The Asymmetric Effect of Diffusion Processes: Risk Sharing and Contagion

In this paper we provide a general characterization of diffusion processes, allowing us to analyze both risk-sharing and contagion effects at the same time. We illustrate the relevance of our theory with reference to the subprime mortgage crisis and more in general to the processes of securitization and interbank linkages. We show that interdependencies in real and financial assets are beneficial from a social point of view when the economic environment is favorable and detrimental when the economic environment deteriorates. In the latter case, private incentives are such that too many linkages are formed, with respect to what is socially desirable. The risk of contagion increases the volatility of the outcome and thus reduces the ability of the financial networks to provide risk-sharing. Our analysis suggests that a likely major explanation of the subprime mortgage crisis is the process of securitization itself, in addition to the absence of transparency about the characteristics of the underlying assets that the multiple layers of financial intermediation fostered, as commonly claimed. This may call for a different emphasis on the role of public intervention. While a goal to stabilize the economy in good times should be to disrupt the channels that bring contagion, that is a positive correlation in the returns, in a period of worsening economic conditions our analysis suggests regulatory intervention aimed at disconnecting the economy at crucial nodes. Moreover, we show that policy interventions should be aimed at rescuing institutions, but not their managers. Diminishing the cost of default actually increases the inefficiency due to the divergence between the social and the individual optimum

Periinfarct rewiring supports recovery after primary motor cortex stroke.

After stroke restricted to the primary motor cortex (M1), it is uncertain whether network reorganization associated with recovery involves the periinfarct or more remote regions. We studied 16 patients with focal M1 stroke and hand paresis. Motor function and resting-state MRI functional connectivity (FC) were assessed at three time points: acute (<10 days), early subacute (3 weeks), and late subacute (3 months). FC correlates of recovery were investigated at three spatial scales, (i) ipsilesional non-infarcted M1, (ii) core motor network (M1, premotor cortex (PMC), supplementary motor area (SMA), and primary somatosensory cortex), and (iii) extended motor network including all regions structurally connected to the upper limb representation of M1. Hand dexterity was impaired only in the acute phase (P = 0.036). At a small spatial scale, clinical recovery was more frequently associated with connections involving ipsilesional non-infarcted M1 (Odds Ratio = 6.29; P = 0.036). At a larger scale, recovery correlated with increased FC strength in the core network compared to the extended motor network (rho = 0.71;P = 0.006). These results suggest that FC changes associated with motor improvement involve the perilesional M1 and do not extend beyond the core motor network. Core motor regions, and more specifically ipsilesional non-infarcted M1, could hence become primary targets for restorative therapies

Association of Assisted Reproductive Technology With Offspring Growth and Adiposity From Infancy to Early Adulthood

IMPORTANCE People conceived using assisted reproductive technology (ART) make up an increasing proportion of the world's population. OBJECTIVE To investigate the association of ART conception with offspring growth and adiposity from infancy to early adulthood in a large multicohort study. DESIGN, SETTING, AND PARTICIPANTS This cohort study used a prespecified coordinated analysis across 26 European, Asia-Pacific, and North American population-based cohort studies that included people born between 1984 and 2018, with mean ages at assessment of growth and adiposity outcomes from 0.6 months to 27.4 years. Data were analyzed between November 2019 and February 2022. EXPOSURES Conception by ART (mostly in vitro fertilization, intracytoplasmic sperm injection, and embryo transfer) vs natural conception (NC; without any medically assisted reproduction). Main OUTCOMES AND MEASURES The main outcomes were length / height, weight, and body mass index (BMI; calculated as weight in kilograms divided by height in meters squared). Each cohort was analyzed separately with adjustment for maternal BMI, age, smoking, education, parity, and ethnicity and offspring sex and age. Results were combined in random effects meta-analysis for 13 age groups. RESULTS Up to 158 066 offspring (4329 conceived by ART) were included in each age-group meta-analysis, with between 47.6% to 60.6% females in each cohort. Compared with offspring who were NC, offspring conceived via ART were shorter, lighter, and thinner from infancy to early adolescence, with differences largest at the youngest ages and attenuating with older child age. For example, adjusted mean differences in offspring weight were -0.27 (95% CI, -0.39 to -0.16) SD units at age younger than 3 months, -0.16 (95% CI, -0.22 to -0.09) SD units at age 17 to 23 months, -0.07 (95% CI, -0.10 to -0.04) SD units at age 6 to 9 years, and -0.02 (95% CI, -0.15 to 0.12) SD units at age 14 to 17 years. Smaller offspring size was limited to individuals conceived by fresh but not frozen embryo transfer compared with those who were NC (eg, difference in weight at age 4 to 5 years was -0.14 [95% CI, -0.20 to -0.07] SD units for fresh embryo transfer vs NC and 0.00 [95% CI, -0.15 to 0.15] SD units for frozen embryo transfer vs NC). More marked differences were seen for body fat measurements, and there was imprecise evidence that offspring conceived by ART developed greater adiposity by early adulthood (eg, ART vs NC difference in fat mass index at age older than 17 years: 0.23 [95% CI, -0.04 to 0.50] SD units). CONCLUSIONS AND RELEVANCE These findings suggest that people conceiving or conceived by ART can be reassured that differences in early growth and adiposity are small and no longer evident by late adolescence.Peer reviewe