Differences in neural connectivity between the substantia nigra and ventral tegmental area in the human brain

Abstract

Objectives: Many animal and a few human studies have reported on the neural connectivity of the substantia nigra (SN) and the ventral tegmental area (VTA). However, it has not been clearly elucidated so far. We attempted to investigate any differences in neural connectivity of the SN/VTA in the human brain, using diffusion tensor imaging (DTI).

Methods: Sixty-three healthy subjects were recruited for this study. DTIs were acquired using a sensitivity-encoding head coil at 1. 5T. Connectivity was defined as the incidence of connection between the SN/VTA and each brain regions in the brain.

Results: The connectivity of SN was higher than that of the VTA. This included in the primary motor cortex, primary somatosensory cortex, premotor cortex, prefrontal cortex, caudate nucleus, globus pallidus, putamen, nucleus accumbens, temporal lobe, amygdala, pontine basis, occipital lobe, anterior and posterior lobe of cerebellum, corpus callosum, and external capsule (p < 0.05). However, no significant differences were observed in the red nucleus, thalamus, pontine tegmentum, and medial temporal lobe between the SN and VTA (p > 0.05).

Conclusions: We found the differences in neural connectivity of the SN/VTA in the human brain. The method and results of this study can provide useful information for clinicians and researchers in neuroscience, especially who work for Parkinson's disease and patients with brain injury.

Keywords: diffusion tensor imaging; dopamine; structural connectivity; substantia nigra; ventral tegmental area.

Figure 1

Neural connectivity of substantia nigra and ventral tegmental area. (A) The region of interest (ROI): a seed ROI for substantia nigra (SN, orange), is placed on the isolated SN of the upper midbrain on the B0 and color-coded map (dorsomedially next to the cerebral peduncle of the upper midbrain). A seed ROI for ventral tegmental area (VTA, sky-blue), is placed on the isolated VTA of the upper midbrain on the B0, and color-coded map. We use other structures to isolate the VTA such as interpeduncular nucleus (anterior boundary, red), central tegmental tract (posterior boundary, white-lined rectangular), midline (medial boundary), red nucleus (blue) and SN (lateral boundary). (B) SN/VTA: results of diffusion tensor tractography for the connectivity of SN/VTA (a: cortex level, b: upper corona radiata level, c: upper internal capsule level, d: lower internal capsule level, e: bicommissure level f: midbrain level, g: upper pons level, h: lower pons level). a to b levels: primary motor cortex, primary somatosensory cortex, premotor cortex, prefrontal cortex, corpus callosum, c to e levels: caudate nucleus, putamen, globus pallidus, nucleus accumbens, thalamus, external capsule, f to h level: red nucleus, amygdala, medial temporal lobe, temporal lobe pontine basis, pontine tegmentum, anterior lobe of cerebellum, posterior lobe of cerebellum.