Intrinsic fluctuations can reduce trail-to-trail variability in fNIRS signal

Functional near-infrared spectroscopy (fNIRS) is emerging brain imaging technique. The trail-to-trail variability in fNIRS signal may reduce the signal analysis performance. However, the source of the trail-to-trail variability remains unknown. Previous functional magnetic resonance image (fMRI) study suggested that the trail-to-trail variability can be attributed to intrinsic low frequency fluctuation in fMRI signal. The intrinsic low frequency fluctuation is known to reflect temporal correlations in signal changes between widely separated brain regions during both the resting state and active state. Meanwhile, recent fNIRS studies confirm that the intrinsic fluctuation can be robustly detected by functional near infrared spectroscopy (fNIRS). In this paper, we investigate the relationship between trail-to-trail variability and the intrinsic hemodynamic fluctuations in the fNIRS signal. The result suggests that the intrinsic frequency significantly contribute to the trail-to-trail variability in fNIRS signal.