Intrasubject reproducibility of prefrontal cortex activities during a verbal fluency task over two repeated sessions using multi-channel near-infrared spectroscopy.

AIM: To determine whether intrasubject reproducibility could be observed in the frontal cortex and to assess the mental-health status of subjects in each session.
METHODS: We measured changes in oxygenated hemoglobin concentration ([oxy-Hb]) during a letter version of the verbal fluency task using near-infrared spectroscopy imaging in twenty healthy adults over two sessions approximately two months apart. Additionally, the mental-health status of the subjects in each session was evaluated according to the State-Trait Anxiety Inventory, the Zung Self-rating Depression Scale, the Profile of Mood States, and the revised edition of the Neuroticism-Extroversion-Openness Personality Inventory. The association between those scores and [oxy-Hb] changes during the verbal fluency task in each session was investigated.
RESULTS: Performance on the verbal fluency task was about equal across the two sessions, and frontal activation during the task was observed globally in approximately the same region. In the test-retest reliability, acceptable values were shown in both the Intraclass Correlation Coefficients of the mean [oxy-Hb] changes and the correlation coefficients of the whole waveforms for each subject in the two sessions. Mental-health status as measured by several questionnaires was within the healthy range, and no correlation with the frontal activation was seen, except in several channels.
CONCLUSION: The current results suggest that the measurement experience exerted very little influence, except for in a very small region. In addition, the intrasubject reproducibility of frontal activation measured by multi-channel near-infrared spectroscopy was well demonstrated in mentally healthy subjects at intervals of two months.