Neural Dedifferentiation with Aging in Focus Switching in Working Memory
Poster No:
872
Submission Type:
Late-Breaking Abstract Submission
Authors:
Chandramallika Basak1, Yiyao Liu1, Paulina Skolasinska2
Institutions:
1University of Texas at Dallas/CVL, Dallas, TX, 2McGill University, Montréal, Quebec
First Author:
Co-Author(s):
Introduction:
Previous research has found that older adults during working memory updating tasks, compared to younger adults, show reduced deactivations (or even overactivations) in the default mode network (DMN), and reduced activity in lateral fronto-parietal network (FPN) (Qin & Basak, 2020; Skolasinska, Basak & Qin, 2023; Turner & Spreng, 2015). These age differences are moderated by cardiovascular risks or cardiorespiratory function. However, the influence of age on brain network activations under increased unpredictable cognitive control and across different stimulus domains remains unclear. In this current study, we investigated age differences in fMRI BOLD signals and task performance (RT, accuracy) during a hybrid block and event-related working memory fMRI task, in younger and older adults. We hypothesized that age differences in accuracy, RT, and brain networks will be significant for focus switching, and may interact with stimulus domain. We also investigated whether the age differences in brain functions, particularly DMN, are attenuated by reduced cardiovascular risks.
Methods:
Twenty-four younger (18-35 years) and 56 older adults (65-85 years) underwent a hybrid block and event-related working memory fMRI task, n-match, with n beinigg 0, 2, or 3, and stimulus domain being visual or verbal. This task is a modified version of an unpredictable n-match task (Qin & Basak, 2020)with location cues. Functional images were acquired using an echo-planar sequence (TR =500 ms; TE =30 ms; flip angle =50º; acquisition matrix =74×74; voxel size =3x3x3 mm3; FOV=220x220; Slice Thickness=3mm; Acceleration factor 2). There were three runs, alternating between 6 task (40 s) and fixation (6 s) blocks. The 6 task blocks were 0-match visual, 2-match visual, 3-match visual, 0-match verbal, 2-match verbal and 3-match verbal. There were 18 task blocks, resulting in a total of 360 trials (20 trials×18 blocks). Preprocessing of fMRI data was conducted using fMRIprep and then submitted to whole brain GLM fittings using FSL FEAT with regressor for each of the six conditions/blocks. For the first-individual level analyses, the amplitude of the hemodynamic response was estimated to differentiate between the 6 conditions, which were entered in group analysis to obtain mean percent signal changes across 3 runs for verbal>visual, 2+3-match>0-match. GLM Z statistic images were thresholded at the whole-brain level using the clusters thresholding at z >2.58. The voxels passing the threshold were combined into clusters. Random field theory was then used to give the p-value of obtaining a cluster of voxels given the set spatial smoothness and the z threshold used. These p-values were thresholded at a p =0.01 to obtain "significant" clusters. Mean percent signal changes from clusters identified by the whole-brain age contrast were extracted from all. Linear mixed-effects models examined whether age-related differences in performance (RT, Accuracy) and brain network activations increased with cognitive control (2+3-match>0-match) or stimulus domains (visual vs verbal).
·fMRI task design (left) and task performance (right) on the N-Match task
Results:
We found overactivations in older adults, incl. the DMN hubs (vmPFC, PCC), and under-recruitment of FPN and thalamus, during cognitive control. These overactivations were only observed for focus switching, with no difference between stimulus domains. These fMRI patterns mirror the findings from task performance (RT and accuracy). Older adults also exhibited overactivation in the right IFG, contralateral to a task-positive region in young, that correlated with poorer task performance. We also report if the lack of DMN suppression is attenuated with reduced cardiovascular risks (Qin & Basak, 2022).
Conclusions:
Our results support the hierarchical architecture of working memory (Basak & O'Connell, 2016) with a single-item focus. The neuroimaging data elucidates the role of the DMN and FPN on focus switching and aging, supporting the dedifferentiation hypothesis of the aging brain.
Higher Cognitive Functions:
Executive Function, Cognitive Control and Decision Making 2
Learning and Memory:
Working Memory 1
Lifespan Development:
Aging
Modeling and Analysis Methods:
Activation (eg. BOLD task-fMRI)
Keywords:
Aging
Cognition
FUNCTIONAL MRI
Memory
1|2Indicates the priority used for review
Abstract Information
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Provide references using APA citation style.
Qin, S., & Basak, C. (2022). Fitness and arterial stiffness in healthy aging: modifiable cardiovascular risk factors contribute to altered default mode network patterns during executive function. Neuropsychologia, 172, 108269.
Qin, S., & Basak, C. (2020). Age-related differences in brain activation during working memory updating: An fMRI study. Neuropsychologia, 138, 107335. https://doi.org/10.1016/j.neuropsychologia.2020.107335
Skolasinska, P.A, Basak, C. & Qin, S (2023). Influence of Strenuous Physical Activity and Cardiorespiratory Fitness on Age-Related Differences in Brain Activations During Varieties of Cognitive Control. Neuroscience, 520, 58-83.
Turner, G. R., & Spreng, R. N. (2015). Prefrontal Engagement and Reduced Default Network Suppression Co-occur and Are Dynamically Coupled in Older Adults: The Default–Executive Coupling Hypothesis of Aging. Journal of Cognitive Neuroscience, 27(12), 2462–2476. https://doi.org/10.1162/jocn_a_00869