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It has several functions, such as the relaying of sensory and motor signals to the cerebral cortex [1] [2] and the regulation of consciousness, sleep, and alertness. [ 3 ] [ 4 ] Anatomically, it is a paramedian symmetrical structure of two halves (left and right), within the vertebrate brain, situated between the cerebral cortex and the midbrain .
Sometimes, it is in two parts – and 20% of the time, it is absent. [2] In other mammals, it is larger. In 1889, a Portuguese anatomist by the name of Macedo examined 215 brains, showing that male humans are approximately twice as likely to lack an interthalamic adhesion as are female humans.
[1] [8] The parallel CBGTC loops have been segregated according to the functions of associated cortical regions. One scheme involves the division into limbic and motor loops, with the motor loops containing indirect and direct pathways, which are in turn interconnected with the limbic loop that projects into the ventral striatum. [9]
The ventrobasal complex (VB) is a relay nucleus of the thalamus for nociceptive stimuli received from nociceptive nerves. The VB consists of the ventral posteromedial nucleus (VPM) and the ventral posterolateral nucleus (VPL). In some species, the ventral posterolateral nucleus, pars caudalis is also a part of the VB. [1]
In humans it makes up roughly 40% of the thalamus making it the largest of its nuclei. [16] Significant research has been undertaken in the marmoset examining the role of the retinorecipient region of the inferior pulvinar (medial subdivision), which projects to visual cortical area MT, in the early development of MT and the dorsal stream, as ...
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]
Before activation of the direct pathway, these two nuclei were actively sending inhibitory signals to the ventrolateral nucleus of the thalamus, which prevented the development of significant activity in the motor cerebral cortices. This behavior ceases on activation of the direct pathway.
The ganglion cells of the retina project in an orderly fashion to the lateral geniculate nucleus (LGN) of the thalamus and from there to the primary visual cortex (V1); adjacent spots on the retina are represented by adjacent neurons in the lateral geniculate nucleus and the primary visual cortex.