Shading and texture: separate information channels with a common adaptation mechanism?

Georgeson, Mark A.; Schofield, Andrew J.

doi:10.1163/15685680260433913

Cited by 29 publications

(42 citation statements)

References 26 publications

(36 reference statements)

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“…Lu & Sperling, 1995;Scott-Samuel & Georgeson, 1999;Wilson, Ferrera, & Yo, 1992). Our studies of first-and second-order grating detection, and perceptual aftereffects, revealed a similar picture of separate encoding pathways responding to the spatial structure of luminance modulation (LM) and contrast modulation (CM) (Georgeson & Schofield, 2002;Schofield & Georgeson, 1999). In this paper we focus specifically on contrast modulation (CM) as a second-order property (see Fig.…”

Section: Introductionmentioning

confidence: 82%

Binocular functional architecture for detection of contrast-modulated gratings

Georgeson

Schofield

2016

Vision Research

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Running head: Binocular summation for contrast modulationCorresponding author: m.a.georgeson@aston.ac.uk Highlights• Detection of contrast modulation (CM) shows full binocular summation • Similarity or dissimilarity of the carriers has no effect on summation • Out-of-phase envelopes don't cancel, but are a bit less detectable than monocular ones • Model: monocular envelope extraction, then contrast-weighted binocular summation • Monocular CM outputs in parallel with binocular ones; largest response wins AbstractCombination of signals from the two eyes is the gateway to stereo vision. To gain insight into binocular signal processing, we studied binocular summation for luminance-modulated gratings (L or LM) and contrast-modulated gratings (CM). We measured 2AFC detection thresholds for a signal grating (0.75 c/deg, 216msec) shown to one eye, both eyes, or both eyes out-of-phase. For LM and CM, the carrier noise was in both eyes, even when the signal was monocular. Mean binocular thresholds for luminance gratings (L) were 5.4dB better than monocular thresholdsclose to perfect linear summation (6dB). For LM and CM the binocular advantage was again 5-6dB, even when the carrier noise was uncorrelated, anti-correlated, or at orthogonal orientations in the two eyes. Binocular combination for CM probably arises from summation of envelope responses, and not from summation of these conflicting carrier patterns. Antiphase signals produced no binocular advantage, but thresholds were about 1-3dB higher than monocular ones. This is not consistent with simple linear summation, which should give complete cancellation and unmeasurably high thresholds. We propose a three-channel model in which noisy monocular responses to the envelope are binocularly combined in a contrast-weighted sum, but also remain separately available to perception via a max operator. Vision selects the largest of the three responses. With in-phase gratings the binocular channel dominates, but antiphase gratings cancel in the binocular channel and the monocular channels mediate detection. The small antiphase disadvantage might be explained by a subtle influence of background responses on binocular and monocular detection.3

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Section: Introductionmentioning

confidence: 82%

Binocular functional architecture for detection of contrast-modulated gratings

Georgeson

Schofield

2016

Vision Research

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“…One plausible explanation for such a finding (in the context of the above research) would be that the discrimination task probes a later processing stage, where first-and second-order pathways have been re-integrated. This idea is further supported by a cross-over of the tilt after-effect between first-and second-order cues (Georgeson and Schofield, 2002), and the finding that the tilt illusion transfers between first-and second-order cues (Dakin et al, 1999;.…”

Section: Independence Of First and Second-order Visionmentioning

confidence: 76%

“…The cross-over of after-effects between cues has been taken to indicate the integrated detection of those cues. However, in the light of apparently conflicting detection and adaptation results (such as those of Georgeson and Schofield, 2002) it seems likely that aftereffects are more indicative of cue integration after detection has taken place, rather than at the detection stage.…”

