The investigation of patients treated for bilateral congenital cataracts allows to study the development of visual and multisensory functions after a period of visual deprivation in early infancy. In the present study, cataract patients were tested for their capability to recognize faces and to integrate auditory and visual speech information.
In Experiment 1, 12 cataract patients were tested with the Benton Facial Recognition Test. In Experiment 2, a McGurk paradigm was used that investigated audio-visual interaction and lip-reading capabilities. Here, fifteen cataract patients participated and were compared to normally sighted controls and to visually impaired controls.
In the Benton Facial Recognition Test, cataract patients' performance was unimpaired when target and test face were identical. By contrast, they performed worse than a normally sighted control group when head orientation and/or lighting conditions of the test faces were changed. In the McGurk paradigm, cataract patients displayed impaired lip-reading abilities and a reduced audio-visual interaction compared to normally sighted controls. The latter deficit prevailed even in a sub-group matched for lip-reading capacities with a normally sighted control sub-group.
These results suggest that visual input in early infancy is a prerequisite for a normal development of visual and multisensory functions.
"A subsequent study corroborated the deficit in varying head position and lighting conditions and revealed a deficit for lip reading using a more complex task (Putzar et al., 2010b). Specifically, Putzar et al. (2010b) investigated lip reading with the McGurk effect, which relies on the integration of visual and auditory speech cues. A follow-up study using fMRI found that observers with amblyopia exhibited a different pattern of cortical activation when lip reading. "
[Show abstract][Hide abstract] ABSTRACT: Amblyopia is a neurodevelopmental disorder of the visual system that is associated with disrupted binocular vision during early childhood. There is evidence that the effects of amblyopia extend beyond the primary visual cortex to regions of the dorsal and ventral extra-striate visual cortex involved in visual integration. Here, we review the current literature on global processing deficits in observers with either strabismic, anisometropic, or deprivation amblyopia. A range of global processing tasks have been used to investigate the extent of the cortical deficit in amblyopia including: global motion perception, global form perception, face perception, and biological motion. These tasks appear to be differentially affected by amblyopia. In general, observers with unilateral amblyopia appear to show deficits for local spatial processing and global tasks that require the segregation of signal from noise. In bilateral cases, the global processing deficits are exaggerated, and appear to extend to specialized perceptual systems such as those involved in face processing.
Frontiers in Psychology 06/2014; 5:583. DOI:10.3389/fpsyg.2014.00583 · 2.80 Impact Factor
"Neurophysiological studies conducted in mammals have shown that multisensory neurons and the ability to integrate crossmodal information require an extensive time of sensory experience during early development in order to fully mature , . This predicts that sensory deprivation may impair multisensory processing, as has been extensively documented in visually deprived animals ,  and in blind humans too , . In particular,  have suggested that there may be a sensitive period for the development of multisensory integration, after which – if adequate experience has not been made - multisensory processing will remain impaired. "
[Show abstract][Hide abstract] ABSTRACT: Several studies conducted in mammals and humans have shown that multisensory processing may be impaired following congenital sensory loss and in particular if no experience is achieved within specific early developmental time windows known as sensitive periods. In this study we investigated whether basic multisensory abilities are impaired in hearing-restored individuals with deafness acquired at different stages of development. To this aim, we tested congenitally and late deaf cochlear implant (CI) recipients, age-matched with two groups of hearing controls, on an audio-tactile redundancy paradigm, in which reaction times to unimodal and crossmodal redundant signals were measured. Our results showed that both congenitally and late deaf CI recipients were able to integrate audio-tactile stimuli, suggesting that congenital and acquired deafness does not prevent the development and recovery of basic multisensory processing. However, we found that congenitally deaf CI recipients had a lower multisensory gain compared to their matched controls, which may be explained by their faster responses to tactile stimuli. We discuss this finding in the context of reorganisation of the sensory systems following sensory loss and the possibility that these changes cannot be "rewired" through auditory reafferentation.
PLoS ONE 06/2014; 9(6):e99606. DOI:10.1371/journal.pone.0099606 · 3.23 Impact Factor
"About half of these 28 generate nuclear cataract which requires as early a clinical intervention as possible. Congenital bilateral nuclear opacity, which appears to be the most common autosomal dominant inherited form of cataracts , blocks the central visual axis and causes complications such as nystagmus and developmental amblyopia in the growing infant –, and pediatric ophthalmologists need to intervene at the earliest , . On the other hand, cortical and other types of peripheral cataracts do not demand early action, since they do not block the visual axis. "
[Show abstract][Hide abstract] ABSTRACT: We highlight an unrecognized physiological role for the Greek key motif, an evolutionarily conserved super-secondary structural topology of the βγ-crystallins. These proteins constitute the bulk of the human eye lens, packed at very high concentrations in a compact, globular, short-range order, generating transparency. Congenital cataract (affecting 400,000 newborns yearly worldwide), associated with 54 mutations in βγ-crystallins, occurs in two major phenotypes nuclear cataract, which blocks the central visual axis, hampering the development of the growing eye and demanding earliest intervention, and the milder peripheral progressive cataract where surgery can wait. In order to understand this phenotypic dichotomy at the molecular level, we have studied the structural and aggregation features of representative mutations.
Wild type and several representative mutant proteins were cloned, expressed and purified and their secondary and tertiary structural details, as well as structural stability, were compared in solution, using spectroscopy. Their tendencies to aggregate in vitro and in cellulo were also compared. In addition, we analyzed their structural differences by molecular modeling in silico.
Based on their properties, mutants are seen to fall into two classes. Mutants A36P, L45PL54P, R140X, and G165fs display lowered solubility and structural stability, expose several buried residues to the surface, aggregate in vitro and in cellulo, and disturb/distort the Greek key motif. And they are associated with nuclear cataract. In contrast, mutants P24T and R77S, associated with peripheral cataract, behave quite similar to the wild type molecule, and do not affect the Greek key topology.
When a mutation distorts even one of the four Greek key motifs, the protein readily self-aggregates and precipitates, consistent with the phenotype of nuclear cataract, while mutations not affecting the motif display 'native state aggregation', leading to peripheral cataract, thus offering a protein structural rationale for the cataract phenotypic dichotomy "distort motif, lose central vision".
PLoS ONE 08/2013; 8(8):e70336. DOI:10.1371/journal.pone.0070336 · 3.23 Impact Factor
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