Biology subjects

Rajah, M. N.

Publications and source records attributed to Rajah, M. N..

3 recordsLinked to original sources

bioRxiv2018

Preparing for the worst: Evidence that older adults proactively downregulate negative affect

Age-related differences in processing emotional stimuli are well established. However, previous studies have only assessed the impact of age on emotional processing and encoding in response to, not in anticipation of, emotional stimuli. In the current study, we investigated age-related differences in the impact of emotional anticipation on affective responses and episodic memory for emotional images. Young and older were scanned while encoding negative and neutral images preceded by cues that were either valid or invalid predictors of image valence. Participants were asked to rate the emotional intensity of the images and to complete an episodic recognition task immediately after scanning. Using multivariate behavioral partial least squares (PLS) analysis, we found that young and older adults recruit the same set of brain regions to differentially support emotional processing during the anticipation of emotional images. Specifically, anticipatory recruitment of the amygdala, ventromedial PFC, and hippocampus in older adults predicts reduced memory for negative than neutral images for older adults and the opposite for young adults. Seed PLS analyses further show inverse coupling between the amygdala and ventromedial PFC activation following negative cues, consistent with the top-down spontaneous suppression of negative affect. To the best of our knowledge, this is the first study to provide evidence that the \"positivity effect\" seen in older adults memory performance is related to the spontaneous suppression of negative affect in anticipation of, not just in response to, negative stimuli.

neuroscience↗

bioRxiv2018

Cortical thickness in right frontal and left lingual gyri differentially mediate episodic memory for spatial contextual details across the adult lifespan

Healthy aging is associated with declines in episodic memory and with widespread cortical thinning. These parallel declines suggest that age-related changes in cortical thickness may contribute to episodic memory decline with age. The current study uses a cross-sectional study design to examine whether regional cortical thickness mediates the relationship between age and episodic memory, as measured by a context memory task for faces. Mediation and conditional mediation models were tested using bootstrapping in order to determine how age-associated changes in regional cortical thickness mediated age-associated changes in performance on the context memory task. We observed that right superior frontal cortical thickness conditionally mediated spatial context memory only in middle-aged and older adults; and right caudal middle frontal cortical thickness conditionally mediated context memory only in older adults. Left lingual cortical thickness mediated spatial context memory across the adult lifespan, but this effect was most evident at midlife. Right parahippocampal cortical thickness mediated context memory, independent of age. We conclude that our cortical thickness results were generally consistent with the posterior-to-anterior shift in aging hypothesis (Davis et al., 2008) for episodic memory.

neuroscience↗

bioRxiv2017

Family history and APOE4 risk for Alzheimer’s Disease impact the neural correlates of episodic memory by early midlife

Episodic memory impairment is a consistent, pronounced deficit in pre-clinical stages of late-onset Alzheimers disease (AD). Individuals with risk factors for AD exhibit altered brain function several decades prior to the onset of AD-related symptoms. In the current event-related fMRI study of spatial context memory we tested the hypothesis that middle-aged adults (MA; 40-58yrs) with a family history of late onset AD (MA+FH), or a combined +FH and apolipoprotein E {varepsilon}4 allele risk factors for AD (MA+FH+APOE4), will exhibit differences in encoding and retrieval-related brain activity, compared to - FH-APOE4 MA controls. We also hypothesized that the two at-risk MA groups will exhibit distinct patterns of correlation between brain activity and memory performance, compared to controls. To test these hypotheses we conducted multivariate task, and behavior, partial least squares analysis of fMRI data obtained during successful context encoding and retrieval. Our results indicate that even though there were no significant group differences in context memory performance, there were significant differences in brain activity and brain-behavior correlations involving hippocampus, left angular gyrus, cingulate, and precuneus in MA with AD risk factors, compared to controls. In addition, we observed that brain activity and brain-behavior correlations in anterior-medial PFC and in ventral visual cortex differentiated the two MA risk groups from each other, and from MAcontrols. This is the first study to show that there are differences in the brain areas engaged during context memory encoding and retrieval in middle-aged adults with +FH and +APOE-4 risk factors for late onset AD, compared to controls.

neuroscience↗