Figure and Table Captions
Figure 1: Time course of the sequential task protocol. Mental tasks: Experimental group = Modified Incongruent Stroop task; Control group = Documentary viewing task. MVC: Maximal voluntary contraction. Handgrip task: Time-to-exhaustion task. HG1: Measurement of MVC before the time-to-exhaustion task. HG2: Measurement of MVC after the time-to-exhaustion task. TTE-1: Time-to-exhaustion handgrip task performed before the mental task. TTE-2: Time-to-exhaustion performed after the mental task.
Figure 2: Overview of the experimental setup. The participants equipped with a 64-channel Biosemi EEG headset while performing the handgrip task. The maximized version of the force gauge is displayed on the screen of the computer. The green arc defines the target zone (i.e., a range between 12% and 14% of MVC), which was visible throughout the duration of the task. The participants had to maintain the gauge indicator in this green area until exhaustion. The perimeter of the gauge represents 100% of the participant’s maximal voluntary contraction (MVC).
Figure 3: Box and whisker plots illustrating the comparison of the decrease in time-to-exhaustion (time-to-exhaustion delta) between the experimental and control groups. The participants who performed the Stroop task as the depleting task (experimental group) showed a larger decrease in performance after this task than the decrease in performance observed in the group of participants who performed the documentary viewing task as the control task (control group). The black dot just above “Experimental” indicates the outlier data of participant 26.
Figure 4: Perception of effort (Panel A) and pain (Panel B) during the two time-to-exhaustion handgrip tasks as a function of individual isotime (0%, 33%, 66%, 100%). A significant, linear increase in the effort and pain level as a function of individual isotime was observed.
Figure 5: Mean reaction time as a function of time on task (T1-T4) and type of trials (reading vs. naming ink color).
Figure 6: Power spectral density analysis during the Mental tasks. The left topographic color plot shows the mean theta power spectral density for all 16 subjects in the experimental group during the 30 min of the Stroop task. The central topographic color plot shows the mean theta power spectral density for all 16 subjects in the control group during the 30 min of the documentary viewing task (Video). The right topographic color plot shows the p values found when using the unpaired t test with FDR multiple comparison correction to compare the theta power differences between the two groups. The color bar scale located in the middle of the figure shows the log power 10 (µV²). The greater that the color tends toward dark red, the higher that the density of the theta waves is. The second color bar scale on the right shows the p value. The greater that the color tends toward dark red, the greater that the p value tends toward 0.001.
Figure 7: Task-related theta power density as a function of time on task (T1-T4) during the modified Stroop task in electrode FC1.
Figure 8: Scalp maps and dipole source locations of the 6 independent component clusters of the 16 participants in the experimental group, which performed the modified Stroop task. The first image on the top represents the scalp maps of each cluster, and the second image on the bottom shows the 3D dipole source locations and their projections onto the MNI brain template. For each set of three figures illustrating a cluster, there are top, coronal and sagittal views from left to right. The blue dots represent each of the bilaterally symmetric dual dipoles originating from the EEG signal sources, and the red dot is the mean of all these dipoles.
Figure 9: Heart rate variability indices (Panel A: standard deviation of NN intervals in ms – SDNN; Panel B: log power of the low-frequency band in log(ms²) – LF power) as a function of time on task and group (experimental and control).
Table 1: Participant characteristics. The top value of each cell of the two “group” columns indicates the mean, and the bottom value in brackets of each cell of the same columns corresponds to the standard deviation.
Table 1