Directional Encoding in the Subiculum

Positional firing ratemaps for a subiculum ‘axis-tuned’ neuron as the animal traversed multiple routes within a complex set of interconnected pathways. The path network was rotated 90 degrees to determine whether firing patterns were spatially organized by the reference frame of the recording room (not shown) or the reference frame of the path network.  To the right are polar firing rate plots that describe the firing rate of the same neuron according to the head orientation of the animal relative to the recording room. Under both the normal (upper plots) and rotated (lower plots) configurations of the path network, the neuron fires whenever the animal travels east OR west, thus exhibiting specificity to movement along the east/west axis. Such ‘axis-tuning’ is organized relative to the space of the larger environment (the recording room) since the positional firing rate map changes upon rotation but the polar firing rate map does not.  Neurons such as these effectively encode the possible directions of travel associated with any given track location as well as the orientations of all pathways relative to the environment.