Superior Temporal Gyrus Spectro-Temporal Abnormalities In Autism Spectrum Disorders

Background: Considerable evidence indicates auditory processing abnormalities in autism spectrum disorders (ASD), including latency delays as well as deficient evoked gamma (e.g., 30 to 50 Hz) oscillatory activity in the superior temporal gyrus (STG).

Objectives: The aim of the study was to examine the full extent of auditory phenomena – in terms of both time and frequency - in children with ASD.

Methods: Magnetoencephalography (MEG) was used to assess baseline and post-stimulus activity in left and right STG auditory areas in a large sample of 73 children with ASD and 34 typically developing (TD) controls. During the MEG exam, 500 Hz sinusoidal tones of 300 ms duration were binaurally presented with a 1 second interstimulus interval. Approximately 105 trials were collected. Measures of time and frequency domain activity at left and right STG auditory areas were obtained by applying a source model to transform each individual's raw MEG surface activity into brain space.

Results: The right-hemisphere 500 Hz 100 ms auditory response peaked later in ASD than TD, t(97)=-2.15, p<0.05. Examining left and right STG oscillatory activity, findings revealed a profile of ASD such that auditory STG processes were characterized by baseline abnormalities across multiple frequencies, then early high-frequency abnormalities followed by theta and alpha abnormalities, then followed by (or concurrent with) beta desynchronization abnormalities. Analyses examining associations with patient symptoms and cognitive ability showed that the STG oscillatory abnormalities in ASD are of clinical significance, with increased baseline gamma activity associated with higher Social Communication Questionnaire scores as well as lower IQ scores.

Conclusions: It is hypothesized that deficits in synaptic integration in the auditory cortex are associated with oscillatory abnormalities in ASD as well as patient symptoms and cognitive ability.