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Social Learning in Anhedonia: A Multimodal, Causal Investigation

Niamh Cameron, First-Year PhD,

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University of Plymouth

BACKGROUND:​

 

Critical to navigating through our dynamic world lies the ability to flexibly adapt our behaviour according to rewarding and punishing events. Yet there is great variability in how individuals respond to positive or negative experiences. This is notable in those with depression, affecting 322 million people globally, whereby a reduced sensitivity to reward manifests in symptoms such as anhedonia, an impaired ability to pursue and learn about pleasure.

 

Imagine no longer experiencing joy from activities you once loved, like spending time with friends or celebrating a special occasion or achievement; this is the reality for individuals living with anhedonia.

 

It is common for those with depression to face reductions in the quality and quantity of social interactions. However, despite the salience of interpersonal relationships in the development and maintenance of depression, few studies have approached reward learning within a social context.

 

Further, while studies have explored whether reward processing is a modifiable risk factor for developing depression, there remains a need to isolate the specific factors that promote psychopathology (e.g., stress) in at-risk individuals to identify potential targets for treatment.

 

My research aims to investigate the neurocognitive mechanisms of reward learning following task-induced, acute social stress in high (i.e., “healthy”) and low (i.e., those at risk of depression) reward-sensitive individuals.

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METHODOLOGY:​

 

Throughout this project, we will explore reward processing in a social context using an observational learning task whereby participants must learn which of two stimuli should be selected to maximise their monetary earnings. To induce competition, the choices and outcomes of a partner are shown in some trials.

 

The first study will identify the behavioural markers of altered reward processing following both acute social (competition) and physiological (CO2 anxiety model) stress. By inhaling a mixture of air and 7.5% CO2, the CO2 model reproduces the symptoms of stress by increasing heart rate and blood pressure.

 

Due to an increased susceptibility to stress, we predict that low reward-sensitive individuals will experience a greater impairment in their task performance following CO2 inhalation compared to high reward-sensitive participants.

 

Our second experiment will attempt to improve reward learning by exploring the effects of a double-blind, placebo-controlled, one-dose tyrosine dietary supplement intervention. Tyrosine, which is available over the counter, is a catecholamine precursor that works by increasing levels of dopamine and noradrenaline in the brain.

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Given the role of dopamine in reward processing, we expect that low reward-sensitive individuals will experience more significant improvements in their task performance following tyrosine (vs. placebo) compared to high reward-sensitive participants.

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RESULTS:​

 

We are currently analysing pilot data and applying computational modelling to potential measures of trait high and low reward sensitivity and begin collecting data for the first study soon. 

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​​​​​​​FUTURE WORK: â€‹

 

My final study will test a novel, non-invasive remediation method for individuals at risk of depression by investigating the causal role of brain regions identified in aberrant reward processing (i.e., the ventral striatum) through modulation via sham-controlled transcranial ultrasound stimulation with fMRI. 

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​​​FUNDED BY:

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​​CONTACT: 

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