Perceptual Deficits and the Activity of the Color-Opponent and Broad-Band Pathways at Isoluminance

Logothetis, NK; Schiller, PH; Charles, E; Hurlbert, Anya

doi:10.1126/science.2294602

Cited by 195 publications

(71 citation statements)

References 19 publications

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“…These two areas were always simultaneously active, but responses of both areas were about 30 ms delayed for the equiluminant stimuli. This delay may correspond to slower conduction of signals through the wavelength-sensitive parvocellular than the broad-band magnocellular retinocortical pathway (35) or to a weaker retinocortical signal at equiluminance (36). At longer latencies, the cortical dynamics was different for each stimulus.…”

Section: Resultsmentioning

confidence: 99%

Coinciding early activation of the human primary visual cortex and anteromedial cuneus

Vanni¹,

Tanskanen²,

Seppä³

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

201

127

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Proper understanding of processes underlying visual perception requires information on the activation order of distinct brain areas. We measured dynamics of cortical signals with magnetoencephalography while human subjects viewed stimuli at four visual quadrants. The signals were analyzed with minimum current estimates at the individual and group level. Activation emerged 55-70 ms after stimulus onset both in the primary posterior visual areas and in the anteromedial part of the cuneus. Other cortical areas were active after this initial dual activation. Comparison of data between species suggests that the anteromedial cuneus either comprises a homologue of the monkey area V6 or is an area unique to humans. Our results show that visual stimuli activate two cortical areas right from the beginning of the cortical response. The anteromedial cuneus has the temporal position needed to interact with the primary visual cortex V1 and thereby to modify information transferred via V1 to extrastriate cortices.A natomy of connections between primate visual cortices suggests a hierarchical organization of signal processing (1). However, the order of processes at different functional areas cannot be directly deduced from the anatomical hierarchy without relevant timing information. In monkeys, several areas become active immediately after the primary visual cortex (V1), while another set of areas is active at clearly longer latencies (2, 3). The areas showing early responses, such as V5͞middle temporal area (MT), medial superior temporal area, and frontal eye field, are specialized in analyzing dynamical visual information and in visuomotor transformation (for reviews, see refs. 4 and 5). The areas with longer latencies, such as V4, are sensitive to object form and color and participate in object recognition (6, 7). The dissimilarities in activation latencies and functional properties of these areas suggest diversity in the type and amount of necessary input and preprocessing before activation. Given the differences between monkey and human visual cortices (for a review, see ref. 8), we aimed to explore the dynamics and distribution of early cortical activation in humans. Neuromagnetic signals were recorded while the subjects viewed pattern reversal or luminance stimuli at the four visual quadrants. The signals were analyzed with minimum current estimates (MCEs), which require minimal human intervention for determining the location and orientation of the cortical currents (9). The individual three-dimensional estimates were aligned with a nonlinear transformation according to individual brain shapes (10, 11), and both the individual and group average MCEs were compared with the existing maps of human visual cortices (12-16). Materials and MethodsSubjects and Stimuli. We studied five female and five male subjects (mean age 27 years, range 20-42 years). The stimuli were generated with a Macintosh computer and presented with a dataprojector (VistaPro, Electrohome Ltd., Ontario, Canada) on a back projection screen, with viewing d...

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Section: Resultsmentioning

confidence: 99%

Coinciding early activation of the human primary visual cortex and anteromedial cuneus

Vanni¹,

Tanskanen²,

Seppä³

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

201

127

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“…Second, a*b* represents colors along two color-opponent dimensions: a* extends from green to red and b* from blue to yellow. It is generally agreed that the visual system processes color along such oppositions (see Logothetis, Schiller, Charles, & Hurlbert, 1989). The second interesting property of L*a*b* is that it is close to perceptual uniformity.…”

Section: Methodological Considerationsmentioning

confidence: 99%

Diagnostic Colors Mediate Scene Recognition

Oliva

Schyns

2000

Cognitive Psychology

372

277

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“…Both psychophysical and neurophysiological experiments have shown that the motion stream pools information from many orientations that are moving in the same direction to generate precise estimates of a moving object's direction and speed [19][20][21][27][28][29] . Lesions of the form system also show that, on its own, the motion system can make only coarse depth estimates 30,31 . Thus it seems reasonable that the orientationally tuned form system generates emergent representations of forms with precise depth estimates, whereas the directionally tuned motion system -on its own -can generate only coarse depth estimates.…”

Section: Complementary Form and Motion Interactionsmentioning

confidence: 99%