Enhanced Processing of Pitch Direction in Children with Autism Spectrum Disorder

Friday, May 18, 2012
Sheraton Hall (Sheraton Centre Toronto)
2:00 PM
N. E. Foster1,2, T. Ouimet1,2, A. Tryfon1,2, K. A. R. Doyle-Thomas3, E. Anagnostou3, .. NeuroDevNet ASD imaging group4 and K. L. Hyde2,5, (1)Faculty of Medicine, Montreal Children's Hospital, McGill University, Montreal, QC, Canada, (2)International Laboratory for Brain Music and Sound (BRAMS), Montreal, QC, Canada, (3)Holland Bloorview Kids Rehabilitation Hospital, Toronto, ON, Canada, (4)http://www.neurodevnet.ca/research/asd, Vancouver, BC, Canada, (5)McGill University, International Laboratory for Brain Music and Sound (BRAMS) , Montreal, QC, Canada
Background: Enhanced pitch perception of simple auditory material (e.g., pure tones) has been reported in individuals with autism spectrum disorders (ASD) relative to typically developing (TD) controls. We previously found superior perception of pure tone pitch direction in adults with ASD, even at fast temporal rates (Hyde et al., IMFAR 2011). ASD performance on this task was positively correlated with age of speech onset and brain structure in auditory cortex (Foster et al., HBM 2011). However, it is unclear whether children with ASD have the same superiority in pitch direction ability as adults, and how increasing spectral complexity affects their performance.

Objectives: Our objectives were to investigate in children with ASD: 1) whether pitch direction categorization is enhanced (as we previously found in adults with ASD), 2) whether increasing spectral complexity negatively affects performance, and 3) whether pitch direction performance is positively correlated with age of speech onset.

Methods: We are currently collecting auditory behavioral data and MRI measures in a large group of children with ASD versus TD controls in a multi-site study on brain and behavioral development (Zwaigenbaum et al., 2011). Here we present preliminary data from 5 children with ASD (mean age 11.0, range 6-15 years; mean IQ 109.4, SD 9.6), and 8 TD children (mean age 11.4, range 7-16 years). In a pitch change direction task, subjects heard two tones of different frequencies on each trial and judged whether the pitch rose or fell. Task difficulty was parametrically manipulated from a reference condition, either by successively dividing tone duration by two, or by dividing the pitch difference between the tones by two. Tones were presented at three different levels of increasing spectral complexity (pure tones, complex tones with 3 harmonics, and 5 harmonics) in separate blocks. Ethical approval was granted by the Montreal Neurological Institute Research Ethics Board.

Results: Preliminary results revealed that both groups performed best in the reference condition, with accuracy diminishing significantly when either the tone duration or the pitch difference between tones was decreased. Performance was significantly better in the ASD group versus the TD group at all tone complexity levels. As previously observed in adults, the ASD group maintained better performance even at the fastest temporal rate. There was no effect of tone complexity. Within the ASD group, performance was positively correlated with age of speech acquisition.

Conclusions: We show for the first time that pitch direction categorization is enhanced in children with ASD (as in adults), even at fast temporal rates, and at greater levels of spectral complexity. We also replicate in children with ASD a positive correlation between later speech acquisition and superior pitch direction perception. These findings contribute to a better understanding of the cognitive architecture of perceptual processing in ASD with respect to the theory of Enhanced Perceptual Functioning (Mottron et al, 2006). These findings are provocative since they contrast with the view that ASD individuals are generally impaired in processing information at fast temporal rates of transition and greater stimulus complexity.

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