UNILATERAL NEGLECT CAN BE AFFECTED BY STIMULI IN THE NEGLECTED FIELD

Neglect patients' attention is usually pathologically captured by stim uli present on the side ipsilateral to the brain damage. In previous r esearch it was shown that not only the mere presence but also the numb er of ''relevant'' stimuli on the right side-influenced patient's perf ormance. However, the influence of stimuli whose presence was complete ly irrelevant for the execution of the task was not previously studied . We asked neglect patients to bisect lines of 28 cm of length, which could be presented alone or with line-drawings of objects placed eithe r only on the left, only on the right or bilaterally on the display. W e found that the presence of irrelevant left-side stimuli improved the bisection performance in 3 out of 5 patients with respect to the base line condition, in which no stimuli were present on either side of the display. Right-side stimuli did not affect the performance, whereas b ilateral stimuli tended to worsen the performance for those patients w ho presented the beneficial effect of left-side stimuli. These finding s were discussed with reference to the hypotheses advanced to explain neglect.