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Pavlovian bias is an innate motivational tendency to approach rewards and remain passive in the face of punishment. The relative reliance on Pavlovian valuation has been found to increase when the perceived control over environmental reinforcers is compromised, leading to behavior resembling learned helplessness (LH). In our study, we used a version of an orthogonalized Go-NoGo reinforcement learning task to examine the relative reliance on Pavlovian and instrumental valuation during and after an intermittent loss of control over rewards and losses. Sixty healthy young adults underwent the task and received anodal high-definition transcranial direct current stimulation (HD-tDCS) over the medial prefrontal/ dorsal anterior cingulate cortex in a randomized, double-blind, sham-controlled study. Furthermore, we evaluated changes in cue-locked mid-frontal theta power derived from electroencephalography. We hypothesized that active stimulation would reduce Pavlovian bias during manipulation of outcome controllability, and the effect would be accompanied by stronger mid-frontal theta activity, representing arbitration between choice strategies in favor of instrumental relative to Pavlovian valuation. We found a progressive decrease in Pavlovian bias during and after the loss of control over feedback. Active HD-tDCS counteracted this effect while not affecting the mid-frontal theta signal. The results were at odds with our hypotheses but also with previous findings reporting LH-like patterns during and after the loss of control without brain stimulation. The discrepancy may be related to different protocols for the controllability manipulation. We argue that the subjective evaluation of task controllability is crucial in mediating the balance between Pavlovian and instrumental valuation during reinforcement learning and that the medial prefrontal/dorsal anterior cingulate cortex is a key region in this respect. These findings have implications for understanding the behavioral and neural underpinnings of LH in humans.

IntroductionPavlovian bias is an innate motivational tendency to approach rewards and remain passive in the face of punishment. The relative reliance on Pavlovian valuation has been found to increase when the perceived control over environmental reinforcers is compromised, leading to behavior resembling learned helplessness (LH).MethodsSixty healthy young adults underwent a Go-NoGo reinforcement learning task and received anodal high-definition transcranial direct current stimulation (HD-tDCS) over the medial prefrontal/dorsal anterior cingulate cortex in our randomized, double-blind, sham- controlled study. Furthermore, we evaluated changes in cue-locked mid-frontal theta power derived from simultaneous electroencephalography (EEG). We hypothesized that active stimulation would reduce Pavlovian bias during manipulation of outcome controllability, and the effect would be accompanied by stronger mid-frontal theta activity, representing arbitration between choice strategies in favor of instrumental relative to Pavlovian valuation.ResultsWe found a progressive decrease in Pavlovian bias during and after loss of control over feedback. Active HD-tDCS counteracted this effect while not affecting the mid-frontal theta signal.DiscussionThe results were at odds with our hypotheses but also with previous findings reporting LH-like patterns during and after loss of control without brain stimulation. The discrepancy may be related to different protocols for the controllability manipulation. We argue that the subjective evaluation of task controllability is crucial in mediating the balance between Pavlovian and instrumental valuation during reinforcement learning and that the medial prefrontal/dorsal anterior cingulate cortex is a key region in this respect. These findings have implications for understanding the behavioral and neural underpinnings of LH in humans.

Male depression is an attempt to extend the definition of depression to address an atypical cluster of symptoms that have been associated with suicide completion in community-dwelling populations. These include externalizing behaviour, avoidance, emotional suppression, irritability, substance misuse, and risk-seeking behaviour. Temporal discounting is a measure of economic impulsivity and a possible transdiagnostic neurocognitive domain that plays an essential role in everyday decision-making. Previous studies have found mixed results relating economic impulsivity to depression. We hypothesized that this divergence could be attributed to the heterogeneity of depression and contrasted temporal discounting between general ICD-10 depression and the specific, and possibly more impulsive male depression.We administered a temporal discounting task to 170 in-ward psychiatric patients and 176 healthy controls (HC). All patients fulfilled the ICD-10 criteria for moderate to severe depression. The patients were separated into a male-depressed group (MD) and a general major depression group (MDD) using median split of the Male Depression Risk Score (MDRS-22). HC had subthreshold scores for depression and had no neuropsychiatric history.We used the Bayesian information criterion (BIC) to compare 3 models of delay discounting. All models were based on the hyperbolic discounting model Q(R,D,k)=R/(1+k*D) where R =reward, k=discounting rate, and D=delay, comparing the subjective value of the immediate option Qi=Q(Ri,0,k) against the delayed option Qd=Q(Rd,D,k). Models differed in their treatment of noise in generating the probability piof making the impulsive choice of the immediate option (withσ(z) = 1/(1 + exp(−z))):(1) preference-temperature model (k, β): pi=σ(β(Qi– Qd))(2) preference-uncertainty model (μ, σ): draw log ks~N(μ, σ):if Qi> Q(Rd,D, ks), pi=1; otherwise pi=0(3) trembling-hand model (k, β, lapse):λ = (3/56)* σ(lapse)+1e-4 pi=(1–2λ(σ(β(Qi– Qd))+λThe preference-temperature model yielded the best fit (BIC(1)=3.817, BIC(2)=3.893, BIC(3)=7.001). There was no significant group difference in the model-specific parameters: discount ratekand inverse temperatureβ. There was a correlation between choosing the immediate reward and MDRS-22 (r=0.234, p<0.001), as well as with Beck’s Depression Inventory (BDI-II) (r=0.191, p<0.001), but no significant group differences (ANOVA: F=0.454, p=0.501).We could not find any model-based differences between the three groups. However, model- agnostic results suggested that male depressiveness, but also ICD-10 depressiveness, were associated with more impulsive choices. A noteworthy limitation was a strong correlation between BDI-II and MDRS-22 in our sample.

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