The role of regional heterogeneity in age-related differences in functional hemispheric asymmetry: an fMRI study

Abstract

Some cognitive functions, such as language processing, utilize one side of the brain more than the other. This pattern of brain organization is known as brain lateralization. However, studies have suggested that brain lateralization is less prominent in older adults. In other words, older adults recruit additional resources from the other side of the brain to achieve similar cognitive functions as with young adults. Heng and colleagues (2017) further examined age-related differences in brain lateralization during language and visuospatial processing. Using functional magnetic resonance imaging (fMRI), the researchers recorded the brain activation of 16 older (60s) and 21 younger (20s) Japanese adults when the participants judged if two characters/sets of lines had similar or different pronunciations/orientations. Compared with young adults, older adults were slower but equally accurate at making the judgments. When judging language pronunciations, older adults showed greater activation and reduced brain lateralization only in the frontal brain area that is crucially involved in language sound processing, and not meaning. As this frontal brain area is necessary for judging language pronunciations, the additional recruitment of this brain region on the other side of the brain is suggested to help in maintaining performance accuracy. Results therefore highlight the importance of considering the functional specificity of brain regions when studying age-related differences in cognitive processes.