In two neuroimaging studies, we aim to examine the role of the hippocampus cortex

(HPC) in binding and differentiating during encoding and retrieval of face-scene

composite images. Two neuroimaging experiments using fMRI were conducted. In

Study 1, we examined to role of HPC in binding during encoding and retrieval of

face-scene composites. During encoding, participants were asked to perform a 2-back

working memory (WM) task. For face-scene composite images, they made an

affirmative response only when the currently displayed image, in terms of both face

and scene, was identical to the one presented two images back. As a control,

participants were asked to undertake the same WM task with face-only and scene-

only images. During recognition, they were shown face-scene composite images and

judged whether their combination was identical to that during encoding and indicated

confidence in their judgments. When they were not identical, the composite images

were recombination of those that were shown during encoding. Results showed that,

in contrast to face-only and scene-only images, both the left and right HPC exhibited

greater activation during encoding of face-scene composites. Likewise, for composite

images, bilateral HPC exhibited greater activation when we contrasted between those

that were exact or partial repetition versus those that were not repeated. During

recognition, bilateral anterior HPC showed greater activation when the recombined

composite images contrasted with the old composites. Moreover, bilateral HPC

showed greater activation when the recombined composites were correctly rejected

than when they were erroneously identified (i.e., false alarm, FA), which may explain

the relatively high correct rejection (CR) rate in judging the recombined composite

images. In Study 2, we examined the neural mechanisms that may underlie the

retrieval of episodic memory for face-scene composite images of differential

associative strength. During encoding, participants were shown face-scene composite

images where a specific face was associated with a specific scene, a single face

associated with multiple scenes, or multiple repetitions of a specific pairing between a

face and a scene. During recognition, participants were shown face-scene images and

asked to judge whether the specific pairing of face and scene was presented during

encoding or was a re-combined version from those presented during encoding. They

performed the recognition test while their brains were scanned with fMRI. The

contrast between Fan 1-1 and Fan 1-5 highlights stronger activations of bilateral FFA

to differentiate the specific links between a face and multiple scenes. On the other

hand, the contrast between Fan 1-1 and its counterpart of five repetitions (i.e., R5)

revealed all the relevant brain regions were more strongly activated because of

multiple encounters. Finally, and somewhat unexpectedly, the activations of bilateral

HPC were diminished in the contrast between R5 and Fan 1-5, suggesting the dual

(and counteracting) role of HPC for binding in the former case and pattern

differentiation in the latter case. Taken together, the findings of the present studies

implicate the role of HPC in binding and differentiating face-scene composites when

participants intentionally encode those composites into and retrieve them from

episodic memory.