The effect of behavioural state on general movements in healthy full-term newborns. A polymyographic study.

In a group a eight healthy full-term newborns 6-h polygraphic recordings, which included EMG recording of eight arm muscles, were made to investigate the effect of behavioural state on general movement (GM) organization. Simultaneous video recordings supplied information about the form of the GMs. Additionally the effect of non-nutritive sucking during State 4 was evaluated. Behavioural state had a distinct effect on the makeup of GMs. GMs during State 4 displayed best the fluency and elegance which are characteristic of normal GMs. State-1-GMs were rare, had a short duration and sometimes had an abrupt onset. During State 2 GMs had a fragmented appearance. EMG differences between GMs in State 2 and State 4 were demonstrated in burst duration (longer during State 2) and tonic background activity in the upper arm muscles (lower during State 2). Occasionally State-2-GMs had an abrupt onset. These abrupt GMs were less often preceded by rapid eye movements and heart rate changes than State-2-GMs with a gradual onset. GMs during State 5 were abrupt and vigorous and often had a high frequency tremor superimposed. The EMGs of State-5-GMs revealed a shorter interval between the EMG bursts and a higher EMG burst amplitude in the upper arm muscles than present during State-4-GMs. Non-nutritive sucking during State 4 induced a reduction of movement amplitude, a increase of EMG burst duration and an increase of tonic background activity in the biceps brachii and the extensor carpi muscles.