Motivation as a Common Cognitive Signature of Physical and Mental Health: Bridging Computational Psychiatry, Chronobiology, and Metabolic Health

Motivation plays a fundamental role in human behaviour and shapes the way we engage with the world. But why do individuals differ in their motivational drive and behaviour? The effort-based decision-making framework helps us formalise cognitive mechanisms involved in motivation, furthering our understanding of motivational pathologies and their neural foundation. However, gaps remain in understanding the mechanistic underpinnings of motivational differences. This thesis contributes to our understanding of motivational deficits by examining two main questions. Firstly, can computational parameters of effort-based decision-making identify individual differences in motivation relevant to transdiagnostic neuropsychiatric symptoms? Secondly, do bodily signals guide motivation via effort-based decision-making, contributing to individual differences in motivation? I investigate these questions using an experimental task and computational modelling approach developed and validated across multiple studies. I first established the reliability of computational parameters in assessing individual differences in effort-based decision-making (Chapter 2). Next, I showed that deficits in a computational parameter describing someone’s bias to choose to exert effort for reward map onto three neuropsychiatric conditions: apathy, anhedonia, and depression (Chapter 3). Exploring bodily influences on motivational processes, I found that individuals with a late chronotype show the same computational signature previously linked to neuropsychiatric symptoms. This effect interacted with the time of day, with late chronotype individuals exhibiting motivational deficits in the morning but not the evening (Chapter 3). I next investigated metabolic health, comparing type-2 diabetic participants to non-diabetic controls. Individuals with type-2 diabetes exhibited reduced motivation, captured by the same computational parameter linked to neuropsychiatric symptoms and circadian rhythm. This group effect was parallelled by a dimensional effect wherein metabolic risk scaled with motivational impairment (Chapter 4). Finally, I explored effects of metabolic health on motivation using a measure of glucose tolerance in healthy participants but found no relationship with effort-based decision-making (Chapter 5). Overall, these findings demonstrate a common cognitive signature of reduced motivation across neuropsychiatric symptoms, late circadian rhythm, and metabolic disorder. Investigating the role of motivation in neuropsychiatric symptoms and comorbidity between physical and mental illness will be crucial to understanding pathophysiological mechanisms and developing comprehensive treatment approaches.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2024

Author dc:creator

• Mehrhof, Sara

Advisor dc:contributor.advisor

• Nord, Camilla

• Cognitive Neuroscience
• Clinical Psychology
• Psychiatry
• Computational Psychiatry
• Computational Modelling
• Transdiagnostic
• Motivation
• Metabolic Psychiatry
• Circadian Rhythm

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/63ea74a7-ab2b-42c4-b232-6fc20d8c7a29/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.117708

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/383198