Mattie Tops

Mental fatigue: Costs and benefits

A framework for mental fatigue is proposed, that involves an integrated evaluation of both expected rewards and energetical costs associated with continued performance. Adequate evaluation of predicted rewards and potential risks of actions is essential for successful adaptive behaviour. However, while both rewards and punishments can motivate to engage in activities, both types of motivated behaviour are associated with energetical costs. We will review findings that suggest that the nucleus accumbens, orbitofrontal cortex, amygdala, insula and anterior cingulate cortex are involved evaluating both the potential rewards associated with performing a task, as well as assessing the energetical demands involved in task performance. Behaviour will only proceed if this evaluation turns out favourably towards spending (additional) energy. We propose that this evaluation of predicted rewards and energetical costs is central to the phenomenon of mental fatigue: people will no longer be motivated to engage in task performance when energetical costs are perceived to outweigh predicted rewards.

Oxytocin Modulates Amygdala, Insula, and Inferior Frontal Gyrus Responses to Infant Crying: A Randomized Controlled Trial

BACKGROUNDnOxytocin facilitates parental caregiving and mother-infant bonding and might be involved in responses to infant crying. Infant crying provides information about the physical status and mood of the infant and elicits parental proximity and caregiving. Oxytocin might modulate the activation of brain structures involved in the perception of cry sounds-specifically the insula, the amygdala, and the thalamocingulate circuit-and thereby affect responsiveness to infant crying.nnnMETHODnIn a randomized controlled trial we investigated the influence of intranasally administered oxytocin on neural responses to infant crying with functional magnetic resonance imaging. Blood oxygenation level-dependent responses to infant crying were measured in 21 women who were administered oxytocin and 21 women who were administered a placebo.nnnRESULTSnInduced oxytocin levels reduced, experimentally, activation in the amygdala and increased activation in the insula and inferior frontal gyrus pars triangularis.nnnCONCLUSIONSnOur findings suggest that oxytocin promotes responsiveness to infant crying by reducing activation in the neural circuitry for anxiety and aversion and increasing activation in regions involved in empathy.

Caffeine, fatigue, and cognition

Effects of caffeine and fatigue are discussed with special attention to adenosine-dopamine interactions. Effects of caffeine on human cognition are diverse. Behavioural measurements indicate a general improvement in the efficiency of information processing after caffeine, while the EEG data support the general belief that caffeine acts as a stimulant. Studies using ERP measures indicate that caffeine has an effect on attention, which is independent of specific stimulus characteristics. Behavioural effects on response related processes turned out to be mainly related to more peripheral motor processes. Recent insights in adenosine and dopamine physiology and functionality and their relationships with fatigue point to a possible modulation by caffeine of mechanisms involved in the regulation of behavioural energy expenditure.

Error-related ERP components and individual differences in punishment and reward sensitivity

Although the focus of the discussion regarding the significance of the error related negatively (ERN/Ne) has been on the cognitive factors reflected in this component, there is now a growing body of research that describes influences of motivation, affective style and other factors of personality on ERN/Ne amplitude. The present study was conducted to further evaluate the relationship between affective style, error related ERP components and their neural basis. Therefore, we had our subjects fill out the Behavioral Activation System/Behavioral Inhibition System (BIS/BAS) scales, which are based on Grays (1987, 1989) biopsychological theory of personality. We found that subjects scoring high on the BIS scale displayed larger ERN/Ne amplitudes, while subjects scoring high on the BAS scale displayed larger error positivity (Pe) amplitudes. No correlations were found between BIS and Pe amplitude or between BAS and ERN/Ne amplitude. Results are discussed in terms of individual differences in reward and punishment sensitivity that are reflected in error related ERP components.

Task engagement and the relationships between the error-related negativity, agreeableness, behavioral shame proneness and cortisol

Previous results suggest that both cortisol mobilization and the error-related negativity (ERN/Ne) reflect goal engagement, i.e. the mobilization and allocation of attentional and physiological resources. Personality measures of negative affectivity have been associated both to high cortisol levels and large ERN/Ne amplitudes. However, measures of positive social adaptation and agreeableness have also been related to high cortisol levels and large ERN/Ne amplitudes. We hypothesized that, as long as they relate to concerns over social evaluation and mistakes, both personality measures reflecting positive affectivity (e.g. agreeableness) and those reflecting negative affectivity (e.g. behavioral shame proneness) would be associated with an increased likelihood of high task engagement, and hence to increased cortisol mobilization and ERN/Ne amplitudes. We had female subjects perform a flanker task while EEG was recorded. Additionally, the subjects filled out questionnaires measuring mood and personality, and salivary cortisol immediately before and after task performance was measured. The overall pattern of relationships between our measures supports the hypothesis that cortisol mobilization and ERN/Ne amplitude reflect task engagement, and both relate positively to each other and to the personality traits agreeableness and behavioral shame proneness. We discuss the potential importance of engagement-disengagement and of concerns over social evaluation for research on psychopathology, stress and the ERN/Ne.

