Comprehensibility and neural substrate of communicative gestures in severe aphasia

- Severe aphasia enhances the amount of information conveyed in gesture.
- Controls communicating without speech convey more gestural information than PWSA.
- Gesture and speech have a trade-off relationship.
- Poor gestural expression is associated with lesions in anterior temporal.
- Poor gestural expression is associated with lesions in inferior frontal regions.

Communicative gestures can compensate incomprehensibility of oral speech in severe aphasia, but the brain damage that causes aphasia may also have an impact on the production of gestures.We compared the comprehensibility of gestural communication of persons with severe aphasia and non-aphasic persons and used voxel based lesion symptom mapping (VLSM) to determine lesion sites that are responsible for poor gestural expression in aphasia.On group level, persons with aphasia conveyed more information via gestures than controls indicating a compensatory use of gestures in persons with severe aphasia. However, individual analysis showed a broad range of gestural comprehensibility. VLSM suggested that poor gestural expression was associated with lesions in anterior temporal and inferior frontal regions. We hypothesize that likely functional correlates of these localizations are selection of and flexible changes between communication channels as well as between different types of gestures and between features of actions and objects that are expressed by gestures.