Monocular and binocular response properties of cells in the striate-recipient zone of the cat's lateral posterior-pulvinar complex

Abstract

1. We have studied response properties of single cells in the striate-recipient zone of the cat's lateral posterior-pulvinar (LP-P) complex. This zone is in the lateral section of the lateral posterior nucleus (LP1). Our purpose was to determine basic response characteristics of these cells and to investigate the possibility that the LP-P complex is a center of integration that is dominated by input from visual cortex. 2. The majority (72%) of cells in the striate-recipient zone respond to drifting sinusoidal gratings with unmodulated discharge. 3. Cells in the LP1 are selective to the orientation of gratings, and tuning functions have a mean bandwidth of 31 degrees. More than one-half of these units are direction-selective. The preferred orientation and the tuning widths for the two eyes are generally well matched. However, a few cells exhibited the interesting property of opposite preferred directions for the two eyes. Orientation tuning for a small group of cells was different for the mean discharge and first harmonic components, suggesting a convergence from different inputs to these cells. 4. Two-thirds of LP1 cells are tuned to low spatial frequencies (less than 0.5 c/deg). The tuning is broad with a mean bandwidth of 2.2 octaves. The remaining one-third of the units are low-pass because they show no attenuation of their responses to low spatial frequencies. Both eyes exhibit the same spatial frequency preference and the same spatial frequency tuning. There is a high correlation between spatial frequency and orientation selectivities. 5. All cells tested are tuned for temporal frequency with a sharp attenuation for low frequencies. The optimal values range between 4 and 8 Hz, and the mean bandwidth is 2.2 octaves. 6. Cells in LP1 are mostly binocular. When monocular, cells are almost always contralaterally driven. Dichoptic presentation of gratings reveals the presence of strong binocular interaction. In almost all cases, these interactions are phase specific. The cell's discharge is facilitated at particular phases and inhibited at phases 180 degrees away. These binocular interactions are orientation dependent. 7. Twenty-five percent of the cells with phase-specific binocular facilitation appear to be monocular when each eye is tested separately. For three cells, we observed a non-phase-specific inhibitory effect of the silent eye. 8. Our findings indicate that LP1 cells form a relatively homogeneous group, suggesting a high degree of integration of multiple cortical inputs.(ABSTRACT TRUNCATED AT 400 WORDS)