Effects of wavelength on the timing and laminar distribution of illuminance-evoked activity in macaque V1

Abstract

Responses to full-field colored flashes (red, blue, and green) were compared with those to illuminancematched white flashes in area V1, optic radiations, and the lateral geniculate nucleus of two alert macaques. Laminar profiles of visual evoked potentials (VEPs), current source density, and multiunit activity were obtained using multicontact electrodes capable of sampling from all layers of cortex or lateral geniculate nucleus, simultaneously. In striate cortex, stimulation with colored flash enhanced transmembrane current flow dramatically in both layer 4c and the supragranular laminae. Stimulation with red evoked the largest enhancement in every electrode penetration. The mean peak amplitudes of current sinks evoked by red were 203% and 537% of those evoked by white light in layer 4c and the supragranular laminae, respectively. Color effects in VI were preceded by an initial epoch of wavelength-insensitive activity. In layer 4c, the red effect reached significance, on average, at 47 ms, or ≈24 ms after the onset of transmembrane current flow. In the supragranular layers, the red effect reached significance, on average, at 55 ms, or ≈14 ms after the onset of current flow. Recordings from optic radiations in the white matter below V1 and from lateral geniculate nucleus showed no significant difference in the responses to color and illuminance-matched white light. Enhancement of supragranular current flow with color stimulation increased the contribution of these laminae to the generation of the surface VHP. Comparison of the surface VHP wave forms evoked by white and color stimuli may, therefore, help to differentiate the responses of the granular and supragranular laminae.

Parvocellular and Magnocellular Contributions to the Initial Generators of the Visual Evoked Potential: High-Density Electrical Mapping of the “C1” Component

“…Subsequent studies suggested that N40 receives relatively little contribution from extrastriate visual areas (Givre et al 1994;Schroeder et al 1998). Use of wavelength limited stimulation, which causes a bias of effective activation toward the P system, causes a dramatic increase in both the amplitude and the latency of the N40, so that its peak latency shifts to between 50 and 60 ms poststimulus (Givre et al 1995). 2 These effects parallel those found with isoluminant stimulation in the present study, insofar as the latency of the C1 increases substantially, although the amplitude does not increase.…”

“…This issue was investigated in earlier experiments that entailed recordings in awake behaving monkeys using linear array multi-electrodes that could record simultaneously from all of the layers of a visual cortical region (Schroeder et al 1991(Schroeder et al , 1997(Schroeder et al , 1998Givre et al 1995). These experiments identified a surface-negative component, termed N40 because it peaks at 40 ms latency under high intensity conditions.…”

On determining the intracranial sources of visual evoked potentials from scalp topography: A reply to Kelly et al. (this issue)

“…Three of the cited publications did not address striate vs. extrastriate latencies. Givre et al (1995) demonstrated that LGN latencies are shorter than V1 latencies, but did not address timing differences between cortical regions. Maunsell and Gibson (1992) were concerned with changes in V1 responses following LGN lesions and did not record from any other area.…”

“…As evidence for this claim they cite a series of macaque studies (Chen et al, 2007;Givre et al, 1994;Givre et al, 1995;Maunsell and Gibson, 1992;Nowak et al, 1999;Raiguel et al, 1989;Schmolesky et al, 1998;Schroeder et al, 1998Schroeder et al, , 2004 stating that all of these studies "… agree on the presence of significant latency offsets across ascending stages." However, these intracranial data from non-human primate also provide examples of simultaneous onset latencies across the visual hierarchy.…”

The dynamics of the spread of selective visual attention

“…For instance, Givre et al (27) have shown color sensitivity in early visual cortices (V1 and V2) with large differences in the response to equiluminant red and white stimuli seen at a latency Ͻ50 ms. Although this finding was in macaques, one would predict color effects in humans well within the first 100 ms of processing (e.g., ref.…”