Lip reading is the ability to partially understand speech by looking at the speaker's lips. It improves the intelligibility of speech in noise when audio-visual perception is compared with audio-only perception. A recent set of experiments showed that seeing the speaker's lips also enhances sensitivity to acoustic information, decreasing the auditory detection threshold of speech embedded in noise [J. Acoust. Soc. Am. 109 (2001) 2272; J. Acoust. Soc. Am. 108 (2000) 1197]. However, detection is different from comprehension, and it remains (...) to be seen whether improved sensitivity also results in an intelligibility gain in audio-visual speech perception. In this work, we use an original paradigm to show that seeing the speaker's lips enables the listener to hear better and hence to understand better. The audio-visual stimuli used here could not be differentiated by lip reading per se since they contained exactly the same lip gesture matched with different compatible speech sounds. Nevertheless, the noise-masked stimuli were more intelligible in the audio-visual condition than in the audio-only condition due to the contribution of visual information to the extraction of acoustic cues. Replacing the lip gesture by a non-speech visual input with exactly the same time course, providing the same temporal cues for extraction, removed the intelligibility benefit. This early contribution to audio-visual speech identification is discussed in relationships with recent neurophysiological data on audio-visual perception. (shrink)

One of the fundamental questions raised by Ruchkin, Grafman, Cameron, and Berndt's (Ruchkin et al.'s) interpretation of no distinct specialized neural networks for short-term storage buffers and long-term memory systems, is that of the link between perception and memory processes. In this framework, we take the opportunity in this commentary to discuss a specific working memory task involving percept formation, temporary retention, auditory imagery, and the attention-based maintenance of information, that is, the verbal transformation effect.

We agree with MacNeilage's claim that speech stems from a volitional vocalization pathway between the cingulate and the supplementary motor area (SMA). We add the vocal self- monitoring system as the first recruitment of the Broca-Wernicke circuit. SMA control for “frames” is supported by wrong consonant-vowel recurring utterance aphasia and an imaging study of quasi-reiterant speech. The role of Broca's area is questioned in the emergence of “content,” because a primary motor mapping, embodying peripheral constraints, seems sufficient. Finally, we reject (...) a uniquely peripheral account of speech emergence. (shrink)

We consider a computational model comparing the possible roles of and in phonetic decoding, demonstrating that these two routes can contain similar information in some communication situations and highlighting situations where their decoding performance differs. We conclude that optimal decoding should involve some sort of fusion of association and simulation in the human brain.