| Advanced signal processing techniques were applied to rat electroencephalograms (EEG's). The EEG's were recorded using microelectrodes chronically implanted in the nucleus tractus solitarius (NTS), the basal region of the amygdala, and the anteroventral third ventricle (AV3V) area of the hypothalamus.; In the first experiment, formerly isolated rats were placed together in a standard cage and their blood pressures and EEG's were recorded. The same rats were then placed in a Henry psychosocial crowd cage in an attempt to use stress to cause hypertension. At two week intervals, systolic blood pressure and EEG were recorded. In the third experiment, formerly isolated experimental rats were placed in a Henry psychosocial crowd cage. At two week intervals, systolic blood pressure and EEG were recorded. Control rats were housed in standard size cages in groups of two. EEG data were processed to obtain power spectral densities and cross-spectral densities.; Results indicate that transient exposures (of several minutes) of formerly isolated rats to other rats had no effect on behavior, systolic blood pressure, or EEG. Exposure to the Henry crowd cage environment led to systolic blood pressure increased in one of two experiments. In the first of the Henry crowd cage trials there were correlations between systolic blood pressure and the energy content of low frequency EEG bands, and inverse correlations between systolic blood pressure and high frequency EEG bands. In the second experimental trial, correlation coefficients between the energy content of low and high frequency EEG bands and systolic blood pressure were lower. Cross-spectral densities were inconsistent in both experimental trials. |
