Fei Gao1, Guangbin Wang1, Bin Zhao1, Muwei Li2, Fuxin Ren1, and Weibo Chen3
1Shandong Medical Imaging Research Institute, Shandong University, JINAN, China, People's Republic of, 2College of Electronics and Information Engineering, Sichuan University, Chengdu, China, People's Republic of, 3Philips Healthcare, Shanghai, China, People's Republic of
Synopsis
Presbycusis is the most common sensory deficit in the ageing population. However, little is known about whether the topological properties of brain functional networks is disrupted in patients with presbycusis. Our study demonstrates decreased clustering coefficient, local efficiency and strength in the primary auditory cortex in patients with presbycusis, as compared to age- and gender-matched healthy controls. Our study provides evidence of presbycusis-related disruptions in brain functional networks in patients with presbycusis. It is believed that our findings could be important for exploring functional changes in the central presbycusis.Purpose
Presbycusis, also known as age-related hearing loss, is the most common sensory deficit in the ageing population. Presbycusis is most often characterized by poor speech discrimination in noise or other difficult listening situations, which reflect a possible central component of presbycusis [1]. Brain functional networks have a small world architecture that reflects a robust functional organization of the brain. However, little is known about whether the topological properties of brain functional networks is disrupted in patients with presbycusis. In this study, therefore, resting-state functional magnetic resonance imaging (rs-fMRI) was used to investigate functional connectivity in patients with presbycusis and healthy controls.
Methods
Fifteen patients (right-handed) with presbycusis (5 males/10 females, mean age 63.2 ± 2.6 years) and fourteen age- and gender-matched healthy controls (5 males/8 females, mean age 62.2 ± 1.9 years) were recruited in this study. Tympanometry and pure tone audiometry from 0.125 to 8 KHz were used to assess the hearing function of all subjects. Hearing loss was defined as a speech-frequency pure tone average (PTA) of thresholds at 0.5, 1, 2, and 4 kHz (air conduction) in the better hearing ear as per the definition of hearing loss adjudicated by the World Health Organization. To retrieve the rs-fMRI data, all subjects were scanned on a 3T scanner (Philips ‘Achieva’ TX, Best, The Netherlands) using an eight-channel phased-array head coil for receive. The rs-fMRI data were slice-time-corrected to adjust for differences in the acquisition time between slices, realigned to the first image using rigid body registration to adjust for motion, and then co-registered to the mean image using SPM rigid body transformation. The rs-fMRI data were transformed to a template image, called “EPI templates”, which was integrated in SPM. All images were then processed through the standard “REST” procedure, including Detrending, Filtering and Regressing out of nuisance covariate. Anatomical Automatic Labeling (AAL) time courses were extracted from 90 regions and then the matrices of inter-parcel correlation coefficients (r) were calculated. Several parameters, such as clustering coefficient, local efficiency and strength can be calculated from the “r” matrices.
Results
The PTA of the presbycusis group was significantly higher than those of the control group (p < 0.001). Tympanometric examination showed a type A curve in all subjects. The type A curve demonstrates that there is normal pressure in the middle ear with normal mobility of the eardrum and the conduction bones. Presbycusis group showed decreased clustering coefficient in the left-side Heschl's gyrus (HG) and increased clustering coefficient in the right-side inferior temporal gyrus (ITG); It showed decreased local efficiency in the bilateral HG and increased local efficiency in the right side ITG; It showed decreased strength in the bilateral HG and increased strength in the bilateral ITG (Fig 1).
Discussion
Our study demonstrates decreased clustering coefficient, local efficiency and strength in the primary auditory cortex in patients with presbycusis, as compared to age- and gender-matched healthy controls. The small scale neural synchrony scales up to the level of whole-brain distributed networks [2]. Therefore, decrease neural synchrony may occur in the auditory cortex in patients with presbycusis. This has been confirmed by other studies: the inability to clearly detect temporal cues is a reason for decreased speech understanding in patients with presbycusis [1]. Processing of temporal cues mainly occurs in the auditory cortex [3] and degraded temporal processing may be based on decreased neural synchrony [4]. ITG plays an important role in intelligible speech processing [5]. Therefore, increased clustering coefficient, local efficiency and strength in the ITG may serve as a compensatory mechanism in patients with presbycusis.
Conclusion
Our study provides evidence of presbycusis-related disruptions in brain functional networks in patients with presbycusis. It is believed that our findings could be important for exploring functional changes in the central presbycusis.
Acknowledgements
No acknowledgement found.References
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