Rypma, Bart
Permanent URI for this collectionhttps://hdl.handle.net/10735.1/2888
Dr. Bart Rypma's research is aimed at exploring the cognitive and neurobiological mechanisms of human memory and how those mechanisms are affected by aging and disease. He serves as Professor of Psychology and is head of the NeuroPsychometric Research Lab.. Learn more about Dr. Rypma's work on his Research Explorer page.
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Item Three‐Dimensional Lesion Phenotyping and Physiologic Characterization Inform Remyelination Ability in Multiple Sclerosis(American Society of Neuroimaging) Sivakolundu, Dinesh K.; Hansen, Madison R.; West, Kathryn L.; Wang, Yeqi; Stanley, Thomas; Wilson, Andrew; McCreary, Morgan; Turner, Monroe P.; Pinho, Marco C.; Newton, Braeden D.; Guo, Xiaohu; Rypma, Bart; Okuda, Darin T.; Sivakolundu, Dinesh K.; West, Kathryn L.; Wang, Yeqi; Stanley, Thomas; Wilson, Andrew; Turner, Monroe P.; Guo, Xiaohu; Rypma, BartBACKGROUND AND PURPOSE Multiple sclerosis (MS) clinical management is based upon lesion characterization from 2‐dimensional (2D) magnetic resonance imaging (MRI) views. Such views fail to convey the lesion‐phenotype (ie, shape and surface texture) complexity, underlying metabolic alterations, and remyelination potential. We utilized a 3‐dimensional (3D) lesion phenotyping approach coupled with imaging to study physiologic profiles within and around MS lesions and their impacts on lesion phenotypes. METHODS Lesions were identified in 3T T₂‐FLAIR images and segmented using geodesic active contouring. A calibrated fMRI sequence permitted measurement of cerebral blood flow (CBF), blood‐oxygen‐level‐dependent signal (BOLD), and cerebral metabolic rate of oxygen (CMRO₂). These metrics were measured within lesions and surrounding tissue in concentric layers exact to the 3D‐lesion shape. BOLD slope was calculated as BOLD changes from a lesion to its surrounding perimeters. White matter integrity was measured using diffusion kurtosis imaging. Associations between these metrics and 3D‐lesion phenotypes were studied. RESULTS One hundred nine lesions from 23 MS patients were analyzed. We identified a noninvasive biomarker, BOLD slope, to metabolically characterize lesions. Positive BOLD slope lesions were metabolically active with higher CMRO₂ and CBF compared to negative BOLD slope or inactive lesions. Metabolically active lesions with more intact white matter integrity had more symmetrical shapes and more complex surface textures compared to inactive lesions with less intact white matter integrity. CONCLUSION The association of lesion phenotypes with their metabolic signatures suggests the prospect for translation of such data to clinical management by providing information related to metabolic activity, lesion age, and risk for disease reactivation and self‐repair. Our findings also provide a platform for disease surveillance and outcome quantification involving myelin repair therapeutics.Item Higher-Order Cognitive Training Effects on Processing Speed-Related Neural Activity: A Randomized Trial(Elsevier) Yezhuvath, Uma S.; Aslan, Sina; Motes, Michael A.; Spence, Jeffrey S.; Rypma, Bart; Chapman, Sandra Bond; 0000 0003 5170 3614 (Chapman, SB); Motes, Michael A.; Aslan, Sina; Spence, Jeffrey S.; Rypma, Bart; Chapman, Sandra BondHigher-order cognitive training has shown to enhance performance in older adults, but the neural mechanisms underlying performance enhancement have yet to be fully disambiguated. This randomized trial examined changes in processing speed and processing speed-related neural activity in older participants (57-71years of age) who underwent cognitive training (CT, N= 12) compared with wait-listed (WLC, N= 15) or exercise-training active (AC, N= 14) controls. The cognitive training taught cognitive control functions of strategic attention, integrative reasoning, and innovation over 12weeks. All 3 groups worked through a functional magnetic resonance imaging processing speed task during 3 sessions (baseline, mid-training, and post-training). Although all groups showed faster reaction times (RTs) across sessions, the CT group showed a significant increase, and the WLC and AC groups showed significant decreases across sessions in the association between RT and BOLD signal change within the left prefrontal cortex (PFC). Thus, cognitive training led to a change in processing speed-related neural activity where faster processing speed was associated with reduced PFC activation, fitting previously identified neural efficiency profiles.Item Investigating the Neural Bases for Intra-Subject Cognitive Efficiency Changes using Functional Magnetic Resonance Imaging(Frontiers Research Foundation) Rao, Neena K.; Motes, Michael A.; Rypma, BartSeveral fMRI studies have examined brain regions mediating inter-subject variability in cognitive efficiency, but none have examined regions mediating intra-subject variability in efficiency. Thus, the present study was designed to identify brain regions involved in intra-subject variability in cognitive efficiency via participant-level correlations between trial-level reaction time (RT) and trial-level fMRI BOLD percent signal change on a processing speed task. On each trial, participants indicated whether a digit-symbol probe-pair was present or absent in an array of nine digit-symbol probe-pairs while fMRI data were collected. Deconvolution analyses, using RT time-series models (derived from the