to whether or not a place field should fire in a certain environment. Metric sensory information is any kind of spatial input that might indicate a distance between two points. For example, the edges of an environment might signal the size of the overall place field or the distance between two points within a place field. Metric signals can be either linear or directional. Directional inputs provide information about the orientation of a place field, whereas linear inputs essentially form a representational grid. Contextual cues allow established place fields to adapt to minor changes in the environment, such as a change in object color or shape. Metric and contextual inputs are processed together in the entorhinal cortex before reaching the hippocampal place cells. Visuospatial and olfactory inputs are examples of sensory inputs that are utilized by place cells. These types of sensory cues can include both metric and contextual information. Visuospatial inputs Spatial cues such as geometric boundaries or orienting landmarks are important examples of metric input. An example is the walls of an environment, which provides information about relative distance and location. Place cells generally rely on set distal cues rather than cues in the immediate proximal environment, though local cues can have a profound impact on local place fields. Visual sensory inputs can also supply important contextual information. A change in color of a specific object or the walls of the environment can affect whether or not a place cell fires in a particular field. Thus, visuospatial sensory information is critical to the formation and recollection of place field. Olfactory inputs Although place cells primarily rely on visuospatial input, some studies suggest that olfactory input may also affect the formation and stability of place fields. Olfaction may compensate for a loss of visual information, or even be responsible for the formation of stable place fields in the same was visuospatial cues are. This has been confirmed by a study in a virtual environment that was composed of odor gradients. Change in the olfactory stimulus in an environment may also cause the remapping of place cells. Vestibular inputs Stimuli from the vestibular system, such as rotations, can cause changes in place cells firing. After receiving vestibular input some place cells may remap to align with this input, though not all cells will remap and are more reliant on visual cues. Bilateral lesions of the vestibular system in patients may