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The loop involves connections between the cortex, the basal ganglia, the thalamus, and back to the cortex. It is of particular relevance to hyperkinetic and hypokinetic movement disorders , such as Parkinson's disease and Huntington's disease , [ 1 ] as well as to mental disorders of control, such as attention deficit hyperactivity disorder ...
The principal subdivision of the thalamus into nucleus groups is the trisection of each thalamus (left and right) by a Y-shaped internal medullary lamina. This trisection divides each thalamus into anterior, medial and lateral groups of nuclei. [8] The medial group is subdivided into the medial dorsal nucleus and midline group.
Simplified diagram of frontal cortex to striatum to thalamus pathways. There are five defined frontostriatal circuits: motor and oculomotor circuits originating in the frontal eye fields are involved in motor functions; while dorsolateral prefrontal, orbital frontal, and anterior cingulate circuits are involved in executive functions, social behavior and motivational states. [2]
The direct pathway, sometimes known as the direct pathway of movement, is a neural pathway within the central nervous system (CNS) through the basal ganglia which facilitates the initiation and execution of voluntary movement. [1] It works in conjunction with the indirect pathway.
In neuroanatomy, the lateral geniculate nucleus (LGN; also called the lateral geniculate body or lateral geniculate complex) is a structure in the thalamus and a key component of the mammalian visual pathway. It is a small, ovoid, ventral projection of the thalamus where the thalamus connects with the optic nerve. There are two LGNs, one on the ...
These disorders are known as hypokinetic disorders. However, a disorder leading to abnormally low output of the basal ganglia leads to reduced inhibition, and thus excitation, of the thalamocortical projection neurons (VA and VL) which synapse onto the cortex. This situation leads to an inability to suppress unwanted movements.
Because all brain areas are bidirectionally coupled, these connections between brain areas form feedback loops. Positive feedback loops tend to cause oscillatory activity where frequency is inversely related to the delay time. An example of such a feedback loop is the connections between the thalamus and cortex – the thalamocortical radiations.
The thalamus supplies all parts of the neocortex with afferents. [3] The main thalamocortical fibers extend from different nuclei of the thalamus and project to the visual cortex, somatosensory (and associated sensori-motor) cortex, and the auditory cortex in the brain. Thalamocortical radiations also innervate gustatory and olfactory pathways ...