Subthalamic Nucleus: Neuroanatomical Review

Discovered in 1865 by Jules Bernard Luys, the subthalamic nucleus is a set of small nuclei located in the diencephalon, inferior to the thalamus and superior to the substantia nigra, that can be visualized in a posterior coronal section. Histologically, it consists of neurons compactly distributed and filled with a large number of blood vessels and sparse myelinated fibers. This review presents an analysis of this anatomical region, considering what is most recent in the literature. Subthalamic neurons are excitatory and use glutamate as the neurotransmitter. In healthy individuals, these neurons are inhibited by nerve cells located in the side globus pallidus. However, if the fibers that make up the afferent circuit are damaged, the neurons become highly excitable, thus causing motor disturbances that can be classified as hyperkinetic, for example ballism and chorea, or hypokinetic, for example Parkinson disease (PD). The advent of deep brain stimulation has given the subthalamic nucleus great visibility. Studies reveal that the stimulation of this nucleus improves themotor symptoms of PD.

As bases neuroanatômicas do comportamento: histórico e contribuições recentes / Neuroanatomical basis of behavior: history and recent contributions

Tendo em vista as mais recentes contribuições, as áreas corticais límbicas - originalmente denominadas em conjunto de grande lobo límbico -, além dos giros do cíngulo e parahipocampal, são constituídas pelas regiões mais posteriores do córtex fronto-orbitário e pelo córtex insular. Em contraposição ao restante do córtex cerebral, que se projeta sobre os gânglios da base (particularmente sobre as porções mais dorsais e mais extensas do striatum, constituídas fundamentalmente pelo núcleo caudado e pelo putame), as áreas corticais límbicas se caracterizam por se projetarem principalmente sobre o hipotálamo e também sobre a porção mais ventral do striatum (principalmente sobre o núcleo accumbens). Uma vez que todo o striatum se projeta para o globo pálido - e este para o tálamo, que se projeta para o córtex cerebral, constituindo-se, assim, circuitos córtico-subcorticais reentrantes -, tem-se que, enquanto as alças relacionadas com o striatum e o pallidum dorsais são responsáveis por atividades e rotinas motoras, as alças relacionadas com o striatum e o pallidum ventrais caracterizam circuitos córtico-subcorticais reentrantes e segregados que se relacionam particularmente com funções comportamentais. A amígdala estendida (amígdala centromedial, componente dorsal ou estria terminal, componente ventral e núcleo da estria terminal), por sua vez, também recebe aferências de todas as áreas corticais límbicas, é particularmente modulada pelas áreas corticais pré-frontais e, ao invés de se projetar sobre o striatum, projeta-se diretamente sobre o hipotálamo e o tronco encefálico. Ao receber também conexões diretas do tálamo, a amígdala estendida pode ainda desencadear respostas principalmente autonômicas, de forma inespecífica, porém rápida, através da ativação de centros do tronco encefálico. Os sistemas macro-anatômicos fronto-basais, estriatal-palidal ventral e amígdala estendida, em conjunto com o núcleo basal de Meynert e com o sistema septo-banda...

Considering the most recent contributions, the limbic cortical areas, originally known as the greater limbic lobe, besides the cingulated and the parahippocampal gyri also includes the insula and the posterior orbital cortex. In contrast to the nonlimbic cortical areas that project to the basal ganglia (particularly over the dorsal aspects of the striatum, constituted by the caudate nucleus and by the putamen), the limbic cortical areas are characterized by projecting to the hypothalamus and also to the ventral striatum (particularly to the nucleus accumbens). Once all the striatum projects to the globus pallidus which projects to the thalamus and then to the cortex, generating cortical-subcortical reentrant circuits, while the dorsal striatum and pallidum related cortico-subcortical loops are involved with motor activities, the ventral cortical-striatal-pallidal system is particularly related with behavior functions. The extended amygdala (central medial amygdala, stria terminalis or dorsal component, ventral component, and bed nucleus of stria terminalis) receives inputs primarily from the limbic cortical areas, is particularly modulated by the prefrontal cortex, and receives also direct connections from the thalamus that enables the amygdala to generate nonspecific and quick responses through its projections to the hypothalamus and to the brainstem. The ventral striatal-pallidal and the extended amygdala are then two basal forebrain macro-anatomical systems, that together with the basal nucleus of Meynert and with the septal-diagonal band system, constitute the main structures that are particularly connected with the limbic cortical areas, and that altogether project to the hypothalamus and to the brainstem which give rise to the autonomic, endocrine and somatosensory components of the emotional experiences, and that regulate the basic activities of drinking, eating, and related to the sexual behavior.