RESUMO
Stochastic resonance is a phenomenon in which noise enhances the response of a system to an input signal. The brain is an example of a system that has to detect and transmit signals in a noisy environment, suggesting that it is a good candidate to take advantage of stochastic resonance. In this work, we aim to identify the optimal levels of noise that promote signal transmission through a simple network model of the human brain. Specifically, using a dynamic model implemented on an anatomical brain network (connectome), we investigate the similarity between an input signal and a signal that has traveled across the network while the system is subject to different noise levels. We find that non-zero levels of noise enhance the similarity between the input signal and the signal that has traveled through the system. The optimal noise level is not unique; rather, there is a set of parameter values at which the information is transmitted with greater precision, this set corresponds to the parameter values that place the system in a critical regime. The multiplicity of critical points in our model allows it to adapt to different noise situations and remain at criticality.
Assuntos
Córtex Cerebral/fisiologia , Modelos Neurológicos , Adulto , Córtex Cerebral/anatomia & histologia , Feminino , Humanos , Masculino , Probabilidade , Processos Estocásticos , Fatores de TempoRESUMO
OBJECTIVES: To investigate the association between early nutritional intake and brain development assessed by magnetic resonance imaging (MRI). STUDY DESIGN: A cohort of neonates born at ≤30 weeks gestational age underwent MRI at term equivalent age. Brain maturation and injury were assessed using the Kidokoro score. Two groups were defined by severity of the scores. The associations between macronutrients intake during the first 2 weeks of life, clinical factors, and imaging scores were analyzed using logistic regression. RESULTS: MRI scores from group 1 patients (n = 27) were normal to mildly abnormal (0-5). Group 2 (n = 15) had more abnormal scores (6-12). The median gestational ages (IQR) were 27.4 (1.9) weeks in group 1 and 27.0 (2.9) weeks in group 2, with birth weights of 900 (318) g (group 1) and 844 (293) g (group 2). In group 2, energy, lipid, and carbohydrate intake were significantly lower than in group 1. Group 2 also showed higher rates of sepsis and clinical risk scores than group 1. After adjustments in bivariate models, higher energy and lipid intake remained significantly associated with improved scores on MRI. This association was stronger for the gray matter component of the score. CONCLUSIONS: Higher energy and lipid intake during the first 2 weeks after birth was associated with a lower incidence of brain lesions and dysmaturation at term equivalent age in preterm neonates.