Autism and brain growth
John H.
neurodevelopmental disorder and schizophrenics showed delayed
lateralisation.
http://news.bbc.co.uk/2/hi/health/3067149.stm
Autism linked to brain growth
Autism may be linked to unusually rapid brain growth during the first year
of life, say researchers.
They found that children with a small head at birth, followed by a sudden
and excessive increase in head circumference during their first year, seemed
to be more at risk of subsequently developing symptoms of autism.
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Emma Chase VanCott
: Interesting because of recent research showing that schizophrenia is a
: neurodevelopmental disorder and schizophrenics showed delayed
: lateralisation.
: http://news.bbc.co.uk/2/hi/health/3067149.stm
: Autism linked to brain growth
: Autism may be linked to unusually rapid brain growth during the first year
: of life, say researchers.
: They found that children with a small head at birth,
Brain, or head growth.
Huge difference.
Maybe they just have oversized ventricles, with a small brain, which still
makes their head "large".
Small head at birth is not surprising. Autism is a "developmental
disorder".
Emma
John H.
The article did seem surprising so I had a quick look (see below). The
preponderance of evidence is towards increased brain size, particularly
prior to 6 years, and this is not accounted for by enlarged ventricles,
though these are present. I wonder if the increased size prevents midbrain
afferents finding their targets in some neocortical regions, hence the loss
of size in later years may reflect loss of tissue because of lack of
sufficient innervation(note loss of white matter in autistics with age
below). Also wonder if the increased size of some regions relates in some
way to the savant like abilities in autistics. No, I do not equate savant
with genius, actually I think these are very different things, but perhaps
the sheer enlargement of cortical surface areas allows some of those
extraordinary skills to emerge in spite of loss of executive functions. Or
given the recent work of Alan Synder, where he can induce savant like
abilities by suppressing some neocortical regions in normal individuals,
perhaps executive functions inhibit savant like abilities. Eg. In some cases
of traumatic brain injury, during the recovery phase individuals may
demonstrate savant like abilities but these fade through recovery (haven't
checked that reference but concordant with Synder's little games).
Certainly a neurodevelopmental disorder and a fascinating one. Research last
year at the opposite end of the spectrum indicated microencephaly is
associated with a particular gene mutation, that may provide a clue.
17/07/03 4:01am
Effects of age on brain volume and head circumference in autism.
Aylward EH Field K Sparks BF ), Singh N Neurology 2002 Jul 59:175-83
Neurology ) . Volume 59 . Issue Abstract
OBJECTIVE: To determine whether brain volume, as assessed on MRI scans,
differs between individuals with autism and control subjects, and whether
such differences are affected by age. BACKGROUND: Previous studies have
found increased brain weight, head circumference, and MRI brain volume in
children with autism. However, studies of brain size in adults with autism
have yielded conflicting results. The authors hypothesize that enlargement
of the brain may be a feature of brain development during early childhood in
autism that normalizes with maturational processes. METHODS: The authors
measured total brain volumes from 1.5-mm coronal MRI scans in 67
non-mentally retarded children and adults with autism and 83 healthy
community volunteers, ranging in age from 8 to 46 years. Head circumference
was also measured. Groups did not differ on age, sex, verbal IQ, or
socioeconomic status. RESULTS: Brain volumes were significantly larger for
children with autism 12 years old and younger compared with normally
developing children, when controlling for height. Brain volumes for
individuals older than age 12 did not differ between the autism and control
groups. Head circumference was increased in both younger and older groups of
subjects with autism, suggesting that those subjects older than age 12 had
increased brain volumes as children. CONCLUSIONS: Brain development in
autism follows an abnormal pattern, with accelerated growth in early life
that results in brain enlargement in childhood. Brain volume in adolescents
and adults with autism is, however, normal, and appears to be due to a
slight decrease in brain volume for these individuals at the same time that
normal children are experiencing a slight increase.
--
17/07/03 4:02am
Brain volume in autism.
