Results

We made extracellular recordings from 113 neurons (38 simple, 75 complex) in the primary visual cortex of 13 macaque monkeys. We characterized each cell with drifting sine wave gratings before testing with dynamic, translational Glass patterns. Neurons were included if they showed orientation tuning to grating stimuli, but no other effort was made to exclude neurons from study with Glass patterns. Not all of the experiments described herein were performed on every cell. In our population of cells, the distribution of orientation bandwidths (mean $=$ 64.5$^\circ$, standard deviation $=$ 25.9$^\circ$) and spatial frequency peak (mean $=$ 2.1 c/deg, standard deviation $=$ 1.2 c/deg) and bandwidth (mean $=$ 2.2 octaves, standard deviation $=$ 0.7) were similar to those found by other investigators at the eccentricities of our recorded cells (DeValois et al., 1982; Foster et al., 1985) and to the larger population of neurons recorded in our laboratory for other experiments.

To provide a framework for interpreting the neuronal responses to Glass patterns, we begin by describing theoretical responses of oriented filters, designed to represent V1 receptive fields, to these stimuli. The intuition gained from this exercise will guide the subsequent data analysis.