MEMORY FOR OBJECT FEATURES VERSUS MEMORY FOR OBJECT LOCATION - A POSITRON-EMISSION TOMOGRAPHY STUDY OF ENCODING AND RETRIEVAL-PROCESSES

Regional cerebral blood flow was measured with positron-emission tomog raphy during two encoding and two retrieval tasks that were designed t o compare memory for object features with memory for object locations, Bilateral increases in regional cerebral blood flow were observed in both anterior and posterior regions of inferior temporal cortex and in ventral regions of prestriate cortex, when the condition that require d retrieval of object locations was subtracted from the condition that required retrieval of object features, During encoding, these changes were less pronounced and Here restricted to the left inferior tempora l cortex and right ventral prestriate cortex, In contrast, both encodi ng and retrieval of object location were associated with bilateral cha nges in dorsal prestriate and posterior parietal cortex. Finally, the two encoding conditions activated left frontal lobe regions preferenti ally, whereas the two retrieval conditions activated right frontal lob e regions, These findings confirm that, in human subjects, memory for object features is mediated by a distributed system that includes vent ral prestriate cortex and both anterior and posterior regions of the i nferior temporal gyrus. In contrast, memory for the locations of objec ts appears to be mediated by an anatomically distinct system that incl udes more dorsal regions of prestriate cortex and posterior regions of the parietal lobe.