To investigate the links between dopamine release and aversive learning, Frick et al. simultaneously measured brain dopamine release and neural activity in a combined PET/MRI scanner before, during, and after fear conditioning (Figure 1). Two shapes were used as conditioned stimuli, one of which was paired with an electric shock 80% of the time, while the other was left unpaired.
Frick et al. demonstrated that human fear conditioning and learning strength is directly linked to endogenous dopamine release in the amygdala. These findings are consistent with previous rodent studies, indicating that this mechanism is evolutionarily conserved . The authors also found that while learning strength was linked to dopamine release, the strength of the unconditioned response was not, providing further evidence of dopamine’s role in learning-related processes. Previous studies have also reported that fear conditioning can induce a greater increase in dopamine concentration than an independent shock.
One possible explanation for this mechanism is that dopamine serves as a neurochemical aid in strengthening aversive memory formation. This process is known as long-term potentiation, which refers to the long-lasting strengthening of synaptic connections following repeated signal transmission between two neurons . Previous studies have shown that dopamine release in the amygdala facilitates fear learning, further validating the results obtained in this study .