IUBio

role of thalamus in intellectual development

Dave L dave at lud-low.freeserve.co.uk
Mon May 24 19:49:07 EST 1999


Prompted by a recent thread entitled "thalamus and cognition" I
decided to make my first tentative contribution to the NG. As will be
obvious, I am not a scientist or neurologist.

My daughter has thalamic brain damage and her case indicates a
possible role for the thalamus in the development of intellect. I
understand that classically the cerebral cortex is responsible for
this function. The following brief outline of my daughter's case will
I hope explain why I suspect such a role for the thalamus. 

She has moderate dyskinetic/dystonic cerebral palsy and moderate to
severe learning disability. 'IQ' assessments were between 30 and 49 at
age 10. The motor deficits were attributed to thalamic damage caused
by acute birth aspyxia (Apgars 0,1,3 at 1,5,10 mins) compounded by
inadequately treated hypoglycaemia (~20 to 40 mg/dl for 12 hours).
Three seizures ocurred, at 20 hours and on the second day.

MRI scans reveal subtle but definite damage to the thalamus (most
conspicuous ventrally) with faint extension into the midbrain in the
area of the aqueduct. No other structural abnormalities to the brain
were identified but she has developed microcephaly (50th centile at
birth falling to 3rd to 5th centile at age 10).

The neurologists could only speculate about the cause of her learning
disability, not least because in this type of CP the motor deficits
are usually more severe than any intellectual deficit. However,
because genetic and intra-uterine causes could be eliminated the
intellectual deficit was eventually attributed to either the same
cause as the motor deficits (thalamus) or 'invisible' damage to the
cerebral cortex. Both possibilities were somewhat speculative but
other causes were thought to be unlikely.

There appears to be little scientific or clinical data to support the
view that learning disability can be caused by damage to the thalamus
alone. But there is a brief reference to this  in Neurology of the
Newborn 2nd edition, by JJ Volpe, who speculated on a possible role of
the thalamus in the "development of intellect". 

Therefore, I am currently searching for the answers to two questions:

1) does the thalamus have an important role in intellectual
development/learning ability and if so, what role?

2) Is there a book or other literature that addresses this issue? 

Thanks in advance for any ideas on this.

Dave L



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