Tracings of the respiration (RESP), blood pressure (BP), and raw muscle sympathetic nerve activity (MSNA) during Valsalva Maneuver. During baseline (period A), MSNA burst activity is at a basal rate, and the recorded amplitudes are close to Gaussian (lower left panel). During Phase II of the Valsalva Maneuver (B), BP drops rapidly causing a significant rise in the and MSNA burst rate. The MSNA amplitudes are no longer fit by a Gaussian (lower middle panel). In Phase IV of the Valsalva Maneuver (C), BP overshoots it baseline values and MSNA ceases. This is assumed to be neural noise and is well fit by a Gaussian distribution (lower right panel).