Association of Hippocampal Substructure Resting-State Functional Connectivity with Memory Performance in Older Adults

Smagula, Stephen F.; Karim, Helmet T.; Rangarajan, Anusha; Santos, Fernando Pasquini; Wood, Sossena; Santini, Tales; Jakicic, John M.; Reynolds, Charles F.; Cameron, Judy L.; Vallejo, Abbe N.; Butters, Meryl A.; Rosano, Caterina; Ibrahim, Tamer S.; Erickson, Kirk I.; Aizenstein, Howard

doi:10.1016/j.jagp.2018.03.003

Cited by 13 publications

(11 citation statements)

References 33 publications

(40 reference statements)

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“…Furthermore, recent studies have shown that RAR characteristics are associated with the neurobiological biological hallmarks of dementia early in the disease process (i.e., in community and pre-clinical samples) including amyloid deposition (22), medial temporal lobe atrophy (21), and cerebrovascular disease (although associations may be region specific) (19, 20). In addition, the study by Sherman et al showed that RAR disruption related to hippocampal hyperactivation (23), which is considered a component of pre-clinical dementia pathophysiology related to early memory decline (e.g., see the study by Smagula et al (38). In this context, findings from longitudinal epidemiological studies (showing RAR disruption predicts future cognitive decline) might be due to RARs already reflecting early-stage neuropathology (which was not controlled for in existing longitudinal studies).…”

Section: Discussionmentioning

confidence: 99%

A Systematic Review of Evidence for a Role of Rest-Activity Rhythms in Dementia

et al. 2019

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Background: Rest-activity rhythm (RAR) disruption may be a risk factor for dementia that can be objectively measured with wearable accelerometers. It is possible that risk monitoring and preventive interventions could be developed targeting RARs. To evaluate whether current evidence supports these applications, we systematically reviewed published studies linking RARs with dementia, its course, and mechanisms.Methods: Entering pre-defined search terms in PsycINFO, MEDLINE, and PubMed databases returned 192 unique titles. We identified 32 articles that met our primary inclusion criteria, namely, that they examined objective RAR measures in the context of dementia, cognition, or brain biomarkers.Results: Cross-sectional studies consistently found that people with dementia had less stable (5/6 studies), more fragmented (4/6 studies), lower amplitude rhythms (5/5 studies), that had a worse fit to 24-h models (3/3 studies). Findings from studies relating RARs to cognitive test performance (rather than diagnostic status) were more nuanced. RAR fragmentation was associated with neurodegeneration biomarkers in 2/2 studies; and 1/1 study found 24-h model fit related to hippocampal hyperactivation. Although 2/2 studies found RARs related to markers of cerebrovascular disease, the specific RARs and cerebrovascular disease measures were not consistent. Longitudinal studies (3/3 articles) reported that lower amplitude and worse 24-h rhythm fit predicted future cognitive impairment and executive function. However, interventions aimed at modifying RARs had mixed effects (e.g., 0/4 studies demonstrated effects of morning light on 24-h model fit; evening light was associated with improved 24-h fit in 2/2 studies reporting); these effects may be more evident in subgroups.Conclusions: Consistent evidence shows that dementia is associated with disrupted RARs. Importantly, recent studies have shown that RAR disruption is associated with dementia biomarkers and, prospectively, with the risk of cognitive impairment. Interventions mostly tried using bright light to modify RARs in people who already have dementia; these studies produced modest effects on RARs and did not show modification of dementia’s course. Altogether, these findings suggest studies are needed to understand how RARs relate to changes in brain health earlier in the disease process. Better understanding of the biopsychosocial mechanisms linking RARs with future dementia risk can help further target intervention development.

