Neural activity in human V1 correlates with dynamic lightness induction

Abstract

Two circles of the same luminance will appear to have different lightness if one is embedded in a dark and another in a light surround. Known as simultaneous lightness contrast, this phenomenon demonstrates that our perceptions are not simply a reflection of the input from the retina but instead an inference about surface properties. Using functional magnetic resonance imaging (fMRI), we investigated whether the response in primary visual cortex (V1) more closely follows retinal information or perception. We induced illusory lightness changes of a disk by temporally modulating the surround luminance. In addition, we varied the luminance of the disk in order to disambiguate the fMRI response to perceived lightness modulation from the response to luminance contrast at the border of the disk. Perceptually, the disk with the lowest luminance (and the highest border contrast) had little or no induced lightness change while the disk with luminance equal to the time-averaged luminance of the surround (and the lowest border contrast) had the strongest induced lightness change. We found that neural activity in V1 strongly correlates with perceived lightness changes of the disk, suggesting significant involvement of early visual areas in processing surface lightness information.

Dynamic brightness induction in V1: Analyzing simulated and empirically acquired fMRI data in a “common brain space” framework

“…In contrast, activity related to neon color spreading has been established in monkey V1 (Murakami et al, 1997;Komatsu et al, 2000) and human V1 (Sasaki and Watanabe, 2004). Also for brightness induction, which is the type of brightness illusion used in the present study, correlates of perceived brightness have been observed in V1 (Pereverzeva and Murray, 2008;van de Ven et al, in preparation;but see Cornelissen et al, 2006) in V1. Together, these findings suggest that, at least for brightness induction, both physical as well as perceived brightness-related surface information is represented in V1.…”

“…The most convincing evidence comes from neurophysiological recordings in the cat (Rossi and Paradiso, 1999;Rossi et al, 1996), which showed that in about 10% of area 17 neurons with their receptive fields (RFs) placed within the probing region, activity was modulated in anti-phase to inducer luminance (i.e., activity correlated to perceived brightness changes). Two human studies using functional magnetic resonance imaging (fMRI) have reported data that appear in agreement with the neurophysiological data (Pereverzeva and Murray, 2008; van de Ven et al, in preparation), whereas a third fMRI study (Cornelissen et al, 2006) did not observe a brightness induction correlate in early visual cortex.The model we propose contains three main parts (Fig. 1).…”

Prior knowledge of illumination for 3D perception in the human brain

“…We propose that the representation of prior knowledge about the illumination direction early in the visual system is important, as light affects the contrast of an image (32); that is, a basic visual property that needs to be processed before more interesting image understanding takes place. Other types of visual prior knowledge do not necessarily have to be represented in early visual areas.…”

Neuromagnetic Correlates of Perceived Brightness in Human Visual Cortex

“…However, in the present study, perceived brightness was partly confounded with physical luminance. Clearly, we need further study to separate perceived brightness from physical luminance (e.g., Pereverzeva & Murray, 2008). It is well-known that perceived brightness depends not only on luminance but also on luminance distribution in the surrounding visual field.…”