[The coherence between the frontal-parietal cortex and cardiac sympathetic nerve activity in cats]

Experiments were performed on 86 cats anesthetized with chloralose, paralyzed with gallamine triethiodide and ventilated artificially. Autospectral and coherence analysis revealed that the frontal-parietal cortex activity (EEG) and cardiac sympathetic nerve discharge (SND) were remarkably correlated in 33/44 cats. SND lagged EEG by 50 +/- 20 ms with a cross-correlation value of 0.4 +/- 0.1. Coherence value was 0.25 +/- 0.05, indicating a statistically significant relationship between the two signals. Midbrain transection at stereotaxic plane A3 preferentially decreased SND power at frequencies 3-4.2 Hz, accompanied by a fall in mean blood pressure (5.47 +/- 0.13 kPa). The coherence of SND to EEG was eliminated after decerebration. However, the total power in EEG was not significantly affected. The SND rhythm and blood pressure returned nearly to control level within 1 h after decerebration. The effects of midbrain transection were significantly attenuated by prior minor lesions of the lateral hypothalamus or medial thalamus. These results suggest that the forebrain is responsible significantly for a component of sympathetic tone in anesthetic cats. The integrity of diencephalon is required for the participation of forebrain in setting the level of basal SND. Reduction in SND following decerebration was due in part to interruption of the descending influence from diencephalon and brain stem sympathetic rhythm generators are involved in compensating for the loss of the forebrain dependent component of SND.