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Title: The perception and cortical processing of communication sounds
Author: Walker, Kerry M. M.
ISNI:       0000 0004 0123 4132
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2008
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The neural processes used to extract perceptual features of vocal calls, and subsequently to re-integrate those features to form a coherent auditory object, are poorly understood. In this thesis, extracellular recordings were carried out in order to investigate how the temporal envelope, pitch, timbre and spatial location of communication sounds are represented by neurons in two core and three belt areas of ferret (Mustela putorius furo) auditory cortex. Potential neural underpinnings of auditory perception were tested using neurometric analysis to relate the reliability of neural responses to the performance of ferret and human listeners on psychophysical tasks. I found that human listeners' discrimination of the temporal envelopes of vocalization sounds matched the best neurometrics calculated from the temporal spiking patterns of ferret cortical neurons. Neurometric scores based on the spike rates of cortical neurons accounted for ferrets' discrimination of the pitch of artificial vowels. I show that most auditory cortical neurons are modulated by a number of stimulus features, rather than being tuned to only one feature. Neurons in the core auditory cortical fields often respond uniquely to particular combinations of pitch and timbre features, while those in belt regions respond more linearly to feature combinations. Subtle differences in the sensitivity of neurons to pitch, timbre and azimuthal cues were found across cortical areas and depths. These results suggest that auditory cortical neurons provide widely distributed representations of vocalizations, and a single neuron can often use combinations of spike rate and temporal spiking responses to encode multiple sound features.
Supervisor: King, Andrew J. ; Schnupp, Jan Sponsor: Rothermere Foundation ; Wellcome Trust ; BBSRC ; BNC Hector Pilling Scholarship
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Neuroscience ; Bioinformatics (life sciences) ; Computational Neuroscience ; Perception ; ferret ; hearing ; pitch ; timbre ; auditory cortex ; neural encoding ; psychophysics ; neurophysiology