Supplementary Figure 3: Unilateral Purkinje cell activation induced motor learning

In a separate cohort of animals to that shown in Figure 1, training was done with stimulation of floccular Purkinje cells in only one hemisphere during the contraversiveor ipsiversivephase of the vestibular stimulus. (a) Schematic of the unilateral optogenetic training paradigms for modifying the VOR. A sinusoidal vestibular stimulus was used for training and testing (black trace, angular velocity of the head). Unilateral optogenetic stimulation of Purkinje cells was paired with the contraversive phase of the vestibular stimulus (red, light on when the head was rotating away from the side of Purkinje cell stimulation) or the ipsiversive phase of the vestibular stimulus (blue, light on when the head was rotating toward the side of stimulation). (b) Motor learning induced by Purkinje cell activation depended on the training condition (F_{(2, 36)} = 3.513, P = 0.04, two-way repeated measures ANOVA). Purkinje cell activation paired with contraversive vestibular stimulation (red circles) was different than the vestibular-alone control (black open squares; *P = 0.025, Fisher test; n = 13 mice). The learning induced by the unilateral training paradigm was approximately half that induced by bilateral training (compare with Figure 1b, red circles). The effects on the behavior were associative, since the timing of the Purkinje cell activity relative to the vestibular stimulus was critical to the induction of VOR learning (Purkinje cell contra vs. ipsistim, *P = 0.030, Fisher test; n = 13 mice).There was no significant difference between training with Purkinje cell stimulation during the ipsiversive phase of the vestibular stimulus (blue squares) and the vestibular-alone control (open black squares; P = 0.94, Fisher test; n = 13 mice). This is consistent with the previous finding that electrical stimulation of the flocculus induced no learning when paired with stimulation of the ipsilateral vestibular nerve to mimic an ipsiversive vestibular stimulus (Babalian & Vidal, 2000, J Neurophysiol 84: 2514). Thus, neither the Purkinje cell activation itself, nor any calcium influx or non-associative plasticity it may have caused were sufficient to alter the behavior. Mean ± s.e.m.