Di Caprio V, et al. - Through a reaching stop-signal task, experts evaluated whether Parkinson disease (PD) individuals at Hoehn and Yahr stage 1 showed a global or selective impairment in inhibitory control and tested whether left-dominant PD patients suffered from a more critical deficiency in this executive function compared with right-dominant PD persons. For the first time, evidence for a deficiency of reactive inhibition in the early-stage PD people in the absence of evidence for deficiencies in proactive inhibition was discovered. These findings have clinical significance since they give critical insights into the time course of the disease. Moreover, on a population of PD individuals at Hoehn and Yahr stage 1, former results showing that the onset of the disease does not influence inhibition was validated.