The relationship between reward and punishment processing and the 5-HT _1A receptor as shown by PET

Rationale: The serotonin (5-HT) system has been reported to be involved in decision-making. A key component of this neurotransmitter system is the 5-HT_1A receptor, and research is beginning to show how this receptor can influence decision-making. However, this relationship has rarely been studied in humans. Objectives: This study assessed whether individual variability in 5-HT_1A availability correlates with decision-making in healthy volunteers. Methods: We measured regional availability of the 5-HT _1A receptor in the hippocampal complex and striatum using positron emission tomography and correlated this with performance on two decision-making tasks measuring sensitivity to probability, rewards and punishments and temporal discounting, respectively. Results: No relationship between decision-making behaviour and 5-HT_1A availability in the striatum was found. However, a positive correlation was detected between participants' 5-HT_1A availability in the hippocampal complex and their sensitivity to the probability of winning. Furthermore, there was a negative correlation between the degree to which participants discounted future rewards and 5-HT_1A availability in the hippocampal complex. Conclusions: These data support a role for the 5-HT_1A receptor in the aberrant decision-making that can occur in neuropsychiatric disorders such as depression.