Modality-specific sustained attention deficits in aphasia: task performance and lesion analysis.

People with aphasia experience cognitive deficits in addition to their well-documented language impairments, with attention being a frequently affected domain. While numerous studies highlight the impact of attention deficits on language abilities in people with aphasia, research examining the neural correlates of these deficits and the influence of stimulus modality on attention performance remains limited. In this cross-sectional study, in Experiment 1, we investigated sustained attention deficits in people with aphasia using four matched tasks that varied by modality (visual versus auditory) and linguistic content (verbal versus non-verbal). In Experiment 2, we further explored whether the neural resources supporting sustained attention differ by modality. Participants included 56 people with aphasia following left-hemisphere stroke (Experiments 1 and 2), 14 individuals after right-hemisphere stroke and 23 age-matched healthy controls (only Experiment 1). Participants completed four sustained attention tasks. Structural MRI scans were obtained for stroke participants, and neural correlates of attention were explored in people with aphasia. Behavioural analyses revealed that people with aphasia, as a group and across subtypes, performed significantly worse on auditory tasks with notably slower reaction times compared to healthy controls, indicating sustained attention deficits, particularly in the auditory modality. Compared to individuals with right-hemisphere stroke, people with aphasia made significantly more errors only on the auditory verbal task, which may reflect the combined impact of language impairment and attentional demands. No significant differences were observed between non-fluent and fluent aphasia subtypes, indicating comparable sustained attention deficits across these groups. However, participants with non-fluent aphasia demonstrated slower reaction times across nearly all tasks compared to healthy individuals, while those with fluent aphasia showed slower reaction times only in the auditory modality. Lesion-symptom mapping analysis did not reveal distinct brain-behaviour associations specific to the auditory modality. However, for the visual verbal task, poorer performance was associated with lesions in the inferior and middle frontal gyri and underlying white matter fasciculi (inferior fronto-occipital fasciculus, uncinate fasciculus and corpus callosum), regions implicated in written word comprehension. Taken together, these findings suggest that people with aphasia exhibit modality-specific sustained attention deficits, particularly in the auditory domain, likely reflecting impaired processing of auditory information.