Saccade-induced activity of dorsal lateral geniculate nucleus X- and Y-cells during pharmacological inactivation of the cat pretectum

The influence of neurons projecting from the prerectal nuclear complex to the ipsilateral dorsal lateral geniculate nucleus (LGNd) was investigated in awake cats. Responses from relay cells in the A-laminae of the LGNd were extracellularly recorded and analyzed during saccadic eye movements and visual stimulation in association with reversible inactivation of the ipsilateral pretectum with the GABA agonist, muscimol. Prerectal inactivation (PTI) resulted in spontaneous nystagmic eye movements in the dark with slow phases directed away from the injected side. In the control situation, all Y-cells and about two thirds of X-cells were excited during saccades or saccade-like visual stimulation but one third of X-cel:ls were inhibited. During PTI all recorded X-cells were inhibited, either during saccades or saccade-like visual stimulation. The PTI-associated inhibition was stronger than in inhibited X-cells in control experiments only during saccades but not during stimulation with a moving pattern while the eyes were stationary. In Y-cells a reduction in the response peak width at half-height was seen during PTI, again only during saccades but not during stimulation with a moving pattern. These results indicate that during saccades the pretecto-geniculate pathway has a stronger influence on X LGNd relay cells than on Y-cells. The findings are discussed in terms of saccadic suppression and postsaccadic facilitation.