Decision-making, environmental enrichment and the mesolimbic dopamine system in adult and aged rats

Abstract

The dopaminergic system plays a crucial role in learning, reward-processing, motivation, motor control and attention. The population of midbrain dopamine neurons projects extensively to many areas of the brain. This system is maintained in a homeostatic way, and it can self-regulate to maintain behavioural function in extreme cases such as Parkinson’s disease. However, Huttunen (2016) discovered a significant correlation between midbrain dopamine neuron number in male rats and their behavioural performances in a gambling task. It was unexpected that such non-clinical variation in dopamine neuron number can lead to differences in observable behaviours. Our project aims to investigate the link between dopamine structure and function in risk decision-making, and to explore possible factors that can manipulate the brain and behaviour. Chapter 1 reviewed the dopaminergic system and its adaptive role in conditions such as environmental enrichment and stress. Chapter 2 described the experiment using a modified risk task which failed to replicate the original results from Huttunen (2016). Chapter 3 examined the possible sex difference in the brain of behaviour of rats. Chapter 4 and 5 explored factors that can influence this dopamine-loss-stay relationship, including environmental enrichment and neurogenesis. We demonstrated that dopamine-expressing neurons in the rat midbrain may underlie loss-stay behaviours, which may reflect the animals’ risk-attitude. Moreover, the correlation was significant only when the age of the animal was considered. Therefore, this correlation may be a result of aging, or the compensatory mechanisms that often accompany ageing. Future research may shed light on possible treatment and interventions for neural decline in ageing and other clinical conditions.

Date of Award	15 Jun 2023
Original language	English
Awarding Institution	University of St Andrews
Supervisor	Eric MacDonald Bowman (Supervisor)