Neural Signatures of Handgrip Fatigue in Type 1 Diabetic Men and Women

Figures

• 

  FIGURE 1. Experiment setup (top) and experiment protocol (bottom) for the handgrip fatigue experiment. Early phase is the first one-third of the 30% MVC period, Middle phase is middle one-third and Late phase is last-one third of the 30% MVC period. Force data and fNIRS data were recorded throughout the experiment. Participant had real-time feedback of their handgrip performance through a display monitor.

• 

  FIGURE 2. fNIRS probe placement based on the international 10–20 system, with 8-sources (shaded), 8-detectors (unshaded), and 20 channels (solid black line) between them. Channel numbered 1–20 were divided into five regions of interest (Cao et al., 2015).

• 

  FIGURE 3. Data analysis steps performed on ρHbO signals from the period of fatigue test to the calculation of functional connectivity.

• 

  FIGURE 4. Brain activation for all participants in the (A) early, (B) middle, and (C) late phases, and the difference in activation between each phase represented as (D) middle – early, (E) late – middle, (F) late – early. Significant phase effects were found for channels 2, 4, 6, 8, 12, 14, and 18 in the ipsilateral hemisphere and in channels 5, 7, 9, and 11 for the contralateral hemisphere for (D) middle – early and (F) late – early. For (E) late – middle, the only significant differences were found in channels 14 and 11.

• 

  FIGURE 5. Brain activation for Healthy participants, T1D participants, and the difference between them (T1D – Healthy) for Early, Middle and Late phases. T1D participants showed significantly lower neural activation than the healthy controls in the early phase (p = 0.035) and marginally lower activation in the middle phase (p = 0.0626). A marginal main effect of condition was observed in channel 3, highlighted in the figure above, of the SMA (p = 0.077).

• 

  FIGURE 6. Functional connectivity maps of Healthy (left) and T1D (right) males and females during the early phase of hand-grip motor task. The color of each edge depicts the Pearson correlation between ROIs. Nodes connected with solid lines show intra-hemispheric connectivity and nodes connected with dotted lines show inter-hemispheric connectivity. Healthy females exhibited higher intra-hemispheric functional connectivity between the SMA and LM1 and between RPM and RM1 in the early phase. There was no significant difference between the connectivity of healthy and T1D males.