Section: Adaptationmentioning

confidence: 97%

“…ScottSamuel and used this lack of integration to show that the early (pre-cortical) non-linearity found by He and MacLeod (1998) cannot account for the detection of moving CM gratings, so long as they are relatively slow moving or based on a low contrast carrier. Further, peri-threshold, static first-(LM) and second-order (CM) cues do not facilitate each others' detection (Georgeson and Schofield, 1998;Nishida et al, 1997;Schofield and Georgeson, 1999), there is neither linear summation nor amplitude summation between static LM and CM cues (Schofield and Georgeson, 1999), and it is possible to discriminate between LM and CM, and mixtures of the two, at threshold (Georgeson and Schofield, 2002).…”

Section: Independence Of First and Second-order Visionmentioning

confidence: 99%

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Transfer of tilt after-effects between second-order cues

Cruickshank

Schofield²

2005

Spatial Vis

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Second-order cues are visual stimuli that are detectable by human observers, without eliciting a peak in Fourier energy that corresponds to their perceptual properties. The most commonly studied exemplars of second-order cues are those defined by modulation of local contrast (CM). It is widely accepted that such cues are initially detected separately from first-order, luminance modulated (LM), cues. However, after-effects have been shown to transfer between first- and second-order cues (LM and CM, respectively). This suggests the existence of a late link in the mechanisms that subserve their processing. To extend the investigation of the mechanisms for processing second-order cues we consider cues defined by modulations in local orientation (OM). Using a tilt-after-effect (TAE) paradigm, we found partial transfer of adaptation between LM and OM cues, confirming the presence of a link between first and second-order cues. Furthermore, we found a partial transfer of TAE between OM and CM cues. These results suggest that, at or before the site of adaptation, information from all visual cues is combined. However, as transfer of adaptation is below 100% in all cases, this is only a partial integration of information.

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“…The present findings of phase-dependent combination are not incompatible with either of these schemes. Models based on human psychophysics have involved separate early detection of the two kinds of stimuli, with subsequent interactions at a later stage (Georgeson and Schofield, 2002) As a baseline reference, it is worth considering that a cortical neuron might just linearly add the separately computed responses to LM and CM stimuli. In the case of a simple-type cell, the modulated responses to the LM and CM stimuli would sum maximally at one phase and cancel out at the opposite phase, giving a PDI approaching unity.…”

Section: Neural Mechanismsmentioning

confidence: 99%

Phase-Dependent Interactions in Visual Cortex to Combinations of First- and Second-Order Stimuli

2016

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A fundamental task of the visual system is to extract figure-ground boundaries between objects, which are often defined, not only by differences in luminance, but also by "second-order" contrast or texture differences. Responses of cortical neurons to both first-and second-order patterns have been studied extensively, but only for responses to either type of stimulus in isolation. Here, we examined responses of visual cortex neurons to the spatial relationship between superimposed periodic luminance modulation (LM) and contrast modulation (CM) stimuli, the contrasts of which were adjusted to give equated responses when presented alone. Extracellular single-unit recordings were made in area 18 of the cat, the neurons of which show responses to CM and LM stimuli very similar to those in primate area V2 (Li et al., 2014). Most neurons showed a significant dependence on the relative phase of the combined LM and CM patterns, with a clear overall optimal response when they were approximately phase aligned. The degree of this phase preference, and the contributions of suppressive and/or facilitatory interactions, varied considerably from one neuron to another. Such phase-dependent and phaseinvariant responses were evident in both simple-and complex-type cells. These results place important constraints on any future model of the underlying neural circuitry for second-order responses. The diversity in the degree of phase dependence between LM and CM stimuli that we observed could help to disambiguate different kinds of boundaries in natural scenes.

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Shading and texture: separate information channels with a common adaptation mechanism?

Cited by 29 publications

References 26 publications

Binocular functional architecture for detection of contrast-modulated gratings

Binocular functional architecture for detection of contrast-modulated gratings

Transfer of tilt after-effects between second-order cues

Phase-Dependent Interactions in Visual Cortex to Combinations of First- and Second-Order Stimuli

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