Introduction. Multimodal tactile, visual, and auditory neurons with maximal activity when lights and sounds are delivered in peripersonal space have been recently described in the monkey premotor cortex. The present study is aimed at investigating in brain-damaged patients with or without extinction whether or not processing of trimodal stimuli is influenced by the distance between the patient's body and visual and auditory stimuli. Subjects, materials and methods. Ten brain-damaged patients were preliminarily assessed for the presence of unimodal (tactile, visual, and auditory) extinction by means of a series of single and double stimuli. Five patients detected at least 70% of the contralesional stimuli in the single stimulation condition and omitted more than 30% of the contralesional stimuli in the double stimuli condition, in at least one modality. Thus, these patients were assigned to the E+ group. The other five patients, who did not show unimodal extinction, belonged to the E- group. The experimental stimuli consisted of a series of single (left, L or right, R) or trimodal stimuli delivered simultaneously within a single hemispace (3 L or 3 R) or across hemispaces (2L/1R or 2R/1L). Tactile, visual, and auditory stimuli lasted 30 ms and were delivered by means of: (a) electrodes with a 1 mm diameter (controlled by monophasic electric current stimulator) attached to the L or the R little fingers; (b) red LEDs positioned at about 25° L or R from a central fixation point; and (c) beeps delivered through loudspeakers positioned close to the L or the R LED. In separate blocks of trials, visual and auditory stimuli were presented close to the hands (near condition) or 60 cm away from the hands (far condition). On each trial, patients were requested to report verbally on the modality (tactile, visual, or auditory) and position (L or R) of the stimuli. Correct detections of single and triple stimuli in the near and far conditions were compared in the two groups. Results and discussion: The two groups rather accurately detected and localized single stimuli in ipsilesional and contralesional hemispace (84 % of hits in both cases) and in the near (85 % of hits) and far space (83 % of hits). In contrast, performance of E+ on trimodal stimuli was significantly worse when visual and auditory stimuli were in the peripersonal (58 % of hits) than in extrapersonal space (63 % of hits). Since the intensity of visual and auditory stimuli is higher in near space, the effect cannot be accounted for by sensory variables. Thus, the performance of E+ patients may be attributed to the impairment of neural systems and mechanisms for multisensory integration in peripersonal space.
|Issue number||4 SUPPL.|
|Publication status||Published - 2000|
ASJC Scopus subject areas
- Clinical Neurology