A preliminary analysis of effect of onset age on prefrontal activation during working memory task in patients with bipolar disorder

Abstract

Objectives To assess the effect of onset age on prefrontal activation during a working memory task in patients with bipolar disorder using a 52 multichannel functional near-infrared spectroscopy (NIRS). Methods Sixteen patients with early-onset (EO, onset age≤24 years old) and 14 with non-early-onset (NEO, onset age>24 years old) bipolar Ⅰ disorder were consecutively recruited from wards of Peking University Sixth hospital between October 2013 and May 2014, also including 16 healthy controls (HC) from community. Three groups of participants were diagnosed using MINI, then accepted a cross-sectional comparison of the relative changes in oxygenated hemoglobin (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb) during 1-back working memory task. Results Results from single factor analyses suggested that EO group showed a significantly reduced activation in deoxy-Hb in the right inferior prefrontal gyrus region than HC (CH34: -0.091 vs. 0.009, Z=-2.542, P=0.033), while a significant increase of deoxy-Hb changes in the right dorsolateral prefrontal cortex (CH13: 0.145 vs. -0.025, Z=2.412, P=0.048) and right frontopolar cortex (CH15: 0.053 vs. -0.032, Z=2.890, P=0.012) regions than NEO group. There were no significant differences in the oxy-Hb changes among three groups in any channel during task. After being adjusted by multiple factor analyses, no significant difference in prefrontal activation among three groups was observed in any channel. Conclusions Similar pattern of prefrontal activity during 1-back working memory task exits between EO and NEO group, indicating that onset age may have no effect on NIRS prefrontal activation under low memory load in patients with bipolar disorder, which provides a reference for further NIRS studies in bipolar disorder. Key words: Bipolar disorder; Spectroscopy, near-infrared; Prefrontal cortex; Onset age