Bipolar mood tendency and frontal activation using a multichannel near infrared spectroscopy

This study aims to examine the association of frontal functioning with subclinical bipolar spectrum by a newly developed convenient method. We investigated subclinical bipolar tendency and frontal lobe activation during word productions using multi-channel near infrared spectroscopy. Participants: 44 healthy university students (mean ages 20.5 years old, and 29 female) gave their written informed consent, and we strictly protected privacy and anonymity was carefully preserved. A 13-items self-report questionnaire (Mood Disorders Questionnaire; MDQ) and a 16-channel near-infrared spectroscopy were used to compare frontal activations between two samples divided by median (4 points) of the total MDQ scores and to analyze correlations between relative changes of cerebral blood volume and bipolarity levels. There was no case suspected as bipolar disorders by MDQ screening (mean 3.4, max 10). Significant differences in lower activations were noted in the right and left pre-frontal cortex (PFC) with higher bipolarity scores using the specific software to analyze the NIRS waveform (P<0.05). Total MDQ were correlated significantly with frontal activation negatively in many channels; therefore, we conducted multiple linear regression to select significant frontal activations using the MDQ as a dependent variable. Stepwise method revealed that activation in left lateral PFC was negatively associated to bipolar tendency, and this regression model was significant (R2=0.10, F=4.5, P=0.04). Differences in frontal functioning suggest that subclinical bipolar tendencies might be related to left lateral PFC activations. It should be confirmed whether the identical pattern can be identified for clinical subjects with bipolar disorders.