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Section: Discussionmentioning

confidence: 99%

A Systematic Review of Evidence for a Role of Rest-Activity Rhythms in Dementia

et al. 2019

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“…Therefore, correction of small motions and then correction of bias field (ie, standardization of gray level values) have been performed in the preprocessing stage to increase the performance of the proposed technique. Motion correction has been provided by the open source and freely available FreeSurfer tool, which is widely used in medical practice . The technical details of the motion correction function were described in several publications .…”

Section: Proposed Methodsmentioning

confidence: 99%

“…Motion correction has been provided by the open source and freely available FreeSurfer tool, 38 which is widely used in medical practice. [39][40][41] The technical details of the motion correction function were described in several publications. [42][43][44] Briefly, when multiple source volumes are available, the function corrects small motions and then average them together.…”

Section: Preprocessing Stagementioning

confidence: 99%

Diagnosis of Alzheimer's disease with Sobolev gradient‐based optimization and 3D convolutional neural network

Göçeri

2019

Numer Methods Biomed Eng

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Alzheimer's disease is a neuropsychiatric, progressive, also an irreversible disease. There is not an effective cure for the disease. However, early diagnosis has an important role for treatment planning to delay its progression since the treatments have the most impact at the early stage of the disease. Neuroimages obtained by different imaging techniques (for example, diffusion tensor‐based and magnetic resonance‐based imaging) provide powerful information and help to diagnose the disease. In this work, a deeply supervised and robust method has been developed using three dimensional features to provide objective and accurate diagnosis from magnetic resonance images. The main contributions are (a) a new three dimensional convolutional neural network topology; (b) a new Sobolev gradient‐based optimization with weight values for each decision parameters; (c) application of the proposed topology and optimizer to diagnose Alzheimer's disease; (d) comparisons of the results obtained from the recent techniques that have been implemented for Alzheimer's disease diagnosis. Experimental results and quantitative evaluations indicated that the proposed network model is able to achieve to extract desired features from images and provides automated diagnosis with 98.06% accuracy.

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“…The B 1 + homogeneous RF shim case (Fig. 5b) is currently being heavily used with the sTx mode on more than 20 NIH patient/disease studies conducted in our facility 13,14 due to its high B 1…”

Section: Experimental Verificationmentioning

confidence: 99%

“…This RF coil system is currently being used in more than 20 patient/diseasebased studies funded by NIH (National Institutes of Health). To date, the current fully implemented version of the RF coil system has helped acquire more than 1300 neuro in-vivo scans in ongoing 7T human MRI studies 13,14 .…”

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confidence: 99%

Improved 7 Tesla transmit field homogeneity with reduced electromagnetic power deposition using coupled Tic Tac Toe antennas

Santini

Wood

Krishnamurthy

et al. 2021

Sci Rep

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Recently cleared by the FDA, 7 Tesla (7 T) MRI is a rapidly growing technology that can provide higher resolution and enhanced contrast in human MRI images. However, the increased operational frequency (~ 297 MHz) hinders its full potential since it causes inhomogeneities in the images and increases the power deposition in the tissues. This work describes the optimization of an innovative radiofrequency (RF) head coil coupled design, named Tic Tac Toe, currently used in large scale human MRI scanning at 7 T; to date, this device was used in more than 1,300 neuro 7 T MRI scans. Electromagnetic simulations of the coil were performed using the finite-difference time-domain method. Numerical optimizations were used to combine the calculated electromagnetic fields produced by these antennas, based on the superposition principle, resulting in homogeneous magnetic field distributions at low levels of power deposition in the tissues. The simulations were validated in-vivo using the Tic Tac Toe RF head coil system on a 7 T MRI scanner.

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Association of Hippocampal Substructure Resting-State Functional Connectivity with Memory Performance in Older Adults

Cited by 13 publications

References 33 publications

A Systematic Review of Evidence for a Role of Rest-Activity Rhythms in Dementia

A Systematic Review of Evidence for a Role of Rest-Activity Rhythms in Dementia

Diagnosis of Alzheimer's disease with Sobolev gradient‐based optimization and 3D convolutional neural network

Improved 7 Tesla transmit field homogeneity with reduced electromagnetic power deposition using coupled Tic Tac Toe antennas

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