A chronic experimental study to compare the electrocorticogram of certain brain areas in the drowsy cat

Abstract

The spontaneous electrocorticogram of the first somatosensory (area 53), first auditory (area 22), visual (area 17), association (area 5), and second auditory (area 52) projection areas was studied in chronic experiments on drowsy unanesthetized cats. In the intermediate periods between waking and sleep and vice versa, maximal differences expressed as heterogeneity of the spindle component and low coefficients of cross correlation (0.21±0.04) were found in the slow-wave activity of the areas studied. During deepening of sleep the synchronization of the potentials recorded from the different areas increased and the coefficients of cross correlation rose to 0.40±0.18. The level of differences between the coefficients of correlation compared in the different phases of sleep was 0.19 and was significant by Student's criterion. It is postulated that functional changes in the thalamic pacemaker mechanisms take place during changes in the depth of sleep. In response to afferent stimulation of different modalities no differences were found in the desynchronization response in the projection areas. After extinction of the orienting reflexes and application of stimulation of adequate strength, specific differences in the development of the desynchronization response to adequate stimulation were found in the projection zones. The need for certain conditions being present before signs of specificity of the responses in the projection areas can be detected is emphasized.