MENTAL NAVIGATION ALONG MEMORIZED ROUTES ACTIVATES THE HIPPOCAMPUS, PRECUNEUS, AND INSULA

POSITRON emission tomography was used to investigate the functional an atomy of mental simulation of routes (MSR) in five normal volunteers. Normalized regional cerebral blood flow was measured while subjects me ntally navigated between landmarks of a route which had been previousl y learned by actual navigation. This task was contrasted with both sta tic visual imagery of landmarks (VIL) and silent Rest. MSR appears to be subserved by two distinct networks: a non-specific memory network i ncluding the posterior and middle parts of the hippocampal regions, th e dorsolateral prefrontal cortex and the posterior cingulum, and a spe cific mental navigation network, comprising the left precuneus, insula and medial part of the hippocampal regions.