Encoding of 2D self-centered plans and world-centered positions in the rat frontal orienting field

Abstract

The neural mechanisms of motor planning have been extensively studied in rodents. Frontal cortical areas seem to encode upcoming choice, but limitations of typical tasks make it challenging to determine whether activity represents a planned movement direction in a self-centered reference frame or a goal position in a world-centered reference frame. Here, we trained rats to make delayed visually-guided orienting movements to six different directions, with four different target positions for each direction, which allowed us to disentangle position versus direction tuning in neural activity. We recorded single unit activity from the rat frontal orienting field (FOF) in secondary motor cortex, a region involved in planning orienting movements. We found neurons in the FOF that were tuned for specific directions of movement and also neurons that fired while animals were at specific port positions. Interestingly, after the visual cue onset, movement direction tuning emerged earlier than target position tuning. At the level of individual neurons, the current head position modulated the planned movement direction as a gain field. These results suggest the FOF participates not only in the motoric processes of sensorimotor behavior, which could happen strictly in egocentric coordinates, but in more complex aspects like reference frame transformation or maintaining a stable model of the world during movements.