Poster B18, Tuesday, August 20, 2019, 3:15 – 5:00 pm, Restaurant Hall
Aging patterns of Japanese auditory semantic processing: an fMRI study
Hengshuang Liu1, Makoto Miyakoshi2, Toshiharu Nakai3, SH Annabel Chen4;1Guangdong University of Foreign Studies, 2University of California, San Diego, 3National Center for Geriatrics and Gerontology, 4Nanyang Technological University
Introduction: The comprehension of auditory semantics could be viewed as the ultimate goal of verbal communication. Its efficacy is relatively sustained over life span, contradictory with the negative stereotype that older adults always encounter cognitive decline. Methods: The current study adopted the Japanese language to help pinpoint a generic pattern for auditory semantic aging. Twenty-two younger and 21 older Japanese participants performed an auditory semantic-tone task in a 3 Tesla magnetic resonance imaging (MRI) scanner. Results: Results showed that (1) the spared accuracy and slowed response for older adults were accompanied by their intensified long-range inter-hemispheric connectivity and largely unchanged activation and laterality; (2) higher accuracy amongst the older cohort manifested a more economical neural pattern with stronger functional connectivity and decreased brain activation; (3) neural dedifferentiation from semantic-specific to domain-general networks was the aging pattern most saliently seen in spoken Japanese comprehension, resembling past findings of visually-presented alphabetic languages. This implied that neural dedifferentiation was powerful and irresistible in aging such that it may occur irrespective of languages (alphabetic vs. character) and modalities (visual vs. auditory). With age, neural compensation appeared to develop in the connectivity system, given the stronger functional connectivity seen in the better-performing older. The HAROLD model was weakly supported by the connectivity data but not by the laterality results, as reduced hemispheric asymmetry was likely inferable from older adults’ intensified cross-hemisphere connectivity but not from their increased regional lateralization. Summary: In short, the auditory semantic function as a preserved cognitive ability seemed to experience greater age-related changes in interregional connectivity than in activation or laterality, underpinned by a relatively intact activation pattern whereas a rewired connectivity network over aging. In addition, the connectivity reorganization was likely predictable through existing neurocognitive aging models such as neural dedifferentiation, compensation, and the HAROLD model. Apparently functional connectivity revealed some unique neural mechanisms not observable through activation analysis, ascertaining the need to examine functional connectivity data in relation to brain activity within the networks. Taken together, the present study advances our knowledge of the aging effect on auditory semantic processing, through examining the relationships amongst behavioral performance, neural activation, activity laterality and functional connectivity of the cortical network.
Themes: Development, Meaning: Lexical Semantics
Method: Functional Imaging