Alterations in functional activation in euthymic bipolar disorder and schizophrenia during a working memory task.

Area of Science:

• Neuroscience
• Psychiatry
• Cognitive Psychology

Background:

• Working memory (WM) deficits are common in bipolar disorder and schizophrenia.
• Prefrontal cortex (PFC) dysfunction is implicated in these WM impairments.
• It is unclear if WM-related brain activity patterns differ between bipolar disorder and schizophrenia patients.

Purpose of the Study:

• To investigate differences in blood oxygen level dependent (BOLD) activation during a WM task in euthymic bipolar I patients, schizophrenia patients, and healthy controls.
• To compare WM-related hemodynamic responses across these three groups.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to measure brain activity.
• Participants included 21 euthymic bipolar I patients, 20 schizophrenia patients, and 38 healthy controls.
• A delayed match-to-sample task involving abstract designs was employed.

Main Results:

• All groups activated PFC, motor cortex, and visual cortex during the WM task.
• Healthy controls showed significantly greater PFC activation than schizophrenia patients.
• Bipolar patients exhibited intermediate PFC activation, with significant differences only between schizophrenia patients and controls.
• Schizophrenia patients demonstrated more severe WM-related dysfunction in the dorsolateral prefrontal cortex (DLPFC) compared to bipolar patients.

Conclusions:

• WM-related brain activity patterns suggest diagnostic specificity between bipolar disorder and schizophrenia.
• Both patient groups exhibit some regional hypoactivation compared to controls.
• Schizophrenia is associated with more pronounced WM-related dysfunction in the DLPFC than bipolar disorder.