Evolution of EEG Fractal Dimension Along a Sequential Finger Movement Task

We used dual EEG and EMG recordings to assess the neural dynamics of motor activity during a stereotyped sequential finger movement. We analyzed the evolution of EEG complexity, assessed using Katz fractal dimension (KFD), in three brain regions involved in the task (multisensory association (MA), sensory and left and right motor areas) and its relation with response time, defined by EMG onset. The KFD was calculated for multiple time windows, defined with respect to the go cue or the EMG onset. We observed a positive correlation between the KFD and the EMG onset latency in various time windows in all the areas. This relationship reversed for trials with a late EMG onset. While all the areas manifested a similar pattern of correlations, the motor area showed the lowest, and the MA area the highest, complexity values between these four brain regions. The KFD tended to decrease as the task progressed, consistently with previous observations of reduced neural variability with task engagement.