Coding of acoustic information in the auditory pathway
Contact Name: Prof. Alan R Palmer
Alan Palmer received his first degree in Biological Sciences from the University of Birmingham UK in 1972 and his PhD in Communication and Neuroscience from the University of Keele UK in 1977. After postdoctoral research at Keele he established his own laboratory at the National Institute for Medical Research in London. Following a Royal Society University Research Fellowship held at the University of Sussex he became a programme leader at the MRC Institute of Hearing Research in 1986.
His is currently Director and Programme Leader at the MRC Institute of Hearing Research, Research Area Lead NIHR Nottingham Hearing Biomedical Research Unit and Honorary Professor of Neuroscience, School of Biomedical Sciences, University of Nottingham. He leads a research team that uses neurophysiological, neuroanatomical and imaging techniques to study the way the brain processes sound.
As a result of the mechanical action of the basilar membrane and transduction in the cochlear hair cells, responses of auditory nerve fibres are tuned like a series of overlapping band pass filters allowing a good representation of the frequency content of any sound, which becomes less clear at high levels as the filters broaden. Activity in the auditory nerve signals the frequency content, the timing and the sound level of the sounds. Pathways from the first brainstem nucleus (the cochlear nucleus) converge in the brainstem to allow combination of information from the two ears for analysis of the location of the sound source, which is then sent to the auditory midbrain. Pathways from the cochlear nucleus also send information about the sound spectrum and its pitch directly to the auditory midbrain where it is integrated with inputs from all lower brainstem nuclei, before sending the information on to the auditory cortex via the thalamus. The auditory cortex has several frequency mapped areas which process sounds in parallel. There is some evidence for processing of different aspects of sounds in different cortical areas, giving rise to suggestions of different anatomical and functional processing streams for different aspects of sound perception. The deeper layers of the cortex send projections back down the auditory pathway enabling the cortex to modulate the ascending flow of auditory information