The role of primary visual cortex (V1) in visual awareness

Lamme, Victor A. F.; Supèr, Hans; Landman, Rogier; Roelfsema, Pieter R.; Spekreijse, H.

doi:10.1016/s0042-6989(99)00243-6

Cited by 154 publications

(82 citation statements)

References 93 publications

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“…Thus, our results undermine the strong assertion ''that the firing of none of the neurons in V1 directly correlates with what we consciously see'' (16). Instead, our results are consistent with interactive models in which V1 constitutes an essential component in a recurrent circuit whose activation represents the neural signature of visual awareness (49)(50)(51).…”

Section: Discussioncontrasting

confidence: 71%

Strength of early visual adaptation depends on visual awareness

Blake

Tadin

Sobel

et al. 2006

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

170

143

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We measured visual-adaptation strength under variations in visual awareness by manipulating phenomenal invisibility of adapting stimuli using binocular rivalry and visual crowding. Results showed that the threshold-elevation aftereffect and the translational motion aftereffect were reduced substantially during binocular rivalry and crowding. Importantly, aftereffect reduction was correlated with the proportion of time that the adapting stimulus was removed from visual awareness. These findings indicate that the neural events that underlie both rivalry and crowding are inaugurated at an early stage of visual processing, because both the threshold-elevation aftereffect and translational motion aftereffect arise, at least in part, from adaptation at the earliest stages of cortical processing. Also, our findings make it necessary to reinterpret previous studies whose results were construed as psychophysical evidence against the direct role of neurons in the primary visual cortex in visual awareness. binocular rivalry ͉ crowding ͉ vision V isual adaptation has been dubbed the psychologist's microelectrode (1) because the resulting visual aftereffects presumably reveal response properties of neural mechanisms that are activated by adapting stimuli. Also, measuring visual adaptation under visual conditions that render the adapting stimulus invisible allows one to draw inferences about the neural concomitants of the conditions that produce stimulus invisibility. Specifically, a result showing a full-strength aftereffect that is generated by an invisible stimulus implies normal, unperturbed neural activation at the site of adaptation. This outcome implies that the neural correlates of the visual phenomenon that are used to render the adapting stimulus invisible lie beyond the neural mechanisms that are responsible for the aftereffect. This line of reasoning has been applied to the study of binocular rivalry and visual crowding, which are two extensively studied visual phenomena that are used to ''erase'' visual stimuli from awareness (2). The results have shown that full-strength pattern and motion aftereffects (MAEs) can be induced even when the high-contrast inducing stimuli were absent from awareness for a substantial portion of the adaptation period during binocular rivalry (3-7) and crowding (8, 9). Because adaptation producing these aftereffects includes neural events that presumably occur within cortical areas ranging from the primary visual cortex (V1) (10-12) to the middle-temporal visual area (12, 13), these psychophysical findings have reasonably been interpreted as evidence for the high-level origin of both rivalry (14, 15) and crowding (8,14). Also, these same results were regarded by some workers as key psychophysical evidence against the direct involvement of V1 neurons in conscious visual awareness (16)(17)(18)(19). Measurement of full-strength aftereffects under conditions of rivalry and crowding shows a clear dissociation between the abolished perceptual awareness of the adapting stimulus and unperturbe...

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Section: Discussioncontrasting

confidence: 71%

Strength of early visual adaptation depends on visual awareness

Blake

Tadin

Sobel

et al. 2006

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

170

143

View full text Add to dashboard Cite

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“…These views on reentrant processing are not necessarily contradicting, as visual awareness might simply be the way surface segregation and related processes express themselves phenomenologically. The view that reentrant activity in the visual cortex correlates with visual awareness is now supported by converging evidence from monkey physiology (e.g., Lamme, Super, Landman, Roelfsema, & Spekreijse, 2000), EEG (the present study), transcranial magnetic stimulation (Pascual-Leone & Walsh, 2001), and fMRI (e.g., Haynes et al, 2005).…”

