BCHE and Parkinson disease: There was no significant difference in GABA+/Cr levels between participants with PD taking cholinesterase inhibitors vs those not taking them (0.098 SD 0.012 vs 0.093 SD 0.008; t31 = 1.16, p = 0.26), between those taking antipsychotic agents (quetiapine) vs those not (0.088 SD 0.007 vs 0.097 SD 0.011; t31 = 1.42, p = 0.17), and there was no significant correlation between levodopa dose and GABA+/Cr (ρ = 0.018, p = 0.9).