National Antivisection Society
2004-05 Brain Research - MEG and auditory processing
Drs Caroline Witton and Paul Furlong at the Neurosciences Research Institute, Aston University, have been funded by the LDF to conduct experiments expected to highlight the redundancy of animal models in hearing research and assist the shift towards non-invasive experimentation in humans. They are using magnetoencephalography (MEG) to investigate nerve responses to sound in the human brain.
Auditory processing may fail in certain diseases and hearing research is vital to the understanding of the ability to perceive speech. Neuroimaging techniques such as fMRI, and MEG are becoming a popular approach to such research and have identified specific areas of the human brain that respond to sounds. MEG can functionally characterise the auditory cortex, the area of the brain that processes sound, by measuring responses to sound over time (temporal) and the location of the sound (spatial).
The project uses MEG to differentiate between brain responses to sound patterns (frequency and amplitude) and sound movement. Also, to test the hypothesis that auditory motion is dependent on inhibitory nerve activity, MEG responses in patients with clinical conditions such as epilepsy, in which there is a reduced level of inhibition, will be assessed and compared with healthy control subjects. The effects of certain anti-epileptic drugs on auditory processing will also be examined.
A series of experiments is being conducted to measure brain responses to basic sounds. The researchers are attempting to find human analogues to areas in the brains of animals that have been studied previously by others. They are concentrating on the areas specialised for spatial and temporal information. Areas that respond to the stimuli are measured by a data analysis technique called Synthetic Aperture Magnetometry (SAM). The introduction of SAM means that not only can the region of brain responsible for the signals be identified, but the depth of the signals within the brain can also be measured. Previously, it was only possible to measure this depth via invasive brain surgery.
This is a significant field of research because elsewhere large numbers of animals are being experimented on for this purpose. Some involve brain recordings from conscious cats and monkeys, others the destruction or removal of brain tissue from ferrets or dogs followed by behavioural tests. There were 437 published papers involving animal research into hearing in 2002 worldwide. In November 2002 there were 16 such papers in one monthly journal (Hearing Research) alone, using 73 chinchillas, 124 guinea pigs, 34 frogs, 8 gerbils, 114 rats, 10 toads, and 12 cats. Animal experiments concerned with recordings from the area of the brain to be studied (the auditory cortex) include studies on cats and monkeys. Large numbers of marmosets, bats and gerbils have died after being used for auditory cortex experiments.
According to Drs Witton and Furlong: “Neuroimaging has the potential to save the lives of many animals, if researchers are provided with experimental evidence of the benefits of this technique.”
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