[neuroling] Genetics of Language
- From: "giancarlo" <giancarlo@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
- To: neuroling@xxxxxxxxxxxxx
- Date: Fri, 08 Nov 2002 17:50:44 -0700
Dear Neurolingers,
this theoretical thread has been discussed on non-neuro-specialized lists,
and at the moment it's really hot.
After Vargha-Khadem et al. 1995 paper (Praxic and Nonverbal Cognitive
Deficits in a Large Family with a Genetically Transmitted Speech and
Language Disorder. Proceedings of the National Academy of Sciences, Vol 92,
930-933, others have studied genetics-langiuage relationship:
Lai et al. Nature (2001) 413:519, and in the review of this paper by Andrew
(S Andrew, Communicating a new gene vital for speech and
language.Clinical Genetics.(61) 2002, 97-100).
The family studied by Lai et al. would miss FOXP2 gene, that for these
reasons has been linked to language faculty. It is interesting to note that
the reported abnormalities probably due to this missing gene concern
frontal lobe and basal ganglia, i.e. fronto-striatal circuits that are
thought to be essential in verbs production (SF Cappa et al., Object
and action naming in Alzheimer's disease and frontotemporal dementia,
Neurology, Vol. 50, 351-355, 1998; A Daniele et al., Evidence for a
possible neuroanatomical basis for lexical processing of nouns and
verbs, Neuropsychologia, 32, 1325-1341, 1994).
A genetic mutation as the basis for language origin had been
hypothesized by T Crow 2000a (TJ Crow. Schizophrenia as the price that
Homo sapiens pays for language: a resolution of the central paradox in
the origin of the species. Brain Research Reviews, (31) 2000,
118-129) as a factor of hemispheric specialization. Crow 2000b is more
precise on the causes of genetic mutation: "the critical change (a
"saltation") in the transition from a precursor hominid to modern Homo
sapiens occurred in a gene for cerebral lateralisation located on the
Y chromosome in a block of sequences that had earlier transposed from
the X. Sexual selection acting upon an X-Y homologous gene to
determine the relative rates of development of the hemispheres across
the antero-posterior axis ("cerebral torque") allowed language to
evolve as a species-specific mate recognition system...." (Timothy
J. Crow (2000) Did Homo Sapiens Speciate on the y Chromosome?.
Psycoloquy: 11(001).
Crow's hypothesis seems supported by the reported brain abnormalities
observed in schizophrenic subjects (in vivo and post-mortem), as reversal of
planum temporale and right hemisphere dominance for inferior parietal
lobule.
So it seems that also if not yet fully identified, a language gene not only
exists, but its alterations can provoke psychoses and other disabilities
(see Crow 2000). This issue opens a window on the language-thought-behavior
relationships, but this last topic deserves further and wider discussion.
Any suggestion?
Giancarlo Buoiano, PhD
Neuroscience Dpt.
Univ. of Pisa
Italy
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