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Functional Imaging of Auditory Cortex in Adult Cats using High-field fMRI
Published on: February 19, 2014
Level dependence of spatial processing in the primate auditory cortex.
1Laboratory of Auditory Neurophysiology, Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205-2195, USA. zhouyi@jhu.edu
Journal of Neurophysiology
|May 18, 2012
Summary
Neural mechanisms of sound localization were investigated in marmoset monkeys. While individual neurons showed varied spatial tuning with sound levels, population responses remained stable, indicating level-tolerant sound localization.
Area of Science:
- Neuroscience
- Auditory Processing
- Sensory Systems
Background:
- Sound localization in humans and monkeys is remarkably tolerant to changes in sound intensity.
- The neural basis for this level tolerance in sound localization remains poorly understood.
- Investigating the auditory cortex provides insight into the neural computations underlying spatial hearing.
Purpose of the Study:
- To investigate the level dependence of spatial receptive fields (SRFs) in the auditory cortex (A1) and caudal field of awake marmoset monkeys.
- To determine how individual neuronal tuning and population-level responses change with sound intensity.
- To elucidate the role of excitatory and suppressive components of SRFs in sound localization.
Main Methods:
- Recorded neuronal activity in the primary auditory cortex (A1) and adjacent caudal field of awake marmoset monkeys.
- Measured spatial receptive fields (SRFs) using broadband noise stimuli at varying sound levels.
- Investigated forward suppression using pairs of sequentially presented stimuli to assess suppressive components of SRFs.
Main Results:
- Most neurons exhibited spatially confined excitatory SRF components.
- About half of the neurons showed stable spatial tuning width across a ~20-dB sound level change; others showed expansion or contraction.
- Population-averaged responses remained tuned across sound levels (30-80 dB SPL), demonstrating level tolerance.
- Suppressive components of SRFs increased in strength with stimulus level, potentially limiting SRF size at higher intensities.
Conclusions:
- Individual neuronal spatial tuning in the auditory cortex can vary with sound level.
- Ensemble neuronal activity in the auditory cortex exhibits robust level tolerance for sound localization.
- Spatial suppression may play a critical role in maintaining spatial tuning precision at higher sound levels.
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