Good Morning,
You have my sympathies concerning your daughter's misfortune.
Your observations are well presented and evoked recollections of Sagan's
"Dragons of Eden". From an evolutionary perspective the thalamus and
indeed the entire diencephalon are quite probably antecedant to functions
now handled by the major components of the cerebrum (cortex and basal
nuclei.) That vague hypothesis is however, a long step from causal
relationships in the genesis or development of intellect.
If we presume intellect develops as a response to stimulation, then some
component of thalamic participation in cognitative development must include
relay of sensory input to "higher" centers. T^he consequences of damage to
the relay of stimulation to the brain is probably easier to test than any
other possible explanation. In which case, either the absence of
stimulation or the excess of irrelevant stimulation might be tested for the
potential to disrupt intellectual development.
Myriad other possibilities exist, but from my arm chair, this is likely the
simplest.
Sincerely,
rlh
At 12:49 AM +0000 5/25/99, Dave L wrote:
>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
Richard Hall, Associate Professor of
Comparative Animal Physiology
Division of Sciences and Mathematics
University of the Virgin Islands
St. Thomas, USVI 00802
340-693-1386
rhall at uvi.edu