On Mechanisms of Specialized Reactions of Central Auditory Neurons to Frequency-Modulated Sounds
Responses of 231 units in the inferior colliculus of anesthetized white rats to pure tones and FM signals of various modulation patterns have been studied. The tuning curves display a wide distribution in characteristic carrier frequency (CF), threshold and bandwidth. The response to FM modulated sounds follows different patterns. The majority of neurons (66%) responds mainly or exclusively to signals of upgoing (42%) or downgoing frequency (24%) in the whole range of frequencies in the response area. The remaining units showed various patterns, (16%) responding less to FM modulated signals than to sine-waves. Characteristics of inhibition areas (IA) also differ much. In most cases (89%) IA are found both above and below the carrier frequency. The inhibition from a tone of a frequency above CF was generally less pronounced than the low frequency inhibition. Tests of the temporal dynamics of inhibition showed that the most expressed inhibition occurred when the inhibitory tone is switched on 10 to 50 ms before the CF (test) tone. With increasing separation of onsets the frequency region of the IA narrowed and the threshold of inhibition was raised. The recovery of the response at CF occurs much more quickly after low-frequency inhibition than for inhibiting tones of frequencies above the CF. The asymmetry of response to rising and falling direction of FM becomes more apparent at certain modulation speeds. No simple relation was found between the dynamics of IA and FM response asymmetry. The biological match between sound generation and perception apparently relies on specialized reactions of central auditory neurons to frequency modulated sounds.
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Document Type: Research Article
Publication date: December 1, 1974
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- Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
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