Detection of circadian rhythm disturbance of carbachol-induced beta wave dynamics in rat hippocampal slices using neural networks

Rats exhibit a circadian rhythm of locomotor activity. Recently, the relation between circadian rhythm and memory has been elucidated. Brain waves are related to memory processes and are modulated by circadian rhythm. Beta wave-like oscillations within 13–30 Hz can be induced by using carbachol, a cholinergic agonist, in rat hippocampal slices. In this study, we prepared hippocampal slices from rats maintained under light/dark (LD) or dark/dark (DD) conditions. We previously reported that carbachol-induced beta oscillations (CIBO) appeared at all times of the day, and oscillatory parameters, such as duration and inter-burst intervals, demonstrated significant diurnal changes. We also studied whether the time of day can be predicted using CIBO parameters and whether circadian disturbances can be detected with these parameters. Using CIBO parameters, a higher accuracy rate was obtained for time-of-day prediction than that when using the amount of locomotor activity during the day. The time of day was not correctly predicted when the parameters were applied under the DD condition, using the CIBO-parameter-trained neural network under LD conditions. Using the oscillatory parameters of the brain waves induced in the neuronal circuit will estimate the internal subjective time of the day and detect circadian disturbances such as DD condition. (199 words).