Noise-induced synchronization and anti-resonance in excitable systems; Implications for information processing in Parkinson's Disease and Deep Brain Stimulation

We study the statistical physics of a surprising phenomenon arising in large networks of excitable elements in response to noise: while at low noise, solutions remain in the vicinity of the resting state and large-noise solutions show asynchronous activity, the network displays orderly, perfectly synchronized periodic responses at intermediate level of noise. We show that this phenomenon is fundamentally stochastic and collective in nature. Indeed, for noise and coupling within specific ranges, an asymmetry in the transition rates between a resting and an excited regime progressively builds up, leading to an increase in the fraction of excited neurons eventually triggering a chain reaction associated with a macroscopic synchronized excursion and a collective return to rest where this process starts afresh, thus yielding the observed periodic synchronized oscillations. We further uncover a novel anti-resonance phenomenon: noise-induced synchronized oscillations disappear when the system is driven by periodic stimulation with frequency within a specific range. In that anti-resonance regime, the system is optimal for measures of information capacity. This observation provides a new hypothesis accounting for the efficiency of Deep Brain Stimulation therapies in Parkinson's disease, a neurodegenerative disease characterized by an increased synchronization of brain motor circuits. We further discuss the universality of these phenomena in the class of stochastic networks of excitable elements with confining coupling, and illustrate this universality by analyzing various classical models of neuronal networks. Altogether, these results uncover some universal mechanisms supporting a regularizing impact of noise in excitable systems, reveal a novel anti-resonance phenomenon in these systems, and propose a new hypothesis for the efficiency of high-frequency stimulation in Parkinson's disease

Solitons in a Baby-Skyrme model with invariance under area preserving diffeomorphisms

We study the properties of soliton solutions in an analog of the Skyrme model in 2+1 dimensions whose Lagrangian contains the Skyrme term and the mass term, but no usual kinetic term. The model admits a symmetry under area preserving diffeomorphisms. We solve the dynamical equations of motion analytically for the case of spinning isolated baryon type solitons. We take fully into account the induced deformation of the spinning Skyrmions and the consequent modification of its moment of inertia to give an analytical example of related numerical behaviour found by Piette et al.. We solve the equations of motion also for the case of an infinite, open string, and a closed annular string. In each case, the solitons are of finite extent, so called "compactons", being exactly the vacuum outside a compact region. We end with indications on the scattering of baby-Skyrmions, as well as some considerations as the properties of solitons on a curved space.Comment: 30 pages, 5 figures, revtex, major modifications, conclusions modifie

Soliton-potential interaction in the nonlinear Klein-Gordon model

The interaction of solitons with external potentials in nonlinear Klein-Gordon field theory is investigated using an improved model. The presented model has been constructed with a better approximation for adding the potential to the Lagrangian through the metric of background space-time. The results of the model are compared with another model and the differences are discussed.Comment: 14 pages,8 figure

Establishing an Independent Mobile Health Program for Chronic Disease Self-Management Support in Bolivia

Background: Mobile health (m-health) work in low and middle-income countries (LMICs) mainly consists of pilot programmes with an unclear path to scaling and dissemination. We describe the deployment and testing of an m-health platform for non-communicable disease (NCD) self-management support in Bolivia. Methods: 364 primary care patients in La Paz with diabetes or hypertension completed surveys about their use of mobile phones, health and access to care. 165 of those patients then participated in a 12-week demonstration of automated telephone monitoring and self-management support. Weekly Interactive Voice Response (IVR) calls were made from a platform established at a university in La Paz, under the direction of the regional health ministry. Results: 37% of survey respondents spoke indigenous languages at home, and 38% had six or fewer years of education. 82% had a mobile phone; half (45%) used text messaging with a standard phone, and 9% had a smartphone. Smartphones were least common among patients who were older, spoke indigenous languages, or had less education. IVR programme participants completed 1007 self-management support calls, with an overall response rate of 51%. IVR call completion was lower among older adults, but was not related to patients’ ethnicity, health status or healthcare access. IVR health and self-care reports were consistent with information reported during baseline interviews. Patients’ likelihood of reporting excellent, very good, or good health (versus fair or poor health) via IVR increased during programme participation, and was associated with better medication adherence. Patients completing follow-up interviews were satisfied with the programme, with 19/20 (95%) reporting that they would recommend it to a friend. Conclusions: By collaborating with LMICs, m-health programmes can be transferred from higher-resource centres to LMICs and implemented in ways that improve access to self-management support among people with NCDs

