The hippocampus is thought to play a role in the formation of memories of relations among items in a scene (Cohen and Eichenbaum, 1993). Recently, we described a change detection task in which visual scanning of objects in a scene indicated explicit memory for those objects, and is thought to require hippocampal function (Chau, Murphy, Rosenbaum, Ryan, & Hoffman, 2010). In contrast, a task pairing faces and scenes revealed that the scanning of faces can be used as a measure of implicit memory, yet it, too, is associated with hippocampal function (Hannula & Ranganath, 2009). One difference between tasks is that the latter was never tested with objectscene pairs. In this study, we replicated the face-scene task, and added an object-scene condition to determine if the difference in scanning of previously shown pairs exists for objects-scene pairs and if, as with faces, this bias exists in the absence of explicit recall. Paired items were viewed preferentially, whether the items were faces or objects, and irrespective of whether recall was implicit or explicit. The bias towards the paired image emerged within the first 500 ms of viewing for all pairs, and the protracted response was stronger for explicit than implicit pairs. These results suggest that this task is effective whether using face or object stimuli, and could be used to tease apart the role of the hippocampus in explicit and implicit memory formation. Furthermore, its use of non-verbal measurements makes it amenable for use in animal models.Authors: Branfield Day, Leora R.; Bartlett, Adrian M.; Leonard, Timothy K. and Hoffman, Kari L.
Bayes, Time Perception, and Relativity: The Central Role of Hopelessness.