Left and right hemispheric contributions to discourse coherence and cohesion.

Linguistic coherence and cohesion were examined in patients with unilateral left brain damage (LBD), unilateral right brain damage (RBD), and normal control (NC) right-handed adults. Groups were matched for age, gender, occupation, and education. Brain-damaged groups did not differ for months post onset or intrahemispheric lesion site. Contrary to previous literature, results indicated that LBDs, all of whom were aphasic, demonstrated impairments in coherence but not cohesion, relative to NCs and RBDs. Surprisingly, among RBDs, overall coherence and cohesion were spared. When the relationship between measures of coherence and cohesion was examined, there were few significant correlations and no systematic patterns. Results support the notion that coherence and cohesion represent coexisting and independent linguistic systems. Further, the findings suggest that descriptions of discourse integrity need to account for the perspective of both the speaker and listener.