Simulated Annealing for Topological Solitons

The search for solutions of field theories allowing for topological solitons requires that we find the field configuration with the lowest energy in a given sector of topological charge. The standard approach is based on the numerical solution of the static Euler-Lagrange differential equation following from the field energy. As an alternative, we propose to use a simulated annealing algorithm to minimize the energy functional directly. We have applied simulated annealing to several nonlinear classical field theories: the sine-Gordon model in one dimension, the baby Skyrme model in two dimensions and the nuclear Skyrme model in three dimensions. We describe in detail the implementation of the simulated annealing algorithm, present our results and get independent confirmation of the studies which have used standard minimization techniques.Comment: 31 pages, LaTeX, better quality pics at http://www.phy.umist.ac.uk/~weidig/Simulated_Annealing/, updated for publicatio

Post‐discharge tobacco cessation rates among hospitalized US veterans with and without diabetes

Aims  Smoking is a major risk factor for cardiovascular complications among patients with diabetes. Hospitalization has been shown to enhance cessation rates. The purpose of this study was to compare 6‐month post‐hospitalization tobacco cessation rates among US veterans with and without diabetes. Methods  This was a longitudinal study among inpatient veterans who used tobacco in the past month ( n  = 496). Patients were recruited and surveyed from three Midwestern Department of Veterans Affairs hospitals during an acute‐care hospitalization. They were also asked to complete a follow‐up survey 6 months post‐discharge. Bivariate‐ and multivariable‐adjusted analyses were conducted to determine differences in tobacco cessation rates between patients with and without a diagnosis of diabetes. Results  The mean age of patients was 55.2 years and 62% were white. Twenty‐nine per cent had co‐morbid diabetes. A total of 18.8% of patients with diabetes reported tobacco cessation at 6 months compared with 10.9% of those without diabetes ( P  = 0.02). Cotinine‐verified cessation rates were 12.5 vs. 7.4% in the groups with and without diabetes, respectively ( P  = 0.07). Controlling for psychiatric co‐morbidities, depressive symptoms, age, self‐rated health and nicotine dependence, the multivariable‐adjusted logistic regression showed that patients with diabetes had three times higher odds of 6‐month cotinine‐verified tobacco cessation as compared with those without diabetes (odds ratio 3.17, P  = 0.005). Conclusions  Post‐hospitalization rates of smoking cessation are high among those with diabetes. Intensive tobacco cessation programmes may increase these cessation rates further.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92145/1/j.1464-5491.2012.03635.x.pd

Interactive Voice Response-An Innovative Approach to Post-Stroke Depression Self-Management Support

Automated interactive voice response (IVR) call systems can provide systematic monitoring and self-management support to depressed patients, but it is unknown if stroke patients are able and willing to engage in IVR interactions. We sought to assess the feasibility and acceptability of IVR as an adjunct to post-stroke depression follow-up care. The CarePartner program is a mobile health program designed to optimize depression self-management, facilitate social support from a caregiver, and strengthen connections between stroke survivors and primary care providers (PCPs). Ischemic stroke patients and an informal caregiver, if available, were recruited during the patient's acute stroke hospitalization or follow-up appointment. The CarePartner program was activated in patients with depressive symptoms during their stroke hospitalization or follow-up. The 3-month intervention consisted of weekly IVR calls monitoring both depressive symptoms and medication adherence along with tailored suggestions for depressive symptom self-management. After each completed IVR call, informal caregivers were automatically updated, and, if needed, the subject's PCP was notified. Of the 56 stroke patients who enrolled, depressive symptoms were identified in 13 (23 %) subjects. Subjects completed 74 % of the weekly IVR assessments. A total of six subjects did not complete the outcome assessment, including two non-study-related deaths. PCPs were notified five times, including two times for suicidal ideation and three times for medication non-adherence. Stroke patients with depressive symptoms were able to engage in an IVR call system. Future studies are needed to explore the efficacy of an IVR approach for post-stroke self-management and monitoring of stroke-related outcomes

Collision-Induced Decay of Metastable Baby Skyrmions

Many extensions of the standard model predict heavy metastable particles which may be modeled as solitons (skyrmions of the Higgs field), relating their particle number to a winding number. Previous work has shown that the electroweak interactions admit processes in which these solitons decay, violating standard model baryon number. We motivate the hypothesis that baryon-number-violating decay is a generic outcome of collisions between these heavy particles. We do so by exploring a 2+1 dimensional theory which also possesses metastable skyrmions. We use relaxation techniques to determine the size, shape and energy of static solitons in their ground state. These solitons could decay by quantum mechanical tunneling. Classically, they are metastable: only a finite excitation energy is required to induce their decay. We attempt to induce soliton decay in a classical simulation by colliding pairs of solitons. We analyze the collision of solitons with varying inherent stabilities and varying incident velocities and orientations. Our results suggest that winding-number violating decay is a generic outcome of collisions. All that is required is sufficient (not necessarily very large) incident velocity; no fine-tuning of initial conditions is required.Comment: 24 pages, 7 figures, latex. Very small changes onl