Regarding Compass Response Functions For Modeling Path Integration: Comment on "Evolving a Neural Model of Insect Path Integration"

Recently, Haferlach, Wessnitzer, Mangan, and Webb (2007) reported on the production of a novel neural model of the animal behavior known as path integration, a navigation process requiring a compass and an odometer. Here, we comment on comparisons that their paper makes with our earlier work (Vickerstaff & Di Paolo, 2005) where we also evolved a neural model of path integration. The authors make prominent mention of the similarity of their compass sensors to the known properties of the polarization-sensitive (POL) neurons found in insects. They give the impression that their compass response function, expressed as a dot-product equation (Haferlach et al., 2007, p. 274, equation 1; see below), has a closer similarity to POL neurons than does the cosine function we employed for our earlier model. In fact, this is not the case. An examination of the equation shows that it simplifies to exactly the same function as the compass response function used in our paper: