Coupling of Oxy- and Deoxyhemoglobin concentrations with EEG rhythms during motor task

Area of Science:

• Neuroscience
• Cognitive Science
• Biomedical Engineering

Background:

• Understanding the relationship between brain electrical activity and blood flow is crucial for neuroscience.
• Simultaneous electroencephalogram (EEG) and functional near-infrared spectroscopy (fNIRS) offer complementary insights into brain function.
• Motor tasks provide a well-defined paradigm to study brain responses.

Purpose of the Study:

• To investigate the temporal relationship between brain rhythmic activity (EEG) and hemodynamic responses (fNIRS) during a self-paced motor task.
• To quantify the correlation between specific EEG frequency bands (alpha and beta) and changes in oxygenated and deoxygenated hemoglobin concentrations.

Main Methods:

• Simultaneous measurement of EEG (32 electrodes, 10-10 system) and fNIRS (8 optodes) in 10 healthy subjects.
• Participants performed self-paced right finger movements.
• Analysis focused on changes in alpha and beta EEG amplitudes and hemodynamic parameters (oxyhemoglobin - HbO, deoxyhemoglobin - HbR) in the sensorimotor cortex.

Main Results:

• A decrease in alpha and beta EEG amplitudes (desynchronization) was observed during the motor task.
• This desynchronization was accompanied by an increase in HbO and a decrease in HbR, predominantly in the hemisphere contralateral to the finger movement.
• Significant negative correlations were found between HbO and alpha/beta rhythms, and positive correlations between HbR and these rhythms.
• A delay of approximately 2.8 seconds was noted between hemodynamic and electrophysiological signals.

Conclusions:

• The study demonstrates a clear inverse relationship between EEG rhythmic activity (alpha and beta desynchronization) and hemodynamic changes (HbO increase, HbR decrease) during motor execution.
• These findings support the neurovascular coupling theory, highlighting the brain's metabolic and electrical activity linkage.
• The contralateral dominance of the observed effects underscores the lateralization of motor control.