Mapping the network for planning: a correlational PET activation study with the Tower of London task

We used the Tower of London task (TOL) and (H2O)-O-15-PET to map the networ k of brain structures involved in planning, Six healthy right-handed subjec ts had 12 measurements of relative regional cerebral blood flow (rrCBF) dur ing six conditions, each performed twice. There was one rest condition, and five sets of TOL problems at different complexity levels, performed on a t ouch-sensitive computer monitor with the right arm, Complexity was defined as the number of moves required to solve each problem. Activation was analy sed in two ways: a category analysis comparing levels of rrCBF during rest and task was done to identify all structures involved in performance of the TOL; and a correlation analysis was carried out to delineate a subset of s tructures where the levels of rrCBF correlated with task complexity. Activa ted brain areas in which rrCBF increases did not correlate with complexity could be grouped into: (i) regions belonging to the dorsal stream of visual input processing, namely visual cortical areas 17, 18 and 19, and posterio r parietal cortical areas 7 and 40; and (ii) regions involved in the execut ion and sequencing of arm movements (right cerebellum, left primary motor c ortex and supplementary motor area), Brain regions where levels of rrCBF co rrelated with task complexity included lateral premotor cortex (area 6), ro stral anterior cingulate cortex (areas 32 and 24), dorsolateral prefrontal cortex (areas 9 and 46) bilaterally, and right dorsal caudate nucleus, We p ropose that dorsolateral prefrontal, lateral premotor, anterior cingulate a nd caudate areas form a network for the planning of movement that interacts with brain areas primarily involved in visual processing and movement exec ution.