Slide Slam Q7
The resting-state functional connectivity relates to aging and language production
Haoyun Zhang1, Abigail Cosgrove1, Michele Diaz1; 1The Pennsylvania State University
While many studies have examined age-related differences in resting-state functional connectivity, few studies have focused on the language network. This may be due in part, to the relative stability of many language functions across the lifespan. However it is unclear whether the characteristics of a resting-state language network are comparable in older and younger adults. In contrast to the language network, studies have shown that the connectivity within the multiple-demand (MD) network decreases with age. Yet, it is unclear if characteristics of the language and MD networks are associated with age-related differences in language production. The current study investigated the functional connectivity within resting-state language and MD networks, the connectivity between the two networks, and their relationship with age and language production. Participants across adulthood were tested (N = 169, 20-78 years, mean = 46 years). Participants completed a battery of neuropsychological tests to assess basic cognitive functions. Most relevant to this study, participants completed a story elicitation task using the picture book Frog Where Are you, where participants generated a story using the book as a guide. Discourse measures were calculated from the story to evaluate participants’ language ability. Specifically, the Mean Length of Utterances (MLU) captures speech complexity by calculating the mean number of words in each utterance. The Moving Average Type/Token Ratio (MATTR) measures vocabulary by calculating the ratio of the number of different words divided by the total number of words in a moving window (N = 50). Functional resting-state images were collected while participants were instructed to relax in the scanner with their eyes open and to look at a fixation cross (duration = ~6 minutes). We focused on a pre-defined language network (Fedorenko et al., 2010) and a MD network (Fedorenko et al., 2013) using 4-mm radius sphere ROIs (8 for the language network, 20 for the MD network). We calculated the within-network connectivity for each network, the between network connectivity, and the mean network segregation ((within-between)/within) for each participant. To investigate the effect of age on network connectivity, we first conducted linear regressions on the network measures. We found that increased age was significantly associated with decreased within-network connectivity in the MD network, but there were no age-related differences in within-network connectivity in the language network, or in the between-network connectivity. These results suggest that the MD network was more sensitive to age effects while the language network connectivity was stable across adulthood. Additionally, increased age was associated with decreased network segregation, suggesting that resting-state networks become dedifferentiated with age. Preliminary results relating network characteristics to language ability showed that there was a significant interaction between age and within language network connectivity on MLU. Specifically, only in younger adults, but not in middle-aged or older adults, higher within language network connectivity was associated with higher MLU, indicating that stronger language network connectivity at rest in younger adults is related to the ability to produce more complex speech.