Limbic Dysfunction Correlates
with the Autistic Phenotype
Structural abnormalities in a central brain region, the limbic system, are seen in individuals with ASD. The question arises – could altered limbic function be the cause of ASD? The precise role of the limbic brain, particularly the hippocampus and adjoining amygdala, remains elusive. But different investigators have prominently highlighted the contribution of the hippocampus and amygdala to seemingly diverse and unrelated functions, including memory encoding, anxiety, and epilepsy.
These central roles are to be contrasted with the triad of impairments seen in ASD – impaired social interaction, deficits or marked abnormalities of language and communication, and a restricted and often repetitive behavioral repertoire. Such divergent views clearly must be reconciled before limbic damage (see Chapter 5) can be invoked as a plausible cause of ASD.
There are many examples inwhich damage to the hippocampus or amygdala, not only in rodents but also in primates including man, produces real and measurable behavioral changes. These are examined below, and compared with what is known of ASD.
It is important to state from the outset that the consequences of damage to the limbic system in early life (as inferred for the young cohorts of recent ASD) may be very different from the effects of damage sustained as an adult. For this reason, data on adult subjects are not easily extrapolated to ASD. With this reserve, this chapter addresses whether limbic damage is consistent with ASD.