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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

Psychometric, behavioral and physiological evidence for MF. Error bars represent standard errors of the mean. (A) Mean score on the general fatigue subscale of the Multidimensional Fatigue Inventory (MFI) before and after the experiment. Following the experiment, smaller average MFI indicates a higher level of subjective fatigue. (B–E) Block-related behavioral and physiological changes indicative of MF in the WM task. (B) Mean accuracy in the WM task across block repetition. (C) Mean values for IBI in the WM task across block repetition. (D) Short- and long-term HRV in the WM task as a function of the block order. (E) Average blink rate in the WM task as a function of block order.
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Figure 3: Psychometric, behavioral and physiological evidence for MF. Error bars represent standard errors of the mean. (A) Mean score on the general fatigue subscale of the Multidimensional Fatigue Inventory (MFI) before and after the experiment. Following the experiment, smaller average MFI indicates a higher level of subjective fatigue. (B–E) Block-related behavioral and physiological changes indicative of MF in the WM task. (B) Mean accuracy in the WM task across block repetition. (C) Mean values for IBI in the WM task across block repetition. (D) Short- and long-term HRV in the WM task as a function of the block order. (E) Average blink rate in the WM task as a function of block order.

Mentions: The Sudoku task was performed with high accuracy (95.84% of correct responses) with a median RT ranging between 3.16 and 8.53 s per Sudoku cell; this task was successful in inducing MF, as shown in the following psychometric, behavioral and physiological analyses. Scores on the general fatigue subscale of the MFI showed that the subjects were significantly more fatigued after the experiment than before (paired samples t-tests: t(17) = 5.56, p < 0.0001, see Figure 3A). In the WM task, two-way RM ANOVA on accuracy revealed a significant main effect of BLOCK (F(4,68) = 2.52, p < 0.05, see Figure 3B). An ANCOVA including the BLOCK condition as a continuous variable was performed to investigate the nature of this effect. The best result was obtained when using the square of the block number (quadratic BLOCK effect: F(1,485) = 4.15, p = 0.0436, linear BLOCK effect: F(1,485) = 4.01, p = 0.047), showing that the subjects’ performance, following an initial improvement, got gradually worse over time (see Figure 3B).


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

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

Psychometric, behavioral and physiological evidence for MF. Error bars represent standard errors of the mean. (A) Mean score on the general fatigue subscale of the Multidimensional Fatigue Inventory (MFI) before and after the experiment. Following the experiment, smaller average MFI indicates a higher level of subjective fatigue. (B–E) Block-related behavioral and physiological changes indicative of MF in the WM task. (B) Mean accuracy in the WM task across block repetition. (C) Mean values for IBI in the WM task across block repetition. (D) Short- and long-term HRV in the WM task as a function of the block order. (E) Average blink rate in the WM task as a function of block order.
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Related In: Results  -  Collection

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Figure 3: Psychometric, behavioral and physiological evidence for MF. Error bars represent standard errors of the mean. (A) Mean score on the general fatigue subscale of the Multidimensional Fatigue Inventory (MFI) before and after the experiment. Following the experiment, smaller average MFI indicates a higher level of subjective fatigue. (B–E) Block-related behavioral and physiological changes indicative of MF in the WM task. (B) Mean accuracy in the WM task across block repetition. (C) Mean values for IBI in the WM task across block repetition. (D) Short- and long-term HRV in the WM task as a function of the block order. (E) Average blink rate in the WM task as a function of block order.
Mentions: The Sudoku task was performed with high accuracy (95.84% of correct responses) with a median RT ranging between 3.16 and 8.53 s per Sudoku cell; this task was successful in inducing MF, as shown in the following psychometric, behavioral and physiological analyses. Scores on the general fatigue subscale of the MFI showed that the subjects were significantly more fatigued after the experiment than before (paired samples t-tests: t(17) = 5.56, p < 0.0001, see Figure 3A). In the WM task, two-way RM ANOVA on accuracy revealed a significant main effect of BLOCK (F(4,68) = 2.52, p < 0.05, see Figure 3B). An ANCOVA including the BLOCK condition as a continuous variable was performed to investigate the nature of this effect. The best result was obtained when using the square of the block number (quadratic BLOCK effect: F(1,485) = 4.15, p = 0.0436, linear BLOCK effect: F(1,485) = 4.01, p = 0.047), showing that the subjects’ performance, following an initial improvement, got gradually worse over time (see Figure 3B).

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