The Neural Substrate of Picture Naming Susan Murtha Sir Mortimer B. Davis-Jewish General Hospital, Montreal McGill University Centre Hospitalier Cote-des-Neiges, Montreal Howard Chertkow Sir Mortimer B. Davis-Jewish General Hospital, Montreal McGill University Centre Hospitalier Cote-des-Neiges, Montreal Mario Beauregard Centre Hospitalier Cote-des-Neiges, Montreal University of Montreal Alan Evans Montreal Neurological Institute Abstract A PET study of 10 normal males was carried out using the bolus H 2 15 O intravenous injection technique to examine the effects of picture naming and semantic judgment on blood ow. In a series of conditions, subjects (1) passively viewed ashing plus signs, (2) noted the occurrence of abstract pat- terns, (3) named animal pictures, or (4) carried out a semantic judgment on animal pictures. Anticipatory scans were carried out after the subjects were presented with the instructions but before they began the cognitive task, as they were passively viewing plus signs. Our results serve to clarify a number of current controversies regarding the neural substrate of picture naming. The results indicate that the fusiform gyrus is unlikely to be the region where low-level perceptual processing such as shape analysis is undertaken. In fact, our evidence suggests that activation of the fusiform gyrus is most likely related to visual perceptual semantic processing. In addition, the infe- rior/middle frontal lobe activity observed while performing the picture naming and semantic judgment tasks does not appear to be due to the effects of anticipation or preparation. Further- more, there appears to be a set of regions (a semantic network) that becomes activated regardless of whether the subjects perform a picture naming or semantic judgment task. Finally, picture naming of animals did not activate either parietal re- gions or anterior inferior left temporal regions, regardless of what subtraction baseline was used. INTRODUCTION Pictures make up one of the comprehensive classes of symbols for objects that constitute the inventory of our everyday world. Cognitive theories of object identica- tion and language suggest that for picture naming to occur, a number of stages of processing must be ac- cessed subsequent to viewing the object but prior to producing its verbal label. Subsequent to low-level visual sensory processing, it is thought that progressively more abstract representations are computed (Marr, 1982), ar- riving nally at a level of structural description or stored structural knowledge of the object. Object identication, in addition, almost certainly entails gaining access to some measure of semantic information regarding per- © 1999 Massachusetts Institute of Technology Journal of Cognitive Neuroscience 11:4, pp. 399–423 ceptual (and perhaps even functional) attributes of the item (Chertkow, Bub, & Caplan, 1992; Riddoch & Hum- phreys, 1987). Finally, the stored phonological repre- sentation of the object’s name must be accessed. There is ample evidence obtained from disorders of picture naming that demonstrate the dissociability of these stages of object recognition. For example, there are dis- orders in which the failure appears to be at the level of discrimination of visual attributes, cases in which the impairment is related to problems in perceiving percep- tual dimensions, and disorders at the level of assigning meaning to an adequately structured percept (Hum- phreys & Riddoch, 1984; Farah, 1990; Funnell, 1987; War- rington, 1982). Evidence for the localization of these processing