Functional Near-Infrared Spectroscopy-Based Evidence of the Cerebral Oxygenation and Network Characteristics of Upper Limb Fatigue

Figure 1. Graph of 51 measurement channels detected by fNIRS. The corresponding area of each channel is marked by a different color. The prefrontal lobe is divided into the frontopolar area, the orbitofrontal area, the dorsolateral prefrontal lobe, and the ventrolateral prefrontal lobe. The motor area includes the pre-motor cortex, supplementary motor cortex, and the primary motor cortex. Finally, there are the primary somatosensory cortex and the somatosensory association cortex.

Figure 2. Functional connection strength matrix, which represents the correlation between channels. (A) represents the functional connectivity strength prior to fatigue, while (B) depicts the strength post-fatigue. Within the matrix, edges symbolize the channels, and nodes indicate the correlation amongst various channels. The color bar on the right signifies the Z-values of functional connectivity strength, with larger values denoting greater connection strength.

Figure 3. The functional connectivity visual map. The changes in the strength of functional connections between channels before and after fatigue. The connecting lines represent the differences in functional connectivity strength pre- and post-fatigue. The color bar indicates the T-values of the difference in functional connectivity strength between the two states. A redder hue on the line signifies a larger difference in functional connectivity post-fatigue compared to pre-fatigue, while a bluer hue indicates a smaller difference. (A) presents all channels with significant differences, while (B) highlights channels with pronounced differences between the left and right hemispheres.

Figure 4. HR and RPE at each level of exercise.