Proceedings of the Thirteenth International Society of Sports Nutrition (ISSN) Conference and Expo

Meeting Abstracts: Proceedings of the Thirteenth International Society of Sports Nutrition (ISSN) Conference and Expo Clearwater Beach, FL, USA. 9-11 June 201

Abnormalities in Gamma-band Responses to Language Stimuli in First-degree Relatives of Children with Autism Spectrum Disorder: An MEG Study

Background Synchronous neural oscillatory activity in the gamma range (30–80 Hz) has been shown to be abnormal in individuals with autism spectrum disorders (ASD) and their first-degree relatives in response to simple auditory stimuli. Gamma-band abnormalities in ASD probands have been seen in response to language stimuli, but this has not been investigated in first-degree relatives. This is of particular interest given that language impairments are a core symptom of ASD and may be part of the broad autism phenotype (BAP) seen in relatives. Methods Magnetoencephalography recordings during a continuous word recognition task were obtained for 23 parents of a child with ASD (pASD) and 28 adult control participants. Total and evoked gamma-band activity, as well as inter-trial phase-locking factor (PLF), were measured in response to the task. Beta-band activity was also measured, due to its suggested role in language processing. Participants completed a series of language measures to assess the relationship between brain activity and language function, and lateralization of task-related activity was assessed. Results The pASD group showed increased evoked gamma and beta activity, while controls had decreased evoked activity. Additionally, while both groups showed a reduction in total gamma power (commonly seen in language tasks), this reduction was more prominent in the control group. The pASD group demonstrated significantly worse performance on a measure of phonology compared to controls. Significant but distinct relationships were found between gamma/beta activity and language measures within the two groups. In addition, while the overall task generally elicited left lateralized responses, pASD showed greater left lateralization than controls in some regions of interest. Conclusions Abnormalities in oscillatory responses to language were seen in pASD that are consistent with previous findings in ASD probands. Gamma-band responses to language stimuli have not previously been assessed in first-degree relatives of ASD probands and these findings are supportive of gamma-band activity as a heritable, neurophysiological biomarker of ASD. The possible relationship seen between language function and neural activity in the current study should be investigated further to assess if oscillatory response abnormalities may contribute to behavioural manifestations of the BAP

Test-Retest Reliability of the 40 Hz EEG Auditory Steady-State Response

<div><p>Auditory evoked steady-state responses are increasingly being used as a marker of brain function and dysfunction in various neuropsychiatric disorders, but research investigating the test-retest reliability of this response is lacking. The purpose of this study was to assess the consistency of the auditory steady-state response (ASSR) across sessions. Furthermore, the current study aimed to investigate how the reliability of the ASSR is impacted by stimulus parameters and analysis method employed. The consistency of this response across two sessions spaced approximately 1 week apart was measured in nineteen healthy adults using electroencephalography (EEG). The ASSR was entrained by both 40 Hz amplitude-modulated white noise and click train stimuli. Correlations between sessions were assessed with two separate analytical techniques: a) channel-level analysis across the whole-head array and b) signal-space projection from auditory dipoles. Overall, the ASSR was significantly correlated between sessions 1 and 2 (<i>p</i><0.05, multiple comparison corrected), suggesting adequate test-retest reliability of this response. The current study also suggests that measures of inter-trial phase coherence may be more reliable between sessions than measures of evoked power. Results were similar between the two analysis methods, but reliability varied depending on the presented stimulus, with click train stimuli producing more consistent responses than white noise stimuli.</p></div

Correlation values (Pearson's r) between sessions 1 and 2 for the baseline normalized auditory steady-state response (40 Hz, 200–500 ms): Fourier analyses.

<p>SD =  standard deviation; SSP =  signal-space projection; CT =  click train; WN =  white noise. Electrode data taken from peak gamma-band electrode (FCz). The correlations reported are for the ratios of post-stimulus/pre-stimulus power at 40 Hz.</p

Correlation values (Pearson's r) between sessions 1 and 2 for the auditory steady-state response (40 Hz): time-frequency analyses.

<p>SD =  standard deviation; EP =  evoked power; ITPC =  inter-trial phase coherence; SSP =  signal-space projection; Pre =  pre-stimulus window (−200–0 ms); Post  =  post-stimulus window (200–500 ms). Electrode data taken from peak gamma-band electrode (FCz).</p><p>**p<0.01.</p

Signal to noise ratio (SNR) across sessions for the auditory steady-state response (40 Hz, 200–500 ms).

<p>CT =  click train; WN =  white noise; SD =  standard deviation; TFT =  time-frequency transformed data; FFT =  Fast Fourier transformed data; ITPC =  inter-trial phase coherence; SSP =  signal-space projection; EP =  evoked power (absolute). Significant left vs. right hemisphere comparisons: TFT SSP EP (click train***; white noise*); TFT SSP ITPC (click train*; white noise*); FFT SSP EP (click train**; white noise*).</p><p>*p<0.05;</p><p>**p<0.01;</p><p>***p<0.001.</p