Impact du vieillissement sur la perception multisensorielle et les processus cérébraux sous-jacents. Etude de la kinesthésie et de la perception de textures

Abstract : The coherent perception of our body and the environment is achieved by the on-going integration of different sensory sources. While the understanding of the rules governing these integrative processes and their brain substrates have been well described in young adults, their age-related changes are poorly understood. Due to the gradual decline of all sensory systems during normal aging, integration strategies could be modified by an unequal reliability given to each of the sensory inputs. They could also change depending on whether the purpose of perception is to estimate the movements of our body or the properties of our environment. We also explored the brain changes associated with these perceptual alterations using fMRI. By stimulating touch, muscle proprioception, vision, and audition separately, or in combination, we studied the integrative processes underlying two types of perception: the speed of our hand movements and the texture of a surface. Through psychophysical approaches, we have highlighted an unequal perceptual alteration according to the modality considered: perceptions from touch being less altered with age, whether in the context of perception of the body 1,2 or the environment3, while muscle proprioception seems to be particularly affected in kinesthetic perception. However, integrative processes seem to be well preserved, or even enhanced, in older adults. Indeed, the combination of congruent information in kinesthetic perception improved performance in the same proportions in young and old adults2. Moreover, the addition of an incongruent audio distractor, in a haptic exploration task, more strongly disrupted older adults3, suggesting an easier integration even though the stimuli were incongruent. Our results obtained in neuroimaging (fMRI) showed that inhibitory processes were altered in elderly adults. Therefore, we found an alteration in the interhemispheric balance between primary sensorimotor regions correlated to kinesthetic deficits in the proprioceptive condition but not tactile condition4. The study about texture discrimination has also showed a functional reorganization of brain activations involved in multisensory integration in elderly adults in audio-haptic conditions5. This work highlights both a reweighting of sensory information and a general facilitation of multisensory processes in elderly, leading to a limited compensatory phenomenon when sensory information are consistent. At the cerebral level, the decline of inhibitory processes with age may explain perceptual disorders and less specific brain recruitment. Nevertheless, older people could benefit from this phenomenon of dedifferentiation by extending their inter-network connectivity to at least partially compensate the declines of sensory integration processes.
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Submitted on : Thursday, August 8, 2019 - 1:43:40 PM
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Caroline Landelle. Impact du vieillissement sur la perception multisensorielle et les processus cérébraux sous-jacents. Etude de la kinesthésie et de la perception de textures. Neurosciences [q-bio.NC]. Aix-Marseille Université, 2019. Français. ⟨tel-02265084⟩

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