and facilitation of plasticity at the entorhinal-dentate synapse in mice is sufficient to enhance place recall. Place cells are also found in the hippocampus. Posterior parietal cortex The parietal cortex encodes spatial information using an egocentric frame of reference. It is therefore involved in the transformation of sensory information coordinates into action or effector coordinates by updating the spatial representation of the body within the environment. As a result, lesions to the parietal cortex produce deficits in the acquisition and retention of egocentric tasks, whereas minor impairment is seen among allocentric tasks. Rats with lesions to the anterior region of the posterior parietal cortex reexplore displaced objects, while rats with lesions to the posterior region of the posterior parietal cortex displayed no reaction to spatial change. Parietal cortex lesions are also known to produce temporally ungraded retrograde amnesia. Entorhinal cortex The dorsalcaudal medial entorhinal cortex (dMEC) contains a topographically organized map of the spatial environment made up of grid cells. This brain region thus transforms sensory input from the environment and stores it as a durable allocentric representation in the brain to be used for path integration. The entorhinal cortex contributes to the processing and integration of geometric properties and information in the environment. Lesions to this region impair the use of distal but not proximal landmarks during navigation and produces a delay-dependent deficit in spatial memory that is proportional to the length of the delay. Lesions to this region are also known to create retention deficits for tasks learned up to 4 weeks but not 6 weeks prior to the lesions. Memory consolidation in the entorhinal cortex is achieved through extracellular signal-regulated kinase activity. Prefrontal cortex The medial prefrontal cortex processes egocentric spatial information. It participates in the processing of short-term spatial memory used to guide planned search behavior and is believed to join spatial information with its motivational significance. The identification of neurons that anticipate expected rewards in a spatial task support this hypothesis. The medial prefrontal cortex is also implicated in the temporal organization of information. Hemisphere specialization is found in this brain region. The left prefrontal cortex preferentially processes categorical spatial memory including source memory (reference to spatial relationships between a place or event), while the right prefrontal cortex preferentially processes coordinate spatial memory including item memory (reference to spatial relationships between features of an item). Lesions to the medial prefrontal cortex impair the performance of