Mapping peripheral misreaching in a large cohort of stroke patients

Peripheral reaching to objects outside the direct line of sight supports motor flexibility. Deficits in this ability are the hallmark of optic ataxia, yet impairments may exist along a continuum and warrant investigation in larger, unselected samples. This study examined peripheral misreaching and its neuroanatomical correlates in stroke patients. Peripheral reaching was assessed using a standardized reach-to-grasp task in 86 ischemic stroke patients and 22 mean age-matched controls. Group-level analyses assessed effects of target location and reaching hand, and case-control comparisons quantified deficit prevalence. Lesion symptom mapping examined associations between lesion location and peripheral misreaching, and structural disconnection mapping assessed the impact of structural connectivity damage. At group level, stroke patients showed significantly greater peripheral misreaching than controls, with group differences emerging at older ages. Peripheral reaching deficits were present in 31 out of 86 stroke patients and were most pronounced in the contralesional field. Ipsilesional deficits were also observed, particularly after left hemisphere lesions. Lesion symptom mapping across 77 stroke patients with available MRI data associated left-field peripheral misreaching with the right supramarginal gyrus, while structural disconnection mapping implicated the right optic radiation. No lesion-behaviour associations were observed for right-field peripheral misreaching, though right hemisphere lesion volume correlated with misreaching in this condition. These findings indicate that peripheral reaching deficits after stroke are more common and heterogeneous than previously recognized. The involvement of the supramarginal gyrus suggests a broader role in visuomotor control, including attentional and proprioceptive processes. The right hemisphere dominance in lesion-behaviour associations raises questions about hemispheric specialization.