Hardan AY , Mallikarjuhn M ), Keshavan MS J Child Neurol 2001 Jun
16:421-4
BROWSE: J Child Neurol Volume 16 . Issue 6
Abstract
Increased brain size has been observed in individuals with autism with a
wide range of cognitive functioning. The purpose of this investigation was
to obtain measurements of the brain volume in a sample of nonmentally
retarded autistic individuals. Magnetic resonance imaging scans from 16
nonmentally retarded individuals with autism and 19 male volunteer
comparison subjects were obtained and the following structures were
measured: third, fourth, and lateral ventricles and intracranial and
cerebral volumes. Mean cerebral and third ventricle volumes in the autistic
subjects were significantly greater than in the controls when adjusted for
intracranial volume. No other significant results were found. Our finding of
increased brain volume in autism is consistent with previous reports in the
literature. Additional longitudinal neuroimaging and, more importantly,
neuropathologic studies are warranted to provide a better understanding of
the complexities underlying increased brain size in autism.
MeSH
--
17/07/03 4:05am
International Journal of Developmental Neuroscience Structural and
functional magnetic resonance imaging of autism
Heather Cody Kevin Pelphrey and Joseph Piven
....
Brain size in that study was measured as a covariate for cerebellar size,
where robust increases in mid-sagittal brain area were noted in autistic
individuals in contrast to two normal comparison groups, after taking
gender, cognitive ability, age and socioeconomic status (SES) into account.
Subsequently, Piven et al. (1996) ( \l "bib89") reported enlargement of
brain volume in 22 autistic males compared to 36 non-autistic males of
comparable age and cognitive ability. Lateral ventricular volume was also
noted to be enlarged, but this did not account for the observation of brain
volume enlargement as cortical brain tissue volume was also noted to be
significantly enlarged. Subsequently, this same group of investigators
employed a semi-automated technique to divide the brain into cortical lobes
based on the method of Talairach and Tournoux (1988) ( \l "bib111") in a
larger, overlapping sample of 35 autistic individuals (age range 12-29
years) and 36 controls (age range 13-28 years). The total brain volume in
the male autistic individuals was found to be significantly larger than male
controls, however, the sample of autistic females was too small to make any
definitive comments. Analyses using the Talairach coordinate system
suggested significant enlargements in the temporal, parietal, and occipital
lobes in the autistic subjects compared to controls, whereas no differences
were detected in the frontal lobe. These findings suggested that the pattern
of brain enlargement was regional and not global.
Postmortem studies support findings of megalencephaly (increased brain
weight) in autism (Bailey et al., 1993 ( \l "bib11")). Further documentation
of increased head size associated with autism come from head circumference
studies ( Bailey ( \l "bib12"); Lainhart ( \l "bib65") and Stevenson ( \l
"bib109")) showing that approximately 20% of autistic individuals have head
circumferences above the 98th percentile (i.e. macrocephaly). In a
retrospective chart review study of autistic individuals with macrocephaly,
Lainhart et al. (1997) ( \l "bib65") found evidence suggesting that while
enlarged head size is often present at birth, macrocephaly is not present
until the first few years of life. Other studies have found results
consistent with this finding ( Stevenson ( \l "bib109") and Courchesne ( \l
"bib26")). Thus, the timing of the enlargement, which clearly encompasses
the early postnatal period, is most consistent with an underlying mechanism
that involves a decrease in the normal course of elimination of neuronal
processes during early development (e.g. a decrease in the rate of dendritic
pruning) ( Huttenlocher, 1990 ( \l "bib59")).
...
Segmentation of the brain volumes into gray and white tissue in the
Courchesne et al. (2001) ( \l "bib26") study revealed that the 2-4-year-old
autistic subjects also had increased gray and white tissue volumes in the
cerebrum that were not present in the older autistic subjects (5-16-year
old). Their data suggested that cortical white matter volume increased
linearly with age, a finding similar to that of Giedd et al. (2001) ( \l
"bib36"), but that the rate of increase was smaller in the autistic group
than in normal controls. Also similar to the findings by Giedd et al. (2001)
( \l "bib36"), cortical gray tissue volumes were found to peak in early
childhood for autistic and control subjects, although the autistic group had
a decrease in gray tissue volume between 2 and 9 years while the normal
controls continued to show an increase. By middle childhood, gray tissue
volumes began to decrease for both groups, with the autism cases showing
smaller gray tissue volumes than the normal controls.
