Electrocortical spectral analysis and fractal methods for assessing the effects of unilateral brain injury on rat cerebellum.

We used electrocortical spectral analysis and fractal methods for assessing the effects of unilateral, single brain injury on cerebellum. Cerebellar electrocortical activity was recorded in control state (before the injury) and after a single brain injury of the cerebellar cortex in anesthetized rats. We noticed that the mean power in gamma high-frequency domain (32-128 Hz) of the cerebellum, was increased after the first brain injury, while after a two-week recovery, it was larger than before the injury. The unilateral brain injury induced a permanent increase of the mild gamma activity in both the left and the right side of cerebellum cortex, but there was no further increase after the lesion was repeated. Our recent electrophysiological study on the cerebellum (Culic et al., 2005) suggested that the mean power spectra of the cerebellar cortical activity in the gamma frequency range might be the indicator of acute single focal brain injury. However, there is insufficient information on the effects of the repeated brain injury on the cerebellar electrocortical activity and morphology. There was no significant difference between the absolute and the relative mean power of the left and the right paravermal cortical activity (before, as well as, after the injury), in each of the animals tested afterwards, but there were differences between the left and the right side of cerebellum in experimental animals. Repeated injury of the cerebellar cortical areas, is strengthened by morphological changes in the cerebellar hemisphere, and shows a decrease in delta and an increase in gamma range.

Fractal analysis of rat brain activity after injury.

With application of the Higuchi algorithm, fractal dimension (FD) values of the electrocortical activity of the rat parietal cerebral and paravermal cerebellar cortex were calculated, before and after unilateral discrete injury of the left parietal cortex. Immediately following the first acute injury, in a group of six rats, a reversible increase in mean FD was found at the left (ipsilateral side to the injury) cerebral cortex, from 1.38 to 1.59, and at the left cerebellar cortex from 1.51 to 1.73. In addition, an indication of plastic changes after repeated (third) injury was found as an irreversible increase in mean FD: 1.54 on the left and 1.48 on the right side of parietal cortex.