Substantia Nigra
Published: Jul 17, 2023
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Updated: Aug 3, 2023
Written by Oseh Mathias
Founder, SpeechFit
The substantia nigra, which means "black substance" in Latin, is a part of the brain that is crucial for movement, reward, and addiction[1]. It is situated in the mesencephalon, also called the midbrain, which is a part of the brain located near the centre, ventral to (underneath) the cerebral cortex and dorsal to (above) the hindbrain[2].
The substantia nigra is composed of two parts: the pars compacta (SNc) and the pars reticulata (SNr)[4].
The SNc contains dopaminergic neurons that produce dopamine, a neurotransmitter critical for coordinating smooth and balanced muscle movement[5]. These neurons appear dark due to the presence of neuromelanin, a substance that derives from dopamine and gives the substantia nigra its name[6].
The SNr works in conjunction with the basal ganglia circuitry. It serves as a major output center of the basal ganglia and helps regulate muscle activity, eye movements, and even cognitive functions[7].
The substantia nigra, particularly the SNc, is an essential component of the basal ganglia system. This system plays a crucial role in voluntary motor control, procedural learning, habit formation, and reward mechanisms[9].
Dopaminergic neurons in the SNc project to the striatum (which includes the caudate nucleus and putamen) via the nigrostriatal pathway, a part of the basal ganglia circuitry[10]. These neurons release dopamine in the striatum, which is fundamental to initiating and executing voluntary movements[11].
Apart from motor control, the substantia nigra is also linked with reward and addiction through the mesolimbic pathway[12]. Dopaminergic neurons in the substantia nigra and ventral tegmental area project to regions like the nucleus accumbens and prefrontal cortex, modulating the brain's reward system and influencing behavior related to motivation, pleasure, and addiction[13].
The degeneration of dopaminergic neurons in the SNc is a pathological hallmark of Parkinson's disease, leading to the motor symptoms that characterise this neurodegenerative disorder, including tremors, bradykinesia (slowness of movement), and postural instability[14].
Oseh is a software engineer, entrepreneur and founder of SpeechFit. Oseh is passionate about improving health and wellbeing outcomes for neurodiverse people and healthcare providers alike.
References
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Cleveland Clinic. (2022). Substantia Nigra (SN). Retrieved from https://my.clevelandclinic.org/health/body/23010-substantia-nigra-sn. Reviewed by a Cleveland Clinic medical professional on 05/15/2022.
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