Summary 23The sense of direction is a vital computation, whose neural basis is considered to be carried out 24 by head-direction cells. One way to estimate head-direction is by integrating head angular-25 velocity over time. However, this process results in error accumulation resembling a random 26 walk, proportional to √ , which constitutes a mark for a path integration process. In the present 27 study we analyzed previously recorded data to quantify the drift in head-direction cells of rat 28 pups before and after eye-opening. We found that in rat pups before eye-opening the drift 29 propagated as a random walk, while in rats after eye-opening the drift was lower. This suggests 30 that a path-integration process underlies the estimation of head-direction, such that before eye-