Long-term correlation of the electrocorticogram as a bioindicator of brain exposure to ionizing radiation.

L.A.A Aguiar,T.S Fernandes,R.A Nogueira,I.M.S Silva

doi:10.1590/1414-431x20154473

Abstract

Understanding the effects of radiation and its possible influence on the nervous system are of great clinical interest. However, there have been few electrophysiological studies on brain activity after exposure to ionizing radiation (IR). A new methodological approach regarding the assessment of the possible effects of IR on brain activity is the use of linear and nonlinear mathematical methods in the analysis of complex time series, such as brain oscillations measured using the electrocorticogram (ECoG). The objective of this study was to use linear and nonlinear mathematical methods as biomarkers of gamma radiation regarding cortical electrical activity. Adult Wistar rats were divided into 3 groups: 1 control and 2 irradiated groups, evaluated at 24 h (IR24) and 90 days (IR90) after exposure to 18 Gy of gamma radiation from a cobalt-60 radiotherapy source. The ECoG was analyzed using power spectrum methods for the calculation of the power of delta, theta, alpha and beta rhythms and by means of the α-exponent of the detrended fluctuation analysis (DFA). Using both mathematical methods it was possible to identify changes in the ECoG, and to identify significant changes in the pattern of the recording at 24 h after irradiation. Some of these changes were persistent at 90 days after exposure to IR. In particular, the theta wave using the two methods showed higher sensitivity than other waves, suggesting that it is a possible biomarker of exposure to IR.

Highlights

The possible effects of ionizing radiation (IR) on the nervous system are of great clinical interest, because this technology is widely applied in brain imaging as well as in the treatment of brain tumors [1]
The focus of this study was on the investigation of the sensitivity of the power spectrum and detrended fluctuation analysis (DFA) to identify changes in the ECoG profile at 24 h after IR exposure (IR24 group) and 3 months after IR exposure
The power spectrum of the ECoG showed that for the IR24 group, the ECoG activity regarding theta and alpha rhythms increased relative to the control, and was www.bjournal.com.br consistently elevated even at 90 days after IR exposure

Summary

Introduction

The possible effects of ionizing radiation (IR) on the nervous system are of great clinical interest, because this technology is widely applied in brain imaging as well as in the treatment of brain tumors [1]. The available data on structural damage to the brain and to neurophysiological functions caused by IR and the repercussions for animal behavior are not yet conclusive [2]. After accidental exposure to IR in humans, as in the case of Chernobyl, an increased incidence of schizophrenia was identified. Since the first radiobiological experiments, the sensitivity of the human brain to radiation has been a point of discussion [4]. Evidence has accumulated indicating significant neurophysiological alterations as a result of exposure to ionizing radiation, such as changes in electroencephalogram (EEG) patterns, the presence of epileptiform waves and neuropsychiatric disorders [5,6]

Objectives

Methods

Conclusion