The effects of a luminanace-modulated background on the grating-evoked cortical potential in the cat

Abstract

Averaged grating-evoked cortical potentials were recorded from area 17 of awake cats. Peak latency of early components of the visual-evoked potential (VEP) response to stimulus onset increased as a function of spatial frequency, while amplitude tended to be largest at intermediate spatial frequencies. Latency increased and amplitude generally decreased to lower spatial-frequency stimuli (<0.25 cycle/deg) in the presence of a uniform flickering field (UFF). The UFF had a relatively small or opposite effect on peak latency and amplitude for higher spatial-frequency stimuli (>0.50 cycle/deg). The VEP response to stimulus offset was present only at low spatial frequencies and was virtually eliminated by the presence of the UFF. The effects were similar whether the target and UFF background were simultaneously presented or briefly separated; however, the UFF had no effect when the two were spatially separated. The effects of the UFF background on VEP onset response increased with increasing temporal frequency from 2-8 Hz; offset responses were affected similarly at all temporal frequencies. These effects are similar to those observed in humans and suggest that two spatio-temporally tuned mechanisms contribute to the early VEP response. In the cat, the mechanisms seem to correspond to X and Y cells in the dorsal lateral geniculate nucleus.

The effects of luminance and chromatic background flicker on the human visual evoked potential

“…Asynchronous flicker of the background increased the latency of the VEP only for stimuli with spatial frequencies below 1 cpd. This result confirms those reported by Baro and Lehmkuhle (1990). However, unlike the results of Baro and Lehmkuhle, asynchronous flicker reduced pattern-onset N1-P2 amplitude at all spatial frequencies used in this study by 19%-53% depending on subject.…”

“…It has been suggested that the pattern-reversal VEP is produced by a motion-detection pathway (Spekreijse et al, 1985;Berninger et al, 1989) and that it is similar to the contrast offset response (Estevez & Spekreijse, 1974). Baro and Lehmkuhle (1990) found that 10-Hz flicker abolished the pattern-offset response for all spatial frequencies, whereas flicker increased the latency and reduced the amplitude of the pattern-onset component only for low spatial frequency stimuli. If the patternreversal response is a motion response, with more in common with the pattern-offset response than the pattern-onset response, then it should be abolished by peripheral flicker.…”

“…In this experiment, we compare the effects of peripheral flicker on the pattern-appearance and pattern-reversal VEP. We postulate that flicker should have a more dramatic effect on the pattern-reversal response if this response is primarily a response to apparent motion (Spekreijse et al, 1985;Berninger et al, 1989) and if the effect of peripheral flicker is to saturate the m-pathway, yielding a p-pathway dominated response (Baro & Lehmkuhle, 1990).…”

“…Berninger et al, 1989;Baro & Lehmkuhle, 1990;Nelson & Seiple, 1992;Probst et al, 1993). In general, the argument has been made that the effects of stimulus chromaticity (Berninger et al, 1989), contrast (Nelson & Seiple, 1992), motion (Probst et al, 1993), or peripheral flicker (Baro & Lehmkuhle, 1990) on the VEP are analogous to those seen in m-or p-pathways, and therefore judicious selection of these parameters will result in a VEP mediated by a single pathway. However, the complexity of the origins of the VEP (Celesia, 1986;Maier et al, 1987;Ossenblok & Spekreijse, 1991;Schroeder etal., 1991) makes it unlikely that any stimulus manipulation will isolate a single pathway.…”

The effects of uniform field flicker and blurring on the global precedence effect

“…time, visible persistence, and evoked potentials, the global precedence effect should be influenced by manipulations that are known to influence those phenomena. For instance, it has been shown that a uniform field flicker (UFF) mask increases reaction times , evoked potential latencies, as well as contrast detection thresholds for low but not high spatial frequencies (Baro & Lehmkuhle, 1989Breitmeyer, Levi, & Harwerth, 1981). To the extent that the global precedence effect also reflects the differential processing of low and high spatial frequencies, its magnitude should be reduced in the presence of a UFF mask .…”