Fatigue and memory are modulated by the neurotransmitter dopamine. This study aimed to explore the modulating effects of dopamine on mental fatigue and how this relationship affects memory...Show moreFatigue and memory are modulated by the neurotransmitter dopamine. This study aimed to explore the modulating effects of dopamine on mental fatigue and how this relationship affects memory performance. We hypothesised that the administration of tyrosine would lead to lower reported mental fatigue levels relative to placebo. Additionally, we hypothesised that participants who reported lower levels of mental fatigue would obtain higher memory scores in comparison to those who reported high levels of mental fatigue. 30 participants were tested on a word recall and word recognition task. Mental fatigue levels were measured using the multidimensional fatigue inventory (MFI). Our results showed no significant effect of treatment on mental fatigue. However, we found that mental fatigue did impair recognition performance in both immediate and delayed conditions, though inconsistently across sessions. The effect of time on memory was found; performance in both recognition and recall tasks deteriorated after 24 hours, regardless of treatment or mental fatigue. We discuss several study limitations, including a small, gender-imbalanced sample size, subjective mental fatigue reports and our tyrosine administration approach. We encourage further research on the topic as it is highly relevant for clinical populations who experience persistent fatigue symptoms, as well as healthy populations who regularly engage in cognitively demanding tasks.Show less