How Do Autistic Brains Differ in Communication?

Patients with ASD can vary considerably in the extent of communication impairment. Up to one-half of children with ASD are unable to speak throughout life[1]. Another subgroup shows deficits in certain aspects of language, including auditory processing, vocabulary production, perception of phonemes (the building blocks of words), higher-order semantics, syntax, pragmatics, or prosody. Still others, however, can communicate within the normal range of function.

Semantics refers to the meaning of words; this is the most common linguistic deficit in children with ASD. Syntax means the rules we have for combining words into phrases and sentences, and for understanding the relationship among words.  Children with ASD often show reduced length of sentences. Pragmatics is the implied meaning underlying a sentence, such as irony or satire. Prosody is the pitch, tone, rhythm, or intonation of a sentence[2].

The use of language can also vary. Unlike neurotypical children who use language primarily for social purposes, some children with ASD use language one-sidedly and non-reciprocally.

While impairment can occur in both the comprehension and production of language, a recent study showed greater impairment in comprehension[3]. For example, children with ASD show deficits in identifying emotional information, or the mental state of a speaker, can show indifference to their mother’s voice, and demonstrate reduced brain activation in prefrontal and temporal brain regions under scenarios that involve irony[4].

Children with ASD can also be impaired in their understanding of nonverbal cues from others. Such cues include discerning the intentions of others and having the ability to make rapid intuitive judgments of social context. In particular, high-functioning ASD patients have difficulty in recognizing negative facial expressions[5].

Differences between neurotypical children and children with ASD can be seen in the brain. Evoked potential studies (ERP) demonstrated that some children with ASD preferred listening to mechanical sounds rather than speech. These children showed no change in evoked potentials for two different syllables, in contrast to neurotypical children[6].  Another ERP study showed that children with ASD perceived but did not attend to speech. Functional imaging studies have found reduced activation in Broca’s area in contrast to Wernicke’s area.  The scientists hypothesize that the reduced activation in Broca’s area indicates a deficit in integrating the meaning of words within sentences. The left lateralization, or specialization, of language processing seen in neurotypical children can also be reversed in children with ASD[7].  These children show larger language areas in the right cerebral cortex. The neural consequence of this difference is unknown.