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Auditory and Vestibular Systems

開催日 2014/9/13
時間 14:00 - 15:00
会場 Poster / Exhibition(Event Hall B)

Contrast between Activations Evoked by Forward and Backward Reproduction of a Natural Sound in the Auditory Cortex Increases after Classical Conditioning

  • P3-136
  • 小島 久幸 / Hisayuki Ojima:1,2 石田 倫裕 / TOMOHIRO ISHIDA:3 泰羅 雅登 / MASATO TAIRA:1,2 堀川 順生 / JUNSEI HORIKAWA:3 
  • 1:東京医歯大・院・認知神経生物 / Grad Sch, Tokyo Med and Dent Univ, Tokyo, Japan 2:東京医歯大・CBIR / CBIR, Tokyo Med and Dent Univ, Tokyo, Japan 3:豊技大・院・工 / Comp Sci and Engi, Grad Sch Engi, Toyohashi Univ Tech, Toyohashi, Japan 

Activation patterns of auditory cortex (AC) by a natural sound and its temporally reversed version were optically imaged and the contrast of such activations was compared between trained and untrained guinea pigs (GPs).
A human-generated footstep sound (Fss), consisting of 10 segments of each 110 ms in duration, was played back as forward stimulus. Fss was reversed in time on a sound editing software and reproduced backward (revF). GPs were conditioned to Fss using food as reinforcement and subjected to voltage sensitive dye optical imaging under ketamine anesthesia.
First, to see time-reversing effects of the stimulus sound on the global activation, we compared the activations evoked by Fss and revF. The revF sound activated AC much less vigorously than Fss. Compared between different training groups, activation by revF obtained from conditioned ACs was generally weaker than from naive ACs. Moreover, to clarify distinct roles of different components of the stimulus segment, each segment was separated into 3 consecutive portions to use as the independent stimulus. Activation patterns by them revealed that onset peak was critical to the generation of maximum activation, while the gradually decaying tail worked to suppress subsequent activation if applied backward.
Second, to explore possible alterations in contrasts during leaning, we compared activation contrasts obtained from naive animals with those obtained from the Fss-conditioned animals. Two-week conditioning resulted in distinct response behavior evoked following Fss reproduction, while virtually no behavior following revF playback. Contrast expressed by activation ratio defined as drevF/dFss (d; net fluorescence change at peak activation following Fss and revF) was significantly smaller in the conditioned than naive group, reflecting alterations of global network responsible for temporal processing of Fss during conditioning.

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