Abstract
Substantia nigra is an important neuronal structure, located in the ventral midbrain, that exerts a regulatory function within the basal ganglia circuitry through the nigro-striatal pathway. Although its subcortical connections are relatively well-known in human brain, little is known about its cortical connections. The existence of a direct cortico-nigral pathway has been demonstrated in rodents and primates but only hypothesized in humans. In this study, we aimed at evaluating cortical connections of substantia nigra in vivo in human brain by using probabilistic constrained spherical deconvolution (CSD) tractography on magnetic resonance diffusion weighted imaging data. We found that substantia nigra is connected with cerebral cortex as a whole, with the most representative connections involving prefrontal cortex, precentral and postcentral gyri and superior parietal lobule. These results may be relevant for the comprehension of the pathophysiology of several neurological disorders involving substantia nigra, such as parkinson's disease, schizophrenia, and pathological addictions.
Highlights
Substantia Nigra (SN) is a neuronal structure located in the ventral part of the midbrain, between crus cerebri and tegmentum
Challenging the classical view of the basal ganglia network based on the “direct,” “indirect” (Leblois et al, 2006), and “hyperdirect” pathways (Nambu et al, 1996, 2002), we have recently demonstrated the existence of a possible corticopallidal connectivity in humans (Milardi et al, 2015; Smith and Wichmann, 2015), which was corroborated by a magnetoencephalography-local field potentials study in dystonic patients (Neumann et al, 2015)
There was no correlation between connectivity and Fractional Anisotropy index (FA)
Summary
Substantia Nigra (SN) is a neuronal structure located in the ventral part of the midbrain, between crus cerebri and tegmentum. The antero-lateral zone, the “pars reticulata” (SNr), consists of GABAergic neurons which receive afferents from the striatum and subthalamic nucleus (STN) and in turn project to ventral-anterior (VA) and ventral-lateral (VL) thalamic nuclei (Zhou and Lee, 2011). It is well-known that SN exerts a regulatory function on the basal ganglia circuitry (Guatteo et al, 2009), and it is involved in several neurological and neuropsychiatric disorders, such as Parkinson’s Disease (Carman, 1968), schizophrenia (Weinberger, 1987), and pathological addictions (Wise, 2009).
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