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Hemodynamic Changes in the Prefrontal Cortex during Digit Span Task: A Near-Infrared Spectroscopy Study

Background/Aims: In this study, we examined changes in the concentrations of oxygenated and deoxygenated hemoglobin (oxy- and deoxy-Hb, respectively) in the prefrontal cortex (PFC) during the digit span task by using near-infrared spectroscopy (NIRS). Methods: The digit span task consists of the digit span forward and backward tasks. The tasks were performed by 22 healthy undergraduate students who participated in this study. Differences in the mean concentrations of oxy-Hb and deoxy-Hb between the baseline and task intervals were evaluated. Results: In digit span backward, oxy-Hb was significantly higher during the task interval than during the baseline. Further, deoxy-Hb was significantly lower during the task interval than during the baseline in both digit span forward and digit span backward. Digit span forward performance was significantly higher for the right-PFC-dominant group than for the left-PFC-dominant group. Conclusion: These results suggest that the digit span backward task is more demanding and requires greater activation of the prefrontal cortex than the digit span forward task. Our NIRS findings suggest that the digit span backward task involves executive functioning.