Synchronization and Redundancy: Implications for Robustness of Neural Learning and Decision Making

Learning and decision making in the brain are key processes critical to survival, and yet are processes implemented by non-ideal biological building blocks which can impose significant error. We explore quantitatively how the brain might cope with this inherent source of error by taking advantage of two ubiquitous mechanisms, redundancy and synchronization. In particular we consider a neural process whose goal is to learn a decision function by implementing a nonlinear gradient dynamics. The dynamics, however, are assumed to be corrupted by perturbations modeling the error which might be incurred due to limitations of the biology, intrinsic neuronal noise, and imperfect measurements. We show that error, and the associated uncertainty surrounding a learned solution, can be controlled in large part by trading off synchronization strength among multiple redundant neural systems against the noise amplitude. The impact of the coupling between such redundant systems is quantified by the spectrum of the network Laplacian, and we discuss the role of network topology in synchronization and in reducing the effect of noise. A range of situations in which the mechanisms we model arise in brain science are discussed, and we draw attention to experimental evidence suggesting that cortical circuits capable of implementing the computations of interest here can be found on several scales. Finally, simulations comparing theoretical bounds to the relevant empirical quantities show that the theoretical estimates we derive can be tight.Comment: Preprint, accepted for publication in Neural Computatio

Acanthosis nigricans: relation with type 2 diabetes mellitus, anthropometric variables, and body mass in Indians

Objective: To determine the prevalence of acanthosis nigricans (AN) in type 2 diabetes mellitus (T2DM) and its correlation with various anthropometric measurements in Indians. Methods: One hundred and fifty consecutive subjects with T2DM attending the diabetes clinic at a tertiary referral centre in North India were considered as cases and 150 age and sex matched healthy attendants of non-diabetic subjects as controls. All the cases and controls were screened for the presence of AN and its severity. Anthropometric measurements of all of them were measured in standard method. Regression analysis was done to determine the association of AN with T2DM and various anthropometric measurements. Results: The prevalence of AN in subjects with diabetes and healthy controls was 62.6% and 40% respectively, and this difference was significant (p<0.05). Body mass index (BMI) between cases and controls was comparable by chance. There was a statistically significant correlation of increasing severity of AN with increasing BMI, waist circumference, hip circumference, waist-hip ratio, skinfold thickness, and body fat percentage in diabetic patients. However, in regression analysis after considering all the confounding factors there was a significant correlation of AN, only with diabetes mellitus and BMI. Conclusions: Indians have high prevalence of AN and it is an independent cutaneous marker of both T2DM and BMI

Lesões múltiplas de osteoma cutis na face: terapêutica minimamente invasiva em pacientes com sequela de acne - relato de casos Multiple injuries of osteoma skin in the face: therapeutical least invasive in patients with acne sequela - case report

Osteoma cutis é a formação óssea no interior da pele, podendo ser primária ou secundária. Única ou múltipla, de tamanhos variados e acometendo ambos os sexos, é uma lesão cutânea rara, de etiopatogenia e classificação ainda discutidas. Nosso objetivo foi relatar o diagnóstico e a terapêutica minimamente invasiva de lesões múltiplas de osteoma cutis na face em pacientes com sequelas de acne. Fizemos a retirada dos osteomas com agulhas BD 0,70 x 25 22G1, sem anestésicos tópicos ou injetáveis no local. As pequenas incisões foram deixadas expostas, com pomada cicatrizante. Obteve-se um excelente resultado estético em 15 dias.<br>Osteoma cutis is a bone formation in the dermis can to be primary or secondary forms. Only, multiples, many forms, occurring on either sex, they are a rare cutaneous disease. The pathogenesis and classification remains unclear. Our objective was the diagnostic and small invasive surgery treatment of the osteoma cutis multiple of the face, in patients as a sequel of acne. To remove the osteoma we used needle BD 0,70x25 22G1, without anesthetic topic or inject able site. The small wounds were exposed with scarring balsam. We got an excellent esthetic result after 15 days