Investigation Of Cognitive Impairment In Presbycusis Using Structural And Functional Magnetic Resonance Imaging

PART ?.Hearing Loss and Cognition among Older Adults in the Han Chinese PopulationBackground and Purpose:Presbycusis(PC)has a strikingly detrimental impact on cognitive function.However,to date,there has been a paucity of studies exploring the association between hearing loss and cognitive function in the Han Chinese population.Moreover,speech reception thresholds(SRT)are used to assess speech detection,which points toward a central component of PC.To our knowledge,no previous study has reported the relationship between SRT and cognitive function in older adults.The purpose of this part of the study was to investigate the association of hearing loss,indexed using pure tone average(PTA)and SRT,with cognitive function in the Han Chinese population using a standardized neurocognitive battery.Materials and Methods:Subjects aged>60 years with no history of neurological or psychiatric diseases were recruited.All participants underwent a battery of neuropsychological and auditory tests.According to the PTA of the better ear,the subjects were further divided into PC and normal hearing(NH)groups.Results:Cognitive function was significantly associated with PTA and SRT in all subjects.The correlations between nonverbal cognitive scores and SRT were stronger than those between nonverbal cognitive scores and PTA,whereas the correlations between verbal cognitive scores and PTA were stronger than those between verbal cognitive scores and SRT.Moreover,the correlations between PTA or SRT and cognitive function in the PC group were stronger than those in the NH group.Conclusions:Our findings indicate that cognitive function is significantly associated with PTA and SRT inolder adults in the Han Chinese population.Moreover,the correlations between PTA or SRT and cognitive function in the PC group were stronger than those in the NH group.Based on these findings,we argue that SRT could be an important auditory test for exploring cognitive decline in PC and could complement PTA.PART ?.Gray matter atrophy is associated with cognitive impairment in patients with presbycusis:a comprehensive morphometric studyBackground and Purpose:Presbycusis(PC)is characterized by bilateral sensorineural hearing loss at high frequencies and speech-perception difficulties in noisy environments and has a strikingly detrimental impact on cognitive function.The purpose of this part of the study was to use surface-based morphometry(SBM)analysis to elucidate whole-brain structural differences between patients with PC and age-matched normal hearing controls.Materials and Methods:Three-dimensional T1-weighted MR images of twenty-six patients with mild PC andtwenty-six age-,sex-and education-matched healthy controls(HCs)were acquired.All participants underwent a battery of neuropsychological and auditory tests.Results:Our results revealed gray matter atrophy in several auditory cortical areas,nodes ofthe default mode network(DMN),including the bilateral precuneus and inferior parietal lobule,the right posterior cingulate cortex(PCC),and the right insula of patients with PC compared to that in the HCs.Our findings also revealed that hearing loss was associated with reduced gray matter volume in the right primary auditory cortex of patients with PC.Moreover,structural alterations in the nodes of the DMN were associated with cognitive impairments in PC patients.Additionally,this study provides evidence that a thicker right insula is associated with better speech perception in patients with PC.Conclusions:Our findings indicate that GM atrophy of key nodes in the DMN may be imagingmarkers for PC-related cognitive decline.Moreover,this study provides evidence that a thicker right insula is associated with better speech perception in patients with PC.Based on these findings,we argue that the onset of PC appears to trigger its own cascade of conditions,including the need for increased cognitive resources for speech comprehension,which might lead to auditory and cognition-related cortical reorganization.PART ?.Abnormal Intrinsic Brain Activity Patterns in Patients with Presbycusis:A resting-state functional MRI studyBackground and Purpose:Presbycusis(PC)is characterized by bilateral sensorineural hearing loss at high frequencies and speech-perception difficulties in noisy environments and has a strikingly detrimental impact on cognitive function.The purpose of this part of the study was to use amplitude of low-frequency fluctuation(ALFF)analysis to elucidate whole-brain functional differences between patients with PC and age-matched normal hearing controls.Materials and Methods:Resting-state fMRl images of twenty-six patients with PC and twenty-six age-,sex-and education-matched healthy controls(HCs)were acquired.All participants underwent a battery of neuropsychological and auditory tests.Results:Compared with healthy controls,presbycusis patients manifested decreased spontaneous activity mainly in the right superior temporal gyrus,nodes of the default mode network(DMN),including the bilateral precuneus,posterior cingulate cortex,angular gyrus and right middle temporal gyrus,and the right supramarginal gyrus and middle frontal gyrus.Moreover,ALFF alterations in the nodes of the DMN were associated with cognitive impairments in PC patients.Additionally,this study provides evidence that a higher ALFF of right posterior cingulate cortex is associated with better speech perception in patients with PC.Conclusions:Patients with presbycusis have disrupted spontaneous neural activity in several brain regions.Decreased ALFF of key nodes in the DMN may be imaging markers for PC-related cognitive decline.Moreover,this study provides evidence that a higher ALFF of right posterior cingulate cortex is associated with better speech perception in patients with PC.Our findings is likely to yield more precise information about underlying neurochemical mechanism of cognitive impairment in patients with presbycusis.