Biomedical subjects

D M Barch

Publications and source records attributed to D M Barch.

25 records · Page 2Linked to original sources

PubMed1998

The Stroop task and attention deficits in schizophrenia: a critical evaluation of card and single-trial Stroop methodologies.

The Stroop task, considered by many to be a paradigmatic measure of selective attention, has often been employed to investigate attention deficits in schizophrenia. Card and single-trial versions of this task have yielded different results. In this study both card and single-trial versions were administered to healthy controls (n = 24) and patients with schizophrenia (n = 55). No differences in reaction time (RT) interference were found on either version. On the single-trial version, patients showed greater RT facilitation and error rate interference, evidence for a deficit in selective attention. Methodologic and analytic issues that account for the mixed results from earlier card Stroop studies are addressed. It is concluded that single-trial versions provide greater sensitivity to selective attention pathology in schizophrenia.

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PubMed1997

The effect of language production manipulations on negative thought disorder and discourse coherence disturbances in schizophrenia.

This study was designed to test the following hypotheses about the mechanisms underlying language disturbances in schizophrenia: (1) negative thought disorder (reduced verbosity and syntactic complexity, increased pausing) reflects a deficit generating a discourse plan; and (2) discourse coherence disturbances (tangential responses, loss of goal, derailment, non-sequiturs, distractible speech) reflect a deficit maintaining a discourse plan. Thirty-nine participants with, DSM-III-R schizophrenia listened to two stories and answered a series of questions after each story. We manipulated two factors: (1) the presence of context before the stories (to influence generating a discourse plan); and (2) question type (structured vs. unstructured; designed to influence maintaining a discourse plan). Consistent with our hypotheses, low context was associated with less verbose and syntactically complex speech. In addition, patients produced more discourse coherence disturbances when responding to unstructured than when responding to structured questions.

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PubMed1997

Dissociating working memory from task difficulty in human prefrontal cortex.

A functional magnetic resonance imaging (fMRI) study was conducted to determine whether prefrontal cortex (PFC) increases activity in working memory (WM) tasks as a specific result of the demands placed on WM, or to other processes affected by the greater difficulty of such tasks. Increased activity in dorsolateral PFC (DLPFC) was observed during task conditions that placed demands on active maintenance (long retention interval) relative to control conditions matched for difficulty. Furthermore, the activity was sustained over the entire retention interval and did not increase when task difficulty was manipulated independently of WM requirements. This contrasted with the transient increases in activity observed in the anterior cingulate, and other regions of frontal cortex, in response to increased task difficulty but not WM demands. Thus, this study established a double-dissociation between regions responsive to WM versus task difficulty, indicating a specific involvement of DLPFC and related structures in WM function.

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PubMed1997

Language generation in schizophrenia and mania: the relationships among verbosity, syntactic complexity, and pausing.

We examined the relationships among verbosity, syntactic complexity, and pausing in the speech of 21 Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev.) (DSM-III-R) diagnosed schizophrenic participants and 19 DSM-III-R diagnosed manic participants. We found that less verbosity was associated with both less syntactic complexity and greater pausing. In addition, less syntactic complexity was associated with greater pausing. The strength of these associations did not differ significantly between the two diagnostic groups. We propose that deficits in verbosity, syntactic complexity, and pausing are all related to a disturbance in message generation. We discuss the consistency of this hypothesis with previous research linking information processing and frontal lobe deficits to disturbances in verbosity, syntactic complexity, and pausing.

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PubMed1997

Issues concerning relative speed of processing hypotheses, schizophrenic performance deficits, and prefrontal function: comment on Schooler et al. (1997)

The authors have found the data presented in the C. Schooler, E. Neumann, L. J. Caplan, and B. R. Roberts (1997) article to be interesting and of potential value in constraining the further development of detailed theoretical models of Stroop performance. However, the authors have found that the relative speed of processing account of stimulus onset asynchrony (SOA) effects given by Schooler et al. in Experiment 1 fails to address several important and vexing issues faced by such accounts, which have been highlighted by existing formal models. The authors also have expressed concerns about Schooler et al.'s, interpretation of the reduction in Stroop interference observed among individuals with schizophrenia in Experiment 2. Whereas the authors have acknowledged that it is plausible to relate this to a dysfunction of prefrontal cortex, they have pointed to equally plausible alternative explanations, which are not addressed by the experiment or in the discussion in the Schooler et al. article.

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PubMed1996

Language production and thought disorder in schizophrenia.

The authors examined the relationship between language production (LP) processes and thought disorder. Thirty-nine schizophrenic or schizoaffective participants completed tasks measuring discourse planning, monitoring, and grammatical-phonological encoding, as well as an interview used to rate thought disorder. The authors found that different LP processes were differentially related to different thought disorder subtypes. Incompetent references were strongly and selectively related to discourse planning performance. In addition, word approximations-neologisms were strongly and specifically associated with grammatical-phonological encoding performance. The article concludes with a discussion of the implications of these results for understanding the multifaceted nature and etiology of thought disorder.

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PubMed1996

Semantic priming in schizophrenia: an examination of spreading activation using word pronunciation and multiple SOAs.

Semantic priming in word pronunciation was examined at 5 stimulus onset asynchronies (SOAs) in 75 medicated and 25 unmedicated people with schizophrenia (SCZ) and in 10 depressed and 28 normal controls. At SOAs < 950 ms, SCZ displayed priming similar to that of normal and depressed controls. At the 950-ms SOA, SCZ displayed less priming than controls. Medication dosage, but not conceptual disorganization scores, was positively associated with priming at SOAs < 950 ms. These results suggest that prior reports of enhanced priming in schizophrenia may have been confounded by methodological problems and that automatic priming processes operate normally in SCZ. The failure of SCZ to display significant priming at the 950-ms SOA is consistent with a hypothesized disturbance in higher level processes.

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