Attention attracts action in healthy participants: An insight into optic ataxia?

Attentional modulation of peripheral pointing hypometria in healthy participants: An insight into optic ataxia?

Damage to the superior parietal lobule and intraparietal sulcus (SPL-IPS) causes optic ataxia (OA), characterized by pathological gaze-centered hypometric pointing to targets in the affected peripheral visual field. The SPL-IPS is also involved in covert attention. Here, we investigated the possible link between attention and action. This study investigated the effect of attention on pointing performance in healthy participants and two OA patients. In invalid trials, targets appeared unpredictably across different visual fields and eccentricities. Valid trials involved cued targets at specific locations. The first experiment used a central cue with 75% validity, the second used a peripheral cue with 50% validity. The effect of attention on pointing variability (noise) or time was expected as a confirmation of cueing efficiency. Critically, if OA reflects an attentional deficit, then healthy participants, in the invalid condition (without attention), were expected to produce the gaze-centered hypometric pointing bias characteristic of OA. RESULTS: revealed main effects of validity on pointing biases in all participants with central predictive cueing, but not with peripheral low predictive cueing. This suggests that the typical underestimation of visual eccentricity in OA (visual field effect) at least partially results from impaired endogenous attention orientation toward the affected visual field.

Peripheral and bimanual reaching in a stroke survivor with left visual neglect and extinction

Whether attentional deficits are accompanied by visuomotor impairments following posterior parietal lesions has been debated for quite some time. This single-case study investigated reaching in a stroke survivor (E.B.) with left visual neglect and visual extinction following right temporo-parietal-frontal strokes. Unlike most neglect patients, E.B. did not present left hemiparesis, homonymous hemianopia nor show evidence of motor neglect or extinction allowing us to examine, for the first time, if lateralised attentional deficits co-occur with deficits in peripheral and bimanual reaching. First, we found a classic optic ataxia field effect: E.B.'s accuracy was impaired when reaching to peripheral targets in her neglected left visual field (regardless of the hand used). Second, we found a larger bimanual cost for movement time in E.B. than controls when both hands reached to incongruent locations. E.B.'s visuomotor profile is similar to the one of patients with optic ataxia showing that attentional deficits are accompanied by visuomotor deficits in the affected field.