In non-PD samples, no relationship was observed between SERT availability and cognitive performance in young adult healthy participants with normal cognition (Burke et al., 2011), while another found reduced SERT availability in patients with mild cognitive impairment (MCI) in various brain regions, including the thalamus, that correlated with worse memory performance (Smith et al., 2017). Here, SLC6A4 is linked to Parkinson disease.