Max Planck Institute for Dynamics and Self-Organization -- Department for Nonlinear Dynamics and Network Dynamics Group
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BCCN/BFNT AG-Seminar

Tuesday, 28.06.2011 17 c.t.

Parallel and Efficient Neural Pathway Encoding of the Acoustic Scene

by Prof. Dr. Heather Read
from Departments of Psychology & Biomedical Engineering, University of Connecticut, USA

Contact person: Dominika Lyzwa

Location

Ludwig Prandtl Hörsaal, Am Faßberg 11 AI-Gebäude

Abstract

The efficient-coding hypothesis asserts that neural and perceptual sensitivity evolved to faithfully represent biologically relevant sensory signals. Here we characterized the spectrotemporal modulation statistics of several natural sound ensembles and examined how neurons encode these statistics in the central nucleus of the inferior colliculus (CNIC) of cats. We report that modulation-tuning in the CNIC is matched to equalize the modulation power of natural sounds. Specifically, natural sounds exhibited a tradeoff between spectral and temporal modulations, which manifests as 1/f modulation power spectrum (MPS). Neural tuning was highly overlapped with the natural sound MPS and neurons approximated proportional resolution filters where modulation bandwidths scaled with characteristic modulation frequencies, a behavior observed in human psychoacoustics. We demonstrate that this neural scaling opposes the 1/f scaling of natural sounds and enhances the natural sound representation by equalizing their MPS. Furthermore, this wide range of characteristic modulation frequency sensitivities was distributed across parallel pathways within th CNIC. These observations suggest that modulation tuning in the CNIC represents natural sound modulations in an efficient and parallel fashion.

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