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PubMed1991

Judging speech communication effectiveness in oral cancer patients.

An experiment was conducted to assess the effects of different types of sentences and recording methods on naive judges' evaluations of the speech communication effectiveness of four patients who had undergone surgery for oral cancer. As expected, judges understood patients better if they read meaningful rather than meaningless sentences and if their speech was evaluated under video rather than audio conditions. However, these general findings were qualified because of the powerful influence of individual differences among patients. For example, whereas the intelligibility of three of the patients increased under the audio condition if the sentences being read were meaningful, one patient was poorly understood no matter what type of sentence he read under the same condition. The results suggested that the identification of the unique personality characteristics of patients that are related to their intelligibility merits serious consideration by both researchers and rehabilitation clinicians.

Adolescent↗
PubMed1986

Developmental changes in visual and auditory contributions to speech perception.

Previous research has demonstrated that listeners make use of both auditory and visual information in bimodal speech perception. Preschool children appear to evaluate and integrate the two sources of information in the same manner as adults, but the children are less influenced by the visual source. The current experiments test a possible explanation of this difference and extend the question to younger children. It is possible that children are poorer lip-readers than adults and thus have less complete information about the visual source. Children and adults were tested with both auditory and visual sources and were also required to identify speech events on the basis of only the visual source. In addition to replicating the previous findings in the bimodal situation, the current experiments found that children are poorer lip-readers than adults. Furthermore, a positive correlation was observed between lip-reading ability and the size of the visual contribution to bimodal speech perception. A fuzzy logical model of speech perception provided a good quantitative description of the results even with the assumption that the visual information was equivalent in both the bimodal and lip-reading conditions. The results also contradict the categorical perception of speech events and any nonindependence in the evaluation of auditory and visual information in speech perception.

Adolescent↗
PubMed1990

Neuropsychological studies of auditory-visual fusion illusions. Four case studies and their implications.

A heard speech sound which is not the same as the synchronized speech sound can sometimes give rise to an illusory phonological percept. Typically, a heard /ba/ combines with a seen /ga/ to give the impression that /da/ has been heard (McGurk, H. and MacDonald, J. Nature Lond. 264, 746-748, 1976). We report the susceptibility to this illusion of four individuals with localized brain lesions affecting perceptual function. We compare their performance to that of ten control subjects and relate these findings to the efficiency of processing seen and heard speech in separate and combined modalities. The pattern of performance strongly suggests LH specialization for the phonological integration of seen and heard speech. The putative site of such integration can be effectively isolated from unilateral and from bilateral inputs and may be driven by either modality.

Adult↗
PubMed1996

The lateralization of lip-reading: a second look.

Photographs of unfamiliar speaking faces were matched by normal right-handed subjects on the basis of perceived mouth-shape (i.e. visible speech sound) across different face-views. A clear left-hemisphere (RVF) processing advantage emerged, which was absent when the task was that of identity matching. In contrast to earlier proposals, the extraction of lip-shape from face photographs may be better managed by left-hemisphere- than right-hemisphere mechanisms even at its initial stages. This may contribute to the observed patterns of dissociations in speech-reading and in audiovisual speech-processing in neurological patients.

Adult↗
PubMed1991

Speech discrimination and lip reading in patients with word deafness or auditory agnosia.

The purpose of this study was to assess the ability of four patients with word deafness or auditory agnosia to discriminate speech by reading lips. The patients were studied using nonsense monosyllables to test for speech discrimination, a lip reading test, the Token Test for auditory comprehension, and the Aphasia test. Our results show that patients with word deafness or auditory agnosia without aphasia can improve speech comprehension by reading lips in combination with listening, as compared with lip reading or listening alone. In conclusion, lip reading was shown to be useful for speech comprehension among these patients.

Adult↗
PubMed1993

The optimization of hearing-impaired children's speechreading.

As more hearing-impaired and deaf children are mainstreamed into regular schools and as age related hearing loss in advanced countries become more prevalent, so the need for optimal methods to teach speechreading increases. The numbers of children and adults who would benefit from improved methods of teaching speechreading must be considerable. No new methods of teaching speechreading have been developed since 1938. Speechreading is a skill that does not require complex technology, although it does augment the effectiveness of hearing aids. Increased knowledge of this skill would have great benefits in psychological, social and economic terms. Some relevant experimental psychological literature and the views of educators are discussed with the goal of contributing to the optimization of hearing-impaired children's speechreading.

Child↗
PubMed1986

The lateralization of lip-read sounds: a first look.

