Stimulating human prefrontal cortex increases reward learning

Sarrazin, Verena; Browning, Michael; O’Shea, Jacinta

doi:10.1016/j.neuroimage.2023.120029

Cited by 4 publications

(10 citation statements)

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“…DLPFC is part of a brain network involved in reinforcement learning and has been found to be activated in response to volatility (23)(24)(25). In our previous study, we found that bifrontal tDCS increased reward learning rates in healthy volunteers (26). However, due to the alterations in reinforcement learning in depression, it is unclear whether the same tDCS effect should be expected in individuals with low mood.…”

Section: Introductionmentioning

confidence: 87%

“…All participants completed two testing session in which they received real or sham tDCS in counter-balanced order. An a-priori power analysis based on the effect size from our previous study in healthy participants (26) indicated that a sample size of 38 participants per group was required to reach a power level of 80% for contrasting the effect of real vs. sham tDCS (paired ttest, two-tailed, Cohen's dz = 0.472). This study was approved by the University of Oxford Central University Ethics Committee (R67041/RE002).…”

Section: Samplementioning

confidence: 99%

“…To investigate the effect of low mood on learning behaviour in our experimental paradigm, we compared task performance during sham tDCS between participants with low mood and the sample of healthy participants from our previous study (26). To avoid confounds with learning effects from task repetition, only individuals (from either study) who received sham tDCS in their first session were included in this analysis (low mood: n = 43, healthy: n = 40).…”

Section: Samplementioning

confidence: 99%

“…However, due to the alterations in reinforcement learning in depression, it is unclear whether the same tDCS effect should be expected in individuals with low mood. To assess this, we compared task performance between healthy volunteers from our previous study and individuals with depressive symptoms (26). We hypothesised that individuals with depressive symptoms would show increased punishment vs. reward learning rates (20)(21)(22) and/or reduced adjustment of learning rates to volatility (16,17).…”

Section: Introductionmentioning

confidence: 99%

“…Our secondary aim was to test the hypothesis that tDCS would have a greater functional impact when applied during rather than before task performance. When applied during activity-dependent neuroplasticity ('online') tDCS has been shown to change brain and behaviour, with no such effect when stimulation was instead applied 'offline' prior to plasticity induction (26)(27)(28)(29). We therefore hypothesised that tDCS would normalise alterations in reinforcement learning only if applied during, but not before task performance.…”

Section: Introductionmentioning

confidence: 99%

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Bifrontal transcranial direct current stimulation normalises learning rate adjustment in low mood

Sarrazin

Overman

Mezossy-Dona

et al. 2023

Preprint

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Background: Transcranial direct current stimulation (tDCS) applied to dorsolateral prefrontal cortex has mild to moderate antidepressant effects. Little is known about the mechanisms of action. Other antidepressant treatments have been shown to act in part by reducing negative biases, which are thought to play a causal role in the maintenance of depression. Negative biases are hypothesized to stem from aberrant reinforcement learning processes, more precisely from overestimation of the informativeness of negative outcomes. The aim of this study was to test whether bifrontal tDCS might normalise such aberrant reinforcement learning processes in depressed mood. Methods: 85 community volunteers with low mood received tDCS during (or before) the performance of a reinforcement learning task that manipulated the informativeness (volatility) of positive and negative outcomes. In two sessions participants received real or sham tDCS in counter-balanced order. Baseline performance (sham tDCS) was compared to a sample of healthy individuals (n = 40) to identify the effect of low mood on task performance. The impact of tDCS on task performance was assessed by contrasting real and sham tDCS. Results: Low mood was characterised by decreased adjustment of loss relative to win learning rates in response to changes in informativeness. Bifrontal tDCS applied during task performance normalised this deficit by increasing the adjustment of loss learning rates to informativeness. Bifrontal tDCS applied before task performance had no effect indicating that the stimulation effect is cognitive state dependent. Conclusions: Our study provides preliminary evidence that bifrontal tDCS can normalise aberrant reinforcement learning processes in low mood. Crucially, this was only the case if stimulation was applied during task performance, suggesting that combining tDCS with a concurrent cognitive manipulation might increase the functional impact on cognitive functions and potentially on emotional symptoms. Future studies are needed to test if the effect on learning processes might have a beneficial effect on mood itself.

