INHIBITORY INTERACTION IN THE RETINA 



281 



A 



.^^ 



iO 20 30 40 



Time- seconds 



Fig. 26. Plot of the time-course of the frequency of discharge of an ommatidium 

 suddenly illuminated together with several nearby receptors, showing oscillations 

 resulting from the time delay in the action of the mutual inhibitory influences. 



retinal illumination, and also respond to minute movements of a spot of light 

 or a shadow across their receptive fields (Hartline, 1940). Similarly, as the eye 

 itself moves — even minutely — neural responses occur. That minute motions 



Fig. 27. Oscillations in the output of one of a pair of interacting amplifiers 

 connected to "inhibit" one another through electrical delay circuits, to imitate 

 the receptor responses shown in Figs. 25 and 26. The amplifiers were "excited" 

 by a wave form imitating approximately the response (frequency of discharge) 

 of an ommatidium when suddenly illuminated and showing the usual sensory 

 adaptation. Upper trace shows the response of just one amplifier excited alone; 

 lower trace the output of the same amplifier when interconnected through the 

 delay circuits with the second amplifier (similarly excited). 