Two tachistoscopic studies on the lateralization of lip-read still photographs in normal right handers are reported. In the first, subjects matched a still lip photograph with a heard speech sound. A clear right hemisphere (LVF) advantage emerged, despite the phonological requirements of this task. This pattern of laterality failed to interact with the type of response (same/different) or with the status of the heard phoneme; both consonant and vowel matching showed the same pattern of LVF advantage, despite the significantly greater difficulty of consonant than vowel matching in this particular task. In the second study subjects were required to speak the sound they saw being spoken by a centrally displayed face photograph. The displayed face was chimeric; that is, one side of the face was seen saying one sound, one side another. Here, a rather complex pattern of results ensued. For the speakers seen a clear expressor asymmetry emerged; speech sounds were judged more accurately when they issued from the right side of the speaker's face. However, in the LVF, and only the LFV, accuracy in reporting chimeric face sounds correlated with speed in learning to lip-read, suggesting that the LVF is systematically involved even when task demands (speaking the response, phonological analysis, small, more central displays) do not, at first sight, suggest that they should. Taken together, these studies suggest that the right hemisphere could support some aspects of the processing of seen speech in normally hearing, normally lateralized individuals.

Adolescent↗
PubMed1991

Seeing speech: visual information from lip movements modifies activity in the human auditory cortex.

Neuromagnetic responses were recorded over the left hemisphere to find out in which cortical area the heard and seen speech are integrated. Auditory stimuli were Finnish/pa/syllables presented together with a videotaped face articulating either the concordant syllable/pa/(84% of stimuli, V = A) or the discordant syllable/ka/(16%, V not equal to A). In some subjects the probabilities were reversed. The subjects heard V not equal to A stimuli as/ta/ or ka. The magnetic responses to infrequent perceptions elicited a specific waveform which could be explained by activity in the supratemporal auditory cortex. The results show that visual information from articulatory movements has an entry into the auditory cortex.

Adult↗
PubMed2006

Asymmetries for the visual expression and perception of speech.

This study explored asymmetries for movement, expression and perception of visual speech. Sixteen dextral models were videoed as they articulated: 'bat,' 'cat,' 'fat,' and 'sat.' Measurements revealed that the right side of the mouth was opened wider and for a longer period than the left. The asymmetry was accentuated at the beginning and ends of the vocalization and was attenuated for words where the lips did not articulate the first consonant. To measure asymmetries in expressivity, 20 dextral observers watched silent videos and reported what was said. The model's mouth was covered so that the left, right or both sides were visible. Fewer errors were made when the right mouth was visible compared to the left--suggesting that the right side is more visually expressive of speech. Investigation of asymmetries in perception using mirror-reversed clips revealed that participants did not preferentially attend to one side of the speaker's face. A correlational analysis revealed an association between movement and expressivity whereby a more motile right mouth led to stronger visual expressivity of the right mouth. The asymmetries are most likely driven by left hemisphere specialization for language, which causes a rightward motoric bias.

Adolescent↗
PubMed2004

Seeing to hear better: evidence for early audio-visual interactions in speech identification.

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.

Cues↗
PubMed2004

Audio-visual speech perception is special.

In face-to-face conversation speech is perceived by ear and eye. We studied the prerequisites of audio-visual speech perception by using perceptually ambiguous sine wave replicas of natural speech as auditory stimuli. When the subjects were not aware that the auditory stimuli were speech, they showed only negligible integration of auditory and visual stimuli. When the same subjects learned to perceive the same auditory stimuli as speech, they integrated the auditory and visual stimuli in a similar manner as natural speech. These results demonstrate the existence of a multisensory speech-specific mode of perception.

Association Learning↗
PubMed2006

Eye movements of monkey observers viewing vocalizing conspecifics.

Primates, including humans, communicate using facial expressions, vocalizations and often a combination of the two modalities. For humans, such bimodal integration is best exemplified by speech-reading - humans readily use facial cues to enhance speech comprehension, particularly in noisy environments. Studies of the eye movement patterns of human speech-readers have revealed, unexpectedly, that they predominantly fixate on the eye region of the face as opposed to the mouth. Here, we tested the evolutionary basis for such a behavioral strategy by examining the eye movements of rhesus monkeys observers as they viewed vocalizing conspecifics. Under a variety of listening conditions, we found that rhesus monkeys predominantly focused on the eye region versus the mouth and that fixations on the mouth were tightly correlated with the onset of mouth movements. These eye movement patterns of rhesus monkeys are strikingly similar to those reported for humans observing the visual components of speech. The data therefore suggest that the sensorimotor strategies underlying bimodal speech perception may have a homologous counterpart in a closely related primate ancestor.

Animals↗
PubMed2004

Spatial and temporal factors during processing of audiovisual speech: a PET study.

