Value-based decision-making between affective and non-affective memories.

Affective biases can change how past events are recalled from memory. To capture mechanisms underlying affective memory formation, recall, and bias, we studied value-based decision-making (VBDM) between reward memories encoded in different mood states. Our findings suggest that following discrete affective events, created by large magnitude wins and losses on a Wheel of Fortune (WoF), healthy volunteers display an overall positive memory bias [favoring higher probability shapes learned after a WoF win compared with those learnt after a WoF loss outcome]. During this VBDM process, participants' pupils constrict before decision-onset for higher-value choices, and remained dilated for a sustained period after choice. Sustained pupil dilation was particularly sensitive to the reward values of abstract memories encoded in a positive mood. Taken together, we demonstrate that experimentally induced affective memories are recalled with a positive bias, and pupil-linked central arousal systems are actively engaged during VBDM between affective and non-affective memories.

Online behavioural activation during the COVID-19 pandemic decreases depression and negative affective bias.

BACKGROUND: The COVID-19 pandemic highlighted the need for mental health interventions that can be easily disseminated during a crisis. Behavioural activation (BA) is a cost-effective treatment that can be administered by non-specialists; however, it is unclear whether it is still effective during a time of lockdown and social distancing, when opportunities for positive activity are significantly constrained. METHODS: Between May and October 2020, we randomised 68 UK participants with mild to moderate low mood to either a 4-week online programme of non-specialist administered BA or to a passive control group. Before and after the intervention, we collected self-report data on mood and COVID-related disruption, as well as measuring emotional cognition as an objective marker of risk for depression. RESULTS: In comparison to the control group, the BA group showed a significant decrease in depression, anxiety and anhedonia after the intervention, as well as an increase in self-reported activation and social support. Benefits persisted at 1-month follow-up. BA also decreased negative affective bias on several measures of the Facial Emotion Recognition Task and early change in bias was associated with later therapeutic gain. Participants rated the intervention as highly acceptable. CONCLUSION: This study highlights the benefits of online BA that can be administered by non-specialists after brief training. These findings can help inform the policy response towards the rising incidence of mental health problems during a crisis situation such as a pandemic. They also highlight the use of objective cognitive markers of risk across different treatment modalities.

A translational perspective on the anti-anhedonic effect of ketamine and its neural underpinnings.

Anhedonia, a pronounced reduction in interest or pleasure in any of life's daily activities, is a cardinal symptom of major depression. In this Perspective article, we synthesise the recent evidence from rodent, monkey and human neuroimaging literature to highlight how the habenula, a small evolutionarily conserved subcortical structure located in the midbrain, may orchestrate the behavioural expression of anhedonia across fronto-mesolimbic networks. We then review how this circuitry can be modulated by ketamine, an NMDA receptor antagonist with rapid antidepressant properties. We propose that experimental paradigms founded in reinforcement learning and value-based decision-making can usefully probe this network and thereby help elucidate the mechanisms underlying ketamine's rapid antidepressant action.