Evaluating Hemodynamic Responses in the Action Observation Network: an fNIRS Study on Motor Task Type and Stimulus Duration

This study presents a comparative statistical analysis of hemodynamic responses in the Action Observation Network (AON) using functional near-infrared spectroscopy (fNIRS) under different motor stimuli and durations. It examines cortical activity in response to 5 - and 8 -second stimuli, comparing right-hand-clenching and finger-tapping tasks. Ten right-handed healthy participants with no history of brain injury or neurological disorders were recruited. Each completed three experiments, analyzed in two groups: one comparing stimulus durations within the same task (hand-clenching) and the other comparing motor tasks (hand-clenching vs. finger-tapping) using 5 -second stimuli. The experiments included movement observation (MO), execution (ME), and motor imagery (MI). Statistical analyses involved t-tests for mean differences, Cohen's d for effect sizes, and visual inspection of hemodynamic maps. Results showed no significant differences between stimulus durations but revealed moderate differences between motor tasks, with greater hemodynamic responses in gross motor tasks. Additionally, oxygenated hemoglobin (HbO) deactivations were observed during MO, while ME exhibited a higher HbO concentration across all three experiments. These findings provide valuable insights for refining fNIRS-based experimental protocols and optimizing motor task selection in neurological research, supporting its potential in detecting altered hemodynamic patterns in brain-injured individuals and advancing clinical diagnosis and rehabilitation.