Lowering the Sampling Rate: Heart Rate Response during Cognitive Fatigue.

Area of Science:

• Physiology
• Biomedical Engineering
• Cognitive Science

Background:

• Cognitive fatigue, marked by tiredness and reduced cognitive function, arises from sustained mental effort.
• Frequency-domain heart rate variability (HRV) features are known indicators of cognitive fatigue.
• The sensitivity of HRV features from low-sampling-rate electrocardiogram (ECG) data to cognitive fatigue requires investigation for wearable applications.

Purpose of the Study:

• To assess the agreement of frequency-domain HRV features derived from lower versus higher ECG sampling rates.
• To determine if frequency-domain HRV features from lower sampling rates can predict cognitive fatigue.

Main Methods:

• Fifty-three participants underwent a 20-minute 2-back task designed to induce cognitive fatigue.
• Electrocardiogram (ECG) data were recorded throughout the task.
• Frequency-domain HRV features were extracted and compared between a 125 Hz sampling rate and the original 2000 Hz sampling rate.

Main Results:

• Near-perfect agreement was observed for frequency-domain HRV features between the 125 Hz and 2000 Hz sampling rates.
• Key frequency-domain HRV features, including normalized low-frequency power, normalized high-frequency power, and the LF/HF ratio, significantly varied with increasing cognitive fatigue.
• These variations in HRV features were consistent across all tested sampling rates.

Conclusions:

• A sampling rate of 125 Hz is sufficient for extracting frequency-domain HRV features that effectively index cognitive fatigue.
• These results have significant implications for designing cost-effective and power-efficient wearable devices for cognitive fatigue monitoring.