Characteristic Deviations of Auditory Evoked Potentials in Individuals with Autism Spectrum Disorder.

BACKGROUND: Neurological, structural, and behavioral abnormalities are widely reported in individuals with autism spectrum disorder (ASD); yet there are no objective markers to date. We postulated that by using dominant and nondominant ear data, underlying differences in auditory evoked potentials (AEPs) between ASD and control groups can be recognized. PURPOSE: The primary purpose was to identify if significant differences exist in AEPs recorded from dominant and nondominant ear stimulation in (1) children with ASD and their matched controls, (2) adults with ASD and their matched controls, and (3) a combined child and adult ASD group and control group. The secondary purpose was to explore the association between the significant findings of this study with those obtained in our previous study that evaluated the effects of auditory training on AEPs in individuals with ASD. RESEARCH DESIGN: Factorial analysis of variance with interaction was performed. STUDY SAMPLE: Forty subjects with normal hearing between the ages of 9 and 25 years were included. Eleven children and 9 adults with ASD were age- and gender-matched with neurotypical peers. DATA COLLECTION AND ANALYSIS: Auditory brainstem responses (ABRs) and auditory late responses (ALRs) were recorded. Adult and child ASD subjects were compared with non-ASD adult and child control subjects, respectively. The combined child and adult ASD group was compared with the combined child and adult control group. RESULTS: No significant differences in ABR latency or amplitude were observed between ASD and control groups. ALR N1 amplitude in the dominant ear was significantly smaller for the ASD adult group compared with their control group. Combined child and adult data showed significantly smaller amplitude for ALR N1 and longer ALR P2 latency in the dominant ear for the ASD group compared with the control group. In our earlier study, the top predictor of behavioral improvement following auditory training was ALR N1 amplitude in the dominant ear. Correspondingly, the ALR N1 amplitude in the dominant ear yielded group differences in the current study. CONCLUSIONS: ALR peak N1 amplitude is proposed as the most feasible AEP marker in the evaluation of ASD.

Effects of Auditory Training on Electrophysiological Measures in Individuals with Autism Spectrum Disorder.

BACKGROUND: Identifying objective changes following an auditory training program is central to the assessment of the program's efficacy. PURPOSE: This study aimed (1) to objectively determine the efficacy of a 12-week auditory processing training (APT) program in individuals with autism spectrum disorder using auditory evoked potentials (AEPs) and (2) to identify the top central AEP predictors of the overall score on the Test of Auditory Processing Skills-3 (TAPS-3), the primary behavioral outcome measure of the APT program published in our earlier article. RESEARCH DESIGN: A one-group pretraining, posttraining design was used. STUDY SAMPLE: The sample included 15 children and young adults diagnosed with autism spectrum disorder. Participants underwent the APT program consisting of computerized dichotic training, one-on-one therapist-directed auditory training, and the use of remote microphone technology at home and in the classroom. DATA COLLECTION AND ANALYSIS: All participants underwent pre- and posttraining auditory brain stem responses (ABRs), complex auditory brain stem responses (cABRs), and auditory late responses (ALRs). Test results from ABRs and ALRs were grouped based on scores obtained in their dominant and nondominant ears. Paired t-tests were used to assess the efficacy of the training program, and least absolute shrinkage and selection operator regression was used to assess the relationship between ALRs and the TAPS-3 overall summed raw score reported in our earlier article. RESULTS AND CONCLUSIONS: When compared with pretraining results, posttraining results showed shorter ABR latencies and larger amplitudes. The cABRs showed decreased latencies of the frequency following waves, a reduction in pitch error, and enhancement of pitch strength and phase shift. ALR results indicated shorter latencies and larger amplitudes. Our earlier article showed that the TAPS-3 overall score was significantly higher after training. This study showed that the top three ALR predictors of TAPS-3 outcomes were P1 amplitude in the dominant ear, and N1 amplitude in the dominant and nondominant ears.

Assessment of Safe Listening Intentional Behavior Toward Personal Listening Devices in Young Adults.

