Curvature population coding for complex shapes in human vision

Habak, Claudine; Wilkinson, Frances; Zakher, Bernadette; Wilson, Hugh R.

doi:10.1016/j.visres.2004.06.019

Cited by 70 publications

(63 citation statements)

References 34 publications

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“…Although our study did not test other stimuli related to local-global pattern processing, previous psychophysical studies have shown similar effects on localglobal pattern processing using different stimuli (e.g., radial frequency patterns; Habak, Wilkinson, Zakher, & Wilson, 2004;Wilkinson, Wilson, & Habak, 1998). Brain imaging studies on local-global tasks using other types of stimuli (Navon figures (Navon, 1977), parametrically degraded objects, etc.)…”

Section: Discussionmentioning

confidence: 83%

A Dorsal Visual Route Necessary for Global Form Perception: Evidence from Neuropsychological fMRI

Lestou

Lam

Humphreys

et al. 2014

Journal of Cognitive Neuroscience

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Hierarchical models of visual processing assume that global pattern recognition is contingent on the progressive integration of local elements across larger spatial regions, operating from early through intermediate to higher-level cortical regions. Here, we present results from neuropsychological fMRI that refute such models. We report two patients, one with lesions to intermediate ventral regions and the other with damage around the intraparietal sulcus (IPS). The patient with ventral damage showed normal behavioral and BOLD responses to global Glass patterns. The patient with IPS damage was impaired in discriminating global patterns and showed a lack of significant responses to these patterns in intermediate visual regions spared by the lesion. However, this patient did show BOLD activity to translational patterns, where local element relations are important. These results suggest that activation of intermediate ventral regions is not necessary to code global patterns; instead global patterns are coded in a heterarchical fashion. High-level regions of dorsal cortex are necessary to generate global pattern coding in intermediate ventral regions; in contrast, local integration processes are not sufficient.

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Section: Discussionmentioning

confidence: 83%

A Dorsal Visual Route Necessary for Global Form Perception: Evidence from Neuropsychological fMRI

Lestou

Lam

Humphreys

et al. 2014

Journal of Cognitive Neuroscience

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“…Circles and RF patterns (Habak et al, 2004; Wilkinson et al, 1998) . Circles are the particular case of an RF pattern (see Figure 2) where the amplitude of modulation of the radius is zero.…”

Section: Methodsmentioning

confidence: 99%

Detecting global form: separate processes required for Glass and radial frequency patterns

Badcock¹,

Almeida²,

Dickinson³

2013

Front. Comput. Neurosci.

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Global processing of form information has been studied extensively using both Glass and radial frequency (RF) patterns. Models, with common early stages, have been proposed for the detection of properties of both pattern types but human performance has not been examined to determine whether the two pattern types interact in the manner this would suggest. The experiments here investigated whether low RF patterns and concentric Glass patterns, which are thought to tap the same level of processing in form-vision, are detected by a common mechanism. Six observers participated in two series of masking experiments. First: sensitivity to the presence of either coherent structure, or contour deformation, was assessed. The computational model predicted that detection of one pattern would be masked by the other. Second: a further experiment examined position coding. The model predicted that localizing the center of form in a Glass pattern would be affected by the presence of an RF pattern: sensitivity to a change of location should be reduced and the apparent location should be drawn toward the center of the masking pattern. However, the results observed in all experiments were inconsistent with the interaction predicted by the models, suggesting that separate neural mechanisms for global processing of signal are required to process these two patterns, and also indicating that the models need to be altered to preclude the interactions that were predicted but not obtained.

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“…The high sensitivity for discriminating amplitude modulations of radial frequency patterns provides strong evidence that shape perception is driven by a global mechanism that combines information across the circumference of the contour Habak, Wilkinson, & Wilson, 2006;Hess et al, 1999;Jeffrey, Wang, & Birch, 2002;Loffler et al, 2003;Schmidtmann et al, 2012;Wilkinson et al, 1998). This global pooling mechanism appears to be restricted to shapes with low radial frequency modulation (Schmidtmann et al, 2012;Wilkinson et al, 1998) and to be tuned to a specific type of shape and amplitude of radial modulations (Bell, Dickinson, & Badcock, 2008;Bell & Kingdom, 2009;Habak, Wilkinson, Zakher, & Wilson, 2004;Schmidtmann et al, 2012Schmidtmann et al, , 2013. Furthermore, several studies have shown that the inputs to the global pooling stage are themselves outputs of intermediate stage curvature detectors that integrate local orientation information to encode curvature and inflection points along the contour (Bell et al, , 2010(Bell et al, , 2011.…”

Section: Discussionmentioning

confidence: 99%

Aging and the integration of orientation and position in shape perception

2014

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The current experiments examined the effect of healthy aging on the integration of orientation and position information in shape perception. Following Day and Loffler (2009), conflicting contours were created by sampling the orientations of one shape (e.g., a rounded pentagon) with Gabors, and positioning them on the circumference of a different shape (e.g., a circle). In Experiment 1, subjects judged whether the conflicting contour looked more circular than a rounded pentagon of varying amplitude, which allowed us to estimate the perceived shape of the conflicting contour. The relative amount of position and orientation information was manipulated by varying the number of Gabors comprising the target contour. Orientation information dominated the percept for contours sampled with 15-40 elements, producing a strong shape illusion, but position information determined the shape with denser sampling. The magnitude of this orientation dominance effect was equal in younger and older subjects across all sampling levels. In Experiment 2, subjects discriminated five contours that differed in orientation and/or position information. Both groups showed poor discrimination between conflicting contours and their perceptually equivalent radial frequency patterns, confirming the main finding of Experiment 1. In addition, older subjects showed worse discrimination between two noncircular radial frequency patterns than younger subjects. In sum, integration of orientation and position information in shape perception is preserved with aging; however, older adults are less able to make fine shape discriminations between noncircular sampled contours.

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Curvature population coding for complex shapes in human vision

Cited by 70 publications

References 34 publications

A Dorsal Visual Route Necessary for Global Form Perception: Evidence from Neuropsychological fMRI

A Dorsal Visual Route Necessary for Global Form Perception: Evidence from Neuropsychological fMRI

Detecting global form: separate processes required for Glass and radial frequency patterns

Aging and the integration of orientation and position in shape perception

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