The neural basis of lip-reading capabilities is altered by early visual deprivation
Biological Psychology and Neuropsychology, University of Hamburg, Von-Melle-Park 11, D-20146 Hamburg, Germany. Neuropsychologia
(Impact Factor: 3.3).
04/2010; 48(7):2158-66. DOI: 10.1016/j.neuropsychologia.2010.04.007
The present study investigated the neural basis of lip-reading in patients treated for congenital bilateral cataracts using functional magnetic resonance imaging (fMRI). These patients represent a model to study the role of visual experience in early infancy for the development of visual functions. Short video clips with an adult speaker's lips mouthing different words were presented. The participants were asked to indicate whether the current word was the same as the previous one (one-back matching task). A control condition consisted of the same stimuli but with the task to judge whether the position of a small black dot superimposed on the lips changed location between trials. During both tasks, neural activity as indexed by fMRI, and behavioral data were recorded. The cataract patients' lip-reading performance was worse than that of a group of normally sighted controls, matched for age, gender, and education. By contrast, these groups did not differ in the visual control task. Only the control group showed reliable lip-reading specific activations in superior and middle temporal areas and in right parietal cortex, resulting in a significant group effect for these brain areas. Additional control participants with a late onset of visual impairments matching those of the cataract group showed comparable behavioral performance and similar fMRI activations in superior temporal areas as the normally sighted controls. These results suggest that a sensitive phase in early infancy might exist during which visual acuity must be sufficiently high to discriminate lip movements in order to allow for the emergence of a regular neural lip-reading system.
Available from: Nichole Morris
- "Studies of patients with bilateral congenital 137 cataracts suggest that the presence of cataracts can interfere with the normal development of visual 138 speech perception. Adults who had had bilateral congenital cataracts show a reduced McGurk 139 effect (Putzar, Hötting, & Röder, 2010), and are significantly poorer at speechreading than age- 140 matched controls who had normal vision during infancy (Putzar et al., 2010). Thus cataracts 141 which affect contrast sensitivity may interfere with speech perception; though limitations in the 142 experimental approaches adopted in these studies precludes clear conclusions being drawn. "
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ABSTRACT: Limited research is available on how well visual cues integrate with auditory cues to improve speech intelligibility in persons with visual impairments, such as cataracts. We investigated whether simulated cataracts interfered with participants' ability to use visual cues to help disambiguate a spoken message in the presence of spoken background noise. We tested 21 young adults with normal visual acuity and hearing sensitivity. Speech intelligibility was tested under three conditions: auditory only with no visual input, auditory-visual with normal viewing, and auditory-visual with simulated cataracts. Central Institute for the Deaf (CID) Everyday Speech Sentences were spoken by a live talker, mimicking a pre-recorded audio track, in the presence of pre-recorded four-person background babble at a signal-to-noise ratio (SNR) of -13 dB. The talker was masked to the experimental conditions to control for experimenter bias. Relative to the normal vision condition, speech intelligibility was significantly poorer, [t(20)=4.17, p<.01, Cohen's d=1.0], in the simulated cataract condition. These results suggest that cataracts can interfere with speech perception, which may occur through a reduction in visual cues, less effective integration or a combination of the two effects. These novel findings contribute to our understanding of the association between two common sensory problems in adults: reduced contrast sensitivity associated with cataracts and reduced face-to-face communication in noise.
Available from: David J. Lewkowicz
- "Lip-reading skills continue to improve until late childhood (up to the 12th year of life), suggesting that adequate visual experience in infancy is a necessary prerequisite for developing normal lip-reading abilities and for setting up neural interactions with the auditory system. Putzar and colleagues investigated audio-visual speech perception in cataract patients by using the McGurk illusion to test cross-modal interference (Putzar, Hötting, et al., 2010) and by presenting congruent visual and auditory speech information to test cross-modal facilitation (Putzar, Goerendt, et al., 2007). McGurk and MacDonald (1976) demonstrated that when participants hear the syllable /ba/ and see lip movements corresponding to a /ga/ they often report a new percept (i.e., /da/) and when they hear /ga-ga/ see the lips mouthing /ba-ba/ they usually hear /gabga/ . "
Available from: Davide Bottari
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ABSTRACT: The aim of the study was to identify possible sensitive phases in
the development of the processing system for human faces. We
tested the neural processing of faces in 11 humans who had been
blind from birth and had undergone cataract surgery between
2 mo and 14 y of age. Pictures of faces and houses, scrambled
versions of these pictures, and pictures of butterflies were presented while event-related potentials were recorded. Participants
had to respond to the pictures of butterflies (targets) only. All
participants, even those who had been blind from birth for several
years, were able to categorize the pictures and to detect the
targets. In healthy controls and in a group of visually impaired
individuals with a history of developmental or incomplete con-genital cataracts, the well-known enhancement of the N170 (negative peak around 170 ms) event-related potential to faces
emerged, but a face-sensitive response was not observed in
humans with a history of congenital dense cataracts. By contrast,
this group showed a similar N170 response to all visual stimuli,
which was indistinguishable from the N170 response to faces in
the controls. The face-sensitive N170 response has been associated
with the structural encoding of faces. Therefore, these data provide evidence for the hypothesis that the functional differentiation
of category-specific neural representations in humans, presumably
involving the elaboration of inhibitory circuits, is dependent on
experience and linked to a sensitive period. Such functional specialization of neural systems seems necessary to archive high processing proficiency.
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