Markov-dependency and spectral analyses on spike-counts in mesencephalic reticular neurons during sleep and attentive states.

Spontaneous activities of the mesencephalic reticular formation (MRF) neurons of head-restrained cats were recorded to investigate their dynamic properties during sleep and waking. The Markov-dependency and spectral analyses were performed on the time series of counts converted from the MRF spike-train. During slow-wave sleep (SWS), MRF neurons fired with low Markovian properties and had a similar spectral-density curve as white noise; during paradoxical sleep (PS), their firing pattern showed high Markovian properties owing to low-frequency fluctuations, with spectral densities inversely proportional to frequency (the l/f spectrum). During the attentive state of bird watching (BW), intermediate Markovian properties were observed. These results confirmed both the rest theory of SWS and the activation of the brain during PS from the viewpoint of dynamic information-processing. Furthermore, the activation of the brain during PS may be greater than in BW.