Brain Connectivity and Neurocognitive Health in Older Adults: The Baltimore Experience Corps Trial Brain Health Study

Background: Cognitive aging is associated with cognitive decline and poor functional connectivity in the brain; however, the lengthening of life also presents additional potential to contribute to society. Addressing both these challenges and opportunities, we studied brain networks and cognitive functions within a randomized controlled trial of a senior service volunteer program, Experience Corps (EC). Methods: Data are from the Brain Health Study (BHS), a longitudinal trial nested within the Baltimore Experience Corps Trial, randomizing 123 socio-demographically diverse community-dwelling adults over the age of 60. At Baseline, 12-month Follow-Up, and 24-month Follow-Up, functional magnetic resonance imaging (fMRI) brain data and neuropsychological test data were collected. We investigated two brain networks whose coupling is known to be associated with cognitive aging and dementia risk, the Task Negative Network (TNN) and the Task Positive Network (TPN). We studied the associations between these biologic measures and the cognitive domains of executive function and memory, which are also known to be important to dementia risk. In particular, we investigated (Aim 1) TNN-TPN functional connectivity at baseline; (Aim 2) how the connectivity between and within the TNN and TPN were associated with dementia-linked cognitive functions; and (Aim 3) how these connectivity scores and cognitive functions changed longitudinally in the EC and Control Groups. Results: In Aim 1, we found that, the TPN and TNN were not strongly anti-correlated. In Aim 2, we found heterogeneous relations between functional connectivity and cognitive functions. In Aim 3, we found that these brain networks remained remarkably stable, and intervention effects were not statistically significant. Additionally, the EC group demonstrated an improvement in the executive functions domain of cognition compared to the Control group. Implications: The BHS is the first of its kind, to have investigated cognitive aging with biological markers in the brain and cognitive measures in a randomized controlled trial design of a volunteer intervention. These results contribute to a better understanding of functional connectivity in older adults, its relations to cognitive functions, and how these outcomes can be modified by senior service. We also developed analytic methodologies that can be standardized and applied to other fMRI studies

Dynamics of Duffing-Holmes oscillator with fractional order nonlinearity

In this work, the dynamics of Duffing-Holmes oscillator with fractional order nonlinearity is explored. Basically, a fractional spatial derivative is introduced to the cubic term, and the order of the derivative  α is varied between zero and two. The evolution of the dynamics of the system from nonlinear behavior to linear behavior is investigated using multiple tools such as phase portraits, Poincare maps, and bifurcation diagrams. We have demonstrated that as α increases the system can alternate between chaotic and periodic states depending on the parameters setting. However, the overall impact transforms the system into simpler dynamics and eventually causes the chaotic regions to fade out regardless of the system settings. The largest α at which the system still exhibits chaotic behavior is estimated to be around 1.17 and for transient chaos is estimated to be 1.25

Sensitive detection schemes for small variations in the damping coefficient based on the Duffing-Holmes oscillator with a potential application in magnetic sensing

In this work we proposed two detection schemes based on the non-linear properties of the Duffing-Holmes oscillator for the detection of small variations in the damping coefficient. Theoretically, variations in the damping coefficient up to 0.001% with the possibility to be pushed further can be detected based on our model. A potential on-off magnetic sensor suitable for biomedical applications is suggested by implementing these two schemes with Giant Magnetoresistance based magnetic sensors