FIGURE 4.

V3 activated contralateral extensor motor activity is correlated with optical stimulation intensity. Representative traces of locomotor activity induced by drug (5-HT 8 μM, NMDA 8 μM) in Sim1^Cre/+; Ai32 cord at low (A), medium (B), and high (C) light intensity. Blue bar on the top of each trace and shaded blue area represent the optical stimulation period. The brightness of blue shaded area indicates light intensity. (D1,D2,E) Dependence of ENG characteristics on light intensity during biased optical stimulation. Average of burst duration difference of L2 (D1) and L5 (D2) between before and during optical stimulation under low, medium and high stimulation intensity during drug-induced locomotor-like activity (low n = 11, medium n = 13, high n = 9). ^∗ Indicates 0.01 < P < 0.05, ^∗∗ indicates 0.001 < P < 0.01. ^† indicates 0.01 < P < 0.05, ^†††† indicates P < 0.0001. Linear regression slope is orange for ipsilateral L5 and light green for contralateral L5 and red for ipsilateral L2 and blue for contralateral L2. (E) Step cycle period difference between ipsilateral and contralateral L5 under low, medium and high stimulation intensity during drug-induced locomotor-like activity (low n = 11, medium n = 13, high n = 9). ^†††† indicates P < 0.0001, ^∗∗ indicates 0.001 < P < 0.01. Slope of contralateral L5 burst duration and step cycle difference are significantly non-zero.