ASYMMETRY OF RAPID EYE-MOVEMENTS IN CHRONIC UNILATERAL NEGLECT DOES NOT CHANGE WITH BEHAVIORAL IMPROVEMENT INDUCED BY REHABILITATION TREATMENT

A strong reduction of leftward rapid eye movements (REMs) during REM s leep was recently documented in patients with severe and chronic left unilateral neglect. The aim of the present research was to study the s tability of the unilateral suppression of REMs before and after a reha bilitative treatment for neglect disorders. Six right-brain-damaged pa tients were tested for neglect at the beginning and at the end of a 2 month cognitive rehabilitation treatment. REMs were recorded during I night of undisturbed sleep before and after the training: Five out of 6 patients improved considerably their ability to attend the previousl y neglected left hemispace; in all patients REM asymmetry remained unc hanged. The lack of relationship between the improvement of the neglec t disorder and the persistence of REM asymmetry suggests that the sens orimotor mechanisms activated by rehabilitation are different from tho se involved in the production of REMs. It is proposed that: (a) the di rectional vectors of REMs are computed on the basis of the exclusive o r predominant endogenous activation of the central attentional mechani sms related to vestibular input; (b) the presence of rightward and lef tward saccades and the positive effects of the rehabilitation treatmen t are functionally linked to attentional oculomotor mechanisms that ar e not active in REM sleep.