Anchor Study
By Suzanne Goh, Ravi Bansal, Dongrong Xu, Xuejun Hao, Jun Liu,
Bradley S. Peterson
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To determine the correlation of cortical thickness in the cerebrum of the
human brain with FSIQ (Full Scale Intelligence quotient) and determine
the moderating effects of sex and age.
To use the results of the cortical findings to determine whether they were
supported by differences in white matter volume.
http://tinyurl.com/62tqytz
http://tinyurl.com/64hzge4
• The participants of this cross-sectional
study included 105 healthy people (no
current or past psychiatric/neurological
disorder) selected randomly from a
telemarketing database.
• Mean age - 17.7 years
•Age range 7-57 years (children < 18years
= 62%)
• FSIQ of 70 and higher
• Gender
Females - 45.7%,
Males - 54.3%
http://tinyurl.com/3kju2v6
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Different instruments were used based on research study protocol.
All instruments tested similar domain of cognitive function.
Intelligence testing was done on the same day of Magnetic Resonance
Imaging (MRI) or within 1 month.
Wechsler Intelligence scales, age determined which version was used.
-For 51 children - Wechsler Intelligence Scale for Children (WISC-III)
-For 34 adults - Wechsler Adult Intelligence Scale revised (WAIS-R)
-For 3 children & 6 adults - Wechsler Abbreviated Scale of
Intelligence(WASI)
Kaufmann Brief Test of Intelligence (K-BIT)
-For 11 children
- 1.5 Tesla Scanner was used to acquire
anatomical image.
- Cantho-meatal landmarks used to
standardized head positioning.
- 3-dimensional spoiled gradient recall
sequence used to acquire image.
http://tinyurl.com/3gtl9o9
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Brain and non-brain tissues were separated using an automated tool and
manual editing.
Cortical gray matter was isolated using representative values of gray and
white matter together with 3 orthogonal views on Sun Ultra 10
workstation (ANALYZE 7.5 software).
The gray scale values of pure representations of cortical gray and white
matter was sampled bilaterally in 4 locations using 8x8 pixel array.
http://tinyurl.com/44gzs63
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Average calculated for each tissue type to reduce bias.
Mean threshhold value used to provide rough classification of gray and
white matter throughout the cerebrum.
This classification was hand-edited in 3 orthogonal views to remove
subcortical gray matter and rims of the ventricles.
White matter was isolated.
Images were flipped to remove bias , then corrected.
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Selected template brain of participant that most demographically
represented all healthy controls. Average brain is not used as template
inorder to ensure accuracy.
Brains for all other participants were coregistered to template brain using a
rigid body similarity transformation.
Coregistered brains were then nonlinearly transformed to the template
brain using a high-dimensional, non-rigid warping algorithm based on
fluid dynamics.
Each brain now the same shape and size as template brain, permitted
identification of points on all participants’ cerebral surfaces to compare
with corresponding points on template.
Distance was computed between points on brain surfaces using least
square analysis.
The cerebrum for which all points across its surface was closest to the
average computed distance was reselected as the template brain.
Processes were repeated.
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Coregistered brain - cortical mantel
3-dimensional morphological operator to distance transform the brain
without the cortex from coregistered brain.
Cortical thickness was calculated as the smallest distance of each point on
the external cortical surface from the outermost surface of the white matter
in the coregistered brain.
Cclculation of cortical thickness was controlled for whole brain volume.
http://tinyurl.com/64hzge4
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VPW warped a binarized image of the brain to form a spatially
normailized image that has varying pixel intensities.
Voxel-wise statistical analyses performed to detect regions of significant
correlation between local brain volume and FSIQ.
Cortical thickness and FSIQ
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In localized regions of the prefrontal cortices ( left ventromedial and
right dorsolateral prefrontal cortices), an inverse correlation between
cortical thickness and FSIQ was found. Specific areas include left
anterior cingulate gyrus, left orbitofrontal cortex, left subgenal gyrus
and right middle frontal gyrus.
http://www.psych-it.com.au/Psychlopedia/article.asp?id=191
http://tinyurl.com/3vvobnk
Cortical thickness and FSIQ
Gender and FSIQ
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Gender-modified correlations in many regions but primarily in the frontal regions. These include the
Broca’s area, left cingulate cortex and right medial prefrontal gyrus.
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Correlation for cortical thickness differed for males and females in prefrontal regions.
- Females showed a positive correlation in nearly all regions
- Males showed an inverse correlation.
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Exception – left anterior cingulate cortex showed a positive correlation for males and negative for
females.
http://tinyurl.com/67a5c25
http://tinyurl.com/3woz5dg
White matter
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A significant FSIQ-by-age interaction was detected in the right frontal
white matter volume and in the white matter underlying the
dorsolateral prefrontal cortex adults but not in children. An inverse
correlation was found, that increased with age.
In the left periventricular matter of adults a positive correlation was
detected between FSIQ and white matter volume.
Observation due to fibers of the superior corona radiata, superior
longitudinal fasciculus and anterior portion of the corpus callosum.
No FSIQ-by-sex correlation observed.
Total Brain Volume
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FSIQ correlated positively with total brain volume
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The inverse correlation between cortical thickness and FSIQ in the prefrontal cortex
could be as a consequence of
Late maturation of prefrontal cortex
Synaptic pruning/ increase myelin coating of fibers
in lower cortical areas, leading to cortical thinning
Inter-individual differences in intellectual ability
observed in adults
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The inverse correlation between white matter volume and FSIQ, means that smaller
volumes of white matter influenced higher FSIQ in adults.
The findings from gray and white matter volume therefore further reinforce the idea
that synaptic pruning in adults accounts for their inter-intellectual differences in
adults
Correlation of cortical thickness with FSIQ in the Broca’s area in females possibly
reflects why females have an advantage over males for verbal fluency.
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The findings of this study overlap with finding from other studies
to indicate that the frontal and parietal regions compose the primary
neurological substrate for “g” , general intelligence as well as the
necessary skills to perform many cognitive functions.
Anchor study findings therefore support the Parieto-Frontal
Integration Theory of Intelligence.
- inverse correlation between cortical thickness and intelligence
- gender specific patterns correlated with intelligence
- cortical and white matter are involved in intelligence
 This theory states that the frontal and parietal lobes in the brain are
the primary areas involve in intelligence.
(http://www.science20.com/news_account/parieto_frontal_integrati
on_theory_p_fit_a_neural_basis_of_intelligence)
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1)
2)
3)
How reflective is the anchor study “ Neuroanatomical correlates of
intellectual ability across the lifespan,of Gardner’s, “Myths and realities
of multiple intelligence”?.
Gardner wrote, “I would recommend that any intelligence be assessed by
a number of complementary approaches that consider the core
components of an intelligence.” Analyzing this statement, how would
you suggest the implementation of assessment based on Gardner’s
Multiple Intelligence?
In the anchor text, the effects of age on intelligence was studied. How
then does the theory nature vs. nurture impact intelligence across
lifespan?