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Dissociation between mental fatigue and motivational state during prolonged mental activity.

Gergelyfi M, Jacob B, Olivier E, Zénon A - Front Behav Neurosci (2015)

Bottom Line: An influential hypothesis states that MF does not arise from a disruption of overused neural processes but, rather, is caused by a progressive decrease in motivation-related task engagement.Finally, alterations of the motivational state through monetary incentives failed to compensate the effects of MF.These findings indicate that MF in healthy subjects is not caused by an alteration of task engagement but is likely to be the consequence of a decrease in the efficiency, or availability, of cognitive resources.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neuroscience, Université Catholique de Louvain Brussels, Belgium.

ABSTRACT
Mental fatigue (MF) is commonly observed following prolonged cognitive activity and can have major repercussions on the daily life of patients as well as healthy individuals. Despite its important impact, the cognitive processes involved in MF remain largely unknown. An influential hypothesis states that MF does not arise from a disruption of overused neural processes but, rather, is caused by a progressive decrease in motivation-related task engagement. Here, to test this hypothesis, we measured various neural, autonomic, psychometric and behavioral signatures of MF and motivation (EEG, ECG, pupil size, eye blinks, Skin conductance responses (SCRs), questionnaires and performance in a working memory (WM) task) in healthy volunteers, while MF was induced by Sudoku tasks performed for 120 min. Moreover extrinsic motivation was manipulated by using different levels of monetary reward. We found that, during the course of the experiment, the participants' subjective feeling of fatigue increased and their performance worsened while their blink rate and heart rate variability (HRV) increased. Conversely, reward-induced EEG, pupillometric and skin conductance signal changes, regarded as indicators of task engagement, remained constant during the experiment, and failed to correlate with the indices of MF. In addition, MF did not affect a simple reaction time task, despite the strong influence of extrinsic motivation on this task. Finally, alterations of the motivational state through monetary incentives failed to compensate the effects of MF. These findings indicate that MF in healthy subjects is not caused by an alteration of task engagement but is likely to be the consequence of a decrease in the efficiency, or availability, of cognitive resources.

No MeSH data available.


Related in: MedlinePlus

Markers of motivation. Error bars represent standard errors of the mean. (A) Mean RT (ms) as a function of the reward condition in the SiRT task. (B) Mean accuracy as a function of the reward condition in the WM task. (C) Mean decision time (s) as a function of reward condition in the WM task. (D) Coefficients of the reward effect on the high gamma band (60–140 Hz) activity in the WM task. Higher incentives led to higher activation on POz, Oz, and O1 electrodes (marked by asterisks, p < 0.05). (E) Mean pupil response as a function of reward condition in the WM task. (F) Mean SCR as a function of reward condition in the WM task.
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Figure 4: Markers of motivation. Error bars represent standard errors of the mean. (A) Mean RT (ms) as a function of the reward condition in the SiRT task. (B) Mean accuracy as a function of the reward condition in the WM task. (C) Mean decision time (s) as a function of reward condition in the WM task. (D) Coefficients of the reward effect on the high gamma band (60–140 Hz) activity in the WM task. Higher incentives led to higher activation on POz, Oz, and O1 electrodes (marked by asterisks, p < 0.05). (E) Mean pupil response as a function of reward condition in the WM task. (F) Mean SCR as a function of reward condition in the WM task.

Mentions: A significant main effect of REWARD on the log-transformed RT gathered during the SiRT task showed that the participants responded faster for higher incentives (two-way RM ANOVA: F(2,34) = 14.34, p < 0.0001, see Figure 4A). For this reward effect, post hoc tests with Bonferroni correction revealed that the subjects were significantly faster in the highest-reward condition (50 points) when compared to the medium (10 points) and to the lowest-reward conditions (1 point). Subjects were also significantly faster in the medium-reward condition than in the lowest-reward condition (all p < 0.005).


Dissociation between mental fatigue and motivational state during prolonged mental activity.

Gergelyfi M, Jacob B, Olivier E, Zénon A - Front Behav Neurosci (2015)

Markers of motivation. Error bars represent standard errors of the mean. (A) Mean RT (ms) as a function of the reward condition in the SiRT task. (B) Mean accuracy as a function of the reward condition in the WM task. (C) Mean decision time (s) as a function of reward condition in the WM task. (D) Coefficients of the reward effect on the high gamma band (60–140 Hz) activity in the WM task. Higher incentives led to higher activation on POz, Oz, and O1 electrodes (marked by asterisks, p < 0.05). (E) Mean pupil response as a function of reward condition in the WM task. (F) Mean SCR as a function of reward condition in the WM task.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4499755&req=5

Figure 4: Markers of motivation. Error bars represent standard errors of the mean. (A) Mean RT (ms) as a function of the reward condition in the SiRT task. (B) Mean accuracy as a function of the reward condition in the WM task. (C) Mean decision time (s) as a function of reward condition in the WM task. (D) Coefficients of the reward effect on the high gamma band (60–140 Hz) activity in the WM task. Higher incentives led to higher activation on POz, Oz, and O1 electrodes (marked by asterisks, p < 0.05). (E) Mean pupil response as a function of reward condition in the WM task. (F) Mean SCR as a function of reward condition in the WM task.
Mentions: A significant main effect of REWARD on the log-transformed RT gathered during the SiRT task showed that the participants responded faster for higher incentives (two-way RM ANOVA: F(2,34) = 14.34, p < 0.0001, see Figure 4A). For this reward effect, post hoc tests with Bonferroni correction revealed that the subjects were significantly faster in the highest-reward condition (50 points) when compared to the medium (10 points) and to the lowest-reward conditions (1 point). Subjects were also significantly faster in the medium-reward condition than in the lowest-reward condition (all p < 0.005).

Bottom Line: An influential hypothesis states that MF does not arise from a disruption of overused neural processes but, rather, is caused by a progressive decrease in motivation-related task engagement.Finally, alterations of the motivational state through monetary incentives failed to compensate the effects of MF.These findings indicate that MF in healthy subjects is not caused by an alteration of task engagement but is likely to be the consequence of a decrease in the efficiency, or availability, of cognitive resources.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neuroscience, Université Catholique de Louvain Brussels, Belgium.

ABSTRACT
Mental fatigue (MF) is commonly observed following prolonged cognitive activity and can have major repercussions on the daily life of patients as well as healthy individuals. Despite its important impact, the cognitive processes involved in MF remain largely unknown. An influential hypothesis states that MF does not arise from a disruption of overused neural processes but, rather, is caused by a progressive decrease in motivation-related task engagement. Here, to test this hypothesis, we measured various neural, autonomic, psychometric and behavioral signatures of MF and motivation (EEG, ECG, pupil size, eye blinks, Skin conductance responses (SCRs), questionnaires and performance in a working memory (WM) task) in healthy volunteers, while MF was induced by Sudoku tasks performed for 120 min. Moreover extrinsic motivation was manipulated by using different levels of monetary reward. We found that, during the course of the experiment, the participants' subjective feeling of fatigue increased and their performance worsened while their blink rate and heart rate variability (HRV) increased. Conversely, reward-induced EEG, pupillometric and skin conductance signal changes, regarded as indicators of task engagement, remained constant during the experiment, and failed to correlate with the indices of MF. In addition, MF did not affect a simple reaction time task, despite the strong influence of extrinsic motivation on this task. Finally, alterations of the motivational state through monetary incentives failed to compensate the effects of MF. These findings indicate that MF in healthy subjects is not caused by an alteration of task engagement but is likely to be the consequence of a decrease in the efficiency, or availability, of cognitive resources.

No MeSH data available.


Related in: MedlinePlus