Schizophrenia: Language Production Deficits


Another major focus of Deanna Barch's research has been to understand how cognitive deficits in schizophrenia contribute to specific symptoms of the illness. In particular, research led by Dr. Barch has focused on the hypothesis that disturbances in context processing/WM in schizophrenia contribute to symptoms of language dysfunction in this illness. More specifically, our work in this area has been guided by the hypotheses that: (1) Coherent thought and language require the development and maintenance of a representation of both the current and past discourse context; (2) WM serves to help maintain such discourse representations, which guide and constrain ongoing thought and language; and (3) deficits in the ability to maintain representations of discourse can explain language symptoms in schizophrenia at a range of levels. Our work provides support for several of these hypotheses, including: (1) the existence of WM and/or discourse representation deficits in schizophrenia (Barch & Berenbaum, 1996a; Barch & Berenbaum, 1997a; Barch, Cohen et al., 1996b; Cohen et al., 1999) ; (2) a relationship between WM and language function in nonpathological language production (Barch & Berenbaum, 1994) ; and (3) a relationship between deficits in WM/context processing and language disturbances in schizophrenia (Barch et al., 1999a; Barch et al., 1997a; Barch et al., 1999c; Cohen et al., 1999). In addition, in more recent completed work with graduate student Meredith Dodge, we have demonstrated that an experimental reduction of WM capacity during language production in schizophrenia increases the frequency of language disturbances (Dodge & Barch, in preparation).

Our current and future work on language deficits in schizophrenia is focused on two issues. First, we have been working on methods to more directly assess the role of PFC and the active maintenance of information in both normal and disordered language production. We have been conducting a series of experiments using a new paradigm that allows for experimental manipulation of cognitive processes influencing reference production. The use of such an experimental paradigm allows for the manipulation of factors that may influence the active representation of information in WM, allowing for a more powerful test of hypotheses regarding the precise role of that WM plays in reference production. The findings are consistent with the hypothesis that individuals actively maintain representations of prior discourse information during ongoing language production, which are used to guide the choice of referents. However, the patient data suggests that language production disturbances in schizophrenia do not stem solely from a memory deficit, but rather that patients have deficits in initially representing discourse information, which may be exacerbated when that information then has to be maintained over a delay (Barch, in preparation). Second, we our extending our work on the role of WM/context processing in language processing in schizophrenia to include the examination of language comprehension. Numerous studies in healthy subjects suggest that WM supports language comprehension, and there is preliminary data to suggest that WM deficits in schizophrenia may also be related to language comprehension disturbances. We are examining the relationships among disturbances in WM, language production and language comprehension in schizophrenia, to test the hypothesis that the same underlying disturbance in WM/context processing contributes to both language production and language comprehension deficits in schizophrenia.