Interaction of receptive field responses and shift-effect in cat retinal and geniculate neurons.
Spike activity of single optic tract fibres and lateral geniculate cells of the lightly anaesthetized immobilized cat were recorded in response to short, small (local) test flashes into the receptive field center before, during and after rapid displacements of a remote, large (global) pattern. 2. The majority of retinal and geniculate neurons failed to produce algebraic summation of the excitatory shift-effect and an excitatory test response. 3. For many cells outside lamina A and A1 of the dorsal lateral geniculate body the test response was smaller than the control even though two excitatory responses were combined. 4. The resonses to displacements of a steady, local spot are weakly affected by simultaneous displacements of a global pattern if the local responses are strong; but if the latter are weak the global shift-effect dominates the response to a displacement of the total pattern. 5. Saccadic suppression may be explained by retinal and geniculate neurons functioning in two modes of local or global responses, both of which cannot be transmitted properly at the same time.