The neural basis of lip-reading capabilities is altered by early visual deprivation.
ABSTRACT 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.
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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.Vision research 06/2012; 66(8):49-54. DOI:10.1016/j.visres.2012.06.003 · 2.38 Impact Factor
- 01/2012; MIT Press.
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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.Proceedings of the National Academy of Sciences 09/2013; DOI:10.1073/pnas.1309963110 · 9.81 Impact Factor