発話と音声知覚の脳情報処理 Neural mechanisms of speech production and perception
S2-4-3-1 The neurobiology of speech perception - the roles of anatomical streams and hemispheric asymmetries ○Sophie Scott1 Institute of Cognitive Neuroscience, University College London1 Developments in the 1990s of our understanding of primate neuroanatomy and neurophysiology have, in combination with developments in functional neuroimaging, enabled us to delineate considerable complexity in the way that the human brain processes sound and speech. There are at least two functional streams of processing, a rostral 'what' pathway associated with the perceptual processing and understanding of speech and a caudal 'how' pathway associated with sensori-motor processing of speech and sound. In this talk I will discuss how different aspects of speech are processed in these different pathways, how this is affected by native and non-native speech sounds, and how both pathways are modulated by speech production. I will also consider ways in which the processing of speech and sound differs across the two cerebral hemispheres, and address the best ways that we can account for these differences.	S2-4-3-2 Reinforcement Learning Helps Define the Sensory Targets that Drive Error-Based Motor Learning ○David Ostry1, Daniel R Lametti1 McGill University1 Motor learning is often modeled by examining how individuals compensate for disturbances that drive a movement away from a sensory target. These error-based models of motor learning assume by default that the sensory targets of movement are well defined, but when an infant first reaches for a toy or speaks her first word the targets of movement are poorly defined if known at all. Here we use speech production to study the effects of reinforcement-driven perceptual training on error-based motor learning. We hypothesized that a simple reinforcement paradigm could be used to alter the perceptual targets of speech. Reinforced alterations in speech perception would be revealed by predictable changes in the amount of error-based adaptation in a speech-learning task. To manipulate perception, we used reinforced perceptual judgments to alter the perceptual distinction between the words head and had. An acoustical effects processor was then used to simulate a speech-learning task. During production of the word head, the effects processor changed the sound of the vowel in real-time. The amount of compensation was examined to test the idea that reinforced alterations in speech perception shape speech motor learning. We found that minutes of perceptual training change the sensory targets of speech. These rapid changes in speech perception subsequently cause alterations in error-based speech motor learning that last for days. The experiments show that the perceptual targets used as benchmarks for the maintenance of accurate speech are easily and rapidly altered. More generally, the work suggests that reinforcement learning plays a central role in defining the sensory targets that drive error-based motor learning.
S2-4-3-3 乳児の視聴覚間音声口形マッチングの発達―発話と知覚は相互に関係するのか？ Audiovisual matching of lips and speech sounds in infants -Is there a link between speech production and perception? ○麦谷綾子1 ○Ryoko Mugitani1 NTT CS研・人間情報研究部1 Human Info. Sci. Lab. NTT CS labs. Kanagawa1 Speech can be heard and also simultaneously seen as the movements of external articulators such as lips. The ability to match speech sounds and appropriate lip movements emerges in the early stages of language development. The fact that even newborns prefer audiovisually matched presentations of vowels suggests that lip-voice matching is, at least to some extent, a property that is inherent at the beginning of life without specific motor and/or perceptual experience of the sounds. This leads us to ask whether infants are born with the ability to integrate intermodal representations of the lips and voice for any type of sound presentation. In this symposium, I will introduce some recent findings for infants suggesting that audiovisual associations are not only inherent, but also learnt in later life through perceptual and/or motor experiences of specific articulation. The presentation will also compare an acoustic analysis of infants' utterances with behavioral data obtained in perceptual discrimination experiments on certain speech sounds, which will help us to explore the link between production and perception during the course of early speech development.	S2-4-3-4 聞くと話すの密接な関係：音声の自然性の影響 A relationship between speaking and listening to speech: Impact of speech sound naturalness ○廣谷定男1 ○Sadao Hiroya1 NTTコミュニケーション科学基礎研究所1 NTT Communication Science Laboratories1 Speech communication is important for our daily life. We normally understand spoken sentences in native language without effort. However, neural mechanisms for the perception of speech sounds remain unclear for more than half a century. Speech sounds are produced by articulatory gestures, but does speech perception mechanism involve the constraints of articulatory gestures? Intriguingly, recent brain imaging studies of speech revealed a common cortical activation during speech production and perception. This suggests that mirror neuron system may play an important role in speech perception. The speech sounds are considered to be differed from the non-speech sounds. Manipulation methods of speech sound naturalness would be useful for understanding neural mechanisms of speech perception. Sinewave speech and noise-vocoded speech have often been used, but these manipulation techniques are based on reducing the frequency information. Thus, a novel speech-sound-naturalness manipulation technique using measured articulatory movements of lips, jaw, and tongue, would be required for investigating effects of naturalness of speaking rhythm on speech perception. The techniques will give us a new possibility of brain imaging study to investigate the neural correlates of the speech rhythmic naturalness in speech perception. In this talk, I will survey recent studies of brain imaging for speech production and perception. Next, I will show a mean opinion score for our speech sound naturalness-controlled stimuli and brain activity during speech perception. Our results suggested that involvement of brain areas related to speech production varies depending on speech naturalness during speech perception.

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