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

Licensing Health Care Professionals, State Action and Antitrust Policy

In this Essay, we raise some economic concerns about the wisdom of conferring antitrust immunity on professional licensing boards, which are often comprised of members of the profession and therefore apt to be motivated by self-interest rather than the public interest. In Part II, we examine the political economy of special interest legislation, which suggests that little public good results from replacing competitive market forces with self-regulation. In Part III, we employ a basic economic model to generate predictions of the economic effects of professional licensing. Part IV provides a survey of the empirical research in this area, which confirms the theoretical predictions. In Part V, we turn our attention to the requirements of the state action doctrine and, in Part VI, close with some concluding remarks and suggestions. In all of what follows, we focus on occupational licensing within health care professions

Factors Influencing Cost-Related Nonadherence to Medication in Older Adults: A Conceptually Based Approach

Although multiple noncost factors likely influence a patient's propensity to forego treatment in the face of cost pressures, little is known about how patients' sociodemographic characteristics, physical and behavioral health comorbidities, and prescription regimens influence cost-related nonadherence (CRN) to medications. We sought to determine both financial and nonfinancial factors associated with CRN in a nationally representative sample of older adults.We used a conceptual model developed by Piette and colleagues that describes financial and nonfinancial factors that could increase someone's risk of CRN, including income, comorbidities, and medication regimen complexity. We used data from the 2004 wave of the Health and Retirement Study and the 2005 HRS Prescription Drug Study to examine the influence of factors within each of these domains on measures of CRN (including not filling, stopping, or skipping doses) in a nationally representative sample of Americans age 65+ in 2005.Of the 3071 respondents who met study criteria, 20% reported some form of CRN in 2005. As in prior studies, indicators of financial stress such as higher out-of-pocket payments for medications and lower net worth were significantly associated with CRN in multivariable analyses. Controlling for these economic pressures, relatively younger respondents (ages 65–74) and depressive symptoms were consistent independent risk factors for CRN.Noncost factors influenced patients' propensity to forego treatment even in the context of cost concerns. Future research encompassing clinician and health system factors should identify additional determinants of CRN beyond patients' cost pressures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78680/1/j.1524-4733.2009.00679.x.pd

Hospital Mergers and Economic Efficiency

Consolidation via merger both from hospital-to-hospital mergers and from hospital acquisitions of physician groups is changing the competitive landscape of the provision of health care delivery in the United States. This Article undertakes a legal and economic examination of a recent Ninth Circuit case examining the hospital acquisition of a physician group. This Article explores the Saint Alphonsus Medical Center-Nampa Inc. v. St. Luke’s Health System, Ltd. (St. Luke’s) decision—proposing a type of analysis that the district court and Ninth Circuit should have undertaken and that we hope future courts undertake when analyzing mergers in the health care sector. First, the Article addresses the question of how best to frame the acquisition of a physician group by a hospital—is the merger horizontal, vertical, or potentially both? In undertaking this analysis the Article examines the broader issue of the treatment of Accountable Care Organizations (ACOs) in antitrust law. ACOs are short of full integration and as such, a potential contractual alternative for hospitals and physician groups to an acquisition. A hospital acquisition of a physician practice also has implications for how to view competitive effects in the context of ACOs. Indeed, in St. Luke’s the Ninth Circuit suggests that integration short of full merger was a possible alternative. Second, the Article examines the justification for integration as a way to address countervailing power in health care, the reduction of transaction costs, and potential cost and quality efficiencies. Third, the Article applies the economics of these issues to merger case law generally and specifically to the St. Lukee’s decision. Ultimately, the Article finds the economic analysis of the Ninth Circuit lacking. Finally, the Article offers policy implications of the decision and concludes with some suggestions to improve health care antitrust analysis in practice for litigated cases to make such analysis better follow economic principles

Hospital Mergers and Economic Efficiency

Consolidation via merger both from hospital-to-hospital mergers and from hospital acquisitions of physician groups is changing the competitive landscape of the provision of health care delivery in the United States. This Article undertakes a legal and economic examination of a recent Ninth Circuit case examining the hospital acquisition of a physician group. This Article explores the Saint Alphonsus Medical Center-Nampa Inc. v. St. Luke’s Health System, Ltd. (St. Luke’s) decision—proposing a type of analysis that the district court and Ninth Circuit should have undertaken and that we hope future courts undertake when analyzing mergers in the health care sector. First, the Article addresses the question of how best to frame the acquisition of a physician group by a hospital—is the merger horizontal, vertical, or potentially both? In undertaking this analysis the Article examines the broader issue of the treatment of Accountable Care Organizations (ACOs) in antitrust law. ACOs are short of full integration and as such, a potential contractual alternative for hospitals and physician groups to an acquisition. A hospital acquisition of a physician practice also has implications for how to view competitive effects in the context of ACOs. Indeed, in St. Luke’s the Ninth Circuit suggests that integration short of full merger was a possible alternative. Second, the Article examines the justification for integration as a way to address countervailing power in health care, the reduction of transaction costs, and potential cost and quality efficiencies. Third, the Article applies the economics of these issues to merger case law generally and specifically to the St. Lukee’s decision. Ultimately, the Article finds the economic analysis of the Ninth Circuit lacking. Finally, the Article offers policy implications of the decision and concludes with some suggestions to improve health care antitrust analysis in practice for litigated cases to make such analysis better follow economic principles

