title: Response characteristics of primary auditory cortex neurons underlying perceptual asymmetry of ramped and damped sounds.
abstract: Sound envelope plays a crucial role in perception: ramped sounds (slow attack and quick decay) are louder in strength and longer in subjective duration than damped sounds (quick attack and slow decay) even if they are equal in intensity and physical duration. To explain the asymmetrical perception, the perceptual constancy hypothesis supposes that the listener eliminates the slow decay of damped sounds from the judgment of perception, while the persistence of perception hypothesis supposes asymmetrical neural responses after the source has stopped. To understand neural mechanisms underlying the perceptual asymmetry, we explored response properties of the primary auditory cortex (A1) neurons during ramped and damped stimuli in awake cats. We found two distinct types of cells tuned to specific features of the sound envelope: edge cells sensitive to the temporal edge, such as quick attack and decay, while slope cells sensitive to slow attack and decay. The former needs a short (<2.5 ms) period of stimulus duration for evoking maximal peak responses, while the latter needs a long (20 ms) period, suggesting that the timescale of processing underlies differential sensitivity between the cell types. The findings suggest that perceptual constancy is not yet be executed at A1 because the specific cells distinguishing the direction of amplitude change (attack or decay) are lacking in A1. On the other hand, there is evidence of persistence of perception: overall response duration during ramped sound reached 1.4 times longer than that during damped sound, originating mainly from the response asymmetry of the edge cell (sensitive to the quick decay of ramped sounds but not to the slow decay of damped sounds), and neuronal persistence of excitation after the termination of ramped sounds was substantially longer than that of damped sounds, corresponding to the psychological evidence of persistence of perception.
authors.affiliation: Department of Physiology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi 409-3898, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Physiology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi 409-3898, Japan; Department of Physiology, China Medical University, Shenyang 110001, People's Republic of China.
authors.forename: L
authors.initials: L
authors.lastname: Qin
authors.affiliation: Department of Physiology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi 409-3898, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Chimoto
authors.affiliation: Department of Physiology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi 409-3898, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Tazunoki
authors.affiliation: Department of Physiology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi 409-3898, Japan. Electronic address: yu_sato@yamanashi.ac.jp.
authors.forename: Y
authors.initials: Y
authors.lastname: Sato
mesh_terms: D000161:Acoustic Stimulation; D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001303:Auditory Cortex / Q000166:cytology*; D001307:Auditory Perception / Q000502:physiology*; D002415:Cats; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D011930:Reaction Time; D013016:Sound; D013997:Time Factors
keywords: A1; BF; PSTHs; RDI; SCI; SPL; auditory cortex; best frequency; integration time; perceptual asymmetry; peri-stimulus time histograms; primary auditory cortex; response asymmetry; response duration; response duration index; sound envelope; sound pressure level; spike count index