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.