"Emma Chase VanCott" <7e...@qlink.queensu.ca> wrote in message
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Peter F
shows that this (to me very plausible and appetizing) idea can actually be
made to work. Have I missed something?
Peter
Dave Bird
writes:
This is a complex subject :-( IMO autism is an o u t c o m e
where the amygdala and nucleus acumbens or their connection to
the frontal lobe are messed up, in fact they are constantly
and inappropriately on but have lost their connection upwards.
There could be many reasons for this... damage to those locations
and paths, chemical blocking of those systems probably by opiates,
which in turn may come from genetic faults in the opiate system
or from various other damage invoking an opiate-driven shutdown.
Autism linked to brain growth
Autistic children's brains grow faster
Autism may be linked to unusually rapid brain growth during the first
year of life, say researchers.
They found that children with a small head at birth, followed by a
sudden and excessive increase in head circumference during their first
year, seemed to be more at risk of subsequently developing symptoms of
autism.
The more excessive the growth, the more severe the later symptoms of
autism were likely to be. The brain may be creating abnormal connections
that make it very hard for autistic children to make sense of the world
Professor Eric Courchesne
The finding may help experts to predict the onset of autism well before
symptoms become apparent.
This could be important as treatment, such as speech and social skills
therapy, is more effective if it is started at an early stage.
Currently, the disorder is not typically detected until the ages of two
to four, when a child develops behavioural signs and symptoms, such as
delayed speech, unusual social and emotional reactions, and poor
attention to and exploration of the environment.
The researchers, from the University of California, San Diego, believe
that excessive brain growth does not allow enough time for a child to
properly process the experiences and emotions that guide and shape
normal behaviour.
It is thought under normal circumstances the brain makes and breaks
internal connections in response to these external stimuli.
Eventually, this leads to the development of the highly sophisticated
thought processes which we take for granted, but which may be lacking in
people with autism.
Abnormal connections
Lead researcher Professor Eric Courchesne said: "During this period of
important learning and plasticity, when the brain is experiencing the
world and deciding how to construct itself, it's growing too fast in the
infant with autism.
"Without the guidance of experience and learning, the brain may be
creating abnormal connections that make it very hard for autistic
children to make sense of the world they live in."
The research focused on 48 children diagnosed with symptoms of autism.
Comparisons with children free of signs of autism showed that on
average, the children's head size was in the bottom 25% at birth.
But by the time they had reached the age of 12-14 months, their average
head size was in the top 15%. From then on, brain growth slowed.
At present, it is not known what causes this sudden spurt of growth.
But Professor Courchesne said: "Once we know what causes this specific
growth defect, it may be possible to use biological treatments to
successfully intervene before the overgrowth begins, thereby allowing
the brain and behaviour to develop down more normal paths."
Similar findings
Stuart Notholt, of the UK National Autistic Society, told BBC News
Online several previous studies had noted a significant proportion of
people with autism had a larger head circumference or brain volume.
The new research differs from previous work in that it charted the brain
growth of individual infants over a period of time.
"The points they make about identifying infants as early as possible for
possible diagnosis and early intervention by monitoring the rate of
brain growth seem very illuminating," he said.
The research is published in the Journal of the American Medical
Association.
-- .---.
It was once believed that a million monkeys at a million { o o }
keyboards would eventually type the works of Shakespeare, _(---)_
but the Internet has since disproved this theory. / \
John H.
find their site, Centre for the Mind, on a search engine. It began with a
great guffaw and attracted various luminaries. To be perfectly honest I
think they overstate their claims but there is a baby in that bathwater
somewhere. What really pisses me off is their association of savant like
skills with genius, this is plain nonsense but makes good press; which
pretty much wraps about the central imperative of Centre for the Mind.
Nonetheless, for certain artists there clearly could be a great deal of
benefit gained from the same and perhaps it casts some light on why certain
great artistic achievements are conceived in rather perilous states of mind.
Recently read an article in New York Times about it and the journalist
himself underwent the therapy. It worked, his drawings improved remarkably
well. Even if this is put down to placebo effect (and I'm damned if I'll
accept that placebo affect can instantly turn you into a drawing savant), it
deserves close attention.
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"Peter F" <fell_spa...@ozemail.com.au> wrote in message
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