Change in background context disrupts performance on visual paired comparison following hippocampal damage

The medial temporal lobe plays a critical role in recognition memory but, within the medial temporal lobe, the precise neural structures underlying recognition memory remain equivocal. In this study, visual paired comparison (VPC) was used to investigate recognition memory in a human patient (YR), who had a discrete lesion of the hippocampus, and a group of monkeys with neonatal hippocampal lesions, which included the dentate gyrus, and a portion of parahippocampal region. Participants were required to view a picture of an object on a coloured background. Immediately afterwards, this familiar object was shown again, this time paired with a novel object. All participants displayed a novelty preference, provided the background on which the objects were shown was the same as the one used during the learning phase. When the background of the familiar object was changed between initial familiarization and test, only the control subjects showed a novelty preference; the hippocampal-lesioned monkeys and patient YR showed null preference. The results are interpreted within Eichenbaum and Bunsey's [Eichenbaum, H., & Bunsey, M. (1995). On the binding of associations in memory: Clues from studies on the role of the hippocampal region in paired-associate learning. Current Directions in Psychological Science, 4, 19-23] proposal that the hippocampus facilitates the formation of a flexible representation of the elements that make up a stimulus whereas the parahippocampal region is involved in the formation of a fused representation.