Research On The Central Remodeling Of The Cross-sensory Model In Patients With Unilateral Deafness

ObjectiveCross-modal plasticity has been demonstrated in bilateral deafness,manifesting as increased involvement of the auditory cortex in the processing of other senses,such as vision,when compared to normal hearing individuals.However,it remains unclear whether partial hearing deprivation like single-sided deafness(SSD)leads to similar cross-modal plasticity.The aim of this study is to clarify whether there is cross-modal plasticity in single-sided deafness.MethodsEighteen left single-sided deafness(LSSD),18 right single-sided deafness(RSSD)and 18 normal hearing controls(NH)were enrolled in the present study.All SSD subjects had a unilateral long-term severe to profound sensorineural hearing loss with the duration of deafness longer than 2 years.Higher-order auditory abilities,including speech recognition in noise and accuracy of sound localization,were assessed for all subjects.Functional magnetic resonance image(fMRI)data were collected from all subjects under resting and visuo-spatial working memory tasks.We compared the brain activation during the task between groups and analyzed the correlation of activation in auditory cortex and auditory abilities.The functional connectivity between auditory cortex and fronto-parietal cortex in resting-state were compared between groups.ResultsContrary to previous findings in bilateral deafness,our study revealed decreased activation in the auditory cortex in RSSD compared to NH during the visual task.And the activation of auditory cortex was positively correlated with auditory abilities including speech recognition in noise and sound localization in RSSD.These observations suggested that SSD can lead to a downward cross-modal plasticity:the more hearing ability lost,the fewer brain resources in the auditory cortex can be applied to visual tasks.In addition,the fronto-parietal cortex was also observed to be less activated during the visual task while the resting-state fMRI revealed increased functional connectivity between the fronto-parietal cortex and the auditory cortex in RSSD,suggesting fronto-parietal resources may be recruited less by vision but more by hearing.LSSD also had a similar tendency of alteration as RSSD,but with no statistical significance.ConclusionThis research may indicate that auditory and visual cortices cooperate with each other during visual processing.When hearing is partially deprived,there may be an underlying competition for brain resources between hearing and vision.Less brain resources,including auditory cortex and fronto-parietal cortex,were available to perform visual processing tasks,probably due to more brain resources were recruited by hearing processing to compensate for the reduction of peripheral auditory signal input.