Differences in brain activities between motor imagery (MI) and motor execution (ME) were investigated by using the late Contingent Negative Variation (late CNV) in groups with different performance levels. The frequency of use and vividness of MI were assessed using the Visual Analogue Scale (VAS). The late CNV enables examining the onset of preparation activities of the brain, prior to movement. Participants in the study were baton twirlers in the Japan Baton Twirling Association (N=6; the expert group) and students in the baton twirling club of a physical education university (N=5; the intermediate group). The CNV paradigm was used as the experimental task with an auditory stimulus as the first stimulus (S1) and a visual stimulus as the second stimulus (S2). The experimental conditions consisted of the ME condition, in which a button was pressed upon the presentation of S2, and the MI condition, in which the button press was imagined upon presenting S2. The VAS results indicated that frequency of MI usage and vividness scores were higher for the expert than for the intermediate group. The amplitudes of the late CNV were not significantly different between the groups. However, there was a trend in both groups for a larger increase in late CNV amplitude in the MI condition compared to the control condition. These results suggest that neural activity in the preparation phase might not be different between experts and intermediates when engaging in MI of a sport irrelevant simple task, such as a button press. However, between group differences were observed in the vividness of MI, although the amplitude of the late CNV was similar. These results suggest that the expert group might recall a more vivid MI than the intermediate group, without increasing neural activity of the preparation phase.