Attentional grasp in far extrapersonal space after thalamic infarction

Studies of animals and humans with focal brain damage suggest that attentio n in near and far extrapersonal space may be mediated by anatomically separ ate systems. Thalamic lesions have been associated with spatial neglect, bu t whether asymmetric attention specific to near or far space occur after th alamic damage has not been explored. It is also unclear if thalamic injury can induce contralesional defective response inhibition. We tested a woman with a left thalamic infarction who reported that, when d riving, she had a tendency to veer towards people or objects on the right s ide of the road. Our patient and foul controls performed a line bisection t ask with a laser pointer in near and far extrapersonal space. The experimen ter marked each bisection either from the right of the presented line (righ t-distractor, RD) or the left (left-distractor. LD). RD and LD trials were pseudo-randomized. Our patient performed similarly to controls (mean -0.7 mm, controls -0.6 mm ) on the line bisection task in near space. In far space she erred signific antly rightward compared to her performance in near space (p < 0.001). Cont rols performed similarly in neat and far space. The experimenter position d id not affect our patient's performance on near line bisections, nor did co ntrols demonstrate a distractor effect for the near condition. In the far c ondition, however, our patient showed a significant distracter effect (LD - 3.3 mm, RD 35.3 mm, p < 0.001). Controls also demonstrated a distractor eff ect in the far condition (LD -6.4 mm. RD 0.7 mm, p < 0.01), though of much smaller magnitude, Our results suggest that frontal-thalamic systems regulating visual attenti on may be disrupted by thalamic infarction. Such damage may produce an atte ntional grasp specific to far extrapersonal space. Published by Elsevier Sc ience Ltd.