Investigating habits in humans with a symmetrical outcome-revaluation task.

The translation of the outcome-devaluation paradigm to study habit in humans has yielded interesting insights but proven to be challenging. We present a novel, outcome-revaluation task with a symmetrical design, in the sense that half of the available outcomes are always valuable and the other half not-valuable. In the present studies, during the instrumental learning phase, participants learned to respond (Go) to certain stimuli to collect valuable outcomes (and points) while refraining to respond (NoGo) to stimuli signaling not-valuable outcomes. Half of the stimuli were short-trained, while the other half were long-trained. Subsequently, in the test phase, the signaled outcomes were either value-congruent with training (still-valuable and still-not-valuable), or value-incongruent (devalued and upvalued). The change in outcome value on value-incongruent trials meant that participants had to flexibly adjust their behavior. At the end of the training phase, participants completed the self-report behavioral automaticity index - providing an automaticity score for each stimulus-response association. We conducted two experiments using this task, that both provided evidence for stimulus-driven habits as reflected in poorer performance on devalued and upvalued trials relative to still-not-valuable trials and still-valuable trials, respectively. While self-reported automaticity increased with longer training, behavioral flexibility was not affected. After extended training (Experiment 2), higher levels of self-reported automaticity when responding to stimuli signaling valuable outcomes were related to more 'slips of action' when the associated outcome was subsequently devalued. We conclude that the symmetrical outcome-revaluation task provides a promising paradigm for the experimental investigation of habits in humans.

Neural activity during the viewing of emotional pictures in veterans with pathological anger and aggression.

Anger and aggression are common mental health problems after military deployment. Anger and aggression have been associated with abnormalities in subcortical and cortical levels of the brain and their connectivity. Here, we tested brain activation during the processing of emotional stimuli in military veterans with and without anger and aggression problems. Thirty military veterans with anger and aggression problems and 29 veterans without a psychiatric diagnosis (all males) participated in this study. During an fMRI scan 32 negative, 32 positive and 32 neutral pictures from the International Affective Picture System were presented in intermixed order. The Aggression group showed heightened activity in brain areas including the supplementary motor area, the cingulum and the parietal cortex, in response to stimuli, regardless of category. Furthermore, the Aggression group showed stronger connectivity between the dorsal anterior cingulate cortex (dACC) and the amygdala during the viewing of negative stimuli, and weaker connectivity between dACC and medial prefrontal cortex during the viewing of positive stimuli. Veterans with anger and aggression problems showed enhanced brain response to all stimuli during the task, irrespective of valence and they rated the pictures more likely as negative. We take this to indicate enhanced preparation for action and attention to the presentation of stimuli that could prove to be threatening. Further, group differences in functional connectivity involving the dACC reveal abnormal processing of stimuli with negative and positive valence. In sum, the results point towards a bias towards an enhanced sensitivity to perceived or potential threat in aggression.

Reduced sleep duration mediates decreases in striatal D2/D3 receptor availability in cocaine abusers.

Neuroimaging studies have documented reduced striatal dopamine D2/D3 receptor (D2/D3R) availability in cocaine abusers, which has been associated with impaired prefrontal activity and vulnerability for relapse. However, the mechanism(s) underlying the decreases in D2/D3R remain poorly understood. Recent studies have shown that sleep deprivation is associated with a downregulation of striatal D2/D3R in healthy volunteers. As cocaine abusers have disrupted sleep patterns, here we investigated whether reduced sleep duration mediates the relationship between cocaine abuse and low striatal D2/D3R availability. We used positron emission tomography with [(11)C]raclopride to measure striatal D2/D3R availability in 24 active cocaine abusers and 21 matched healthy controls, and interviewed them about their daily sleep patterns. Compared with controls, cocaine abusers had shorter sleep duration, went to bed later and reported longer periods of sleep disturbances. In addition, cocaine abusers had reduced striatal D2/D3R availability. Sleep duration predicted striatal D2/D3R availability and statistically mediated the relationship between cocaine abuse and striatal D2/D3R availability. These findings suggest that impaired sleep patterns contribute to the low striatal D2/D3R availability in cocaine abusers. As sleep impairments are similarly observed in other types of substance abusers (for example, alcohol and methamphetamine), this mechanism may also underlie reductions in D2/D3R availability in these groups. The current findings have clinical implications suggesting that interventions to improve sleep patterns in cocaine abusers undergoing detoxification might be beneficial in improving their clinical outcomes.

[Functional MRI for schizophrenia: importance of the type of task being scanned]. / Functionele MRI bij schizofrenie: belang van aangepaste taak in de scanner.

BACKGROUND: Functional magnetic resonance imaging (fMRI) is an important technique for detecting neural network problems in patients with schizophrenia. Very often, however, the professionals involved are insufficiently aware of the fact that when fMRI scans are used for patients with schizophrenia, it is the type of task that patients are performing or failing to perform which is of vital importance for the correct interpretation of the results. AIM: To demonstrate that in scans of patients with schizophrenia the choice of task can influence neuroimaging results, particularly when the neural problems under study are performance-related. METHOD: We begin by presenting a brief history of functional neuroimaging techniques. This provides a context for the study of the potential role of fMRI in detecting dysfunctional brain networks in schizophrenia. In this way we demonstrate more clearly why the rapidly developing scanning techniques and analysis methods are becoming more and more important for measuring specific differences between psychiatric disorders. Then, we discuss the complex relationship between cognitive deficits in patients with schizophrenia, problems in task performance, and disease-related effects on brain activation measured by fMRI. RESULTS: This is illustrated by our own recent work, in which we demonstrate the complex relationship between cognitive deficits in the task performance of patients with schizophrenia and differences in brain activity measured with fMRI. We stress the importance of task-independent neural networks for the interpretation of results. These networks may play a role similar to that of the potentially confounding effects of task choice. Finally, we consider challenges for the future and comment on how fMRI needs to be developed so that it can be used successfully in clinical practice in order to assist with the diagnosis, prognosis and treatment of schizophrenia. CONCLUSION: It is crucial for neuroimaging research into schizophrenia, and for potential clinical applications, that new types of tasks are developed that avoid the confounding effects on neural activity which are caused by performance differences stemming from aspecific factors such as demotivation or task-disengagement.

Ventral striatum is related to within-subject learning performance.

Learning from feedback involves a network of various cortical and subcortical regions. Although activation in this network has been shown to be especially strong in successful learners, it is currently unclear which of these regions are related to within-subject variation in learning performance. To this aim, 21 subjects performed a probabilistic feedback-learning task consisting of multiple independent Learning blocks and non-learning Control blocks, while functional magnetic resonance imaging data were acquired. In agreement with previous studies, activation in anterior, lateral and medial left prefrontal cortex, insula and superior and inferior parietal cortical regions were found when contrasting Learning and Control blocks. Furthermore, activation in the supplementary motor area, anterior cingulate cortex and bilateral striatum was associated specifically with the learning phase and not the application phase during Learning blocks. Finally, activation only in the ventral striatum was associated with within-subject learning performance across the Learning blocks. Taken together, these latter two results are argued to provide the answer to the main research question: ventral striatum activation is associated with within-subject variations in learning performance. The ventral striatum appears to play a vital role in learning by adjusting behavior based on feedback.