The shift-effect enhances X- and suppresses Y-type response characteristics of cat retinal ganglion cells.

Responses to a number of stimuli have been studied during the continuous movement of a "global" pattern covering a large part of the retina but excluding the receptive field of the ganglion cell under investigation. With remarkable consistency, the motion of the pattern induced a reinforcement of response properties usually associated with X-cells. In particular, the following responses characteristic of Y-cells were abolished or strongly reduced: (1) the response to simultaneous increment and decrement switching in a bipartite field in the receptive field center; (2) the "discrete" shift-effect, elicited by a jerk of the global pattern; and (3) the relative elevation of the mean discharge rate as a response to a fine drifting grating. Futhermore, responses to center illumination became sustained, and the ongoing discharge rose ("continuous shift-effect"). Y-type responses were most strongly affected, except for the sustained components of center responses which increased in a rather unpredictable way. The results strengthen the view that the shift-effect accounts for most of the functional differences between X- and Y-cells. Saturating the shift-effect mechanism by continuous stimulation is a tool by which the shift-effect components in Y-type responses can be largely removed so that essentially X-type responses are left. Possible neuronal pathways involved in the transmission of the resposes are discussed.