Each spike in LGMD faithfully triggers a spike in DCMD at frequencies up to 400 Hz. We found that for a wide range of sizes and velocities, the mean firing rate of DCMD in response to such stimuli was well described by the product of the angular velocity of the object edge multiplied by an exponential function of the angular size subtended by the object on the eye. This functional fit predicts that the peak firing rate of DCMD should occur a fixed time after such an approaching object has reached a fixed angular size on the eye, in agreement with electrophysiological and behavioral experiments. We have started to investigate this hypothesis and its biophysical implementation by intracellularly recording the activity of LGMD in response to looming stimuli. Branch p is thought to collect feedforward inhibitory inputs from neurons sensitive to wide-field OFF and ON stimuli.
Arrows indicate the direction of information flow.
Figure 2 Location of LGMD within the lobula of the locust, and its pattern of activity in response to an approaching visual stimulus.