Place Cells' Role in the Hippocampus

Place Cells' Role in the Hippocampus

 Place cells play a role in spatial detection. Each cell caters to a specific area, typically a square, and fires within it. This essay will explore two research projects that studied place cells. Brian Sweiss conducted a mouse maze test and measured place cell activation during salient events. On the other hand, Marcus K. Benna and Stefano Fusi studied their implications in memory regarding altering the stability of decoding. This analysis discusses the similarities and differences between the two studies.

Benna and Fusi attempted to determine the possibility of creating correlation-based place cell activation within episodic memory. Place cells are limited by their variance and alterations in synaptic weight. They theorized if the memories are compressed prior to being processed by the hippocampus, it may strengthen the correlation between spatial processing and episodic memory. Furthermore, autoencoders’ role in memory suggested the usage of a sparse autoencoder model to build sparse compressions. 

Sparse compressions are formed in three stages: sensory input, modification, and storing. Sensory input registers the stimuli and forward-feeds it, improving plasticity. Subsequently, it increased memory capacity. Modification is the continuous compression of the memory prior to storage. Place cells were found in the modification and storing stage. Compression allows cells to emerge and activate based on a position in the environment. Interestingly, the sensory input develops receptive fields serving as suitable storage based on the nature in which the cell is activated. The diminishing of lack of correlation is impossible as the nature of plasticity is altered by external experiences. This correlation between both hippocampal spatial mapping and episodic memory generated stability to allow for the decoding process to occur. 

Sweiss’s work on decoding place cells during the mouse maze test lacked application of this research. The mouse was starved and food was provided within four corners of the maze. The amount of time spent in one area, and the true time spent was measured. “True time spent” refers to the duration the mouse spent in one area when not engaging in time wasting behavior or idle. This was done by dividing out the trajectory of the place cells causing localized locations to define. He found an illusionary passing of time prior to the division. This depicted an inaccurate representation of which corners were most engaged with. 

Unfortunately, the mouse’s movement disrupted the decoding. Prior to disruption, the division occurred and the decoded location of the mouse was highly precise and accurate. Movement constituted high error. The unstable nature of the decoding suggests sparse autoencoders are not being utilized within Sweiss’s memory mechanism. The unstable nature of the decoding consequently deviates the location of the decoder proportionally to the extent the mouse moved. After a moment, the new decoded location would form and the loop occurs once more. 

Applying sparse autoencoders, the mouse would register the map through sensory processing. Subsequently, the compression of the stimuli may alter the mouse’s travel through the maze. Once stored, the receptive fields assist in forming a correlation between the spatial recognition and episodic memory. Thus, it generates a stable application of decoding and may prevent high decoding location error during movement. 

References

• Benna, Marcus K., and Stefano Fusi. “Place Cells May Simply Be Memory Cells: Memory Compression Leads to Spatial Tuning and History Dependence.” Proceedings of the National Academy of Sciences of the United States of America, vol. 118, no. 51, 2021, pp. 1–12. JSTOR, https://www.jstor.org/stable/27117566. Accessed 27 Apr. 2025.

• Brain Sweiss “Tools, analysis, & approaches in decision neuroscience” Neuroscience Seminar, Loyola University Chicago