Evidence for central command activation of the human insular cortex during exercise

Area of Science:

• Neuroscience
• Exercise Physiology
• Cardiovascular Regulation

Background:

• The insular cortex plays a role in interoception and autonomic control.
• Understanding brain activation during exercise is crucial for elucidating central command's influence.
• Previous research has not fully isolated central command's effect from peripheral feedback.

Purpose of the Study:

• To investigate if central command activates insular cortex regions independently of muscle metaboreflex and blood pressure increases.
• To differentiate neural responses to volitional exercise from those triggered by sustained blood pressure elevation.

Main Methods:

• Eight subjects underwent static handgrip exercise (SHG) and post-exercise cuff occlusion (PECO) to match mean blood pressure (MBP).
• Regional cerebral blood flow (rCBF) was measured using single-photon-emission computed tomography (SPECT).
• Heart rate, MBP, and perceived exertion were also recorded.

Main Results:

• Heart rate and perceived exertion were significantly higher during SHG compared to PECO when MBP was matched.
• Significant increases in rCBF were observed in sensorimotor cortex, right inferior posterior insula, left inferior anterior insula, and anterior cingulate during SHG, but not PECO.
• Both SHG and PECO activated the inferior thalamus and right inferior anterior insula.

Conclusions:

• Central command during handgrip exercise induces specific changes in regional cerebral blood flow within the insular and anterior cingulate cortex.
• These findings demonstrate central command's independent role in brain activation during volitional exercise, separate from metaboreflex and blood pressure effects.
• The insular cortex shows differential activation patterns related to the central command signal itself.