Fig. 11. Temporal relationship between the neuronal and the behavioral response to the looming stimulus. Peristimulus time histograms show (A) the mean (± s.e.m.) running speed of the animals and (B,C) the mean (± s.e.m.) spike rate of M1 (B) and M2 (C) neurons, calculated over 100-ms bins and plotted against time during the object approach. (D) Angular size and (E) speed of expansion of the looming object. Arrowheads mark the beginning of the stimulus expansion; the dotted line marks the moment at which the escape behavior was initiated; the broken line indicates the moment when the stimulus reached its maximum expansion and velocity; the vertical solid line marks the point in time at which collision would have occurred; arrows in B and C point to the neuronal activity 120 ms before the first movement of the animals. Behavioral data are from 14 crabs (one trial per crab). Neurophysiological data are from 19 trials recorded from a total of 10 M1 neurons and 18 trials from 13 M2 neurons, each neuron from a different animal (i.e. no more than 2 records per crab were included).