This document summarizes research on brain abnormalities associated with autism spectrum disorders. It finds that individuals with autism often have enlarged brains and heads during early development. Specifically, the cerebrum, cerebellum, and amygdala are larger on average in individuals with autism between ages 3-4. Differences are also found in gray and white matter volumes. Certain areas like the amygdala, hippocampus, and entorhinal cortex show the most consistent changes. Brain abnormalities tend to be more severe in girls with autism compared to boys.

1. Autism,
Aspergers, and
the Brain
Adrienne Dorrah

2. Definition
 Autism and Aspergers are developmental disorders on a
larger spectrum called Autism Spectrum Disorders (ASDs).
 Autism – usually have significant language delays, social
and communication challenges, unusual behaviors and
interests; may have intellectual disability
 Aspergers – may have social challenges and unusual
behaviors and interests; typically do not have language
problems or intellectual disability
 http://www.cdc.gov/NCBDDD/autism/videos/whatisautism.
html - this is a link to a short video that explains the signs
and symptoms related to ASDs.
Source: (Center for Disease Control, 2012)

3. General Information
1 in 88 children have been identified with
an autism spectrum disorder
 Typically diagnosed between the ages of
2 and 4
 Because of the late diagnosis, brain
development in autism is largely
unstudied during the first 2 years of life –
the “crucial period”
Source: (Center for Disease Control, 2012)

4. Source: (Center for Disease Control, 2012)

5. Head Circumference
 Typically normal average at birth – 25th %ile
 By 6-14 months, head circumference is at 84th
%ile; growth slows down at end of 2nd year
 Brain volume of autistic 3-4 years old about
10% larger than normal (1.5 cm)
 Cerebrum, cerebellum, and amygdala also
larger than normal
Source: (Courchesne, 2004)

6. Source: (University of California, San Diego, 2003)

7. Gray Matter & White Matter
 In2-4 year olds, brain enlargement was found
to be due to significant increases in cerebral
white matter (18%), cerebral gray matter (12%),
cerebellar white matter (39%), but not
cerebellar gray matter.
 Grey matter volume reaches a peak between
ages 4 & 6, then decreases constantly
 White matter volume increase in the first
decade of life and stays relatively stable
Sources: (Courchesne 2004)
(Predescu, et. al. 2010

8. Photo Credit: (Courchesne, et. al., 2007)

9. Brain dysfunction
in autism is
correlated with
abnormal patterns
of development
affecting the
whole brain as
well as circuits
involving the
prefrontal cortex,
the limbic system,
and cerebellum.
The amygdala
and hippocampus
increase in size
through
adolescence.
Picture Source: (Health on Care) Source: Predescu et. al. 2010)

10. Affected Parts of the Brain
 The most consistent changes were in the
amygdala, hippocampus, and functionally
related entorhinal cortex and mammillary
body.
 Using SPECT techniques, researchers reported
that blood flow is significantly reduced in the
left temporal region in high-functioning
autism, while a more recent study reported a
correlation between reduced temporal lobe
blood flow and the severity of the disorder.
Source: (Lathe, 2006)

11. Boys vs. Girls
 Girls with autism showed substantial reduction
in cerebellar gray matter volumes as
compared to normal girls as well as to boys
with autism
 Brain development abnormalities appear to
be more severe in girls than in boys with
autism
 Every structural volume abnormality present in
boys with autism was also present in girls with
autism
Source: (Courchesne, 2004)

12. Reference List
 Center for Disease Control. (29, March 2012). Data and statistics. Retrieved
from http://www.cdc.gov/ncbddd/autism/data.html/
This site gave statistical information and data related to Autism. It also talks about
diagnosis and economic costs of autism. A basic chart with data about the
prevalence of ASDs was extracted from this site.
 Center for Disease Control. (29, March 2012). Facts about asds. Retrieved from
http://www.cdc.gov/ncbddd/autism/facts.html
This website gave general information about Autism Spectrum Disorders. It
discusses the different types of ASDs, signs and symptoms, treatments, and risk
factors, among other information.
 Courchesne, E. (2004). Brain development in autism: Early overgrowth
followed by premature arrest of growth. Mental Retardation & Developmental
Disabilities Research Reviews, 10(2), 106-111.
*This article discusses brain development and growth in autism. Circumference of
the head, rate of growth, growth at different ages, and regional differences are
all discussed.

13. References Cont’d
 Courchesne, E., K. Pierce, C. M. Schumann, E. Redcay, J. A. Buckwalter, D. P.
Kennedy, and J. Morgan. "Mapping Early Brain Development in Autism."
Neuron. 56.2 (2007): 399-413. Web. 13 Aug. 2012.
*This article talks about findings during the first few years of life and argues that
early brain overgrowth is a key factor in the onset of autism. The article also
includes graphs that map out data related to overgrowth in the brain.
 Health on Care. (n.d.). Autism – causes, symptoms and treatment. Retrieved
from http://www.healthoncare.com/autism-causes-symptoms-and-
treatment.html
This website gave a brief overview of what autism is and the causes and
symptoms of autism. The site has a picture of the brain that shows which parts of
the brain which are affected by autism. This photo was extracted for my
presentation.

14. References Cont’d
 Lathe, Richard. Autism, Brain and Environment. London: Jessica Kingsley Publishers,
2006.
*This is a book about autism that discusses how autism affects the brain and the
abnormalities and dysfunction associated with the disorder. The book also discusses how
the environment has an effect on the onset of autism.
 Predescu, E., Sipos, P., Sipos, R., Iftene, F., & Balázsi, R. (2010). BRAIN VOLUMES IN
AUTISM AND DEVELOPMENTAL DELAY -- A MRI STUDY. Journal Of Cognitive &
Behavioral Psychotherapies, 10(1), 25-38.
This article compared children with ASD and children with developmental delay. It
compared total brain volume of both sets of children as well as volume of gray matter
and white matter between the groups of children.
 University of California, San Diego. (2003). Ucsd researchers find brain
overgrowth during first year of life in autism. Retrieved from
http://health.ucsd.edu/news/2003/07_15_courchesne.html
This website contained an article talking about brain growth in children with autism
during their first year of life. The website contained a photo comparing the size of an
average brain with the size of a brain with autism. This photo was extracted for my
presentation.