Orientation bias of cat dorsal lateral geniculate cells: directional analysis of the major axis of the receptive field centre.

The receptive field centre of cells in the dorsal lateral geniculate nucleus were mapped as iso-sensitivity contours. 94% of the cells were found to have elliptical centres, and analysis of the major axis orientation showed that 29% and 59% of units had their major axis oriented within +/- 20 degrees of the radial and horizontal directions, respectively. The data for Y-cells showed a greater dispersion in their orientation biases (R = 0.57) compared with X-cells (R = 0.79). Nevertheless, a horizontal orientation bias was found in both classes of cells: 47% of Y-cells and 73% of X-cells. In addition, an examination of the major axis orientations was undertaken for cells with receptive field centres located along the radial direction of 35 degrees below the horizontal meridian. In this 35 degree Radial Group a horizontal bias was also confirmed. Analysis of the dispersion of major axis orientations with eccentricity from the area centralis showed a statistically significant decrease in scatter and, hence, indicated an increase in the horizontal bias with eccentricity.