Recreational noise-induced hearing loss (RNIHL) is a highly preventable disorder that is commonly seen in teenagers and young adults. Despite the documented negative effects of RNIHL, it is still challenging to persuade people to adopt safe listening behaviors. More research is needed to understand the underlying factors guiding listeners' intentions to engage in safe listening habits. We used the Theory of Planned Behavior (TPB) to identify attitudes, social norms, and behavioral control in 92 young adults toward two intentional behaviors related to safe listening habits while listening to their personal listening devices: (1) lowering the intensity of loud music, and (2) shortening the listening duration of loud music. Using a Qualtrics survey, the major factors of the TPB model as they relate to the participants' intention to engage in risk-controlling behavior were assessed. Behavioral intentions to turn the music down and listen for shorter durations were thought to be predicted by the TPB factors (attitudes, social norms, and perceived behavioral control). Linear regression findings indicated that the overall TPB models were significant. Positive attitudes toward turning the music down and shortening the durations were significantly associated with intentions to engage in non-risky behavior, more so for the former behavior.

Risk Assessment of Recreational Noise-Induced Hearing Loss from Exposure through a Personal Audio System-iPod Touch.

BACKGROUND: Recreational noise-induced hearing loss (RNIHL) is a major health issue and presents a huge economic burden on society. Exposure to loud music is not considered hazardous in our society because music is thought to be a source of relaxation and entertainment. However, there is evidence that regardless of the sound source, frequent exposure to loud music, including through personal audio systems (PAS), can lead to hearing loss, tinnitus, difficulty processing speech, and increased susceptibility to age-related hearing loss. PURPOSE: Several studies have documented temporary threshold shifts (TTS) (a risk indicator of future permanent impairment) in subjects that listen to loud music through their PAS. However, there is not enough information regarding volume settings that may be considered to be safe. As a primary step toward quantifying the risk of RNIHL through PAS, we assessed changes in auditory test measures before and after exposure to music through the popular iPod Touch device set at various volume levels. RESEARCH DESIGN: This project design incorporated aspects of both between- and within-subjects and used repeated measures to analyze individual groups. STUDY SAMPLE: A total of 40 adults, aged 18-31 years with normal hearing were recruited and randomly distributed to four groups. Each group consisted of five males and five females. DATA COLLECTION AND ANALYSIS: Subjects underwent two rounds of testing (pre- and postmusic exposure), with a 30-min interval, where they listened to a playlist consisting of popular songs through an iPod at 100%, 75%, 50%, or 0% volume (no music). Based on our analysis on the Knowles Electronic Manikin for Acoustic Research, with a standardized 711 coupler, it was determined that listening to the playlist for 30 min through standard earbuds resulted in an average level of 97.0 dBC at 100% volume, 83.3 dBC at 75% volume, and 65.6 dBC at 50% volume. Pure-tone thresholds from 500-8000 Hz, extended high-frequency pure tones between 9-12.5 kHz, and distortion product otoacoustic emissions (DPOAE) were obtained before and after the 30-min music exposure. Analysis of variance (ANOVA) was performed with two between-subjects factors (volume and gender) and one within-subjects factor (frequency). Change (shift) in auditory test measures was used as the outcome for the ANOVA. RESULTS: Results indicated significant worsening of pure-tone thresholds following music exposure only in the group that was exposed to 100% volume at the following frequencies: 2, 3, 4, 6 and 8 kHz. DPOAEs showed significant decrease at 2000 and 2822 Hz, also only for the 100% volume condition. No significant changes were found between pre- and postmusic exposure measures in groups exposed to 75%, 50%, or 0% volume conditions. Follow-up evaluations conducted a week later indicated that pure-tone thresholds had returned to the premusic exposure levels. CONCLUSIONS: These results provide quantifiable information regarding safe volume control settings on the iPod Touch with standard earbuds. Listening to music using the iPod Touch at 100% volume setting for as little as 30 min leads to TTS and worsening of otoacoustic emissions, a risk for permanent auditory damage.