Neural correlates of motor imagery and execution in real-world dynamic behavior: evidence for similarities and differences

Abstract

A large body of evidence shows that motor imagery and action execution behaviors result from overlapping neural substrates, even in the absence of overt movement during motor imagery. To date it is unclear how neural activations in motor imagery and execution compare for naturalistic whole-body movements, such as walking. Neuroimaging studies have not directly compared imagery and execution during dynamic walking movements. Here we recorded brain activation with mobile EEG during walking compared to during imagery of walking, with mental counting as a control condition. We asked 24 healthy participants to either walk six steps on a path, imagine taking six steps, or mentally count from one to six. We found beta and alpha power modulation during motor imagery resembling action execution patterns; a correspondence not found performing the control task of mental counting. Neural overlap occurred early in the execution and imagery walking actions, suggesting activation of shared action representations. Remarkably, a distinctive walking-related beta rebound occurred both during action execution and imagery at the end of the action suggesting that, like actual walking, motor imagery involves resetting or inhibition of motor processes. However, we also found that motor imagery elicits a distinct pattern of more distributed beta activity, especially at the beginning of the task. These results indicate that motor imagery and execution of naturalistic walking involve shared motor-cognitive activations, but that motor imagery requires additional cortical resources.

Keywords: EEG; brain oscillations; cognitive processes; functional equivalence; motor imagery; simulation.

Figure 1

(A) Scalp maps topography of beta (13–25 Hz) spectral power across conditions and time. Dashed black lines represent the start and the end of the trial. (B) Averaged beta percentage change of power relative to baseline pooling the ROIs (central, parietal and occipital) for each condition in each time window. Significant comparisons are flagged with an asterisk.

Figure 2

(A) Scalp maps topography of alpha (8–12 Hz) spectral power across conditions and time. Dashed black lines represent the start and the end of the trial. (B) Averaged alpha percentage change of power relative to baseline pooling the ROIs (central, parietal and occipital) for each condition in each time window. Significant comparisons are flagged with an asterisk.

Figure 3

Averaged alpha and beta percentage change of power from baseline across conditions and time in each ROI.