spectral power density in the 0.5-4.0 Hz band during slow wave sleep (SWS) attained highest values in the first part of the night, then declined. This trend in EEG spectra, which occurred across the night, probably reflects a homeostatic process strikingly similar to that observed in mammals. The reactivity tp natural calls during SWS episodes also decreased across the night. Episodes of interhemispheric EEG asymmetry, which typically lasted from 2 to 4 s, occurred when birds displayed the front sleep posture and they constituted 140-200 s of each night. Unihemispheric sleep episodes probably result from unilateral activation of the visual system, and they could be considered as an evolutionary adaptation. KR was highest in wakefulness and lower in sleep but, due to large variability, reliable discrimination between sleep and wakefulness could not be made. Comparison of the blackbird's behavior during 4 different nights revealed a strong effect of the first night on sleeping behavior. A significant reduction in back sleep posture occurred during the baseline night, when lead wires were connected.

Note: Article JT Szymczak, Nicholas Copernicus Univ, Dept Anim Physiol, Ul Gagarina 9, PL-87100 Torun, Poland

Keyword(s): blackbird; slow wave activity; unihemispheric sleep; auditory stimulation; heart rate; effect of adaptation; BASELINE CONDITIONS; PIGEON COLUMBA; TURDUS-MERULA; EEG SPECTRA; DEPRIVATION; LIVIA

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