Fig. 2. Summary of responsesto full turn rotation in RS neurons of compensated UL-animals, tested in light. (Ai,Aii) Number of active neurons as a function of the roll angle. This value was calculated as the number of neurons activated in each angular step in each of the animals, and then averaged over all six animals. (Bi,Bii) Average discharge frequency of neurons as a function of roll angle. This value was calculated as the number of spikes per second generated by each neuron in each step and then averaged over all active neurons in the group (N=31 and 30 for Bi and Bii, respectively). The 0° angle corresponds to the dorsal-side-up orientation of the lamprey. The angular zones where the ipsilateral (i) or contralateral (co) labyrinth was facing downward are indicated. Rotation was performed towards the contralateral labyrinth in turn a, and towards the ipsilateral one in turn b. Each step of rotation was divided into three intervals, and responses were calculated separately for each interval (see inset and legend in Fig. 1). In each of the steps, the dynamic response (activity during rotation) is shown by a black bar, the early and late static responses are shown by two successive shaded bars. Values are means ± S.E.M.