Deep and surface hemodynamic signal from functional time resolved transcranial near infrared spectroscopy compared to skin flowmotion.

The potential disturbance in the prefrontal cortex hemodynamic signal measured by functional near infrared spectroscopy (NIRS), due to forehead skin flowmotion, detected by laser Doppler flowmetry, was investigated by a standard protocol of hemodynamic challenge by Valsalva maneuver, aimed at assessing and disentangling local regulatory responses in skin vasomotion and in cerebral perfusion in presence of a strong systemic drive, and to quantify the common information in the two signals. The deep cortical NIRS signal did not appear to be affected by surface vasomotor activity, and autoregulation dynamics were dominant with respect to autonomic control of circulation.