Section: Discussionsupporting

confidence: 65%

Masking Disrupts Reentrant Processing in Human Visual Cortex

Fahrenfort

Scholte

Lamme

2007

Journal of Cognitive Neuroscience

300

305

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In masking, a stimulus is rendered invisible through the presentation of a second stimulus shortly after the first. Over the years, authors have typically explained masking by postulating some early disruption process. In these feedforward-type explanations, the mask somehow “catches up” with the target stimulus, disrupting its processing either through lateral or interchannel inhibition. However, studies from recent years indicate that visual perception—and most notably visual awareness itself—may depend strongly on cortico-cortical feedback connections from higher to lower visual areas. This has led some researchers to propose that masking derives its effectiveness from selectively interrupting these reentrant processes. In this experiment, we used electroencephalogram measurements to determine what happens in the human visual cortex during detection of a texture-defined square under nonmasked (seen) and masked (unseen) conditions. Electro-encephalogram derivatives that are typically associated with reentrant processing turn out to be absent in the masked condition. Moreover, extrastriate visual areas are still activated early on by both seen and unseen stimuli, as shown by scalp surface Laplacian current source-density maps. This conclusively shows that feedforward processing is preserved, even when subject performance is at chance as determined by objective measures. From these results, we conclude that masking derives its effectiveness, at least partly, from disrupting reentrant processing, thereby interfering with the neural mechanisms of figure-ground segmentation and visual awareness itself.

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“…In contradiction to various theoretical predictions of different models of visual masking (Enns, 2002;Lamme, Super, Landman, Roelfsema, & Spekreijse, 2000;Purushothaman, Ogmen, & Bedell, 2000;Thompson & Schall, 1999;Francis, 1997;Breitmeyer & Ganz, 1976;Matin, 1975;Weisstein, Ozog, & Szoc, 1975;Kahneman, 1968;Weisstein, 1968), physiological recordings within the lateral geniculate nucleus of the thalamus (LGN) showed that responses to targets are inhibited by masks in both forward masking Bridgeman, 1975;Coenen & Eijkman, 1972;Schiller, 1968Schiller, , 1969 and backward masking conditions. However, these LGN physiology experiments did not rule out the possibility that the circuits mediating visual masking were primarily cortical, and that subcortical neurons were then modulated in their response through feedback mechanisms (Enns, 2002).…”

Section: Introductionmentioning

confidence: 75%

Dichoptic Visual Masking Reveals that Early Binocular Neurons Exhibit Weak Interocular Suppression: Implications for Binocular Vision and Visual Awareness

Macknik

Martínez-Conde

2004

Journal of Cognitive Neuroscience

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Abstract& Visual masking effects are illusions in which a target is rendered invisible by a mask, which can either overlap or not overlap the target spatially and/or temporally. These illusions provide a powerful tool to study visibility and consciousness, object grouping, brightness perception, and much more. As such, the physiological mechanisms underlying the perception of masking are critically important to our understanding of visibility. Several models that require cortical circuits have been proposed previously to explain the mysterious spatial and timing effects associated with visual masking. Here we describe single-unit physiological experiments from the awake monkey that show that visual masking occurs in at least two separate and independent circuits, one that is binocular and one that is monocular (possibly even subcortical), without feedback from higher-level visual brain areas. These and other results together fail to support models of masking that require circuits found only in the cortex, but support our proposed model that suggests that simple ubiquitous lateral inhibition may itself be the fundamental mechanism that explains visual masking across multiple levels in the brain. We also show that area V1 neurons are dichoptic in terms of excitation, but monoptic in terms of inhibition. That is, responses within area V1 binocular neurons reveal that excitation to monocular targets is inhibited strongly only by masks presented to the same eye, and not by masks presented to the opposite eye.

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The role of primary visual cortex (V1) in visual awareness

Cited by 154 publications

References 93 publications

Strength of early visual adaptation depends on visual awareness

Strength of early visual adaptation depends on visual awareness

Masking Disrupts Reentrant Processing in Human Visual Cortex

Dichoptic Visual Masking Reveals that Early Binocular Neurons Exhibit Weak Interocular Suppression: Implications for Binocular Vision and Visual Awareness

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