1. Responses of single units were recorded from Macaca fascicularis anesthetized with sufentanil citrate and with eyes immobilized with vecuronimum bromide as described [
2. Lennie P., Krauskopf J., Sclar G., J. Neurosci. 10, 649 (1990);
3. Lankheet M. J. M., Lennie P., Krauskopf J., Vis. Neurosci. 15, 37 (1998);
4. ]. Each neuron was stimulated with an achromatic sinusoidal grating of optimal size and spatial frequency displayed on the screen of a calibrated NEC P750 monitor controlled by a Macintosh computer. The screen subtended between 4.9° (170 pixels/°) and 14.5° (57 pixels/°) depending on viewing distance; its space-time average luminance was 54 cd/m 2 and the display was refreshed at 75 Hz. Action potentials from isolated single units were recorded with 0.1-ms accuracy. All receptive fields lay within 3° of the center of the fovea. Simple and complex cells were distinguished by their responses to moving gratings.
5. A rapidly decaying response to a step stimulus implies low sensitivity to low temporal frequencies of stimulation and this is found [