Vector-based analysis of cortical activity associated with dumbbell exercise using functional near-infrared...

Area of Science:

• Neuroscience
• Physiology
• Biomedical Engineering

Background:

• Understanding the intricate interplay between brain and muscle activity is crucial for neuroscience and rehabilitation.
• Current neuroimaging techniques have limitations in simultaneously assessing neural activation and localized oxygen dynamics during motor tasks.

Purpose of the Study:

• To introduce and validate a novel vector-based functional near-infrared spectroscopy (fNIRS) method for quantifying brain-muscle interaction.
• To investigate the spatial relationship between cerebral oxygen consumption and supply during dumbbell-lifting exercises.

Main Methods:

• Developed a vector-based fNIRS approach measuring oxyhemoglobin (oxyHb) and deoxyhemoglobin (deoxyHb) to calculate oxygen exchange angle (k) and amplitude (L).
• Simultaneously monitored the left primary motor cortex (left M1) and right biceps brachii muscle activity in seven healthy adults performing dumbbell lifts (0, 4.5, 9.5 kg).

Main Results:

• Dumbbell exercises led to increased local oxygen consumption (indicated by oxygen exchange) in the left M1.
• Cerebral oxygen exchange decreased around the left M1, suggesting increased oxygen supply without consumption in adjacent areas.
• The spatial correlation between peak oxygen exchange (k) and response intensity (L) was less than 20%.

Conclusions:

• Cerebral oxygen consumption associated with neural activation during motor tasks is spatially distinct from cerebral oxygen supply distribution.
• The vector-based fNIRS method provides a quantitative approach to understanding brain-body oxygen dynamics during physical exertion.