Gamma power was not visually increased compared to the 1/f power log decay either for low gamma or high gamma. Because of a substantial level of 60 cycle noise, we were not able to conduct event related analyses of gamma power. We did,

however, examine whether the activity of individual cells was modulated by low gamma or high gamma. Of 69 cells for which LFPs were available, 64% showed significant phase-locking to low gamma (Figure S2A) and 93% showed significant phase-locking to high gamma (Figure S2B). In contrast to phase locking to theta, spiking of individual Sirolimus cost cells was phase locked only to the same-electrode LFP and not the nonlocal field potential (recorded on a different POR electrode than the cell). There were no task differences in phase locking to low or high gamma. Numbers of cells phase locked to gamma were similar across epochs, correct versus incorrect trials, and selleck chemicals task versus nontask phases. Anatomical, functional imaging, and experimental lesion evidence supports the hypothesis that the POR in the rodent brain and the PHC in the primate brain are involved in processing information about space, places, scenes, and contexts. There is little agreement, however, about the relevance of individual objects to representations of places and contexts. We used single-unit recording in rats performing a novel visual discrimination task to test the

hypothesis that the POR encodes contextual information, in

part, by combining spatial information with object information to form representations that link objects to places. We found that a substantial proportion of POR cells exhibited object-location conjunctive encoding. We also report that POR LFPs show increased power in the theta band, that the activity of individual cells is modulated by theta, and that POR theta modulation is PDK4 associated with both spatial and nonspatial behavior. Object-location conjunctions were identified in more than a third of all recorded POR cells, nearly half of responsive cells, and in roughly equal numbers across the stimulus, selection, and reward epochs. The occurrence of such correlates during the stimulus epoch is especially interesting, because during that epoch the animal is not physically located at the position of the object. Rather, the animal is in the center of the maze, viewing the object from a distance, as if viewing a scene. Our identification of object-location cells in POR is consistent with experimental lesion studies in which POR damage in rats and posterior PHC damage in monkeys impaired performance on object-place tasks (Gaffan et al., 2004; Malkova and Mishkin, 2003). Our findings extend a report that PHC neurons in monkeys respond to both object and spatial stimuli (Sato and Nakamura, 2003); selectivity for particular stimulus in different locations, as shown in the present study, was not tested.