Caracterização das propriedades elétricas do córtex cerebral por espectrospocia de impedância eletroquímica e suas implicações

Abstract

Brain functions emerge from complex electrochemical processes generated, propagated, and integrated by nerve cells at multiple spatial and temporal scales. Several techniques have been developed to measure and characterize the properties of these electrochemical processes. One of them, impedance spectroscopy (EI), consists of evaluating the impedance of brain tissue in response to applied disturbances of small amplitude sinusoidal current (or voltage) at various frequencies. The resulting impedance spectrum of such can be analyzed in the frequency domain and correlated with models of equivalent electrical circuits, thereby providing a quantitative basis for evaluating different types of signal propagation mechanisms in the brain. After a general description of the theoretical bases of IE, the present review analyzes the contribution of this technique in the field of neuroscience. In particular, the still open question about the resistive character of the extracellular propagation of electrical currents in the brain is discussed. Resolving this issue is particularly important in view of its broad causes for the interpretation of results obtained by electrophysiological recording techniques based on mass potentials such as electroencephalography.