Tuning of Human Modulation Filters Is Carrier-Frequency DependentReport as inadecuate

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Recent studies employing speech stimuli to investigate ‘cocktail-party’ listening have focused on entrainment of cortical activity to modulations at syllabic 5 Hz and phonemic 20 Hz rates. The data suggest that cortical modulation filters CMFs are dependent on the sound-frequency channel in which modulations are conveyed, potentially underpinning a strategy for separating speech from background noise. Here, we characterize modulation filters in human listeners using a novel behavioral method. Within an ‘inverted’ adaptive forced-choice increment detection task, listening level was varied whilst contrast was held constant for ramped increments with effective modulation rates between 0.5 and 33 Hz. Our data suggest that modulation filters are tonotopically organized i.e., vary along the primary, frequency-organized, dimension. This suggests that the human auditory system is optimized to track rapid phonemic modulations at high sound-frequencies and slow prosodic-syllabic modulations at low frequencies.

Author: Andrew J. R. Simpson , Joshua D. Reiss, David McAlpine

Source: http://plos.srce.hr/


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