Brain stem modulation of spatial receptive field properties of single cells in the dorsal lateral geniculate nucleus of the cat.

1. We studied the effect of electrical stimulation of the peribrachial region (PBR) in the brain stem on the visual response of single cells in the dorsal lateral geniculate nucleus (dLGN) to a light slit presented in a series of positions across the receptive field. The response was plotted against slit position, giving a spatial receptive field profile. 2. PBR stimulation markedly increased the visual response. In the middle of the receptive field center, the absolute response increase was considerably larger than in the peripheral parts of the receptive field or than the increase of spontaneous activity. The PBR stimulation also led to a small increase of the diameter of the receptive field center. 3. The maximum steepness of the receptive field profile for the dLGN cells increased by PBR stimulation. We suggest that the visual resolution in the dLGN cell is directly related to this maximal slope of the receptive field profile rather than to the width of the receptive field center. This would mean that increased input from the PBR, as presumably occurs during arousal, increases the visual resolution of the dLGN cells. 4. For some of the cells we could record S-potentials (slow potentials) in addition to action potentials. This allowed us to directly compared the receptive field center size of a dLGN cell with that of its retinal input. For these cells, the center size was considerably reduced by the geniculate relay. During PBR stimulation, the center size of these cells also increased slightly, but even in this condition it was reduced compared with the retinal input. The maximal slope of the receptive field profile in the dLGN cell during PBR stimulation was larger than for the retinal input. 5. We also examined the effect of ionophoretical application of acetylcholine (ACh) and bicuculline methchloride (BMC) on the spatial receptive field properties of dLGN cells. The effects of ACh were similar to those of PBR stimulation. Application of BMC, on the other hand, made the receptive field profile more similar to that of retinal ganglion cells.