Sound Sensitivities in Autism: Evaluation by MEG and Treatment by AIT

Background: Despite the fact that 40% of children with an ASD appear to show sound hypersensitivities, essentially nothing is known about the relevant neurobiology. Nevertheless, there are numerous anecdotal reports that some music-based therapies can alleviate sound sensitivities and provide a general improvement in autistic features. Of particular interest is the Berard method of Auditory Integration Training [AIT] which involves listening to 10 hours of specially modulated music. Recent reviews of AIT universally conclude that there is a lack of scientific data to support or discourage its use for children with autism, but many children still receive AIT, often at considerable expense.

Objectives: This study sought to explore the neurobiology of sound sensitivities and document the possible efficacy of AIT in autism.

Methods: Twenty-two high functioning subjects with an ASD participated in psychophysical and MEG evaluations. During initial interview, ten of these subjects did not self-report sound sensitivities, whereas twelve did. Ten normal comparison subjects were also evaluated. During psychophysical testing, subjects were presented with 5 trials of 250, 2000, and 5000 Hz tones of variable loudness [40, 60, 70, 80, or 90 dB], and on each trial the subject was asked to rate the sound as soft, comfortable, loud, or uncomfortably loud.  MEG was then used to obtain average evoked responses to 100 presentations of each pitch tone at 75 dB. Dipole modeling was then used to characterize the amplitude of the M100 response in each hemisphere and a laterality index was computed. All subjects with reported sound sensitivities subsequently underwent AIT, with 3 month follow-up psychophysical and MEG evaluations.

Results: Subjects without sound sensitivities demonstrated average uncomfortable loudness levels [UCL] at 86 dB, with no differences between the control and ASD group without sound sensitivities. For both of these subject groups, individual laterality indices on the MEG were all between -0.25 and +0.25. For each ASD subject with sound sensitivities, UCLs were below 80 dB in at least one of the frequency categories, with tones below 80 dB frequently reported as uncomfortable. On MEG, there were two distinct sub-populations of sound sensitive subjects. Five subjects showed laterality indices within the normal range for all pitches, whereas 7 subjects had indices with absolute values of >0.5 for at least one pitch Following AIT, the 5 subjects with normal indices at baseline failed to show any significant improvements in UCLs or changes in laterality indices. In contrast, subjects with highly asymmetric MEG auditory response profiles at baseline showed improvements in UCLs of 5-10 dB, and a reduction of laterality indices into the normal range.

Conclusions:   A subset of subjects with ASDs and sound sensitivities show abnormal auditory processing profiles characterized by an imbalance in auditory response between the two hemispheres. For these subjects, AIT appears to decrease sound sensitivities and normalize auditory processing profiles. For sound sensitive subjects with normal MEG profiles at baseline, AIT is not effective, presumably because they have a different neurobiological basis for their sound sensitivities.