24 Facts About Basal ganglia


The basal ganglia are situated at the base of the forebrain and top of the midbrain.

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Basal ganglia are strongly interconnected with the cerebral cortex, thalamus, and brainstem, as well as several other brain areas.

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The basal ganglia are associated with a variety of functions, including control of voluntary motor movements, procedural learning, habit learning, conditional learning, eye movements, cognition, and emotion.

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Experimental studies show that the basal ganglia exert an inhibitory influence on a number of motor systems, and that a release of this inhibition permits a motor system to become active.

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The "behavior switching" that takes place within the basal ganglia is influenced by signals from many parts of the brain, including the prefrontal cortex, which plays a key role in executive functions.

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Basal ganglia are of major importance for normal brain function and behaviour.

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The basal ganglia have a limbic sector whose components are assigned distinct names: the nucleus accumbens, ventral pallidum, and ventral tegmental area .

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In contrast to the cortical layer that lines the surface of the forebrain, the basal ganglia are a collection of distinct masses of gray matter lying deep in the brain not far from the junction of the thalamus.

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In terms of anatomy, the basal ganglia are divided into four distinct structures, depending on how superior or rostral they are : Two of them, the striatum and the pallidum, are relatively large; the other two, the substantia nigra and the subthalamic nucleus, are smaller.

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Substantia nigra is a midbrain gray matter portion of the basal ganglia that has two parts – the pars compacta and the pars reticulata .

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Subthalamic nucleus is a diencephalic gray matter portion of the basal ganglia, and the only portion of the ganglia that produces an excitatory neurotransmitter, glutamate.

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Generally, the basal ganglia circuitry is divided into five pathways: one limbic, two associative, one oculomotor, and one motor pathway.

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Basal ganglia contains many afferent glutamatergic inputs, with predominantly GABAergic efferent fibers, modulatory cholinergic pathways, significant dopamine in the pathways originating in the ventral tegmental area and substantia nigra, as well as various neuropeptides.

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Neuropeptides found in the basal ganglia include substance P, neurokinin A, cholecystokinin, neurotensin, neurokinin B, neuropeptide Y, somatostatin, dynorphin, enkephaline.

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Extracellular dopamine in the basal ganglia has been linked to motivational states in rodents, with high levels being linked to satiated state, medium levels with seeking, and low with aversion.

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The limbic basal ganglia circuits are influenced heavily by extracellular dopamine.

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One review supported the idea that the cortex was involved in learning actions regardless of their outcome, while the basal ganglia was involved in selecting appropriate actions based on associative reward based trial and error learning.

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Basal ganglia has been proposed to gate what enters and what doesn't enter working memory.

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Basal ganglia disease is a group of movement disorders that result from either excessive output from the basal ganglia to the thalamus – hypokinetic disorders, or from insufficient output – hyperkinetic disorders.

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Thorough reconsideration by Cecile and Oskar Vogt simplified the description of the basal ganglia by proposing the term striatum to describe the group of structures consisting of the caudate nucleus, the putamen, and the mass linking them ventrally, the nucleus accumbens.

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Altogether, the main structures of the basal ganglia are linked to each other by the striato-pallido-nigral bundle, which passes through the pallidum, crosses the internal capsule as the "comb bundle of Edinger", and finally reaches the substantia nigra.

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Additional structures that later became associated with the basal ganglia are the "body of Luys" or subthalamic nucleus, whose lesion was known to produce movement disorders.

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The term Basal ganglia is a misnomer: In modern usage, neural clusters are called "Basal ganglia" only in the peripheral nervous system; in the central nervous system they are called "nuclei".

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Clear emergent issue in comparative anatomy of the basal ganglia is the development of this system through phylogeny as a convergent cortically re-entrant loop in conjunction with the development and expansion of the cortical mantle.

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