Discrimination Between Movements of Eye and Object by Visual Interneurones of Crickets

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Abstract
One large neurone on each side of the cervical and thoracic ventral nerve cord of crickets responds to object motion anywhere in the visual field of the ipsilateral compound eye, but not to the forced or voluntary movement of the eye itself. This discrimination between self-movement and object-movement is accomplished by an inhibitory mechanism mediated by the same eye. Inhibition must be present because a potent moving stimulus becomes ineffective if presented during a forced eye movement. Its visual origin is demonstrated in two ways : (a) abolishing all known mechano-sensory feedback does not disrupt the mechanism, but (b) alteration of visual conditions does so in a predictable way. Sweeping the eye past a complex visual environment suppresses the neurone’s response to a concurrently or subsequently presented moving target, whereas the same movement past a simplified or homogeneous environment produces little or no inhibition. Responses to eye movement itself are greatly enhanced in appropriately simplified visual fields, reinforcing the conclusion that the inhibition preventing response in complex fields is of visual origin. Suggestive evidence for an additional inhibitory mechanism associated with voluntary movement is presented.