Fenfluramine and Cognition

In this study, the investigators will investigate the cognitive effects of fenfluramine, a drug that directly stimulates the release of serotonin in the brain and positively modulates σ1 function. The investigators will use fenfluramine to assess the cognitive effects of modulating serotonin and σ1 function in healthy volunteers using a battery of cognitive tasks that measure learning and memory, executive functioning, reward processing, and emotional processing. The study design is double-blind, and participants will be randomised to either seven days of fenfluramine or placebo administration. All participants will attend two screening visits to assess eligibility. There are two main study visits; during the first, participants will undertake cognitive tasks and questionnaires before taking the initial study dose. One the second study visit, participants will once again complete these tasks and questionnaires after a week of fenfluramine/placebo administration.