Verbal Working Memory Dysfunction in Schizophrenia: An fMRI Investigation

Abstract

Impaired processing of working memory information is one of the cognitive deficits seen in patients with schizophrenia. This study aims at corroborating the differences in the brain activities involved in the process of working memory between patients with schizophrenia and the controls. Twelve patients with schizophrenia and 11 controls participated in the study. Functional magnetic resonance imaging (fMRI) was used to assess cortical activities during the performance of a two-back verbal working memory paradigm using the Korean alphabet as mnemonic content. Group analysis revealed that inferior fontal, middle frontal, and superior temporal region showed decreased cortical activities in the patient group compared to those of the controls. This study showed a decreased activation in inferior fontal (BA 47), middle frontal (BA 6), and superior temporal (BA 22/38) neural networks from the patient group and confirmed the earlier findings on the impaired working memory of schizophrenic patients in the fMRI investigation.

The influence of emotional distraction on verbal working memory: An fMRI investigation comparing individuals with schizophrenia and healthy adults

“…The decreased activation we observed for patients is consistent with some prior research. For example, several investigators have reported decreased activation in prefrontal cortex during an N-back task in individuals with schizophrenia compared to controls (Barch et al, 2001; Pae et al, 2008; Perlstein et al, 2003). Others have reported similar levels of activation between patients and healthy adults when task difficulty is low, but less activation in patients as difficulty increased (Perlstein et al, 2001).…”

“…Several studies suggest that individuals with schizophrenia elicit less brain activation compared to healthy adults during working memory tasks. Using a two-back task with Korean alphabetical letters, individuals with schizophrenia elicited decreased activation in inferior frontal, middle frontal, and superior temporal gyri compared to healthy controls (Pae et al, 2008). Similarly, during an N-back task using English letters patients elicited less activation in right dorsolateral prefrontal cortex (DLPFC) than healthy adults (Perlstein, Dixit, Carter, Noll, & Cohen, 2003).…”

“…Moreover, we predicted that patients would not differentiate emotional and neutral distractors as strongly as healthy adults. With respect to the executive network, previous research suggests that patients inefficiently activate the frontal-parietal network, as evidenced by reduced activations (Barch et al, 2001; Dichter et al, 2009; Pae et al, 2008; Perlstein et al, 2001; Perlstein et al, 2003), and activations that are unrelated to performance measures (Honey et al, 2002; van Raalten et al, 2008). Based on those results we expected that patients would show reduced patterns of activation in the executive frontal-parietal network compared to healthy adults, and that these patterns of activation would not be strongly related to behavioral performance.…”

Emotional effect on cognitive control in implicit memory tasks in patients with schizophrenia

“…Deficits in WM are widely recognized to play a significant role in the functional outcomes of schizophrenia. Especially, verbal memory deficits are among the most severe cognitive impairments in schizophrenia [3,6].…”

“…Cognitive impairment in schizophrenia predicts poor functional outcome, which is important in theories of the pathogenesis of schizophrenia [1]. To address this issue, numerous functional MRI (fMRI) studies [2][3][4][5] focusing on working memory (WM) have been carried out to identify the neural centers related to cognitive dysfunction in patients with schizophrenia, and it is now well known that cognitive deficits in patients are associated with dysfunction of the dorsolateral prefrontal cortex (dlPFC). Deficits in WM are widely recognized to play a significant role in the functional outcomes of schizophrenia.…”