ABNORMAL AUDITORY INFORMATION PROCESSING IN YOUNG CHILDREN WITH AUTISM

Background: Atypical responses to sensory stimuli, particularly in the auditory modality, have often been observed clinically as associated features in many children and adults with autism (Gilberg and Coleman, 2000; Waterhouse et al., 1996). Behavioral responses to auditory stimuli range from completely ignoring sounds to acoustic hypersensitivity. Although impaired auditory processing in children with autism is prominent and likely compromises the development of cognitive functions, particularly speech and language, the unusual sensitivity to sounds in these children has been sparsely investigated.

Objectives: To analyze scalp-recorded event-related brain potentials (ERPs) to index the sensory, perceptual, and cognitive processing of auditory information in children with autism.

Methods:  Children (ages 4-8) who met research criteria for autism were compared with normally developing children. ERPs were collected using a “passive-ignore” auditory paradigm in which the children are watching a cartoon at a low volume setting and are presented with rapid sequences of auditory stimuli, consisting of infrequent deviant tones, unique environmental sounds and frequent standard tones. This paradigm allowed us to investigate: (1) the P1, which is associated with initial sensory detection; (2) the ‘mismatch negativity’ (MMN), which is associated with pre-attentive sensory discrimination; and (3) the P3a, which is associated with orienting and attention-dependent cognitive discrimination.

Results: Preliminary analyses on 16 children suggest group differences are primarily found in the P1 and MMN and to a lesser degree in the P3a.

Conclusions: Children with autism exhibit abnormalities in early processing of sounds as well as in pre-attentive discrimination of sounds but not in orienting and attention-dependent discrimination of sounds. Future study plans include the recruitment of 35 children with autism, 20 developmentally delayed controls and 30 normally developing controls in order to further characterize the relationships between EEG/ERP abnormalities and various measures including, IQ, autism symptom severity, and sensory response patterns.