Sparse Representation Of Sounds In The Unanesthetized Auditory Cortex

How do neuronal populations in the auditory cortex represent sounds? Although sound-evoked neural responses in the anesthetized auditory cortex are
mainly transient, recent experiments in the unanesthetized preparation have emphasized subpopulations with other response properties.

Published this
week in the open-access journal PLoS Biology, Tomas Hromadka, Anthony Zador, and colleagues show how they quantified the relative contributions of
these different subpopulations in the auditory cortex of awake head-fixed rats.


They recorded neuronal activity using cell-attached recordings with a
glass electrode-a method for which isolation of individual neurons does not depend on neuronal activity-while probing neurons with a
representative ensemble of sounds.


Their data therefore address the question: What is the typical response to a particular stimulus? They find that
the population response is sparse, with sounds typically eliciting high activity in less than 5 % of neurons at any instant. Their results represent
the first quantitative evidence for sparse representations of sounds in the unanesthetized auditory cortex.


These results are compatible with a model
in which most neurons are silent much of the time, and in which representations are composed of small dynamic subsets of highly active neurons.



Sparse representation of sounds in the unanesthetized auditory cortex

HromaВґdka T, DeWeese MR, Zador AM (2008)

PLoS Biol 6(1): e16. doi:10.1371/journal.pbio.0060016

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