Reduced but broader prefrontal activity in patients with schizophrenia during n-back working memory tasks: A multi-channel near-infrared spectroscopy study

• Published in: Journal of psychiatric research 2013-09, Vol.47 (9), p.1240-1246
• Main Authors: Koike, Shinsuke, Takizawa, Ryu, Nishimura, Yukika, Kinou, Masaru, Kawasaki, Shingo, Kasai, Kiyoto
• Format: Article
• Language: English
• Subjects: Activity patterns; Adult; Adult and adolescent clinical studies; Biological and medical sciences; Brain Mapping; Case-Control Studies; Cognitive functioning; Cortex; Female; Frontopolar prefrontal cortex; Hemoglobins - metabolism; Hierarchical network; Humans; Male; Medical sciences; Memory Disorders - etiology; Memory load; Memory, Short-Term - physiology; Middle Aged; Near-infrared spectroscopy (NIRS); Neuropsychological Tests; Prefrontal Cortex - metabolism; Prefrontal Cortex - physiopathology; Psychiatry; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Psychoses; Schizophrenia; Schizophrenia - complications; Schizophrenia - pathology; Signals; Spectroscopy, Near-Infrared; Statistics as Topic; Working memory
• ISSN: 0022-3956; 1879-1379
• DOI: 10.1016/j.jpsychires.2013.05.009

Abstract Background Caudal regions of the prefrontal cortex, including the dorsolateral (DLPFC) and ventrolateral (VLPFC) prefrontal cortex, are involved in essential cognitive functions such as working memory. In contrast, more rostral regions, such as the frontopolar cortex (FpC), have integrative functions among cognitive functions and thereby contribute crucially to real-world social activity. Previous functional magnetic resonance imaging studies have shown patients with schizophrenia had different DLPFC activity pattern in response to cognitive load changes compared to healthy controls; however, the spatial relationship between the caudal and rostral prefrontal activation has not been evaluated under less-constrained conditions. Method Twenty-six patients with schizophrenia and 26 age-, sex-, and premorbid-intelligence-matched healthy controls participated in this study. Hemodynamic changes during n-back working memory tasks with different cognitive loads were measured using multi-channel near-infrared spectroscopy (NIRS). Results Healthy controls showed significant task-related activity in the bilateral VLPFC and significant task-related decreased activity in the DLPFC, with greater signal changes when the task required more cognitive load. In contrast, patients with schizophrenia showed activation in the more rostral regions, including bilateral DLPFC and FpC. Neither decreased activity nor greater activation in proportion to elevated cognitive load occurred. Conclusions This multi-channel NIRS study demonstrated that activation intensity did not increase in patients with schizophrenia associated with cognitive load changes, suggesting hypo-frontality as cognitive impairment in schizophrenia. On the other hand, patients had broader prefrontal activity in areas such as the bilateral DLPFC and FpC regions, thus suggesting a hyper-frontality compensatory response.