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Abnormal auditory information processing has been reported in individuals with autism spectrum disorders (ASD). In the present study auditory processing was investigated by recording auditory brainstem responses (ABRs) elicited by forward masking in adults diagnosed with Asperger syndrome (AS). Sixteen AS subjects were included in the forward masking experiment and compared to three control groups consisting of healthy individuals (n = 16), schizophrenic patients (n = 16) and attention deficit hyperactivity disorder patients (n = 16), respectively, of matching age and gender. The results showed that the AS subjects exhibited abnormally low activity in the early part of their ABRs that distinctly separated them from the three control groups. Specifically, wave III amplitudes were significantly lower in the AS group than for all the control groups in the forward masking condition (P , 0.005), which was not the case in the baseline condition. Thus, electrophysiological measurements of ABRs to complex sound stimuli (eg, forward masking) may lead to a better understanding of the underlying neurophysiology of AS. Future studies may further point to specific ABR characteristics in AS individuals that separate them from individuals diagnosed with other neurodevelopmental diseases.

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Background and Aims:Earlier research has shown that schizophrenic individuals process complex sound in aberrant ways (Olsson.O., Dissertation, Lund, 2000). It has also been shown that they abnormally perceive forward and backward masking (Källstrand et al., Psychiatry Res. 2002 Dec 15; 11 (1-2); 115-25). Experiments described in those studies indicate that in schizophrenia, brain-stem activity is involved, where primitive sorting of sound elements takes place. Brain Stem Response Audiometry (BSRA) shows that e.g. dissimilar spectra significantly separates schizophrenics from healthy subjects (Nielzén.S., 15th AEP Congress, March 2007, p. S86). The present study aims at demonstrating effects of loudness change of complex sound stimulation.Method:Eighteen paranoid schizophrenic patients were compared with 25 healthy volunteers regarding BSRA recordings from 2048 sweeps of loud noise stimuli (76 dB) and 2048 quieter ones (73 dB). Analysis of latencies in ms and amplitudes in micro-volts of the peaks and troughs was performed.Results:The amplitude of the highest peak of the region 1-4 ms was significantly lower with quiet noise for the schizophrenic group (P=.0002).The schizophrenics showed significantly prolonged latencies of the highest peak during 4,5-9 ms with the quiet noise (P=.046); they had a significant longer latency from left than from right electrode (P=.049).Conclusion:The results corroborate earlier cumulative BSRA results. These have been collected in a model – S-Detect – which is used as an objective decision support for the diagnosis of schizophrenia.