DEVELOPMENTAL PATTERNS IN CENTRAL NERVOUS SYSTEM OF BIRDS .V. CEREBRAL ELECTRICAL ACTIVITY FOREBRAIN FUNCTION AND BEHAVIOR IN CHICK AT TIME OF HATCHING

A study has been made of the motor activity associated with hatching in the chick, and of the possible role played by any forebrain systems in this behavior. It was found that the forebrain is needed both for sustaining the stereotyped rhythmic motility which causes hatching, and for the maintenance of waking behavior thereafter. Although the latter system starts to be active to some extent immediately upon hatching, it requires 1.5-2 h for it to reach a fully functional condition. The 'awake' state needs a strong proprioceotive stimulus from the neck muscles in order to be initiated, and a continuous lower level of the same type of input for its subsequent maintenance. 'Sleep' in the chick appears to be essentially a functional decerebration, the motor activity level thus returning to that seen both in late embryos and in chicks which lack any of the forebrain. The forebrain system which is involved in hatching is, nevertheless, related intimately to the sleeping state. Thus, rhythmic motility reemerges-at least up to 2 weeks after hatching-in birds which are not allowed to awaken (by preventing them from stretching the neck). There is no visible departure of the cerebral EEG from the normal sleep pattern, nor is 'sleep-struggling' necessarily correlated with electrical indications of activated ('paradoxical') sleep. The forebrain's contribution to behavior at this time is to facilitate a rhythmic motor output which is itself determined at more caudal levels of the nervous system. © 1969.