A Functional Near-Infrared Spectroscopy Study of Auditory Working Memory Load

Brain correlates of cognitive performance have received considerable attention in the area of augmented cognition. Studies focused on the correlation between brain activations and cognitive load have laid their focus on connections integrated by frontal region. Most of the studies have manipulated visual or verbal cognitive load, though the effect of auditory memory load in cognitive performance is still unknown. In this study, functional near-infrared spectroscopy (fNIRS) of twelve subjects were measured when they were performing a paradigm of auditory working memory task. For the auditory n-back task, there are three experimental conditions, including two n-back task conditions of memorizing the stimuli with different memory load, and a condition of passive listening to the stimuli. The stimuli are sound combinations of major, minor, and dissonant chords. Hemodynamic responses from frontal brain regions were recorded using a wireless fNIRS device. Brain activations from ventrolateral and orbital prefrontal cortex are measured with signals filtered and baseline wandering removed. The fNIRS signals are then standardized with statistical test and group analysis carried out. The results revealed that there are significantly stronger hemodynamic responses in bilateral ventrolateral prefrontal cortex when subjects were attending to the auditory working memory task with high load. This study demonstrated the possibility of incorporating fNIRS as an index to evaluate cognitive performance regarding its benefit on the flexibility for portable applications than other neuroimaging techniques. The performance in cognitive function could therefore be quantitatively measured with the proposed method.