Progressive changes in sleep electroencephalogram dynamics in the rat barrel cortex associated with long-term alternation of sensory input activities

Sleep is suggested to be involved in the development and maintenance of neural networks. We investigated how long-term alternation of somatosensory input activities affects electroencephalogram (EEG) dynamics of adult rats during non-REM sleep (NREM). Power spectral densities of NREM EEG activity were analyzed for 10 days under the alternation of sensory input activities caused by unilateral whisker clipping. The progressive reduction of the delta power of the inactivated side of the barrel cortex relative to the activated side was found in terms of the daily mean. This extends our previous study in which only the initial 4-h data in every light period was analyzed. In addition, the circadian variation in power spectral densities of NREM EEG activities in the barrel and visual cortices was found to consist of a common background component and fractional regional difference. Averaging out the background circadian variations and canceling the day-to-day variations and inter-individual differences revealed the progressive monotonic increase and decrease in the delta-band spectral powers in the activated side and inactivated side of barrel cortex, respectively. This concurrent and mutually opposite progressive change in the delta power in NREM might reflect the reorganization process of the cortical circuit, especially inhibitory synaptic transmission, rather than the short-term usage-dependent regional regulation of sleep.