Acute cortisol effects on immediate free recall and recognition of nouns depend on stimulus valence

The present study investigated the acute effects of cortisol administration in normal healthy male volunteers on immediate free recall and recognition of pleasant, unpleasant, and neutral nouns using a between-subjects double-blind design. Two hours after cortisol (10 mg) or placebo administration, impaired recall and recognition of neutral and pleasant words was found in the treatment group, whereas recall and recognition of unpleasant words was similar in both groups. The interaction between treatment and stimulus valence was not mediated by semantic cohesion, nor does it seem to have been mediated by stimulus arousal. Cortisol did not change mood. The changes with cortisol in recall and recognition of pleasant and unpleasant words parallel those found in depression, a condition that is often accompanied by elevated basal cortisol levels.

Serotonin: modulator of a drive to withdraw.

Serotonin is a fundamental neuromodulator in both vertebrate and invertebrate nervous systems, with a suspected role in many human mental disorders. Yet, because of the complexity of serotonergic function, researchers have been unable to agree on a general theory. One function suggested for serotonin systems is the avoidance of threat. We propose and review evidence for an alternative hypothesis, that a phylogenetically primitive of function of serotonin is to oppose the activating neuromodulators (particularly noradrenalin and dopamine). The functional effect of this opposition can be seen as applying a drive to withdraw from dangerous, aversive or high stimulation environments. Proposing that serotonin is involved in a drive to withdraw and seek contentment, instead of a drive to avoid, may be compatible with several lines of evidence on serotonin function and may facilitate a better understanding of serotonergic neuromodulation in human psychopathology.

Rejection sensitivity relates to hypocortisolism and depressed mood state in young women

Rejection sensitivity and the associated fear of negative social evaluation (FNSE) trait are characteristics of hypocortisolemic syndromes such as atypical depression. However, a meta-analysis showed that acute FNSE evokes strong cortisol responses in humans. This is consistent with suggestions that hypocortisolism reflects a protective adaptation to a history of high cortisol responses. This leads us to hypothesize that measures of trait FNSE relate to hypocortisolism. Moreover, because FNSE relates positively to depressed mood state, but negatively to cortisol, we expect that the positive relationship between depressed mood state and cortisol will show up most clearly when controlling for the confounding effect of FNSE on this relationship. In the present study we measured salivary cortisol awakening response and psychological variables in 194 community women aged 18-30 years. The results confirmed our hypotheses. We propose that dispositional FNSE is associated with a history of frequent high cortisol responses, leading to long-term protective inhibition of further cortisol and energy mobilization. The present results have special relevance for mental health problems that have high prevalence among young women.

Absorbed in the task: Personality measures predict engagement during task performance as tracked by error negativity and asymmetrical frontal activity

We hypothesized that interactions between traits and context predict task engagement, as measured by the amplitude of the error-related negativity (ERN), performance, and relative frontal activity asymmetry (RFA). In Study 1, we found that drive for reward, absorption, and constraint independently predicted self-reported persistence. We hypothesized that, during a prolonged monotonous task, absorption would predict initial ERN amplitudes, constraint would delay declines in ERN amplitudes and deterioration of performance, and drive for reward would predict left RFA when a reward could be obtained. Study 2, employing EEG recordings, confirmed our predictions. The results showed that most traits that have in previous research been related to ERN amplitudes have a relationship with the motivational trait persistence in common. In addition, trait—context combinations that are likely associated with increased engagement predict larger ERN amplitudes and RFA. Together, these results support the hypothesis that engagement may be a common underlying factor predicting ERN amplitude.

Acute cortisol administration modulates EEG alpha asymmetry in volunteers: relevance to depression

The acute effects of cortisol (35mg) administration in 11 healthy male volunteers on resting frontal EEG asymmetry measured in the alpha band were investigated, using a within-subjects double-blind design. Results were indicative of a relative increase of right frontal activity with cortisol. This pattern of activity is similar to the deviant pattern that has been reported in patients suffering from depression, a condition often accompanied by elevated plasma cortisol levels. The significant effect on frontal asymmetry provides convergent support for our hypothesis, based upon previous results, that sustained (>30 minutes after stress termination) relative high levels of cortisol inhibit approach motivation.