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Dimensionality and Dynamics in the Behavior of C. elegans

Figure 6

Thermal responses, mode coupling and active steering.

(A) The distribution of phase velocities ρt(ω) in response to a brief thermal stimulus. Within one second, the distribution becomes highly concentrated near ω = 0, corresponding to the pause states identified in Figure 5. (B) Correlations between phase in the {a1,a2} plane and a3, . Shortly after the thermal impulse (t, t′>0) the modes develop a strong anti-correlation which is distinct from normal crawling. (C) Phase dependent thermal response. Worms stimulated during ventral head swings (−2≤φ≤−1) turn dorsally (red) while worms stimulated during dorsal head swings (2≤φ≤π) turn ventrally (blue). When phase is ignored there is no discernible response (grey). Solid lines denote averages while colored bands display standard deviation of the mean. (D) Worm “steering.” A thermal impulse conditioned on the instantaneous phase was delivered automatically and repeatedly, causing an orientation change in the worm's trajectory. In this example lasting 4 minutes, asynchronous impulses produced a time-averaged orientation change 〈〉 = 0.01 rad/s (black), impulses at positive phase produced a trajectory with 〈〉 = 0.10 rad/s (blue), and impulses at negative phase produced 〈〉 = –0.12 rad/s (red). This trajectory response is consistent with the mode correlations seen in Figure 6C. We found 13 out of 20 worms produced statistically different orientation changes under stimulated and non-simulated conditions while only 1 out of 20 worms responded in the same fashion when the phase was randomized (p<0.01, Fisher exact test).

Figure 6