G.D. Kotzalidis, A. Facchi, L. Tarsitani, V. Mantua, P.P.
Colombo, P. Pancheri - Vol. 7, Giugno 2001, num.2
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Summary Riassunto Indice
Thalamic abnormalities in schizophrenia
Anomalie talamiche nella schizofrenia
There has been a recent revival in the interest of the role of the thalamus
in schizophrenia, partly due to availability of better tools for brain imaging
(magnetic resonance imaging [MRI], both structural and functional, positron
emission tomography [PET], single photon emission computerised tomography [SPECT])
and immunohistochemical techniques, as well as to the advancement in the biological
understanding of synaptic function and neurodevelopment.
In vivo structural
studies (MRI), despite not showing clear-cut differences, point at subtle thalamic
alterations; these are better viewed in the light of the multiple connections
of the thalamus with other important brain structures for the pathogenesis of
schizophrenia, in particular with the dorsolateral prefrontal cortex. The thalamocortical
and corticothalamic interconnections show a high degree of specificity; reciprocal
innervation occurs between the highly differentiated parts of the dorsolateral
prefrontal cortex and the densocellular and parvocellular parts of the mediodorsal
thalamic nucleus. Immunohistochemical and volumetric/densitometric
post-mortem
studies support the evidence for altered neuronal composition of the phylogenetically
more advanced mediodorsal nucleus, specially of the parts that are linked with
the dorsolateral/dorsomedial prefrontal cortex, but reveal also a reduction
in the number of glutamatergic perikarya projecting to the cortex in the anteroventral
nucleus, a more primitive structure. Functional studies, such as PET, SPECT,
and proton magnetic spectroscopy, despite some controversial results, consistently
show the existence of an impairment of a thalamic-prefrontocortical-cerebellar
circuit that results in impaired working memory and reduced performance on some
cognitive tasks, supporting the concept of "cognitive dysmetria" as
central to many schizophrenic symptoms.
