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The role of dopamine in visual imagery—An experimental pharmacological study

DOI: 10.1002/jnr.25262
Monzel, M., Karneboge, J., & Reuter, M. (2024). The role of dopamine in visual imagery—an experimental pharmacological study. Journal of Neuroscience Research, 102(1). doi:https://onlinelibrary.wiley.com/doi/pdf/10.1002/jnr.25262

Abstract

Mental imagery enables people to simulate experiences in their minds without the presence of an external stimulus. The underlying biochemical mechanisms are poorly understood but there is vague evidence that dopamine may play a significant role. A better understanding at the biochemical level could help to unravel the mechanisms of mental imagery and related phenomena such as aphantasia (= lack of voluntary mental imagery), but also opens up possibilities for interventions to enhance or restore mental imagery. To test the hypothesis that acute dopamine depletion leads to a decrease in the strength of mental imagery, N = 22 male participants will be administered an amino acid mixture containing branched‐chain amino acids (BCAAs) and tryptophan (TRP) to transiently reduce dopamine synthesis and further N = 22 male participants will receive a placebo. Plasma prolactin (PRL) levels are determined as a peripheral marker of brain dopamine function. The strength of mental imagery will be measured before and after ingestion of the BCAA/TRP mixture using the method of mental imagery priming. Additional exploratory analyses will use genetic data to investigate possible effects of variations on dopaminergic gene loci (e.g., DAT1) on dopamine levels and strength of mental imagery. The results show […].

Authors

  • Merlin Monzel23
  • Jana Karneboge4
  • Martin Reuter15

Understanding the Role of Dopamine in Mental Imagery

Overview/Introduction

Mental imagery is the ability to visualize experiences in our minds without any external stimuli. It's a fascinating process, but the biochemical mechanisms behind it are not well understood. This study explores the role of dopamine, a key neurotransmitter in the brain, in mental imagery. By understanding these mechanisms, researchers hope to shed light on conditions like aphantasia, where individuals cannot voluntarily create mental images, and explore potential interventions to enhance or restore mental imagery.

Methodology

The study involved 44 male participants divided into two groups. One group received an amino acid mixture containing branched-chain amino acids (BCAAs) and tryptophan (TRP) to temporarily reduce dopamine synthesis, while the other group received a placebo. The study was double-blind, meaning neither the participants nor the researchers knew who received the amino acid mixture or the placebo.
  • Measurement of Mental Imagery: Participants' mental imagery strength was assessed using a technique called mental imagery priming before and after the intervention.
  • Biochemical Measures: Blood samples were taken to measure plasma prolactin (PRL) levels, which serve as an indicator of brain dopamine function.
  • Genetic Analysis: Genetic data were collected to explore variations in dopaminergic gene loci and their effects on dopamine levels and mental imagery.

Key Findings

The study aimed to test the hypothesis that reducing dopamine levels would decrease the strength of mental imagery. While the detailed results are not provided, the research sought to determine whether there was a significant difference in mental imagery strength before and after the intervention.

Implications

Understanding the biochemical basis of mental imagery could have several practical implications:
  • Enhancing Mental Imagery: Insights from this study could lead to interventions that enhance mental imagery, benefiting individuals in creative fields or those with aphantasia.
  • Therapeutic Applications: Potential therapies could be developed to restore mental imagery in individuals who have lost this ability due to neurological conditions.

Limitations

While the study provides valuable insights, there are some limitations:
  • Sample Size: The study involved a relatively small sample size of 44 participants, which may limit the generalizability of the findings.
  • Gender Specificity: The study only included male participants, so the results may not apply to females.
  • Short-Term Intervention: The effects of dopamine reduction were only studied over a short period, and long-term effects remain unknown.
In conclusion, this study takes a significant step toward understanding the role of dopamine in mental imagery. While more research is needed to confirm these findings and explore their broader implications, this...