Facilitation of inhibition in the compound lateral eye of limulus.

In the compound eye of Limulus the inhibitory effect of a burst of impulses from one group of ommatidia on the response of a neighboring ommatidium is greater when that burst is preceded by another burst of impulses. This facilitation of inhibition decays slowly, with a time constant of several seconds. Facilitation of inhibition accumulates as the number of impulses in the first burst increases, but there is a maximum that it cannot exceed. The facilitation is localized; one group of ommatidia does not facilitate the inhibition exerted by another group. The mechanism of this facilitation may be similar to that which has been postulated for facilitation of excitatory influences at the neuromuscular junction.