The mediodorsal thalamic nucleus and schizophrenia

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					                                                         Review Paper
                                                        Examen critique


                           The mediodorsal thalamic nucleus
                                 and schizophrenia


                       Raúl Alelú-Paz, MSc; José Manuel Giménez-Amaya, MD, PhD
Departamento de Anatomía, Histología y Neurociencia, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain



  The mediodorsal nucleus of the human thalamus is in a crucial position that allows it to establish connections with diverse cerebral struc-
  tures, particularly the prefrontal cortex. The present review examines existing neurobiologic studies of the brains of people with and with-
  out schizophrenia that indicate a possible involvement of the mediodorsal nucleus in this psychiatric disorder. Studies at synaptic and
  cellular levels of the neurobiology of the mediodorsal nucleus, together with a better anatomic understanding of this diencephalic struc-
  ture owing to neuroimaging studies, should help to establish a more deep and solid pathophysiologic model of schizophrenia.

  Le noyau dorsomédian du thalamus humain se trouve à un endroit crucial qui lui permet d’établir des liens avec diverses structures
  cérébrales, et en particulier le cortex préfrontal. La présente synthèse porte sur des études neurobiologiques existantes du cerveau de
  personnes atteintes ou non de schizophrénie qui indiquent que le noyau médiodorsal peut jouer un rôle dans ce trouble psychiatrique.
  Des études aux niveaux synaptique et cellulaire portant sur la neurobiologie du noyau dorsomédian, ainsi qu’une meilleure compréhen-
  sion anatomique de cette structure du diencéphale découlant d’études de neuro-imagerie, devraient aider à établir un modèle patho-
  physiologique plus profond et solide de la schizophrénie.




Neuromorphology of the mediodorsal nucleus                                 thalamic reticular nucleus and the zona incerta.2
of the thalamus                                                               The main cell groups of the dorsal thalamus are limited by
                                                                           the internal medullary lamina.2 The mediodorsal nucleus
The anatomic location of the thalamus in humans is crucial to              (MD) is part of the medial nuclear group (Fig. 1). In humans,
its principal function: interconnecting different cerebral struc-          as in most other mammals, this nucleus is generally divided
tures, particularly to the cerebral cortex. The thalamus sends             into 3 subnuclei. Thus according to Jones’ extensive review
and receives projections from multiple regions in the cortex               on the thalamus,2 the MD can be parcellated in a magnocellu-
and the brainstem, and it has traditionally been assigned a fun-           lar or medial region (pars fibrosus) composed of large cells; a
damental role in the process of filtering nervous information.1            parvocellular or central and posterior region (pars fasciculo-
   The thalamus comprises a large number of neuronal                       sis) consisting of smaller neurons; and a multiform or lateral
groups involved in a wide range of cognitive, sensorimotor                 region (subnucleus caudalis) with cells of mixed sizes, in-
and limbic functions. The external medullary lamina, a layer               cluding a paralaminar area or nucleus that would probably
of myelinic axons, covers the lateral face of the thalamus, and            be better placed in the central lateral intralaminar nucleus.2,3
the medial thalamic surface abuts on the third ventricle.2 The             However, other authors have claimed that this subnuclear
classic separation between the dorsal and ventral thalamus is              division of the MD is not clear and have suggested that the
determined in part by the fusion between the thalamic fas-                 subdivisions are based on myeloarchitectonic differences,4–6
cicle and the external medullary lamina and between the                    which implies the MD is a single entity.7


Correspondence to: Dr. J.M. Giménez-Amaya, Departamento de Anatomía, Histología y Neurociencia, Facultad de Medicina,
Universidad Autónoma de Madrid, C/ Arzobispo Morcillo s/n. 28029 Madrid, Spain; fax 34 91 497 5338;
josemanuel.gimenezamaya@uam.es

Medical subject headings: mediodorsal thalamic nucleus; schizophrenia.

J Psychiatry Neurosci 2008;33(6):489-98.
Submitted Aug. 5, 2007; Revised Dec. 7, 2007; Feb. 4, 2008; Accepted Feb. 5, 2008


© 2008 Canadian Medical Association

                                                    J Psychiatry Neurosci 2008;33(6)                                                       489
Alelú-Paz and Giménez-Amaya



Connections                                                              dala. 2 The prepiriform and entorhinal cortices and the
                                                                         amygdala project to the same cerebral areas as the magno-
Afferent projections to the magnocellular, parvocellular                 cellular subdivision of the MD, thus forming a circuit that
and multiform regions of the MD                                          is not found in the other 2 subdivisions (Fig. 2). 2 Other
Olfactory impulses from the entorhinal cortex, the prepiri-              GABAergic projections from the ventral pallidum, globus
form cortex and adjacent regions such as the olfactory tu-               pallidus and pars reticulata of the substantia nigra reach all
bercle reach the MD magnocellular subdivision, indicating                3 subdivisions of the MD.2,9–13
the existence of a route that carries olfactory impulses                    The parvocellular and multiform subdivisions receive
through the thalamic MD to neocortical regions.2,8 The same              abundant projections from the brainstem. The projections to
MD subdivision also receives projections from the amyg-                  the parvocellular subdivision from the superior colliculus,




       Fig. 1: (A, B) Photomicrographs of 2 sections of the human thal
				
DOCUMENT INFO
Description: The mediodorsal nucleus of the human thalamus is in a crucial position that allows it to establish connections with diverse cerebral structures, particularly the prefrontal cortex. The present review examines existing neurobiologic studies of the brains of people with and without schizophrenia that indicate a possible involvement of the mediodorsal nucleus in this psychiatric disorder. Studies at synaptic and cellular levels of the neurobiology of the mediodorsal nucleus, together with a better anatomic understanding of this diencephalic structure owing to neuroimaging studies, should help to establish a more deep and solid pathophysiologic model of schizophrenia.
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