Cognitive and motor impulsivity in the healthy brain, and implications for eating disorders and obesity: A coordinate-based meta-analysis and systematic review.

Alterations in the impulse-control balance, and in its neural bases, have been reported in obesity and eating disorders (EDs). Neuroimaging studies suggest a role of fronto-parietal networks in impulsive behaviour, with evaluation and anticipatory processes additionally recruiting meso-limbic regions. However, whether distinct facets of cognitive and motor impulsivity involve common vs. specific neural correlates remains unclear. We addressed this issue through Activation Likelihood Estimation (ALE) meta-analyses of fMRI studies on delay discounting (DD) and go/no-go (GNG) tasks, alongside conjunction and subtraction analyses. We also performed systematic reviews of neuroimaging studies using the same tasks in individuals with obesity or EDs. ALE results showed consistent activations in the striatum, anterior/posterior cingulate cortex, medial/left superior frontal gyrus and left supramarginal gyrus for impulsive choices in DD, while GNG tasks elicited mainly right-lateralized fronto-parietal activations. Conjunction and subtraction analyses showed: i) common bilateral responses in the caudate nucleus; ii) DD-specific responses in the ventral striatum, anterior/posterior cingulate cortex, left supramarginal and medial frontal gyri; iii) GNG-specific activations in the right inferior parietal cortex. Altered fronto-lateral responses to both tasks are suggestive of dysfunctional cortico-striatal balance in obesity and EDs, but these findings are controversial due to the limited number of studies directly comparing patients and controls. Overall, we found evidence for distinctive neural correlates of the motor and cognitive facets of impulsivity: the right inferior parietal lobe underpins action inhibition, whereas fronto-striatal regions and the left supramarginal gyrus are related to impulsive decision-making. While showing that further research on clinical samples is required to better characterize the neural bases of their behavioural changes, these findings help refining neurocognitive model of impulsivity and highlight potential translational implications for EDs and obesity treatment.

High-definition transcranial direct current stimulation of the dorsal anterior cingulate cortex modulates decision-making and executive control.

Previous neuroimaging evidence highlights the translational implications of targeting the dorsal anterior cingulate cortex (dACC), i.e. a key node of the networks underlying conflict monitoring and decision-making, in brain stimulation treatments with clinical or rehabilitative purposes. While the optimized modelling of "high-definition" current flows between multiple anode-cathode pairs might, in principle, allow to stimulate an otherwise challenging target, sensitive benchmark metrics of dACC neuromodulation are required to assess the effectiveness of this approach. On this basis, we aimed to assess the modulatory effect of anodal and cathodal high-definition tDCS (HD-tDCS) of the dACC on different facets of executive control and decision-making in healthy young individuals. A combined modelling/targeting procedure provided the optimal montage for the maximum intensity of dACC stimulation with six small "high-definition" electrodes delivering anodal, cathodal or sham HD-tDCS for 20 min in a within-subject design with three separate sessions. Following stimulation, participants performed Flanker and gambling tasks unveiling individual differences in executive control and both loss- and risk-aversion in decision-making, respectively. Compared to both anodal and sham conditions, cathodal dACC stimulation significantly affected task performance by increasing control over the Flanker conflict effect, and both loss and risk-aversion in decision-making. By confirming the feasibility and effectiveness of dACC stimulation with HD-tDCS, these findings highlight the implications of modelling and targeting procedures for neuromodulation in clinical research, whereby innovative protocols might serve as treatment addressing dysfunctional dACC activity, or combined with cognitive training, to enhance higher-order executive functioning in different neuropsychiatric conditions.