A diffusion tensor imaging (DTI) and [11C]PHNO PET study to measure dopamine release in the functional subdivisions of the basal ganglia

Objectives Basal ganglia(BG) are complex structures consisting of several anatomical nuclei, functionally organised into limbic (Lim), associative (Ass) and sensorimotor (SM). Currently, PET studies use regions of interest (ROI) derived from anatomical boundaries (AROIs). The aim is to subdivide the striatum (ST) and pallidum (PAL) into their functional ROIs (FROIs) using DTI and then quantify dopamine release(DR) in these areas.

Methods DTI and [11C]PHNO data were acquired, pre- and post-administration of amphetamine(0.3mg/kg), for 11 subjects. DTI probabilistic tractography was used to infer information about the anatomical connectivity between brain regions, in order to derive the functional subdivisions of ST and PAL. FROIs were defined using the following projections(a)Lim: medialOrbital, amygdala and hippocampus are connected to Lim ST which projects to Lim PAL,(b)Ass: dorsolateral prefrontal projects to Ass ST which projects to Ass PAL (c)SM: primary, premotor and SMA cortices project to SM ST which projects to SM PAL. The DTI-derived FROIs were used to estimate DR in the PET data (change in receptor binding post-amphetamine). FROI measurements were compared to AROI.

Conclusions The results suggest that there is difference in DR among FROIs. DR was more homogeneous within the FROIs suggesting that it may be more appropriate to report neurotransmitter release from functional subdivisions of the BG

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