Analysis of heart rate variability during mental task with reference to ambient temperature

Area of Science:

• Physiology
• Autonomic Nervous System Research
• Environmental Health

Background:

• Cardiac autonomic control is crucial for maintaining homeostasis.
• Understanding how environmental factors and cognitive load interact with autonomic regulation is essential.
• Previous research has explored temperature and mental stress effects separately, but their combined impact on cardiac autonomic control requires further investigation.

Purpose of the Study:

• To investigate the cardiac autonomic control mechanisms during mental tasks under varying ambient temperatures (21°C, 28°C, 35°C).
• To differentiate the roles of parasympathetic and sympathetic nervous systems in response to combined thermal and cognitive challenges.

Main Methods:

• Seven healthy males performed reaction-time tasks at different ambient temperatures.
• Assessed cardiac autonomic function using respiratory-related heart rate variability (CVRESP) for parasympathetic activity.
• Quantified sympathetic activity by calculating the difference between total heart rate variability (CVIHR) and CVRESP.

Main Results:

• Mean heart rate increased significantly with higher ambient temperatures (35°C) and during mental tasks.
• Both ambient temperature and task conditions significantly affected overall heart rate variability (CVIHR).
• Ambient temperature primarily influenced parasympathetic activity (CVRESP), while mental tasks modulated sympathetic activity (CVIHR - CVRESP).

Conclusions:

• Parasympathetic nervous system activity, modulated by respiration, plays a key role in regulating heart rate responses to ambient temperature.
• Sympathetic nervous system activity contributes significantly to the heart rate elevation observed during mental tasks.
• Combined thermal and cognitive stressors elicit distinct autonomic responses, highlighting the complexity of cardiac autonomic control.