National Antivisection Society
MEG and auditory processing
15 February 2008
The potential for helping people with hearing impairments and language disorders was studied using MEG to look at auditory processing. Animal model auditory research has historically focused on single-unit responses to stimuli, not the interaction of neurones.
As a result of the lack of clarity which is produced by invasive measurements it will now be a challenge to understand how the non-invasive measures relate to them.
Researchers studied how neurones encode types of sounds, which make up speech, such as amplitude (AM) and frequency modulations (FM) by examining the long-term temporal dynamics of auditory responses.
Testing the null hypothesis that AM and FM are encoded by the same neural mechanism in the auditory cortex, psychometric functions were measured for detection of AM and FM for each participant using a two-alternative forced-choice task. Analysis using a spatial filtering technique, Synthetic Aperture Magnetometry (SAM), revealed that peak neuronal activations in response to AM and FM stimuli exist in the same region of the auditory cortex. The magnitude of responses was found to be unstable over the duration of the stimuli, which was reflected in the patterns of the phases and power of the evoked response.
This research puts MEG researchers a step closer to being able to describe their data in ways that reflect the temporal characteristics of responses. This research also uncovers the physiological role that induced oscillatory activity of neurones play in auditory perception. This large scale physiological measurement provides information which has not been generated by single unit studies in animals. Overall, this study provides the opportunity to begin understanding the auditory physiology in atypical developmental disorders eg developmental dyslexia, the information for which could simply not be provided by animal studies.
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