Generally, imagining an action and physically executing it are thought to be controlled by common motor representations. However, imagined walking to a previewed target tends to be terminated more quickly than real walking to the same target, raising a question as to what representations underlie the two modes of walking. To address this question, the present study put forward a hypothesis that both explicit and implicit representations of gait are involved in imagined walking, and further proposed that the underproduction of imagined walking duration largely stems from the explicit representation due to its susceptibility to a general undershooting tendency in time production (i.e., the error of anticipation). Properties of the explicit and implicit representations were examined by manipulating their relative dominance during imagined walking through concurrent bodily motions, and also by using non-spatial tasks that extracted the temporal structure of imagined walking. Results showed that the duration of imagined walking subserved by the implicit representation was equal to that of real walking, and a time production task exhibited an equivalent underproduction bias as in imagined walking tasks that were based on the explicit representation. These findings are interpreted as evidence for the dual-representation view of imagined walking.

Onset primacy is a robust behavioural phenomenon whereby humans identify the sudden appearance of an object in the environment (onset) with greater speed and accuracy than other types of visual change, such as the sudden disappearance of an object from the environment (offset). The default mode hypothesis explains this phenomenon by postulating that onset detection is the default processing mode of the attentional system. The present study aimed to test this notion by investigating whether onset primacy is also reflected on a neural level, as indicated by the comparative efficiency of neural processing for onsets, using electroencephalography. It was hypothesised that this relative efficiency would be reflected in the P300 event-related potential as a greater amplitude across temporal, parietal, and occipital regions during onset detection, compared to offset detection. This prediction was tested through a change detection task in which participants were required to identify the location of onset or offset between paired images of naturalistic scenes. Results showed that P300 amplitude differed between onset and offset conditions in the anticipated direction, supporting the default mode hypothesis. These results suggest that the P300 is a neural marker of onset primacy in visual change detection.