A re-interpretation of the experimental data of Shinder and Taube \"Three-dimensional Tuning of Head Direction Cells in Rats\", Journal of Neurophysiology 121(1), 2019.

In a recent study, Shinder and Taube (2019) concluded that head direction cells in the anterior thalamus of rats are tuned to one-dimensional (1D, yaw-only) motion exclusively, in contrast to recent findings in bats (Finkelstein et al. 2015), mice (Angelaki et al. 2016; Cham et al. 2017; Laurens et al. 2017), and rats (Page et al. 2017). Here we re-interpret the authors experimental results using model comparison and demonstrate that, contrary to their conclusions, their data actually supports the dual-axis rule (Page et al. 2017) and tilted azimuth model (Laurens and Angelaki 2018), where head direction cells use gravity to integrate 3D rotation signals about all cardinal axes of the head. We further show that this study is inconclusive regarding the presence of vertical orientation tuning; i.e. whether head direction cells encode 3D orientation in the horizontal and vertical planes conjunctively. Using model simulations, we demonstrate that, even if 3D tuning existed, the experimental protocol and data analyses used by Shinder and Taube (2019) would not have revealed it. We conclude that the actual experimental data of Shinder and Taube (2019) are compatible with the 3D properties of head direction cells discovered by other groups, yet incorrect conclusions were reached because of incomplete and qualitative analyses.