Summary
Wakefulness and sleep have often been treated as distinct and global brain states. However, an emerging body of evidence on the local regulation of sleep stages challenges this conventional view. Apart from unihemispheric sleep, the current data that support local variations of neural oscillations during sleep are focused on the homeostatic regulation of local sleep, i.e., the role preceding awake activity. Here, to examine local differences in brain activity during natural sleep, we recorded the electroencephalogram (EEG) and the local field potential (LFP) across multiple sites within the avian pallium of zebra finches without perturbing the previous awake state. We scored the sleep stages independently in each pallial site and found that the sleep stages are not pallium-wide phenomena but rather deviate widely across electrode sites. Importantly, deeper electrode sites had a dominant role in defining the temporal aspects of sleep state congruence. Altogether, these findings show that local regulation of sleep oscillations also occurs in the avian brain without prior awake recruitment of specific pallial circuits and in the absence of mammalian cortical neural architecture.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
1) we have extensively rewritten the introduction to provide better clarity n the topic of local sleep. 2) We have extensively redone the analysis after excluding one bird in which the LFP electrode was implanted in the left hemisphere instead of the right hemisphere. The current number of birds analyzed is n=3. 3) We have extended the analysis to include two new figures, Fig. 4 and Fig. 6. Fig. 4 provides visualizations for analysis that complements the congruence analysis. Fig. 6 provides visualizations for a new analysis examining spectral features across SWS to REM and REM to SWS transitions.