Superficial‐layer versus deep‐layer lateral entorhinal cortex: Coding of allocentric space, egocentric space, speed, boundaries, and corners

Abstract

Entorhinal cortex is the major gateway between the neocortex and the hippocampus and thus plays an essential role in subserving episodic memory and spatial navigation.It can be divided into the medial entorhinal cortex (MEC) and the lateral entorhinal cortex (LEC), which are commonly theorized to be critical for spatial (context) and non-spatial (content) inputs, respectively. Consistent with this theory, LEC neurons are found to carry little information about allocentric self-location, even in cue-rich environments, but they exhibit egocentric spatial information about external items in the environment. The superficial and deep layers of LEC are believed to mediate the input to and output from the hippocampus, respectively. As earlier studies mainly examined the spatial firing properties of superficial-layer LEC neurons, here we characterized the deep-layer LEC neurons and made direct comparisons with their superficial counterparts in single unit recordings from behaving rats. Because deep-layer LEC cells received inputs from hippocampal regions, which have strong selectivity for self-location, we hypothesized that deep-layer LEC neurons would be more informative about allocentric position than superficial-layer LEC neurons. We found that deep-layer LEC cells showed only slightly more allocentric spatial information and higher spatial consistency than superficial-layer LEC cells. Egocentric coding properties were comparable between these two subregions. In addition, LEC neurons demonstrated preferential firing at lower speeds, as well as at the boundary or corners of the environment. These results suggest that allocentric spatial outputs from the

Hippocampal spatial view cells, place cells, and concept cells: View representations

“…When egocentric encoding is found, in rodents, for example, by "egocentric boundary cells" (Alexander et al, 2020(Alexander et al, , 2023Wang et al, 2018Wang et al, , 2020Wang et al, , 2023, the most parsimonious account of its utility is in obstacle avoidance (a running rat with poor vision using vibrissae and olfactory cues does not want to run into a boundary), for maintaining distances from other individuals as in flying flocks of birds or bats, and so forth. In conclusion, hippocampal and parahippocampal cortex spatial view cells found in primates including humans may be key to understanding the functions of the hippocampal system in memory and navigation in humans (Georges-François et al, 1999;Robertson et al, 1998;Rolls, 1999Rolls, , 2021aRolls, , 2021bRolls, , 2021cRolls, , 2023aRolls, , 2023bRolls et al, 1998;Rolls, Robertson, & Georges-François, 1997); these cells go beyond rodent place cells, and indeed they compute something different and are used in different ways.…”

“…In Section 2.2, the role of facing location in the encoding of these allocentric neurons is considered (Mao et al, 2021;Zhu et al, 2023). In Section 2.3, evidence for some egocentric encoding in the hippocampal system of rodents (Alexander et al, 2023;Wang et al, 2023) is discussed. In Section 3, the case is made that the issue of the coordinate framework for spatial representations, allocentric versus egocentric, is separate from the interesting issue of view-dependent spatial representations, which relates to which side a scene is viewed from by an observer (Wirth, 2023).…”

“…Egocentric view representations are shown by some rodent hippocampus-related neurons. For example, neurons in the retrosplenial cortex show egocentric coding of the position of boundaries in relation to the rodent (Alexander et al, 2023), and neurons in the rodent lateral entorhinal cortex represent the angular bearing of objects and boundaries in an egocentric frame of reference (Wang et al, 2023). Neurons with egocentric encoding of this type might be suitable for obstacle avoidance (rather than remembering where objects are in the world, or for allocentric navigation).…”

Using multi‐task experiments to test principles of hippocampal function

“…Parallel to the distinction of whether the hippocampus mainly represents one's current location or remote locations, another key open question is whether the hippocampus and surrounding medial temporal lobe regions represent spatial information in allocentric or egocentric coordinates, or both (Alexander et al, 2020(Alexander et al, , 2023Kunz et al, 2021;LaChance et al, 2019;LaChance & Taube, 2023;Wang et al, 2018Wang et al, , 2023. Allocentric neural codes represent spatial locations and directions relative to the external environment, whereas egocentric representations encode them relative to the navigating subject (Bicanski & Burgess, 2018, 2020Burgess, 2006).…”

“…In a study of monkeys performing a context-object association task in a virtual environment, a considerable number of view cells were found in the hippocampus that activated whenever the monkey viewed a left or right side corridor at either end of a central corridor, thus potentially representing particular views in an egocentric rather than an allocentric coordinate framework (Corrigan et al, 2023). In another study, egocentric tuning was found in deep layers of the lateral entorhinal cortex in rats (Wang et al, 2023), extending previous work demonstrating egocentric tuning in the superficial layers of the lateral entorhinal cortex (Wang et al, 2018) and in the retrosplenial cortex (Alexander et al, 2020).…”