Planning Abilities and Prefrontal Cortex: A Parametric efMRI Study with Tower-of-London Task

Objective: Planning abilities are essential for human life, because most of everyday life activities require a coordinated and planful behavior. Patients with damage to the frontal lobes often show noticeable difficulties in the management of everyday situations. Results of previous studies investigating planning abilities with neuroimaging methods were mixed concerning functional dissociation of specific areas within frontal cortex. There are indications that dorsolateral (DLPFC; BA 9/46) and rostrolateral prefrontal cortex (RLPFC; BA 10) are specifically involved in planning (Christoff & Gabriele, 2000). The aim of this study was to differentiate their function. For that purpose we used the Tower-of-London task (TOL) that was often applied to detect frontal impairments. Methods: 17 right-handed healthy subject, 9 men and 8 women, participated in this event-related fMRI study. The TOL task was presented in a pseudo-randomized order and was parametrically varied over the number of moves to plan ahead. To control for irrelevant activations two control conditions were presented, which were matched for the length of single events in the TOL task. For image processing and statistical analyses we used SPM99 and ROI approach. All statistics were corrected for multiple comparisons (p=0.05). Results: In the categorical contrasts TOL specific activations resulted bilaterally in DLPFC (BA 9/46), in the right VLPFC (BA 47), in the left RLPFC (BA 10) and thalamus, bilaterally in parietal (BA 7, 40) and in premotor cortex (BA 6, 8). Complexity dependent analyses revealed that only the left RLPFC showed a BOLD-signal increase over the four planning levels, which could not be observed in control conditions. Conclusions: The current study provides for a clearer functional differentiation of the prefrontal cortex. With the use of a parametrical event-related fMRI design we have shown that the left RLPFC plays a crucial role for planning abilities. Supported by the German BMBF FKZ01ZZ0105, TMWFK B30701–015/-016, IZKF grants.