Spatial memory comprises different representational systems that are sensitive to different environmental cues, like proximal landmarks or local boundaries. Here we examined how sleep affects the formation of a spatial representation integrating landmark-referenced and boundary-referenced representations. To this end, participants (n = 42) were…

Spatial working memory (SWM) is the ability to encode, maintain, and retrieve spatial information over a temporal gap, and relies on a network of structures including the medial septum (MS), which provides critical input to the hippocampus. Although the role of the MS in SWM is well-established, up until recently, we have been unable to use…

Netrin-1 was initially characterized as an axon guidance molecule that is essential for normal embryonic neural development; however, many types of neurons continue to express netrin-1 in the postnatal and adult mammalian brain. Netrin-1 and the netrin receptor DCC are both enriched at synapses. In the adult hippocampus, activity-dependent…

Repeatedly studying information is a good way to strengthen memory storage. Nevertheless, testing recall often produces superior long-term retention. Demonstrations of this testing effect, typically with verbal stimuli, have shown that repeated retrieval through testing reduces forgetting. Sleep also benefits memory storage, perhaps through…

We examined whether increasing retrieval difficulty in a spatial memory task would promote the recruitment of the anterior cingulate cortex (ACC) similar to what is typically observed during remote memory retrieval. Rats were trained on the hidden platform version of the Morris Water Task and tested three or 30 d later. Retrieval difficulty was…

The retrosplenial cortex (RSC) has a well-established role in contextual and spatial learning and memory, consistent with its known connectivity with visuo-spatial association areas. In contrast, RSC appears to have little involvement with delay fear conditioning to an auditory cue. However, all previous studies have examined the contribution of…

In three experiments, the nature of the interaction between multiple memory systems in rats solving a variation of a spatial task in the water maze was investigated. Throughout training rats were able to find a submerged platform at a fixed distance and direction from an intramaze landmark by learning a landmark-goal vector. Extramaze cues were…

Orientation, the spatial organization of animal behavior, is an essential faculty of animals. Bacteria and lower animals such as insects exhibit taxis, innate orientation behavior, directly toward or away from a directional cue. Organisms can also orient themselves at a specific angle relative to the cues. In this study, using…

Because many different sensory modalities contribute to spatial learning in rodents, it has been difficult to determine whether spatial navigation can be guided solely by visual cues. Rodents moving within physical environments with visual cues engage a variety of nonvisual sensory systems that cannot be easily inhibited without lesioning brain…

Using a combination of eye tracking and fMRI in a contextual cueing task, we explored the mechanisms underlying the facilitation of visual search for repeated spatial configurations. When configurations of distractors were repeated, greater activation in the right hippocampus corresponded to greater reductions in the number of saccades to locate…

Intrinsic persistent spiking mechanisms in medial entorhinal cortex (mEC) neurons may play a role in active maintenance of working memory. However, electrophysiological studies of rat mEC units have primarily focused on spatial modulation. We sought evidence of differential spike rates in the mEC in rats trained on a T-maze, cued spatial delayed…

Objects are often remembered with their locations, which is an important aspect of event memory. Despite the well-known involvement of the hippocampus in event memory, detailed intrahippocampal mechanisms are poorly understood. In particular, no experimental evidence has been provided in support of the role of the dentate gyrus (DG) in…

In a previous study we showed a temporally graded retrograde amnesia after hippocampal lesions when rats learned a spatial reference memory task in which two types of signals simultaneously indicated the goal arm (shape of the experimental room and extramaze landmarks). To investigate the effect that the navigational demands of the task have on…

Pattern completion is the ability to retrieve complete information on the basis of incomplete retrieval cues. Although it has been demonstrated that this cognitive capacity depends on the NMDA receptors (NMDA-Rs) of the hippocampal CA3 region, the role played by these glutamatergic receptors in the pattern completion process has not yet been…

Humans and animals form internal representations of external space based on their own body movement (dead reckoning) as well as external landmarks. It is poorly understood, however, how different types of information are integrated to form a unified representation of external space. To examine the role of dentate gyrus (DG) in this process, we…