Basdes Neurologicas

ALTERACIONES DEL LENGUAJE
REVISIÓN

Bases neurobiológicas del lenguaje y sus alteraciones
J. Castaño
NEUROBIOLOGICAL BASES OF LANGUAGE AND ITS DISORDERS
Summary. Aims. The purpose of this study is to offer an update on the anatomofunctional bases of language and the theories
that explain its normal and pathological development. Method. Language is a clear example of one of the higherfunctions of
the brain, the development of which is carried out, on the one hand, in a genetically determined anatomofunctional structure
and, on the other hand, by the verbal stimulus provided by the environment. Several systems and subsystems are at play within
the anatomofunctional structure and these operate in series and in parallel. A large amount of the knowledge we have about
theneurophysiological bases of language come from observations carried out in adult patients with circumscribed lesions and
their clinical consequences (aphasias). Findings from recent studies involving functional imaging in volunteers submitted to
linguistic tests have added more data. According to Damasio, three functional systems are at work in language: 1. The
instrumental system, which corresponds tothe perisylvian region of the dominant hemisphere where phonological processing
takes place; 2. The mediation system, which includes temporal, frontal and parietal areas that surround the anterior region
and are where lexical items are organised in a modular fashion, in terms of categories, actions and functional or connecting
words; 3. The semantic system, which includes extensive areas of thecortex in both hemispheres and is the seat of concepts
and meanings. Throughout a child’s development, the evolution he or she follows to reach the neurolinguistic organisation
of the adult brain requires the integrity and proper functioning of these structures that are for the most part located in the
dominant hemisphere. We review the different theories that appear in the specialisedliterature concerning the causes and
fisiopathogenic mechanisms behind dysphasias in early childhood. Conclusions. Among the numerous functions that take part
in the complex language system, some are essential for its normal development. From the work of Tallal et al. it has been seen
that the sequential and fast phonological processing of consonant-vowel shifts is altered in dysphasic and dyslexicchildren.
This finding is related with the disorders in the normal asymmetry of the temporal planum (the left is larger than the right)
that has been observed in these patients and with the neuropathological findings of Galaburda et al. in dyslexic patients who
had previously been dysphasic, in whom cytoarchitectural anomalies (heterotopias) were found, above all in the left perisylvian region.Obviously not all forms of dysphasia are the result of this alteration. According to Chevrie-Muller’s classical chartadapted by us in accordance with Damasio’s scheme –it is possible to locate the dysphasic syndromes in different loci and
distinguish a different physiopathological mechanism for each of them. [REV NEUROL 2003; 36: 781-5]
Key words. Developmental language disorder. Dysphasias.Hemispheric dominance. Neurobiological bases of language. Phonological processing. Temporal planum.

INTRODUCCIÓN
El lenguaje es un claro ejemplo de una función superior del cerebro cuyo desarrollo se sustenta, por un lado, en una estructura
anatomofuncional genéticamente determinada y, por otro, en el
estímulo verbal que le da el entorno.
Dentro de la estructura anatomofuncional participandiversos
sistemas y subsistemas que actúan en serie y en paralelo. Gran
parte de nuestro conocimiento sobre las bases neurofisiológicas
del lenguaje proviene de las observaciones de pacientes adultos
con lesiones circunscritas y sus consecuencias clínicas (afasias).
A esto se han agregado, en los últimos tiempos, estudios con
imágenes funcionales en voluntarios sometidos a pruebas lingüísticas....