Speech perception can use not only auditory signals, but also visual information from seeing the speaker's mouth. The relative timing and relative location of auditory and visual inputs are both known to influence crossmodal integration psychologically, but previous imaging studies of audiovisual speech focused primarily on just temporal aspects. Here we used Positron Emission Tomography (PET) during audiovisual speech processing to study how temporal and spatial factors might jointly affect brain activations. In agreement with previous work, synchronous versus asynchronous audiovisual speech yielded increased activity in multisensory association areas (e.g., superior temporal sulcus [STS]), plus in some unimodal visual areas. Our orthogonal manipulation of relative stimulus position (auditory and visual stimuli presented at same location vs. opposite sides) and stimulus synchrony showed that (i) ventral occipital areas and superior temporal sulcus were unaffected by relative location; (ii) lateral and dorsal occipital areas were selectively activated for synchronous bimodal stimulation at the same external location; (iii) right inferior parietal lobule was activated for synchronous auditory and visual stimuli at different locations, that is, in the condition classically associated with the 'ventriloquism effect' (shift of perceived auditory position toward the visual location). Thus, different brain regions are involved in different aspects of audiovisual integration. While ventral areas appear more affected by audiovisual synchrony (which can influence speech identification), more dorsal areas appear to be associated with spatial multisensory interactions.

Adult↗
PubMed2005

Listening to talking faces: motor cortical activation during speech perception.

Neurophysiological research suggests that understanding the actions of others harnesses neural circuits that would be used to produce those actions directly. We used fMRI to examine brain areas active during language comprehension in which the speaker was seen and heard while talking (audiovisual) or heard but not seen (audio-alone) or when the speaker was seen talking with the audio track removed (video-alone). We found that audiovisual speech perception activated a network of brain regions that included cortical motor areas involved in planning and executing speech production and areas subserving proprioception related to speech production. These regions included the posterior part of the superior temporal gyrus and sulcus, the pars opercularis, premotor cortex, adjacent primary motor cortex, somatosensory cortex, and the cerebellum. Activity in premotor cortex and posterior superior temporal gyrus and sulcus was modulated by the amount of visually distinguishable phonemes in the stories. None of these regions was activated to the same extent in the audio- or video-alone conditions. These results suggest that integrating observed facial movements into the speech perception process involves a network of multimodal brain regions associated with speech production and that these areas contribute less to speech perception when only auditory signals are present. This distributed network could participate in recognition processing by interpreting visual information about mouth movements as phonetic information based on motor commands that could have generated those movements.

Adult↗
PubMed2005

Audio-visual matching of speech and non-speech oral gestures in patients with aphasia and apraxia of speech.

BACKGROUND: Audio-visual speech perception mechanisms provide evidence for a supra-modal nature of phonological representations, and a link of these mechanisms to motor representations of speech has been postulated. This leads to the question if aphasic patients and patients with apraxia of speech are able to exploit the visual signal in speech perception and if implicit knowledge of audio-visual relationships is preserved in these patients. Moreover, it is unknown if the audio-visual processing of mouth movements has a specific organisation in the speech as compared to the non-speech domain. METHODS: A discrimination task with speech and non-speech stimuli was applied in four presentation modes: auditory, visual, bimodal and cross-modal. We investigated 14 healthy persons and 14 patients with aphasia and/or apraxia of speech. RESULTS: Patients made substantially more errors than normal subjects on both the speech and the non-speech stimuli, in all presentation modalities. Normal controls made only few errors on the speech stimuli, regardless of the presentation mode, but had a high between-subject variability in the cross-modal matching of non-speech stimuli. The patients' cross-modal processing of non-speech stimuli was mainly predicted by lower face apraxia scores, while their audio-visual matching of syllables was predicted by word repetition abilities and the presence of apraxia of speech. CONCLUSIONS: (1) Impaired speech perception in aphasia is located at a supra-modal representational level. (2) Audio-visual processing is different for speech and non-speech oral gestures. (3) Audio-visual matching abilities in patients with left-hemisphere lesions depend on their speech and non-speech motor abilities.

Adult↗
PubMed2006

Imitation during phoneme production.

Does listening to and observing the speaking interlocutor influence phoneme production? In two experiments female participants were required to recognize and, then, to repeat the string-of-phonemes /aba/ presented by actors visually, acoustically and audiovisually. In experiment 1 a male actor presented the string-of-phonemes and the participants' lip kinematics and voice spectra were compared with those of a reading control condition. In experiment 2 female and male actors presented the string-of-phonemes and the lip kinematics and the voice spectra of the participants' responses to the male actors were compared with those to the female actors (control condition). In both experiments 1 and 2, the lip kinematics in the visual presentations and the voice spectra in the acoustical presentations changed in the comparison with the control conditions approaching the male actors' values, which were different from those of the female participants and actors. The variation in lip kinematics induced changes also in voice formants but only in the visual presentation. The data suggest that both features of the lip kinematics and of the voice spectra tend to be automatically imitated when repeating a string-of-phonemes presented by a visible and/or audible speaking interlocutor. The use of imitation, in place of the usual lip kinematics and vocal features, suggests an automatic and unconscious tendency of the perceiver to interact closely with the interlocutor. This is in accordance with the idea that resonant circuits are activated by the activity of the mirror system, which relates observation to execution of arm and mouth gestures.

Adult↗