“…Interestingly, a goal-directed deficit may concur with a separate literature that highlights a shift from internal to external control in PD (van Spaendonck, Berger, Horstink, Borm, & Cools, 1995;Brown & Marsden, 1988;Cools, van den Bercken, Horstink, van Spaendonck, & Berger, 1984). Observations that PD patients have no problem initiating actions when presented with an unambiguous external stimulus (e.g., Rahman, Griffin, Quinn, & Jahanshahi, 2008;Praamstra, Stegeman, Cools, & Horstink, 1998) suggest that if anything remains intact in PD, it is the ability to act on direct S→R associations. Difficulties with the internal generation of actions and cognitive plans as well as enhanced cue-reliance and stimulus-driven behavior are more in line with a goal-directed impairment.…”