Greater gray matter volume in Broca's area in psychiatric patients with preserved verbal working memory – evidence for compensatory neuroplasticity?

Verbal working memory impairments are considered to be core deficits and potential endophenotypic markers in schizophrenia but also in other psychiatric disorders, e.g. in bipolar affective disorder and in attention-deficit/hyperactivity disorder. However, recent experimental neuropsychological studies revealed a remarkable heterogeneity within diagnostic groups regarding the presence or absence of verbal working memory deficits. In the present study, we used optimized voxel-based morphometry in order to investigate gray matter volume differences between two groups of patients with mixed diagnoses (i.e. schizophrenic, bipolar and OCD patients) that only differed from each other with regard to their verbal working memory performance. Those patients with preserved verbal working memory showed a significantly greater gray matter volume in Broca's area, a key structure for verbal working memory function, both when compared to patients with verbal working memory deficit, and when compared to healthy controls (without deficit). Among other possible interpretations, these data could provide first evidence that, in a subgroup of patients, neuroplastic changes in brain areas underlying specific working memory functions may compensate for possible disturbances of these functions due to pathophysiological processes.