Elevated brain temperature under severe heat exposure impairs cortical motor activity and executive function.

Area of Science:

• Neuroscience
• Environmental Physiology
• Human Performance

Background:

• Heat exposure is a physiological stressor that can impair physical and cognitive function.
• The precise effects of severe heat stress on brain physiology and function remain unclear.

Purpose of the Study:

• To investigate how severe heat stress impacts brain temperature, cerebral perfusion, and neural activity.
• To assess the effects of hyperthermia on motor and executive functions.
• To evaluate the efficacy of an internal cooling strategy on heat-related neural disruptions.

Main Methods:

• Eleven healthy participants underwent heat stress via exercise or warm water immersion to induce hyperthermia (rectal temperature of 39.5°C).
• Brain temperature, cerebral perfusion, and brain activity were measured using MRI.
• A cooling strategy involving blended ice ingestion was tested during exercise.

Main Results:

• Brain temperature tightly regulated at rest but increased with hyperthermia, mirroring rectal temperature.
• Hyperthermia suppressed motor cortical activity and reduced gray matter perfusion, impacting executive function.
• Ice ingestion effectively lowered rectal and brain temperatures and reduced neural disruptions.

Conclusions:

• Severe heat exposure elevates brain temperature, disrupts motor cortical activity, and impairs executive function.
• These neural changes contribute to reduced physical and cognitive performance under heat stress.
• Internal cooling strategies show promise in mitigating heat-induced neural impairments.