Slide Slam Q6
Measuring Neural Grey Matter Correlations with Semantic Ability in Younger and Older Adults
Nicholas J. Heller1, Sara B.W. Troutman1, Michele T. Diaz1; 1Pennsylvania State University
Older adults tend to have more difficulty in speech production compared to younger people (Tremblay and Deschamps, 2016; Burke & Shafto, 2007). Recent studies show that there is a relationship between language ability, age, and the brain (Kemmotsu et. al 2012). For example, age-related deficits in grey matter volume were related to lexical-semantic processing. However, studies of grey matter-behavior relationships have focused primarily on receptive language. What has been less studied is how age-related differences in neural structure relate to language production. For instance, younger adults are typically slower to name targets with high intercorrelational feature density (ICFD) because of the competition between targets and the related words (Rabovsky et al., 2016). ICFD is a measure of feature overlap among words or concepts that contributes to semantic selection demands. Since older adults have difficulty with semantic selection, we used sensitivity to ICFD as a proxy for semantic selection abilities and related this to cortical thickness and age. We hypothesized that age would be negatively associated with cortical thickness and that sensitivity to ICFD would be positively associated with cortical thickness in left-hemisphere regions such as the anterior temporal cortex, inferior frontal gyrus, and intra-parietal sulcus. 88 participants, ranging from ages 20 – 75, completed a picture-naming task during a 3T MRI scan. We collected functional and structural images. Of most relevance to the present analyses, T1 weighted anatomical images were collected using a magnetization-prepared rapid acquisition gradient-echo sequence (TR = 2300 ms; TE = 2.28 ms; field of view = 256 mm2; voxel size = 1 mm3). FreeSurfer was used to examine the relationship between cortical thickness and ICFD sensitivity as well as age. Data were preprocessed using the standard freesurfer pipeline (smoothing kernel = 10 mm). Results were cluster corrected for multiple comparisons using a Monte-Carlo simulation. Significance was set at p <.05. As expected, older age was negatively related with cortical thickness throughout the brain. ICFD was positively linked to cortical thickness of the left lingual gyrus (-27, -63, 4; cluster size = 545 mm2), right lingual gyrus (27, -57, 3; cluster size = 780 mm2) and right insula (37, -6, 2; cluster size = 522 mm2). There were no regions where ICFD was negatively related to cortical thickness. We found no significant clusters where the cortical thickness was related to reaction time or accuracy. As hypothesized, we found that Age was negatively related to cortical thickness. Moreover, sensitivity to ICFD was positively related to cortical thickness though in more bilateral regions than we originally anticipated (bilateral lingual gyri and the right insula). These results suggest that sensitivity to semantic competition are supported broadly, including regions outside traditional language hubs.