play, impaired ability to make friends with peers, impaired ability to initiate or sustain a conversation with others, stereotypical, repetitive, or unusual use of language, restricted patterns of interests that are abnormal in intensity or focus, apparently inflexible adherence to specific routines or rituals, and preoccupation with parts of objects (6).
Autism has no single cause (6) but researchers believe several genes, as well as environmental factors such as viruses or chemicals, contribute to the disorder. Studies on autistic patients have found abnormalities in several regions of the brain, including the cerebellum, amygdala, hippocampus, septum, and mammillary bodies. Neurons in these regions appear smaller than normal and have stunted nerve fibers, which may interfere with nerve signaling. These abnormalities suggest that autism results from disruption of normal brain development early in fetal development.
Chiron et al (1) used brain functional imaging using 133XeSPECT (simple photon emission computed tomography) to measure left/right asymmetry and absolute values of regional cerebral blood flow in 18 children with autism aged from four to 17 years and 10 age-matched controls to investigate the theory that autism is associated with abnormal hemispheric specialization and left-hemispheric dysfunction. All controls but only 10 children with autism were right-handed. The left-to-right indices, both hemispheric and regional, were positive in controls, indicating higher left than right cerebral blood flow, but were negative in patients with autism.
This inversion was statistically significant for total hemispheres, sensorimotor and language-related cortex, and was explained by a significant decrease of the left absolute cerebral blood flow values in these regions in the patients with autism. The inversion was independent of handedness, sex, and age. These results confirm the existence of left-hemispheric dys...