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Section: Introductionmentioning

confidence: 87%

Section: Samplementioning

confidence: 99%

Section: Samplementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Bifrontal transcranial direct current stimulation normalises learning rate adjustment in low mood

Sarrazin

Overman

Mezossy-Dona

et al. 2023

Preprint

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Disentangling the neurobiological bases of temporal impulsivity in Huntington's disease

Pardina‐Torner,

De Paepe,

Garcia‐Gorro

et al. 2024

Brain and Behavior

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BackgroundDespite its impact on daily life, impulsivity in Huntington's disease (HD) is understudied as a neuropsychiatric symptom. Our aim is to characterize temporal impulsivity in HD and to disentangle the white matter correlate associated with impulsivity.MethodsForty‐seven HD individuals and 36 healthy controls were scanned and evaluated for temporal impulsivity using a delay‐discounting (DD) task and complementary Sensitivity to Punishment and Sensitivity to Reward Questionnaire. Diffusion tensor imaging was employed to characterize the structural connectivity of three limbic tracts: the uncinate fasciculus (UF), the accumbofrontal tract (NAcc‐OFC), and the dorsolateral prefrontal cortex connectig the caudate nucleus (DLPFC‐cn). Multiple linear regression analyses were applied to analyze the relationship between impulsive behavior and white matter microstructural integrity.ResultsOur results revealed altered structural connectivity in the DLPC‐cn, the NAcc‐OFC and the UF in HD individuals. At the same time, the variability in structural connectivity of these tracts was associated with the individual differences in temporal impulsivity. Specifically, increased structural connectivity in the right NAcc‐OFC and reduced connectivity in the left UF were associated with higher temporal impulsivity scores.ConclusionsThe present findings highlight the importance of investigating the spectrum of temporal impulsivity in HD. As, while less prevalent than other psychiatric features, this symptom is still reported to significantly impact the quality of life of patients and caregivers. This study provides evidence that individual differences observed in temporal impulsivity may be explained by variability in limbic frontostriatal tracts, while shedding light on the role of sensitivity to reward in modulating impulsive behavior through the selection of immediate rewards.

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Prefrontal cortex stimulation normalizes deficient adaptive learning from outcome contingencies in low mood

Sarrazin,

Overman,

Mezossy-Dona

et al. 2024

Transl Psychiatry

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Depression and anxiety are associated with deficits in adjusting learning behaviour to changing outcome contingencies. This is likely to drive and maintain symptoms, for instance, by perpetuating negative biases or a sense of uncontrollability. Normalising such deficits in adaptive learning might therefore be a novel treatment target for affective disorders. The aim of this experimental medicine study was to test whether prefrontal cortex transcranial direct current stimulation (tDCS) could normalise these aberrant learning processes in depressed mood. To test proof-of-concept, we combined tDCS with a decision-making paradigm that manipulates the volatility of reward and punishment associations. 85 participants with low mood received tDCS during (or before) the task. In two sessions participants received real or sham tDCS in counter-balanced order. Compared to healthy controls (n = 40), individuals with low mood showed significantly impaired adjustment of learning rates to the volatility of loss outcomes. Prefrontal tDCS applied during task performance normalised this deficit, by increasing the adjustment of loss learning rates. As predicted, prefrontal tDCS before task performance (control) had no effect. Thus, the effect was cognitive-state dependent. Our study shows, for the first time, that a candidate depression treatment, prefrontal tDCS, when paired with a task, can reverse deficits in adaptive learning from outcome contingencies in low mood. Thus, combining neurostimulation with a concurrent cognitive manipulation is a potential novel strategy to enhance the effect of tDCS in depression treatment.

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Stimulating human prefrontal cortex increases reward learning

Cited by 4 publications

References 44 publications

Bifrontal transcranial direct current stimulation normalises learning rate adjustment in low mood

Bifrontal transcranial direct current stimulation normalises learning rate adjustment in low mood

Disentangling the neurobiological bases of temporal impulsivity in Huntington's disease

Prefrontal cortex stimulation normalizes deficient adaptive learning from outcome contingencies in low mood

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