22. 02. 2021
An exciting review discussing the response of hippocampal pyramidal cells to non-spatial stimuli was just published by Dr. Julija Krupic in collaboration with Prof. John O'Keefe. 
 
Read the full review here: https://doi.org/10.1152/physrev.00014.2020

There are two major theories of hippocampal function. One, the cognitive map theory, argues that the hippocampus acts as the spatial cognitive map of the brain with the generation of spatial representations (i.e. the maps of environments) being its prime functional correlate. Other non-spatial representations such as simple sensory stimuli (e.g. visual, auditory etc), objects, conspecifics, goals and even time are encoded in addition to the main correlate, turning the hippocampal place cells into feature-in-place cells. The second major theory, called the relational theory, instead argues that the hippocampus acts as a more general associative memory system, which encodes all types of features with space being only one of many possible variables and standing on an equal basis with the other non-spatial ones. In this paper, we reviewed the evidence for non-spatial representations in the hippocampal formation and argued that when tested in multiple locations, the hippocampal response to non-spatial stimuli is almost invariably dependent on the animal's location. Looked at collectively, the data provide strong support for the cognitive map theory. The encoding of temporal sequences may present the only non-spatial exception.