Hospital Mergers and Economic Efficiency

Consolidation via merger both from hospital-to-hospital mergers and from hospital acquisitions of physician groups is changing the competitive landscape of the provision of health care delivery in the United States. This Article undertakes a legal and economic examination of a recent Ninth Circuit case examining the hospital acquisition of a physician group. This Article explores the Saint Alphonsus Medical Center-Nampa Inc. v. St. Luke’s Health System, Ltd. (St. Luke’s) decision—proposing a type of analysis that the district court and Ninth Circuit should have undertaken and that we hope future courts undertake when analyzing mergers in the health care sector. First, the Article addresses the question of how best to frame the acquisition of a physician group by a hospital—is the merger horizontal, vertical, or potentially both? In undertaking this analysis the Article examines the broader issue of the treatment of Accountable Care Organizations (ACOs) in antitrust law. ACOs are short of full integration and as such, a potential contractual alternative for hospitals and physician groups to an acquisition. A hospital acquisition of a physician practice also has implications for how to view competitive effects in the context of ACOs. Indeed, in St. Luke’s the Ninth Circuit suggests that integration short of full merger was a possible alternative. Second, the Article examines the justification for integration as a way to address countervailing power in health care, the reduction of transaction costs, and potential cost and quality efficiencies. Third, the Article applies the economics of these issues to merger case law generally and specifically to the St. Luke’s decision. Ultimately, the Article finds the economic analysis of the Ninth Circuit lacking. Finally, the Article offers policy implications of the decision and concludes with some suggestions to improve health care antitrust analysis in practice for litigated cases to make such analysis better follow economic principles

Hospital Mergers and Economic Efficiency

Consolidation via merger both from hospital-to-hospital mergers and from hospital acquisitions of physician groups is changing the competitive landscape of the provision of health care delivery in the United States. This Article undertakes a legal and economic examination of a recent Ninth Circuit case examining the hospital acquisition of a physician group. This Article explores the Saint Alphonsus Medical Center-Nampa Inc. v. St. Luke’s Health System, Ltd. (St. Luke’s) decision—proposing a type of analysis that the district court and Ninth Circuit should have undertaken and that we hope future courts undertake when analyzing mergers in the health care sector. First, the Article addresses the question of how best to frame the acquisition of a physician group by a hospital—is the merger horizontal, vertical, or potentially both? In undertaking this analysis the Article examines the broader issue of the treatment of Accountable Care Organizations (ACOs) in antitrust law. ACOs are short of full integration and as such, a potential contractual alternative for hospitals and physician groups to an acquisition. A hospital acquisition of a physician practice also has implications for how to view competitive effects in the context of ACOs. Indeed, in St. Luke’s the Ninth Circuit suggests that integration short of full merger was a possible alternative. Second, the Article examines the justification for integration as a way to address countervailing power in health care, the reduction of transaction costs, and potential cost and quality efficiencies. Third, the Article applies the economics of these issues to merger case law generally and specifically to the St. Lukee’s decision. Ultimately, the Article finds the economic analysis of the Ninth Circuit lacking. Finally, the Article offers policy implications of the decision and concludes with some suggestions to improve health care antitrust analysis in practice for litigated cases to make such analysis better follow economic principles

Association between depression and concurrent Type 2 diabetes outcomes varies by diabetes regimen

Aims  Although depression has weak associations with several Type 2 diabetes mellitus (DM) outcomes, it is possible that these associations are concentrated within certain patient subgroups that are more vulnerable to their effects. This study tested the hypothesis that depression is related to glycaemic control and diabetes-related quality of life (DQOL) in patients who are prescribed injected insulin, but not those on oral glucose-lowering agents alone. Methods  Participants (103 on insulin, 155 on oral glucose-lowering agents alone) with Type 2 DM were recruited from a large US healthcare system and underwent assessment of glycaemic control (glycated haemoglobin; HbA 1c ), medication adherence and diabetes self-care behaviours, DQOL and depression (none, mild, moderate/severe). Results  There was a significant regimen × depression interaction on HbA 1c ( P  = 0.002), such that depression was associated with HbA 1c in patients using insulin (β = 0.35, P  < 0.001) but not in patients using oral agents alone (β = –0.08, P  = NS). There was a similar interaction when quality of life was analysed as an outcome ( P  = 0.002). Neither effect was mediated by regimen adherence. Conclusions  The generally weak association between depression and glycaemic control is concentrated among patients who are prescribed insulin. Similarly, the association between depression and illness quality of life is strongest in patients prescribed insulin. Because this is not attributable to depression-related adherence problems, psychophysiological mechanisms unique to this group ought to be carefully investigated. Clinicians might be especially vigilant for depression in Type 2 DM patients who use insulin and consider its potential impact upon their illness course. Diabet. Med. 25, 1324–1329 (2008)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73538/1/j.1464-5491.2008.02590.x.pd