Our research proposes to investigate the response properties and functional organization of primary auditory cortex and neighboring areas, in the awake ferret: specifically, the study seeks to determine how timbre, i.e. the shape of the acoustic spectrum, is represented in the single-unit responses in these areas. Our study starts with tones and clicks to characterize cortical neurons and compare their response properties and the maps they form to the results we and others have already obtained in the anesthetized preparation. Nxt, we use broadband stimuli with sinusoidally modulated spectral envelopes (also called ripples), to characterize the purely temporal and purely spectral properties of cells' responses to broadband sounds. The response of cells to these ripples, together with the response to response to combinations of orthogonal ripples are analyzed by data analysis methods based on systems theory which yield auditory units response fields and fully characterize the linear part of their spectral and temporal properties. These methods are founded on the assumption that the auditory responses are linear with respect to the stimulus spectral envelope and its dynamics. Therefore, a fundamental objective of the proposed investigations is to examine the degree of response linearity by determining whether unit responses to complex sounds such as speech can be predicted from their responses to simple ripples. A second objective is to delineate the origin and extent of various types of response nonlinearities such as threshold, halt-wave rectification, saturation, and various forms of adaptation. The separability of the spectral and temporal aspects of the response fields can also be evaluated by comparing the cells response to the different types of sounds. The results that will emerge from this study will enhance our understanding of the encoding of complex acoustic spectra such as speech and music in auditory cortex. More generally, however, they will place auditory cortical processing within the larger framework of visual and other sensory processing in the brain because of the abstract nature of the stimuli and of the theoretical concepts behind them.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC005937-05
Application #
7056654
Study Section
Special Emphasis Panel (ZRG1-IFCN-6 (01))
Program Officer
Platt, Christopher
Project Start
2002-06-01
Project End
2008-05-31
Budget Start
2006-06-01
Budget End
2008-05-31
Support Year
5
Fiscal Year
2006
Total Cost
$316,802
Indirect Cost
Name
University of Maryland Baltimore
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
188435911
City
Baltimore
State
MD
Country
United States
Zip Code
21201
Shechter, B; Depireux, D A (2012) Contrast tuned responses in primary auditory cortex of the awake ferret. Eur J Neurosci 35:550-61
Depireux, D A; Dobbins, H D; Marvit, P et al. (2012) Dynamics of phase-independent spectro-temporal tuning in primary auditory cortex of the awake ferret. Neuroscience 214:28-35
Shechter, B; Depireux, D A (2010) Nonlinearity of coding in primary auditory cortex of the awake ferret. Neuroscience 165:612-20
Shechter, Barak; Marvit, Peter; Depireux, Didier A (2010) Lagged cells in the inferior colliculus of the awake ferret. Eur J Neurosci 31:42-8
Shechter, B; Dobbins, H D; Marvit, P et al. (2009) Dynamics of spectro-temporal tuning in primary auditory cortex of the awake ferret. Hear Res 256:118-30
Kalluri, Sridhar; Depireux, Didier A; Shamma, Shihab A (2008) Perception and cortical neural coding of harmonic fusion in ferrets. J Acoust Soc Am 123:2701-16
Elhilali, Mounya; Fritz, Jonathan B; Chi, Tai-Shih et al. (2007) Auditory cortical receptive fields: stable entities with plastic abilities. J Neurosci 27:10372-82
Simon, Jonathan Z; Depireux, Didier A; Klein, David J et al. (2007) Temporal symmetry in primary auditory cortex: implications for cortical connectivity. Neural Comput 19:583-638
Shechter, B; Depireux, D A (2007) Stability of spectro-temporal tuning over several seconds in primary auditory cortex of the awake ferret. Neuroscience 148:806-14
Dobbins, Heather D; Marvit, Peter; Ji, Yadong et al. (2007) Chronically recording with a multi-electrode array device in the auditory cortex of an awake ferret. J Neurosci Methods 161:101-11

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