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Updated: Aug 7, 2026
Probing the Brain in Autism Using fMRI and Diffusion Tensor Imaging
Published on: September 12, 2011
Unusual brain growth patterns in early life in patients with autistic disorder: an MRI study
E Courchesne1, C M Karns, H R Davis
1Department of Neuroscience, School of Medicine, University of California, San Diego, La Jolla, USA. ecourchesne@ucsd.edu
Insights
Autism involves abnormal brain growth, with early overgrowth in gray and white matter, followed by slowed growth. This study quantizes these developmental brain volume changes in autistic boys.
Area of Science:
- Neuroscience
- Developmental Biology
- Autism Research
Background:
- Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition.
- Understanding brain development in autism is crucial for early intervention.
- Previous studies suggest altered brain growth patterns in individuals with autism.
Purpose of the Study:
- To quantify developmental abnormalities in cerebral and cerebellar volume in autism.
- To investigate early brain overgrowth and subsequent growth alterations in autistic boys.
- To identify specific patterns of gray and white matter volume changes in the brain and cerebellum.
Main Methods:
- Magnetic Resonance Imaging (MRI) was used to study 60 autistic and 52 neurotypical boys aged 2 to 16 years.
- Autistic boys were divided into two groups: diagnosed at 5+ years, and scanned at 2-4 years and diagnosed later.
- Neonatal head circumference data was analyzed for early indicators of brain growth.
Main Results:
- Autistic boys showed normal head circumference at birth but accelerated brain volume by ages 2-4 years (90% larger than average).
- Early childhood (2-3 years) revealed increased cerebral gray matter (12%), cerebral white matter (18%), and cerebellar white matter (39%) in autistic boys.
- Older autistic individuals did not exhibit this early overgrowth; cerebellar gray matter and specific regions (vermis lobules VI-VII) were smaller than controls.
Conclusions:
- Autism is characterized by abnormal brain growth regulation, featuring early overgrowth followed by slowed growth.
- Hyperplasia of cerebral gray matter and white matter (cerebral and cerebellar) occurs in early life in autism.
- These findings highlight critical developmental periods for brain alterations in autism.
Objective:
To quantify developmental abnormalities in cerebral and cerebellar volume in autism.
Methods:
The authors studied 60 autistic and 52 normal boys (age, 2 to 16 years) using MRI. Thirty autistic boys were diagnosed and scanned when 5 years or older. The other 30 were scanned when 2 through 4 years of age and then diagnosed with autism at least 2.5 years later, at an age when the diagnosis of autism is more reliable.
Results:
Neonatal head circumferences from clinical records were available for 14 of 15 autistic 2- to 5-year-olds and, on average, were normal (35.1 +/- 1.3 cm versus clinical norms: 34.6 +/- 1.6 cm), indicative of normal overall brain volume at birth; one measure was above the 95th percentile. By ages 2 to 4 years, 90% of autistic boys had a brain volume larger than normal average, and 37% met criteria for developmental macrencephaly. Autistic 2- to 3-year-olds had more cerebral (18%) and cerebellar (39%) white matter, and more cerebral cortical gray matter (12%) than normal, whereas older autistic children and adolescents did not have such enlarged gray and white matter volumes. In the cerebellum, autistic boys had less gray matter, smaller ratio of gray to white matter, and smaller vermis lobules VI-VII than normal controls.
Conclusions:
Abnormal regulation of brain growth in autism results in early overgrowth followed by abnormally slowed growth. Hyperplasia was present in cerebral gray matter and cerebral and cerebellar white matter in early life in patients with autism.
