Deafness; Perception, Bilateral Clinical Trial
Official title:
Plasticity and Cross-modal Interactions for Oral Communication in Profoundly Deaf Adults
The aim of this study is to evaluate cerebral asymmetry for face processing in a group of
profoundly deaf participants and a group of hearing controls by the mean of fMRI measure. To
this end, we present chimeric faces (faces split into different halves), entire faces, or
faces presented in divided visual field, and subjects perform a gender categorization task
while lying in a fMRI scanner.
It is expected to find a reduced cerebral asymmetry in the Fusiform Face Area in deaf in
comparison with hearing participants.
A rightward asymmetry during face processing is well documented in hearing participants, in
particular in the Fusiform Face Area, a cortical area underlying face processing. This
rightward asymmetry seems to be very robust, present even with inverted faces or line
drawings, and is already present at five years of age. If the brain asymmetry for face
processing emerges during development, early deprivation or dramatic differences the
infant's experience with the world should affect it. For example, infants treated for
bilateral congenital cataracts after 7 weeks of age, who are deprived of patterned visual
input for this duration, fail to develop some of the aspects associated with typical adult
levels of face recognition. Non visual early deprivation can also affect the development of
visual abilities. Several studies showed that deaf participants could detect targets at
larger eccentricities, thus indicating larger visual field . Furthermore, better abilities
have been found in deaf participants for the detection of motion, in particular in the
visual periphery . Higher-level visual abilities have also been shown to be modified by
early deafness, such as visual imagery (image generation, or rotation) or the processing of
faces . Using the Benton Test of Facial Recognition, a previous study tested the recognition
of individual faces in deaf participants. They obtained better scores than hearing non
signers, but only in a difficult condition, in which faces were shadowed. This enhanced
processing in deaf people could thus concern very particular aspects of face processing; it
was found that deaf and normal hearing differed only by the detection of subtle facial
features. Investigating configural processing during face perception, it was found an
increased dependency on this mode of processing in deaf participants.
If visual processing is affected by early deafness, what about visual asymmetries? Several
experimental studies examining hemispheric asymmetry in congenitally deaf individuals found
that it differs from the one observed in hearing individuals . Concerning face processing,
few studies investigated hemispheric lateralization during the perception of faces in deaf
people. When presenting briefly unfamiliar faces in either the left or right visual field
and no differences between deaf and hearing participants were found. In a previous
experiment, using chimeric faces (faces vertically split into two different parts, ie half
male, half female) it was found a reduction of leftward asymmetry for face processing in
deaf participants during a gender categorization task.
The aim of the present study is to broaden the knowledge about asymmetry for face processing
in deaf people, by evaluating if this reduction of asymmetry observed at the behavioral
level results from a reduction of cerebral asymmetry at the level of Fusiform Face Area.
Deaf participants and normal hearing controls will be presented face stimuli, composed of
either chimeric male/female and female/male faces, entire faces or entire face presented in
divided visual field, to investigate Fusiform Face Area asymmetry in these two groups.
Participants will lie in an fMRI scanner, and their cerebral activity will be recorded while
they perform a gender categorization task on our face stimuli.
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| Status | Clinical Trial | Phase | |
|---|---|---|---|
| Completed |
NCT03022227 -
Feasibility of Remote Cochlear Implant Users' Follow-up
|
N/A |