Spontaneous gesture and spatial language: Evidence from focal brain injury.

People often use spontaneous gestures when communicating spatial information. We investigated focal brain-injured individuals to test the hypotheses that (1) naming motion event components of manner-path (represented by verbs-prepositions in English) are impaired selectively, (2) gestures compensate for impaired naming. Patients with left or right hemisphere damage (LHD or RHD) and elderly control participants were asked to describe motion events (e.g., running across) depicted in brief videos. Damage to the left posterior middle frontal gyrus, left inferior frontal gyrus, and left anterior superior temporal gyrus (aSTG) produced impairments in naming paths of motion; lesions to the left caudate and adjacent white matter produced impairments in naming manners of motion. While the frequency of spontaneous gestures were low, lesions to the left aSTG significantly correlated with greater production of path gestures. These suggest that producing prepositions-verbs can be separately impaired and gesture production compensates for naming impairments when damage involves left aSTG.