The role played by the right hemisphere in the organization of complex textual structures.

Eleven patients with right hemisphere damage (RHD), 11 left hemisphere damaged (LHD) nonaphasic subjects, and 11 neurologically intact controls were given three story description tasks. The two brain-damaged groups had no language, visuospatial, memory, or conceptual deficits on standardized neuropsychological testing. In the first experiment, the subjects were asked to retell previously read stories. In the second they had to tell stories which were depicted in cartoon-like fashion. In the third experiment, the story content was also depicted but pictures were given unordered so that the participants had first to arrange them in a plausible sequence. The elicited narratives were analyzed with a method which allowed examining within-sentence (lexical selection and syntactic complexity) and between-sentence (cohesion and coherence) processing abilities of the three groups. In the first experiment all groups performed quite well on both within- and between-sentence measures. In the two picture description tasks, however, the performances of the right hemisphere damaged subjects were poorer than those of normal controls when examined in terms of information content or coherent and cohesive aspects of narrative production. These findings agree with the hypothesis that RHD subjects are impaired in deriving from visual information the mental model of a story. They also indicate that clinical methods for analyzing structural aspects of discourse are suitable to identify these symptoms.