ACTIGRAPHIC MOTOR ASYMMETRIES DURING SLEEP

Much evidence indicates that during sleep there is a repatterning of m otor asymmetries with a relative advantage of the left hand (ie, the l eft hand moves more than the right). This could be due to the ability of the right hemisphere in operating at levels of reduced arousal (aro usal hypothesis) or to its superior spatial abilities (motor specifici ty hypothesis), or it could indicate a greater need for sleep in the l eft hemisphere (homeostatic hypothesis). Since only the latter hypothe sis predicts that the repatterning should be present in the first part of sleep (ie, when the homeostatic processes are more pronounced), th e present study evaluated whether actigraphic data are consistent with this prediction. Sixteen right-handed college students wore actigraph s (AMI 16K) on both upper and lower limbs for about 56 hours. Factoria l ANOVAs were carried out on side (left vs right) and part (first vs s econd) of the recording period during sleep and waking. During waking, the right hand showed more intense motor activity as compared to the left. During sleep, in the first part of the night, the right hand los t this advantage, while in the second part of the night it regained it s superiority. Since this repatterning was specific for hand movements and no difference was found in overall motor activity and in arousal between the two parts of the sleep period, the results are interpreted as consistent with the homeostatic hypothesis.