Perceptual decision-making at fixation is biased by task-irrelevant contralesional stimuli following unilateral stroke
Dr Dragan Rangelov1 (email@example.com), Jason Mattingley1; 1The University of Queensland
Stroke-induced cerebral lesions can cause pathological biases in selective attention, resulting in unilateral spatial neglect for contralesional stimuli in severe cases, particularly for lesions involving the right hemisphere. It remains unclear, however, whether such attentional biases impact evidence accumulation processes involved in perceptual decision-making. Here we characterised the influence of task-irrelevant ipsi- and contra-lesional stimuli on perceptual decisions about centrally presented visual stimuli. Left- and right-hemisphere stroke patients (N=28) judged the direction of coherent motion signals embedded within a central random-dot kinematogram (RDK) while ignoring motion signals presented in two peripheral semi-circular RDKs in the left and right hemifields. Their brain activity was recorded using electroencephalography (EEG). Contrary to expectations, motion signals presented in the contralesional hemifield had a greater effect on central judgements than those in the ipsilesional hemifield. Multivariate EEG analyses revealed robust motion-evoked responses to both task-relevant, central signals and task-irrelevant, peripheral signals. Critically, the neural representations of peripheral stimuli were stronger for contralesional stimuli than for concurrently presented ipsilesional stimuli, consistent with the observed behavioural biases. Our results suggest that unilateral lesions reduce inhibitory control over irrelevant stimuli in the contralesional hemifield, thereby allowing them to interfere with task-relevant processing in central vision.
Topic Area: THINKING: Decision making
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April 13–16 | 2024