Frontotemporal interactions in face encoding and recognition

Cognition may result from different patterns of neural interactions distrib uted across the brain. If this is true then across different cognitive task s different functional interactions should be observed within an anatomical network. To investigate this hypothesis, a network analysis of PET data ob tained from a face memory study was conducted. PET scans were obtained whil e subjects performed face perception, face encoding and face recognition ta sks. Partial least squares (PLS) analysis of rCBF was used to identify brai n regions that were engaged during these tasks, and anatomically based stru ctural equation modeling (SEM) was used to construct functional models for matching, encoding and recognition. There was some overlap in the functiona l interactions observed across the three cognitive tasks. In all three task s, there were positive interactions involving the left occipitotemporal reg ions. These interactions may represent the perceptual component of the thre e tasks. Task-specific functional interactions were also observed. During f ace encoding, there was a bilateral positive influence of occipitotemporal regions on medial temporal regions. In addition, there were positive interh emispheric interactions between middle temporal regions and between limbic regions during encoding. These patterns may reflect the participation of me dial temporal cortex in the formation of new memories. In the face recognit ion task, there was a positive loop in the right hemisphere from occipital cortex to frontal cortex and back from frontal cortex to occipitotemporal c ortex. In addition, there was a strong positive input into the right hippoc ampal region from right occipitotemporal cortex. This pattern of interactio n was specific to the recognition task and might represent the process wher eby the input faces are compared to the internal representation laid down d uring encoding, thus enabling recognition. (C) 1999 Elsevier Science B.V. A ll rights reserved.