Thus far, only two studies have examined relationships between LC structure and PET measures of catecholamine function ([11C]MeNER PET to measure norepinephrine transporter density) and found no direct relationships in Parkinson’s disease patients (Sommerauer et al., 2018; Doppler et al., 2021; though Sommerauer and colleagues found a positive association in the thalamus). The gene discussed is SLC6A2; the disease is Parkinson disease.