Abstract: Objective To elucidate the volume changes of cortical and subcortical reward circuitry in patients with type 2
diabetes mellitus. Methods High-resolution three-dimensional T1-weighted fast spoiled gradient recalled echo MRI images
were obtained from 16 patients with type 2 diabetes mellitus and 16 normal controls, and 11 type 2 diabetic patients also
received the same MRI scans after insulin therapy for 1 year. Volumetric analysis was performed and analysis of covariance
and paired t test were applied. Results A decreased volume was found in the left insular lobe, left nucleus accumbens area,
right hippocampus, putamen and amygdala in type 2 diabetic patients compared with normal controls (P<0.05). After insulin
therapy for 1 year, an increased volume of bilateral cortical reward structures was observed (left, 33.65±3.66 ml; right, 33.35±
4.25 ml) compared the baseline level (left, 31.45 ± 2.90 ml; right, 31.12 ± 2.97 ml) in diabetic patients (P<0.05). No significant
volume change in the bilateral basal ganglia structures was found after insulin therapy for 1 year (P>0.05), and bilateral ventral
diencephalon area showed an increased volume after the treatment (left, 3.26±0.68 ml; right, 3.20±0.78 ml) compared with the
baseline (left, 2.96±0.76 ml; right, 2.82±0.90 ml)(P<0.05). Conclusion Type 2 diabetic patients have a decreased volume of the
cortical and subcortical reward circuitry, and insulin therapy can reverse such changes and improve the damage of reward
circuitry.