Nikki E Hozack | PubMed Health

PubMed2002

Parietal dysfunction is associated with increased outcome-related decision-making in schizophrenia patients.

BACKGROUND: Decision-making is a complex process and depends on a network of fronto-parietal and cingulate areas. Decision-making dysfunctions in schizophrenia patients are characterized by an alternation between stereotypic and unpredictable responses. This study tested the hypothesis that schizophrenia patients show less decision-making-related activation in the prefrontal and parietal cortex. METHODS: Fifteen schizophrenia patients were matched with fifteen normal comparison subjects. During functional magnetic resonance imaging (fMRI) scanning, subjects were tested on the two-choice prediction task (predicting the location of a randomly presented stimulus) and the two-choice response task (responding according to the location of the stimulus). RESULTS: Schizophrenia patients relative to comparison subjects generated more outcome-dependent responses. Schizophrenia patients and normal comparison subjects showed decision-making-related activation in right prefrontal cortex, insula, anterior cingulate, and bilateral precuneus. Schizophrenia patients showed less activation in inferior, medial prefrontal, and right superior temporal cortex and more activation in the postcentral and inferior parietal cortex. Decision-making-related activation in both right prefrontal and bilateral parietal cortex was higher in medicated compared to unmedicated schizophrenia patients. CONCLUSIONS: These results support the hypothesis that the interaction between prefrontal and parietal cortex during decision-making by schizophrenia patients is dysregulated, which results in an increased outcome-dependent response selection.

Adult↗

PubMed2002

Behavioral and functional neuroimaging evidence for prefrontal dysfunction in methamphetamine-dependent subjects.

Stimulant-dependent subjects show dysfunctions in decision-making similar to those seen in subjects with ventromedial prefrontal cortex lesions. Studies of drug craving, reward association, and decision-making have implicated dysfunctions of the dorsolateral and orbitofrontal cortex as a key neural substrate in subjects with stimulant dependence. Here, a functional magnetic resonance imaging (fMRI) study was carried out to determine the relationship between decision-making dysfunction and neural activation in different prefrontal areas. This investigation tested the behavioral hypothesis that methamphetamine-dependent subjects in early sustained remission show decision-making dysfunctions that are consistent with an increased reliance on stimulus-contingent response selection. It was hypothesized that these decision-making dysfunctions are due to differences in task-related activation in the dorsolateral and ventromedial prefrontal cortex. Ten methamphetamine-dependent subjects were compared with ten age- and education-matched controls performing a two-choice prediction task and a two-choice response task during a fMRI session. Response bias, latency, and mutual information measures assessing the underlying strategies of the decision-making sequences were obtained. First, methamphetamine-dependent subjects were more influenced by the immediately preceding outcome during the two-choice prediction task relative to normal comparison subjects. Second, methamphetamine-dependent subjects activated less dorsolateral prefrontal cortex (BA 9) and failed to activate ventromedial cortex (BA 10,11) during the two-choice prediction task compared with the two-choice response task. These results support the basic hypothesis that stimulant-dependent subjects exhibit fundamental cognitive deficits during decision-making that are consistent with both orbitofrontal and dorsolateral prefrontal dysfunction.

Adult↗