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Differences between Primary Auditory Cortex and Auditory Belt Related to Encoding and Choice for AM Sounds

Authors :
Jeffrey S. Johnson
Mitchell L. Sutter
Mamiko Niwa
Kevin N. O'Connor
Source :
The Journal of Neuroscience. 33:8378-8395
Publication Year :
2013
Publisher :
Society for Neuroscience, 2013.

Abstract

We recorded from middle–lateral (ML) and primary (A1) auditory cortex while macaques discriminated amplitude-modulated (AM) noise from unmodulated noise. Compared with A1, ML had a higher proportion of neurons that encoded increasing AM depth by decreasing their firing rates (“decreasing” neurons), particularly with responses that were not synchronized to the modulation. Choice probability (CP) analysis revealed that A1 and ML activity were different during the first half of the test stimulus. In A1, significant CP began before the test stimulus, remained relatively constant (or increased slightly) during the stimulus, and increased greatly within 200 ms of lever release. Neurons in ML behaved similarly, except that significant CP disappeared during the first half of the stimulus and reappeared during the second half and prerelease periods. CP differences between A1 and ML depend on neural response type. In ML (but not A1), when activity was lower during the first half of the stimulus in nonsynchronized, decreasing neurons, the monkey was more likely to report AM. Neurons that both increased firing rate with increasing modulation depth (“increasing” neurons) and synchronized their responses to AM had similar choice-related activity dynamics in ML and A1. These results suggest that, when ascending the auditory system, there is a transformation in coding AM from primarily synchronized increasing responses in A1 to nonsynchronized and dual (increasing/decreasing) coding in ML. This sensory transformation is accompanied by changes in the timing of activity related to choice, suggesting functional differences between A1 and ML related to attention and/or behavior.

Details

ISSN :
15292401 and 02706474
Volume :
33
Database :
OpenAIRE
Journal :
The Journal of Neuroscience
Accession number :
edsair.doi.dedup.....63d79580bc9cc65353139c2e8821231c
Full Text :
https://doi.org/10.1523/jneurosci.2672-12.2013