Spatial cognition is a field of neuroscience involving the understanding and comprehension of the spatial properties of objects and events that physically occur. This field encompasses all concepts regarding individual perceptions of space such as object orientation, spatial memory, and spatial orientation as well as the specialized topics they cover. One of these specialized topics that stem from spatial orientation is the concept of a cognitive spatial map. The cognitive spatial map is a hypothesis by which the brain builds a mental representation of a spatial environment in order to support memory and guide future action. Various cells occurring in the hippocampus play specific roles in cognitive spatial map formation including but not limited to place, grid, border, and head direction cells. The significance of these concepts being that, the cognitive spatial map could be the foundation to all mammalian understanding of navigating in a spatial environment.
One study that aimed to investigate this was “Space in the brain: how hippocampal formation supports spatial cognition” by Hartley et al. In the study the team aimed to explore the role of hippocampal formation and spatial cognition. The study looked at and collected previous research regarding various cells that form along with the hippocampus which encompass spatial cells and their subdivisions including place cells, head direction cells, grid cell, boundary cells, and other spatial cells. The team also looked at trends and relationships between these cells from other studies as well as how spatial understanding differs between humans and animals. The conclusion focused on how this study aids integrative neuroscience and as neuroscientific techniques continue to be refined more refined links will be made between these cells using techniques like optogenetics, optical imaging, and intracellular electrophisiology.
In order to incorporate and utilize these techniques into an experiment that measures the various hippocampal cells Dr. Yost and his research team conducted an experiment using a rat animal model. In the first part of Yost’s experiment, a 10-electrode array was placed into the rats’ hippocampus and varied hippocampal cell groups were measured while the rat walked around in a box. The results of this experiment showed that cell firing was dependent on location of the box. For example cell 1 would only fire in the bottom left corner of the box while cell 6 would only fire in the top right; this data then lead to a map with color coded regions of concentrated neuron firing showing that when creating a cognitive spatial map, spatial memory of certain locations is stored within specific cells. This hypothesis was tested further in another experiment conducted by the team. In which the 10-electrode array was applied to another mouse which was then made to walk through a thin elevated path that ended in a food sample as motivation. The results of this study showed similar results to the last experiment in which at specific segments of the path certain neuronal groups would fire showing that memory of space is stored in specific neuronal groups.
Similar to the Yost experiment, a study conducted by Broadbent et al. Aimed to measure how hippocampal integrity affected spatial memory and object recognition memory in rats. This was done using 92 Long-Evans male rats given varied lesions that encompassed differing percentages of hippocampal volume ranging from 5-100% total volume then tested on their spatial memory using a spatial memory hidden platform test and a novel object recognition (NOR) test. The results of testing showed that with a higher volume lesion, the rats were significantly slower in finding the hidden platform in testing. In the NOR test, rats with lesions ranging from 5-75% exhibited strong preference for the novel object, but the rats with lesions ranging from 75-100% showed no distinguishable preference for the novel object. These results showed that significant lesions above 30% of hippocampal volume severely impair spatial memory, while object recognition is only impaired with large lesions above 75% of hippocampal volume.
In investigating the hypothesis of a cognitive spatial map, it can be understood that the hippocampus plays an incredibly fundamental and key role in the formation of one. The Hartley and Yost studies investigate the specialized hippocampal cells that create spatial memory and as a result the cognitive spatial map, while the Broadbent experiment showed the behavioral results of hippocampal impairment and its effects on spatial memory. The hippocampus and cell it produces being place, grid, head direction, etc. are all major factors in the creation of a cognitive spatial map, and as research of spatial memory and cognition continues we can hope to see a more concrete answer to how the cognitive spatial map works.
Works Cited:
Broadbent, N. J., Squire, L. R., & Clark, R. E. (2004). Spatial memory, recognition memory, and the hippocampus. Proceedings of the National Academy of Sciences, 101(40), 14515–14520. https://doi.org/10.1073/pnas.0406344101
Epstein RA, Patai EZ, Julian JB, Spiers HJ. The cognitive map in humans: spatial navigation and beyond. Nat Neurosci. 2017 Oct 26;20(11):1504-1513. doi: 10.1038/nn.4656. PMID: 29073650; PMCID: PMC6028313.
Hartley T, Lever C, Burgess N, O’Keefe J. 2014 Space in the brain: how thehippocampal formation supports spatialcognition. Phil. Trans. R. Soc. B 369: 20120510. http://dx.doi.org/10.1098/rstb.2012.0510
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