Fig. 8

Signal quality challenges and solutions. 10-s sequences of ECG and EEG with consistent scaling across plots (EEG 20× magnified compared to EEG). Vertical gray lines represented automated peak detection results. 1A, B EEG signals with heart rate (HR) artifacts caused by water intrusion, resolved in later iterations that minimized water intrusion (1C, D). 2A, B VHF transmitter pings obscured ECG peak detection and EEG recordings on land but not in water (2C, D). 3A, B EEG and ECG signals obscured by satellite pings. 3C, D We replaced ~ 5 s of data surrounding the ping with data before or after the ping. Manual ping removal facilitated quantitative analysis by improving automated peak detection but can locally interrupt fine-scale patterns such as irregular heartbeats (visible in 3B but not 3D). 4A, B Wires reinforced by shielding and heat-shrink tubing outperformed insulated electrode wires covered with liquid electrical tape