Unilateral Right Parietal Damage Leads to Bilateral Deficit for High-Level Motion

Abstract

Patients with right parietal damage demonstrate a variety of attentional deficits in their left visual field contralateral to their lesion. We now report that patients with right lesions also show a severe loss in the perception of apparent motion in their "good" right visual field ipsilateral to their lesion. Three tests of attention were conducted, and losses were found only in the contralesional fields for a selective attention and a multiple object tracking task. Losses in apparent motion, however, were bilateral in all cases. The deficit in apparent motion in the parietal patients supports previous claims that this relatively effortless percept is mediated by attention. However, the bilateral deficit suggests that the disruption is due to a bilateral loss in the temporal resolution of attention to transient events that drive the apparent motion percept.

Perception of biological motion in parietal patients

“…Furthermore, it gives important insights about how the visual system analyzes biological motion. According to our previous study with bilateral and right parietal patients (Battelli et al, 2001) and, confirmed by the present results that include a left parietal lesion subject, low-level motion perception is intact in these patients. They can easily segregate a coherently moving pattern within a high level of background noise, profoundly different from the results for V5 patients reported in the literature (Rizzo et al, 1995;Vaina et al, 1990).…”

“…2B). Results for JR and JL have previously been reported elsewhere (Battelli et al, 2001) and here they have been contrasted to the left parietal patient JS. The patients were tested both in the left and right visual field and since there was no significant difference between hemifields the data in the graph have been collapsed.…”

“…Any performance loss with free viewing therefore probably reflects a loss in both fields. We have previous data from the same patients (Battelli et al, 2001) showing that they were impaired in both visual fields in tasks of visual timing, whereas the same patients presented only a contralateral deficit in selective and sustained attention tasks.…”

“…The same patients are impaired in the field contralateral to the lesion on tasks of visual tracking (Battelli et al, 2001) and in the perception of apparent motion in both visual fields (Battelli et al, 2001). A recent study by Thornton et al (2002) has shown that attention related mechanisms are used during biological motion perception and that they depend on the temporal feature of the stimuli.…”

“…A recent study by Thornton et al (2002) has shown that attention related mechanisms are used during biological motion perception and that they depend on the temporal feature of the stimuli. Because of the previous evidence of deficits for tasks requiring temporal attention in parietal patients such as the ability to perceive apparent motion (Battelli et al, 2001) or disorders in discriminating events presented at high temporal frequency (Husain, Shapiro, Martin, & Kennard, 1997) we felt that the losses, if any, in the perception of biological motion in parietal patients could help us understand the role of temporal attention in this task.…”