Measuring Cortical Activity Duringauditory Processing With Functionalnear-Infrared Spectroscopy

Figure 1. Hemodynamic response to auditory stimulation in temporal cortex. The blue line illustrates the increase of HbO2 and the red line the decrease HbR in response to the presentation of a speech stimulus (grey patch, 20 s). The sources and detectors were positioned over the left temporal hemisphere. Image adapted from Van de Rijt et al., 2016 (27).

Figure 2. Positioning of the optodes. A) Layout of optical sources (open circles) and photodetectors (filled circles) on the left hemisphere; B) schematic top view of probe layout. The estimated T7 and T8 positions of a 10/20 system are also indicated, as these are the supposed superficial centers of the deep and shallow channels (red filled circles). Red dotted lines denote the average path from source to detector, estimated to be part of an ellipsoid with a penetration depth of approximately 2–3 cm. Image adapted from Van de Rijt et al., 2016 (27).

Figure 3. Reference channel subtraction. The red lines depict pre–reference-channel subtraction and the blue lines depict post–reference-channel subtraction. Grey patches indicate auditory stimulus presentation. Stimulus presentation was 20 s. A) Averaged normalized HbO2 data for 12 auditory stimuli of a normal-hearing subject (NH1); B) the same for a normal-hearing cohort (n = 33). Image adapted from Van de Rijt et al., 2016 (27).