ABSTRACT
It is now well established that both visual mental imagery and visual perception rely on sets of distinct subsystems (Farah, 1984; Kosslyn, 1994). A major concern of neuroimaging studies that identified the cerebral bases of visual imagery has been to assess the extent to which visual imagery and visual perception share common cerebral structures (Kosslyn et al., 1993; Kosslyn, Thompson, & Alpert, 1997; Mellet, Tzourio, Denis, & Mazoyer, 1995). In agreement with the theoretical framework proposed by Kosslyn (1987, 1994), it has been established that both visual perception and visual imagery rely on a "what" and "where" functional dichotomy (see Mellet, Petit, Mazoyer, Denis, & Tzourio, 1998, for a review). According to this dichotomy, figurative aspects of both mental images and visual percepts are processed along the ventral occipitotemporal route while the dorsal occipitoparietal route processes the spatial features. Note, however, that this distinction is not absolute since most of the neuroimaging studies that dealt with spatial imagery tasks not only reported dorsal activation but also activation along the ventral route. In the same vein, studies that focused on figurative imagery reported occipitoparietal activation together with the activation in the ventral pathway (Ishai, Ungerleider, & Haxby, 2000; Lambert, Sampaio, Scheiber, & Mauss, 2002).
