Meeting Abstract

53.4  Thursday, Jan. 6  The role of vision in coordinating forelimb muscle activity patterns during toad landing GILLIS, Gary B*; TIERNEY, Catherine; Mount Holyoke College; Mount Holyoke College ggillis@mtholyoke.edu

Unlike many anurans, cane toads (Bufo marinus) are exemplary at landing, using their forelimbs after a hop to balance the body for extended periods as the hindlimbs are rocked into contact with the ground. Recent investigations of antagonistic muscles acting at the elbow demonstrated that both the timing and intensity of pre-landing electromyographic (EMG) activity are tuned to hop distance. Longer hops lead to more intense pre-landing EMG activity, and in elbow extensors the onset of activity occurs at a nearly fixed interval before landing, regardless of the length of the hop. Sensory feedback of some kind seems necessary for such flexible and tuned muscle recruitment patterns. To test the importance of vision in mediating pre-landing forelimb muscle activity we used high-speed video and simultaneous electromyographic recordings of the elbow extending anconeus muscle during toad hopping under four conditions: 1) control, level hops, 2) elevated hops from an 11 cm platform, 3) blinded, level hops and 4) blinded, elevated hops. The blinded condition was achieved using an opaque latex mask. Elevated hops led to more intense pre-landing muscle recruitment than level hops of similar distance, suggesting that toads predicted greater impact forces when hopping off a platform. When animals were blinded they no longer exhibited predictable, distance-dependent variation in recruitment intensity or timing in the anconeus. These data indicate that vision is a critical form of sensory feedback for tuning forelimb muscle activity in relation to landing in toads.