XXY Brain Structure

	XXY Brain Structure
	The following material is based on research being conducted by Jay Giedd, M.D. Dr. Giedd is a practising child and adolescent psychiatrist and chief of brain imaging at the Child Psychiatry Branch of the National Institute of Mental Health where he conducts research on the biological basis of behavioural, cognitive, and emotional disorders in children. Particular interests include pharmacology, genetics, and brain imaging. He is currently using magnetic resonance imaging (MRI) to explore brain development in those with 47XXY and other sex chromosome aneuploidies. The information presented here is from a talk he gave Sunday, August 5th, 2001, at the 2nd annual AAKSIS conference in Philadelphia, coupled with notes from Bill Mulkern and Katie Garber from the 2000 NIH conference "Expanding the Phenotype and Identifying New Research Directions," in Bethesda, Maryland. Top XXY and XXYY brains generally smaller than XY and XX controls. Frontal lobes - responsible for executive functions (inhibiting, sustaining, initiating) smaller than in XYs Basal ganglia (Caudate nucleus) responsible for secretarial functions (prioritising input to the frontal lobes) smaller than in XYs "The caudate is closely linked to the frontal lobes and helps organise and execute the actions determined by the frontal lobes. It is hard to sum up the functions of many brain structures because they are like links in many chains. It is sort of like the different brain parts are letters which can be parts of many different words." --Dr. Giedd Temporal Lobes (hearing, language, emotion, memory) smaller than in XYs Parietal lobes (somatosensory, internal map, math, music, tying together information from other parts of the brain) Parietal white matter volume - XXYs relatively larger than controls, while XXYYs much smaller than XYs. Occipital lobes* (vision) XXYS considerably larger than XYs. XXYYs considerably smaller. This may indicate that XXYs are more visual than auditory or process better visually than in an auditory manner. Ventricles (circulate cerebrospinal fluid) Lateral ventricular volume larger in XXYs than XYs; XXYYs about the same as XYs Top Cerebellum - organisation of thinking - about the same - least inheritable, matures late, in 20's I also asked Dr. Giedd: "how does testosterone interact with any of this, if at all, in foetal development, and later. What I'm getting at and am interested in is if these brain differences are because of an androgen deficiency or something else?" His reply: "I think that is one of the compelling questions. To my knowledge nobody knows of the effects of testosterone on any of these processes. Sorry to be so wishy-washy. I wish we knew more with some degree of certainty." * (somatosensory : of, relating to, or being sensory activity having its origin elsewhere than in the special sense organs (as eyes and ears) and conveying information about the state of the body proper and its immediate environment) Back Top

The following material is based on research being conducted by Jay Giedd, M.D. Dr. Giedd is a practising child and adolescent psychiatrist and chief of brain imaging at the Child Psychiatry Branch of the National Institute of Mental Health where he conducts research on the biological basis of behavioural, cognitive, and emotional disorders in children. Particular interests include pharmacology, genetics, and brain imaging. He is currently using magnetic resonance imaging (MRI) to explore brain development in those with 47XXY and other sex chromosome aneuploidies.

The information presented here is from a talk he gave Sunday, August 5th, 2001, at the 2nd annual AAKSIS conference in Philadelphia, coupled with notes from Bill Mulkern and Katie Garber from the 2000 NIH conference "Expanding the Phenotype and Identifying New Research Directions," in Bethesda, Maryland.

Top

XXY and XXYY brains generally smaller than XY and XX controls.

Frontal lobes - responsible for executive functions (inhibiting, sustaining, initiating) smaller than in XYs

Basal ganglia (Caudate nucleus) responsible for secretarial functions (prioritising input to the frontal lobes) smaller than in XYs

"The caudate is closely linked to the frontal lobes and helps organise and execute the actions determined by the frontal lobes. It is hard to sum up the functions of many brain structures because they are like links in many chains. It is sort of like the different brain parts are letters which can be parts of many different words." --Dr. Giedd

Temporal Lobes (hearing, language, emotion, memory) smaller than in XYs

Parietal lobes (somatosensory*, internal map, math, music, tying together information from other parts of the brain) Parietal white matter volume - XXYs relatively larger than controls, while XXYYs much smaller than XYs.

Occipital lobes (vision) XXYS considerably larger than XYs. XXYYs considerably smaller. This may indicate that XXYs are more visual than auditory or process better visually than in an auditory manner.

Ventricles (circulate cerebrospinal fluid) Lateral ventricular volume larger in XXYs than XYs; XXYYs about the same as XYs

Top

Cerebellum - organisation of thinking - about the same - least inheritable, matures late, in 20's

I also asked Dr. Giedd: "how does testosterone interact with any of this, if at all, in foetal development, and later. What I'm getting at and am interested in is if these brain differences are because of an androgen deficiency or something else?"

His reply:

"I think that is one of the compelling questions. To my knowledge nobody knows of the effects of testosterone on any of these processes. Sorry to be so wishy-washy. I wish we knew more with some degree of certainty."

* (somatosensory
: of, relating to, or being sensory activity having its origin elsewhere than in the special sense organs (as eyes and ears) and conveying information about the state of the body proper and its immediate environment)

Back

Top