Boundary cell

Boundary cells (also known as border cells or boundary vector cells) are neurons found in the hippocampal formation that respond to the presence of an environmental boundary at a particular distance and direction from an animal. The existence of cells with these firing characteristics were first predicted on the basis of properties of place cells. Boundary cells were subsequently discovered in several regions of the hippocampal formation: the subiculum, presubiculum and entorhinal cortex.

Left: Firing rate map, one of 5 colours in locational bin indicates spatially-smoothed firing rate in that bin (autoscaled to firing rate peak, dark blue: 0-20%; light blue: 20-40%; green: 40-60%; yellow: 60-80%; red: 80-100%. The maximum firing rate is 14.2 Hz). Right: path taken by rat is shown in black, locations where spikes were recorded indicated by green squares.]]

O'Keefe and Burgess{{Cite journal

Separate studies emerging from different research groups identified cells with these characteristics in the subiculum,{{Cite journal | doi-access = free

While the hippocampal formation largely encodes information regarding the environmental layout through an allocentric (world-oriented) reference frame, organisms must first perceive this information in an egocentric (self-oriented) reference frame before undergoing intentional movement. Egocentric boundary cells (EBCs) located within the dorsomedial striatum are attributed to this self-oriented encoding of environmental boundaries. Testing with mice has revealed evidence of neurons located within the dorsomedial striatum that each have consistent activation when the mouse is at a certain distance and angle from nearby boundaries. Different EBCs have varying firing patterns, suggesting that different neurons within the dorsomedial striatum are specialized to respond to their own unique combination of distance and orientation relative to boundaries regardless of the animal’s familiarity with the environment. Current research suggests that there exists a strong connection between the allocentric and egocentric representations of environments: both the static environmental map and the dynamic positional details are needed for intentional movement.

In medial entorhinal cortex border/boundary cells comprise about 10% of local population, being intermingled with grid cells and head direction cells. During development MEC border cells (and HD cells but not grid cells) show adult-like firing fields as soon as rats are able to freely explore their environment at around 16-18 days old. This suggests HD and border cells, rather than grid cells, provide the first critical spatial input to hippocampal place cells.{{Cite journal | doi-access = free