proportional scaling of an event-related hemodynamic response function model by trial-level RT), were used to evaluate relationships between trial-level RTs and BOLD percent signal change. Although task-related patterns of activation and deactivation were observed in regions including bilateral occipital, bilateral parietal, portions of the medial wall such as the precuneus, default mode network regions including anterior cingulate, posterior cingulate, bilateral temporal, right cerebellum, and right cuneus, RT-BOLD correlations were observed in a more circumscribed set of regions. Positive RT-BOLD correlations, where fast RTs were associated with lower BOLD percent signal change, were observed in regions including bilateral occipital, bilateral parietal, and the precuneus. RT-BOLD correlations were not observed in the default mode network indicating a smaller set of regions associated with intra-subject variability in cognitive efficiency. The results are discussed in terms of a distributed area of regions that mediate variability in the cognitive efficiency that might underlie processing speed differences between individuals.Item Assessment of Unconstrained Cerebrovascular Reactivity Marker for Large Age-Range fMRI Studies(Public Library of Science) Kannurpatti, S. S.; Motes, Michael A.; Biswal, B. B.; Rypma, BartBreath hold (BH), a commonly used task to measure cerebrovascular reactivity (CVR) in fMRI studies varies in outcome among individuals due to subject-physiology and/or BH-inspiration/expiration differences (i.e., performance). In prior age-related fMRI studies, smaller task-related BOLD response variability is observed among younger than older individuals. Also, a linear CVR versus task relationship exists in younger individuals which maybe useful to test the accuracy of CVR responses in older groups. Hence we hypothesized that subject-related physiological and/or BH differences, if present, may compromise CVR versus task linearity in older individuals. To test the hypothesis, empirical BH versus task relationships from motor and cognitive areas were obtained in younger (mean age = 26 years) and older (mean age = 58 years) human subjects. BH versus task linearity was observed only in the younger group, confirming our hypothesis. Further analysis indicated BH responses and its variability to be similar in both younger and older groups, suggesting that BH may not accurately represent CVR in a large age range. Using the resting state fluctuation of amplitude (RSFA) as an unconstrained alternative to BH, subject-wise correspondence between BH and RSFA was tested. Correlation between BH versus RSFA was significant within the motor but was not significant in the cognitive areas in the younger and was completely disrupted in both areas in the older subjects indicating that BH responses are constrained by subject-related physiology and/or performance-related differences. Contrasting BH to task, RSFA-task relationships were independent of age accompanied by age-related increases in CVR variability as measured by RSFA, not observed with BH. Together the results obtained indicate that RSFA accurately represents CVR in any age range avoiding multiple and yet unknown physiologic and task-related pitfalls of BH.Item Prediction of Task-Related BOLD fMRI with Amplitude Signatures of Resting-State fMRIKannurpatti, S. S.; Rypma, Bart; Biswal, B. B.Blood oxygen contrast-functional magnetic resonance imaging (fMRI) signals are a convolution of neural and vascular components. Several studies indicate that task-related (T-fMRI) or resting-state (R-fMRI) responses linearly relate to hypercapnic task responses. Based on the linearity of R-fMRI andT-fMRI with hypercapnia demonstrated by different groups using different study designs, we hypothesized that R-fMRI andT-fMRI signals are governed by a common physiological mechanism and that resting-state fluctuation of amplitude (RSFA) should be linearly related to T-fMRI responses. We tested this prediction in a group of healthy younger humans where R-fMRI, T-fMRI, and hypercapnic (breath hold, BH) task measures were obtained form the same scan session during resting state and during performance of motor and BH tasks. Within individual subjects, significant linear correlations were observed between motor and BH task responses across voxels. When averaged over the whole brain, the subject-wise correlation between the motor and BH tasks showed a similar linear relationship within the group. Likewise, a significant linear correlation was observed between motor-task activity and RSFA across voxels and subjects. The linear rest-task (R-T) relationship between motor activity and RSFA suggested that R-fMRI and T-fMRI responses are governed by similar physiological mechanisms. A practical use of the R-T relationship is its potential to estimateT-fMRI responses in special populations unable to perform tasks during fMRI scanning. Using the R-T relationship determined from the first group of 12 healthy subjects, we predicted theT-fMRI responses in a second group of 7 healthy subjects. RSFA in both the lower and higher frequency ranges robustly predicted the magnitude ofT-fMRI responses at the subject and voxel levels. We propose thatT-fMRI responses are reliably predictable to the voxel level in situations where only R-fMRI measures are possible, and may be useful for assessing neural activity in task non-compliant clinical populations. © 2012 Kannurpatti, Rypma and Biswal.