Future thinking in Parkinson's disease: an executive function?

Contrary to what was originally thought (Hassabis, Kumaran, Vann, & Maguire, 2007) recent data have shown that imagining the future is not entirely dependent on the hippocampus (Squire et al., 2010) and neuroimaging studies have demonstrated a frontopolar activation during future thinking tasks (Okuda et al., 2003). The present study investigated whether the performance of people with Parkinson's disease (PD) on future simulation tasks was dependent on memory or executive control. Thirty-one PD patients, asked to imagine possible future scenarios, generated fewer future episodic details than matched controls. The seven patients who clearly performed below the range of controls in future thinking, were also significantly poorer on the Frontal Assessment Battery (FAB), a battery assessing executive control, but showed no deficits in immediate or delayed memory tests. These results suggest that poor performance in the future thinking task is associated with poor executive control and less so with memory impairment. Flexible searching activities of past details might be crucial capacities for envisaging one's own future.