Decoding movement direction using phase-space analysis of hemodynamic responses to arm movements based on functional near-infrared spectroscopy.

In this study we applied phase-space analysis on the hemodynamic signals recorded from the motor cortex of human subjects using functional near infrared spectroscopy (fNIRS) to decode the direction of intentional hand movements. Our goal is to develop a brain-computer-interface (BCI) based on optical imaging that can control a wheelchair. To establish the relationship between the hemodynamic response and movement direction, participants were asked to perform repetitive arm movements in two orthogonal directions (right-left and front-back) on a horizontal plane, while the time course of the oxy-hemoglobin (oxy-Hb) and deoxy-hemoglobin (deoxy-Hb) responses were recorded. We applied phase-space analysis on oxy-Hb and deoxy-Hb signals to characterize movement direction. Our results show that movement directions taken pairwise (left vs. right, and forward vs. backward) are mapped onto different quadrants in the oxy-Hb vs. deoxy-Hb phase plane. These findings demonstrate that phase-space analysis can be used to decode the movement direction in a BCI controlling a wheelchair. In conclusion, phase-space analysis can be used to differentiate intentional movement direction without correlating the temporal movement kinematics with the hemodynamic response.

Improvement of Processing Speed in Executive Function Immediately following an Increase in Cardiovascular Activity.

This study aims to identify the acute effects of physical exercise on specific cognitive functions immediately following an increase in cardiovascular activity. Stair-climbing exercise is used to increase the cardiovascular output of human subjects. The color-naming Stroop Test was used to identify the cognitive improvements in executive function with respect to processing speed and error rate. The study compared the Stroop results before and immediately after exercise and before and after nonexercise, as a control. The results show that there is a significant increase in processing speed and a reduction in errors immediately after less than 30 min of aerobic exercise. The improvements are greater for the incongruent than for the congruent color tests. This suggests that physical exercise induces a better performance in a task that requires resolving conflict (or interference) than a task that does not. There is no significant improvement for the nonexercise control trials. This demonstrates that an increase in cardiovascular activity has significant acute effects on improving the executive function that requires conflict resolution (for the incongruent color tests) immediately following aerobic exercise more than similar executive functions that do not require conflict resolution or involve the attention-inhibition process (for the congruent color tests).