Medial Nuclear Group
The medial nuclear group (medial complex) (B5) consists of a medial magnocellular nucleus, a lateral parvocellular nucleus, and a caudal nucleus. All nuclei project to the frontal lobe, namely, to thepremotor cortex,the polar cortex, and the orbital cortex (B6). Afferent fiber bundles run via the inferior thalamic radiation from the globus pallidusn(B7) and from the basal nucleus of Meynert(substantia innominata) to the medial nuclear group. The medial magno-cellular nucleus has fiber connections to the hypothalamus (B8) (preoptic area and tuber cinereum) and to the amygdaloid body (amygdala). The lateral parvocellular nu-cleus receives fibers from the adjacent ven-tral nuclei of the thalamus.
The medial nuclear complex is thought to receive visceral and somatic impulses via pathways from the hypothalamus and ven-tral nuclei; the impulses are integrated here and then transmitted via the anterior thalamic radiation to the frontal cortex. The basic affective mood, which is essentially de-termined by unconscious stimuli from the visceral and somatic spheres, is thought to enter consciousness in this way.
Clinical Note: It has been observed in patientswith severe agitation that incision of the thalamocortical tracts (prefrontal lobotomy) had a calming effect but was also associated with in-difference and a regression of personality. The stereotactic destruction of the medial nuclear complex has similar effects.
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