The Role of Posterior Parietal Cortex in Spatial Representation of Time: A TMS Study

The existence of a spatial representation of time, where temporal intervals are represented on a mental temporal line (MTL), oriented in ascending order from left to right, was demonstrated manipulating spatial attention by means of Prismatic Adaptation (PA). In young healthy subjects, prisms adaptation inducing a rightward shift of spatial-attention produced an overestimation of time intervals, whereas prisms adaptation inducing a leftward shift of spatial-attention produced an underestimation of time intervals [4]. The aim of the present study was to investigate the neural basis mediating the effects of PA on spatial time representation. Posterior-Parietal-Cortex (PPC) is the best candidate to discharge this function. Indeed, neuropsychological and neurophysiological studies designate right-PPC as the site of space-time interaction [1,3,7]. Concerning the neural bases of PA procedures, left and right-PPC are involved in different phases of PA procedure [2,5, 6]. Here we investigated, by using TMS, the role of the Posterior-Parietal-Cortex (PPC) in spatial representation of time and in cerebral plasticity phenomena mediating prismatic adaptation effects on time processing. To this aim, healthy subjects were submitted to a tem-