Cardiac and respiratory relationships with neural discharge in the anterior cingulate cortex during sleep-walking states.

The discharge properties of single neurons in the anterior cingulate cortex were correlated with timing aspects of the respiratory and cardiac cycle and with arterial pressure in undrugged, freely moving cats during waking, quiet sleep, and rapid eye movement sleep (REM). Two types of analyses were carried out. Discharge timing relationships with the cardiac or respiratory cycle were examined using cross-correlation histograms. Tonic rate correlations were calculated as a linear regression between breath-by-breath mean discharge rate of the cell and breath-by-breath values of respiratory parameters or arterial pressure. Eight of fifty-five cells recorded showed a discharge timing relationship with either the cardiac or the respiratory cycle. Seven of these were state-dependent (six in waking, one in REM). Thirty cells showed a tonic rate correlation with the respiratory period, and 23 cells had tonic correlations with maximum arterial pressure. All tonic correlations for a given cell were state-dependent, but such correlations were observed in all states. Correlation coefficients, while statistically significant, were generally low, and r2 values rarely exceeded 0.2. The relative paucity of discharge timing relationships, the state dependency, and the low r values of the tonic rate correlations suggest that the anterior cingulate cortex has a complex and indirect relationship to central cardiovascular and respiratory control mechanisms.