An explainable artificial intelligence approach to spatial navigation based on hippocampal circuitry

Learning to navigate a complex environment is not a difficult task for a mammal. For example, finding
the correct way to exit a maze following a sequence of cues, does not need a long training session. Just
a single or a few runs through a new environment is, in most cases, sufficient to learn an exit path
starting from anywhere in the maze. This ability is in striking contrast with the well-known difficulty
that any deep learning algorithm has in learning a trajectory through a sequence of objects. Being
able to learn an arbitrarily long sequence of objects to reach a specific place could take, in general,
prohibitively long training sessions. This is a clear indication that current artificial intelligence methods
are essentially unable to capture the way in which a real brain implements a cognitive function. In
previous work, we have proposed a proof-of-principle model demonstrating how, using hippocampal
circuitry, it is possible to learn an arbitrary sequence of known objects in a single trial. We called
this model SLT (Single Learning Trial). In the current work, we extend this model, which we will call
e-STL, to introduce the capability of navigating a classic four-arms maze to learn, in a single trial,
the correct path to reach an exit ignoring dead ends. We show the conditions under which the e-
SLT network, including cells coding for places, head-direction, and objects, can robustly and efficiently
implement a fundamental cognitive function. The results shed light on the possible circuit organization
and operation of the hippocampus and may represent the building block of a new generation of
artificial intelligence algorithms for spatial navigation.