Mechanisms of discourse comprehension impairment after right hemisphere brain damage: suppression in lexical ambiguity resolution.

Normal comprehension skill is linked with the proficiency of a suppression mechanism, which functions to dampen mental activation that becomes irrelevant or inappropriate to a final interpretation. This study investigated suppression and discourse comprehension in adults with right brain damage (RBD). To index suppression function, 40 adults with RBD and 40 without brain damage listened to sentence stimuli that biased the meaning of a sentence-final lexical ambiguity (e.g., SPADE), then judged whether a probe word (e.g., CARDS) fit the overall sentence meaning. Probes represented the contextually inappropriate meanings of the ambiguities and were presented in two conditions: 175 ms and 1000 ms post-stimulus. The same probes were used with unambiguous comparison stimuli. Probe judgment response times indicated that only the group without brain damage suppressed inappropriate interpretations over time. In a multiple regression analysis, suppression function added significantly to predicting performance on a general measure of narrative discourse comprehension for participants with RBD. The discussion addresses how suppression deficits may account more broadly for comprehension difficulties after RBD; it also considers several unresolved issues concerning the suppression construct and the suppression deficit hypothesis.

Functional outcome assessment of adults with right hemisphere brain damage.

This article addresses functional outcome assessment of adults with cognitive-communicative disorders due to relatively focal right hemisphere brain damage (RBD). Our discussion observes the World Health Organization's orientation on the multidimensional consequences of health conditions. The WHO framework distinguishes specific deficits (impairments) from their functional consequences: disabilities, or restrictions in daily life activities and handicaps, or broader changes in life role participation. Although there is little evidence about the functional aftermath of RBD, especially in relation to cognitive-communicative disorders, we summarize the data and observations that are available and hypothesize about relationships among outcomes at different levels. We also describe some tools and procedures that may be useful for measuring functional outcomes after RBD, along with relevant caveats, and end with a discussion of research needs and future directions, emphasizing gaps that span the range from basic investigation to treatment research to instrument and procedure development.