According to the synaptic tag and capture (STC) theory, dopamine is a crucial neuromodulator for novelty-enhanced memory. This study investigated whether tyrosine, a dopamine precursor, modulates...Show moreAccording to the synaptic tag and capture (STC) theory, dopamine is a crucial neuromodulator for novelty-enhanced memory. This study investigated whether tyrosine, a dopamine precursor, modulates the effect of novelty on memory in humans. Therefore, we expected novelty to increase memory performance, as previous studies showed. Also, we expected tyrosine to increase memory performance. In addition, based on the STC theory, we expected tyrosine to indirectly increase memory performance in the novelty condition. Participants drank orange juice with L-tyrosine or cellulose (placebo) and experienced either novel or familiar environments. An EEG was used to assess the neural mechanism of memory encoding. Memory performance was assessed with recall and recognition tests of word lists. Based on multiple repeated measures ANOVAs we did not find a novelty-enhancing memory effect, a tyrosine-enhancing memory effect or an interaction effect. Unrelatedly, we found evidence for the Ebbinghaus forgetting curve, with recall and recognition significantly decreasing after 24 hours. In addition, we did not find the experienced immersion of the virtual environment to be affecting memory performance. However, the immersion effect decreased after the first session with a virtual environment. Moreover, the EEG indicated higher theta wave activity at the Fz electrode compared to Pz and Cz, with no novelty or tyrosine effect on the neural mechanisms of memory encoding. Future research should explore other pharmacological manipulations, ensure balanced models and apply other brain imaging techniques, like fMRI or DTI.Show less
