L-/M-cone opponency in visual evoked potentials of human cortex

Abstract

L and M cones send their signals to the cortex using two chromatic (parvocellular and blue-yellow koniocellular) and one luminance (magnocellular) pathways. These pathways contain ON and OFF subpathways that respond to excitation increments and decrements respectively. Here, we report on visually evoked potentials (VEP) recordings that reflect L- and M-cone driven increment (LI and MI) and decrement (LD and MD) activity. VEP recordings were performed on 12 trichromats and four dichromats (two protanopes and two deuteranopes). We found that the responses to LI strongly resembled those to MD, and that LD and MI responses were very similar. Moreover, the lack of a photoreceptor type (L or M) in the dichromats led to a dominance of the ON pathway of the remaining photoreceptor type. These results provide electrophysiological evidence that antagonistic L/M signal processing, already present in the retina and the lateral geniculate nucleus (LGN), is also observed at the visual cortex. These data are in agreement with results from human psychophysics where MI stimuli lead to a perceived brightness decrease whereas LI stimuli resulted in perceived brightness increases. VEP recording is a noninvasive tool that can be easily and painlessly applied. We propose that the technique may provide information in the diagnosis of color vision deficiencies.

Melanopsin- and L-cone–induced pupil constriction is inhibited by S- and M-cones in humans

“…Recently, L- and M-cone opponent processing has been demonstrated to affect perceived brightness ( 7 ), the flicker ERG ( 8 , 9 ), and VEPs at occipital scalp locations ( 10 ). In all these parameters, selective increments of L-cone illuminance are encoded as brightness increments, whereas M-cone increments are encoded as brightness decrements.…”

“…This method has recently been used to show that selective decrements in M-cone illuminance are paradoxically perceived as brightness increments ( 7 ). M-cone square-wave modulations furthermore produce electroretinogram (ERG) traces that are in opposite phase with traces resulting from L-cone (or L+M-cone) modulations ( 8 , 9 ), which has also been shown in visually evoked potentials (VEPs) recorded at occipital scalp locations ( 10 ). Thus, at different levels of visual processing, M-cone increments are perceived as brightness decrements, whereas L-cone increments and L+M increments are perceived as brightness increments.…”

Analysis of Color-Specific Visual Processing Speed Differences in Division 1 College Football Players

“…Color vision loss and demyelinating disorders such as optic neuritis have been linked with retinal axonal loss visible in OCT imaging 9,14 and to increased error scores and N-wave latencies in VEP waveforms. [15][16][17][18][19] The players' baseline OCT scans, however, revealed that retina, optic nerve head, and ganglion cell complex anatomy are within normal, healthy limits (data not shown and Bixenmann et al 9 ). This suggests that the players' red/green differences are due to optic nerve or retinal dysfunction.…”

“…While cortical processing is essential for the perception of color, it may not be essential for physiological VEP response. 15,16 Because our players have significant differences in their VEP responses, upper-level visual cortex is not involved but rather simple processing or dysfunction in the lateral geniculate nucleus (LGN) may be responsible for observed differences between red and green. We cannot completely rule out upperlevel involvement, though, because color perception involves multiple areas across a hierarchy of regions interacting with each other in a complex, recursive manner.…”

“…We cannot completely rule out upperlevel involvement, though, because color perception involves multiple areas across a hierarchy of regions interacting with each other in a complex, recursive manner. 15 The neural generators of N75 and P100 are in the primary visual cortex, and the two components are physiologically distinct. 17,18,20,21 Furthermore, L/M cone signal processing already present in the retina and LGN is also observed at the visual cortex and a lack of either photoreceptor types led to a dominance of the ON pathways of the remaining photoreceptor type.…”