Neural correlates of generation and inhibition of verbal association patterns in mood disorders

Randomized controlled trial of a mindfulness-based intervention in adolescents from the general population: The Mindfulteen neuroimaging study protocol

AIM

Adolescence is a period of vulnerability to stress. Increased anxiety during this period has been associated with the later development of mental disorders, hence the growing interest for interventions that could decrease stress reactivity and improve cognitive control in adolescents. Mindfulness-based interventions have demonstrated their efficacy on stress reactivity and anxiety in adults, but evidence is lacking in youth.

METHODS

The Mindfulteen Study is a 3-year longitudinal cohort with a nested randomized controlled trial examining the effectiveness of mindfulness-based interventions for adolescents. Young adolescents from the general population, aged between 13 and 15 years old, with no history of current mental health disorder (apart from past mood disorders or current anxiety disorders) are included and stratified into low or high anxiety based on trait anxiety scores before being randomized to early or late 8-week intervention groups. Primary outcomes are based on neuroimaging data (i.e., structural and functional measures in the cortico-limbic network) while secondary outcomes are psychological (i.e., anxiety and stress-associated dimensions) and biological (i.e., cortisol, inflammatory and redox markers). Assessments are performed at baseline, immediately after intervention or waiting time and after 18 months of intervention.

CONCLUSION

To the best of our knowledge, this is the first randomized controlled trail examining the effect of a mindfulness-based intervention in young adolescents from the general population based on the measurement and analyses of psychological, neuroimaging and biological data.

Metacognition of visuomotor decisions in conversion disorder

Motor conversion disorder (CD) entails genuine disturbances in the subjective experience of patients who maintain they are unable to perform a motor function, despite lack of apparent neurological damage. Abilities by which individuals assess their own capacities during performance in a task are called metacognitive, and distinctive impairment of such abilities is observed in several disorders of self-awareness such as blindsight and anosognosia. In CD, previous research has focused on the recruitment of motor and emotional brain systems, generally linking symptoms to altered limbic-motor interactions; however, metacognitive function has not been studied to our knowledge. Here we tested ten CD patients and ten age-gender matched controls during a visually-guided motor paradigm, previously employed in healthy controls (HC), allowing us to probe for motor awareness and metacognition. Participants had to draw straight trajectories towards a visual target while, unbeknownst to them, deviations were occasionally introduced in the reaching trajectory seen on the screen. Participants then reported both awareness of deviations and confidence in their response. Activity in premotor and cingulate cortex distinguished between conscious and unconscious movement corrections in controls better than patients. Critically, whereas controls engaged the left superior precuneus and middle temporal region during confidence judgments, CD patients recruited bilateral parahippocampal and amygdalo-hippocampal regions instead. These results reveal that distinct brain regions subserve metacognitive monitoring for HC and CD, pointing to different mechanisms and sources of information used to monitor and form confidence judgments of motor performance. While brain systems involved in sensory-motor integration and vision are more engaged in controls, CD patients may preferentially rely on memory and contextual associative processing, possibly accounting for how affect and memories can imbue current motor experience in these patients.

Alterations in neural systems mediating cognitive flexibility and inhibition in mood disorders

Impairment in mental flexibility may be a key component contributing to cardinal cognitive symptoms among mood disorders patients, particularly thought control disorders. Impaired ability to switch from one thought to another might reflect difficulties in either generating new mental states, inhibiting previous states, or both. However, the neural underpinnings of impaired cognitive flexibility in mood disorders remain largely unresolved. We compared a group of mood disorders patients (n = 29) and a group of matched healthy subjects (n = 32) on a novel task-switching paradigm involving happy and sad faces, that allowed us to separate generation of a new mental set (Switch Cost) and inhibition of the previous set during switching (Inhibition Cost), using fMRI. Behavioral data showed a larger Switch Cost in patients relative to controls, but the average Inhibition Cost did not differ between groups. At the neural level, a main effect of group was found with stronger activation of the subgenual cingulate cortex in patients. The larger Switch Cost in patients was reflected by a stronger recruitment of brain regions involved in attention and executive control, including the left intraparietal sulcus, precuneus, left inferior fontal gyrus, and right anterior cingulate. Critically, activity in the subgenual cingulate cortex was not downregulated by inhibition in patients relative to controls. In conclusion, mood disorder patients have exaggerated Switch Cost relative to controls, and this deficit in cognitive flexibility is associated with increased activation of the fronto-parietal attention networks, combined with impaired modulation of the subgenual cingulate cortex when inhibition of previous mental states is needed.