A Continuous-Attractor Model of Flip Cell Phenomena

Abstract

This paper is devoted to the problem of understanding mechanisms underlying behavioral correlates of head direction (HD) cells in the mammalian retrosplenial cortex. HD cells become active when an animal, such as rat, is facing a particular direction in its environment. The robustness of this phenomenon is usually attributed to attractor dynamics of the HD cell system. According to the standard view, a ring attractor exists in some abstract space, with HD cells symbolically allocated on the ring, so that any natural state of the system corresponds to a bump of activity on the ring. In apparent contradiction with this standard model are recent discoveries of so-called “flip cells”, that constitute a minority of HD cells and can either rotate their directional tuning by 180° when an animal transitions between two environments, or interpolate between discordant cues, or demonstrate a bimodal tuning curve. Here a continuous attractor network model is described that is capable of a qualitative reproduction of these phenomena, while being consistent with the ring attractor hypothesis. The model assumes that there is more than one attractor ring in the HD system. Results of the concept-proof simulation suggest a correction to the standard view of how the internal sense of direction is formed in the rat brain.