P242: Discriminate visual neglect from hemianopia by semantic priming effect: a clinical study

There is a wide agreement concerning spared abilities in implicit infor- mation processing for patients with neglect. We then hypothesized that a priming word in the neglected space should produce a semantic activation effect even when it is not consciously perceived. On the contrary, if the priming word occurs in a blind field, as it would be in case of homonymous hemianopia, this should not entail any facilitation effect. We here discuss the results of a 72 y.o. patient with a bilateral hemispheric lesion (right fronto-temporal and left occipital ischemic area) affected by left visual neglect and right homonymous hemianopia in order to study the differences in implicit information processing among neglected space and hemianopic field. After a clinical assessment the patient underwent to an experimental observation by means of a visual priming task. A prime related, unrelated or neutral to the target, occured for 200ms on the horizontal central line in six different positions of the screen (three on the left and three on the right). This task was previuosly tested on 69 control subjects and it determined in each prime position a semantic activation effect, in accordance with literature. As expected, the patient showed a priming effect in the neglected space whilst no facilitations was observed in hemianopic field. Furthermore, we studied patient’s eye movements to support behavioural data. He presented some saccades and fixations only in the neglected side; this evidences are in line with some theoretical accounts concerning a spared automatic attention orientation even towards neglected space. In conclusion these results, even observed on a single case study, seem to support our work hypothesis. Further steps of the research are now ongoing, specifically involving the application of experimental paradigm to group of patients with neglect or with hemianopia.