Wide-dynamic-range forward suppression in marmoset inferior colliculus neurons is generated centrally and accounts for perceptual masking.

Full Abstract

An organism's ability to detect and discriminate sensory inputs depends on the recent stimulus history. For example, perceptual detection thresholds for a brief tone can be elevated by as much as 50 dB when following a masking stimulus. Previous work suggests that such forward masking is not a direct result of peripheral neural adaptation; the central pathway apparently modifies the representation in a way that further attenuates the input's response to short probe signals. Here, we show that much of this transformation is complete by the level of the inferior colliculus (IC). Single-neuron extracellular responses were recorded in the central nucleus of the awake marmoset IC. The threshold for a 20 ms probe tone presented at best frequency was determined for various masker-probe delays, over a range of masker sound pressure levels (SPLs) and frequencies. The most striking aspect of the data was the increased potency of forward maskers as their SPL was increased, despite the fact that the excitatory response to the masker was often saturating or nonmonotonic over the same range of levels. This led to probe thresholds at high masker levels that were almost always higher than those observed in the auditory nerve. Probe threshold shifts were not usually caused by a persistent excitatory response to the masker; instead we propose a wide-dynamic-range inhibitory mechanism locked to sound offset as an explanation for several key aspects of the data. These findings further delineate the role of subcortical auditory processing in the generation of a context-dependent representation of ongoing acoustic scenes.

Author information

Author/s: Nelson, Paul C (PC); Smith, Zachary M (ZM); Young, Eric D (ED);

Affiliation: Center for Hearing and Balance, Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205, USA. pcnelson(-atsign-)jhu.edu

Grants: DC00023 (Agency:NIDCD NIH HHS) ; DC00115 (Agency:NIDCD NIH HHS) ; DC009164 (Agency:NIDCD NIH HHS) ; F32 DC009164-02 (Agency:NIDCD NIH HHS) ; R01 DC000115-33 (Agency:NIDCD NIH HHS)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural

Journal: The Journal of neuroscience : the official journal of the Society for Neuroscience (J Neurosci), published in United States. (Language: eng)

Reference: 2009-Feb; vol 29 (issue 8) : pp 2553-62

Dates: Created 2009/02/26; Completed 2009/03/16; Revised 2009/08/27;

PMID: 19244530, status: MEDLINE (last retrieved date: 8/28/2009)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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