The Spatiotemporal Dynamics of Illusory Contour Processing: Combined High-Density Electrical Mapping, Source Analysis, and Functional Magnetic Resonance Imaging

The Cognitive Neurophysiology Laboratory, Program in Cognitive Neuroscience and Schizophrenia, Nathan S. Kline Institute for Psychiatric Research, Orangeburg, New York 10962, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 07/2002; 22(12):5055-73.
Source: PubMed


Because environmental information is often suboptimal, visual perception must frequently rely on the brain's reconstruction of contours absent from retinal images. Illusory contour (IC) stimuli have been used to investigate these "filling-in" processes. Intracranial recordings and neuroimaging studies show IC sensitivity in lower-tier area V2, and to a lesser extent V1. Some interpret these data as evidence for feedforward processing of IC stimuli, beginning at lower-tier visual areas. On the basis of lesion, visual evoked potentials (VEP), and neuroimaging evidence, others contend that IC sensitivity is a later, higher-order process. Whether IC sensitivity seen in lower-tier areas indexes feedforward or feedback processing remains unresolved. In a series of experiments, we addressed the spatiotemporal dynamics of IC processing. Centrally presented IC stimuli resulted in early VEP modulation (88-100 msec) over lateral-occipital (LOC) scalp--the IC effect. The IC effect followed visual response onset by 40 msec. Scalp current density topographic mapping, source analysis, and functional magnetic resonance imaging results all localized the IC effect to bilateral LOC areas. We propose that IC sensitivity described in V2 and V1 may reflect predominantly feedback modulation from higher-tier LOC areas, where IC sensitivity first occurs. Two additional observations further support this proposal. The latency of the IC effect shifted dramatically later (approximately 120 msec) when stimuli were laterally presented, indicating that retinotopic position alters IC processing. Immediately preceding the IC effect, the VEP modulated with inducer eccentricity--the configuration effect. We interpret this to represent contributions from global stimulus parameters to scene analysis. In contrast to the IC effect, the topography of the configuration effect was restricted to central parieto-occipital scalp.

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    • "In addition, event-related potentials (ERPs) provide a complementary view of the temporal processing dynamics of illusory-figure processing and a means to investigate how pre-selective global shape integration influences subsequent attentional processing stages. ERPs in response to illusory figures start to differ in the time range of the posterior N1, which is typically enhanced for Kanizsa figures compared to local-level baseline configurations (e.g., Herrmann and Bosch, 2001; Murray, Foxe, Javitt, & Foxe, 2004; Proverbio and Zani, 2002; Senkowski, Röttger, Grimm, Foxe, & Herrmann, 2005; see Murray et al., 2002, for even earlier effects). In accordance with the imaging literature, the global-local N1 effect has been interpreted to reflect global shape processing in the LOC (He, Fan, Zhou, & Chen, 2004; Martinez, Ramanathan, Foxe, Javitt, & Hillyard, 2007; Murray, Imber, Javitt, & Foxe, 2006). "
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    ABSTRACT: Visual selection of illusory 'Kanizsa' figures, an assembly of local elements that induce the percept of a whole object, is facilitated relative to configurations composed of the same local elements that do not induce a global form - an instance of 'global precedence' in visual processing. Selective attention, i.e., the ability to focus on relevant and ignore irrelevant information, declines with increasing age; however, how this deficit affects selection of global vs. local configurations remains unknown. On this background, the present study examined for age-related differences in a global-local task requiring selection of either a 'global' Kanisza- or a 'local' non-Kanisza configuration (in the presence of the respectively other configuration) by analyzing event-related lateralizations (ERLs). Behaviorally, older participants showed a more pronounced global-precedence effect. Electrophysiologically, this effect was accompanied by an early (150-225ms) 'positivity posterior contralateral' (PPC), which was elicited for older, but not younger, participants, when the target was a non-Kanizsa configuration and the Kanizsa figure a distractor (rather than vice versa). In addition, timing differences in the subsequent (250-500ms) posterior contralateral negativity (PCN) indicated that attentional resources were allocated faster to Kanisza, as compared to non-Kanisza, targets in both age groups, while the allocation of spatial attention seemed to be generally delayed in older relative to younger age. Our results suggest that the enhanced global-local asymmetry in the older age group originated from less effective suppression of global distracter forms on early processing stages - indicative of older observers having difficulties with disengaging from a global default selection mode and switching to the required local state of attentional resolution.
    Biological Psychology 10/2015; 112:116-124. DOI:10.1016/j.biopsycho.2015.10.006 · 3.40 Impact Factor
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    • "Therefore, the current finding of the independence of the effect of the completion process from the effect of the noncompletion process also provides a key support for the identification of the neural mechanism of the completion process. Moreover, the basic design of the comparison between an illusory contour condition and a control condition (rotating contour fragments so that illusory contours disappear) has been widely used in the research of illusory contour perception, including (but not limited to) studies investigating attentional effects (Conci, Müller, & Elliott, 2007a, 2007b; Davis & Driver, 1994; Gurnsey, Poirier, & Gascon, 1996; Li, Cave, & Wolfe, 2008; Wu, Zhou, Qian, Gan, & Zhang, 2015), awareness modulations (Lau & Cheung, 2012; Wang, Weng, & He, 2012), the effect of inducer contrast (Lesher & Mingolla, 1993; Maertens & Shapley, 2008), feed-forward and feed-back processing (Ffytche & Zeki, 1996; Murray et al., 2002; Stanley & Rubin, 2003), and separate processes at different processing stages (Barlasov-Ioffe & Hochstein, 2008; Foxe, Murray, & Javitt, 2005; Murray, Foxe, Javitt, & Foxe, 2004; Murray et al., 2006; also see Seghier & Vuilleumier, 2006 for a review of neuroimaging studies). Although such a design is supposed to control for the effect of the processing of the contour fragments, it remains unclear whether the comparison indeed reveals the effect of the interpolation processing when perceiving illusory contours (Seghier & Vuilleumier , 2006). "
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    ABSTRACT: Spatially separated object information can be effortlessly completed in the visual system, as demonstrated by the well-known Kanizsa-type illusory contours. The perception of illusory contours is closely associated with the spatial configuration of contour fragments, leading to the long-lasting difficulty in distinguishing the effect of the completion process that interpolates the contour fragments from the effect of the noncompletion process that analyzes the contour fragments. However, a close relationship does not necessarily imply nonindependence, e.g., two people may show similar behaviors in one situation but may not in another situation. Inspired by this simple common sense, we conducted a contour discrimination task (i.e., discriminating between the interpolated contours) and a fragment discrimination task (i.e., discriminating between the physically-specified contour fragments) for Kanizsa squares and Kanizsa circles. The performance difference between the contour and fragment discrimination tasks was much larger for Kanizsa circles than for Kanizsa squares. This independence of the completion effect—as indicated by the performance in the contour task—from the noncompletion effect—as indicated by the performance in the fragment task— provides new insights into the understanding of the mechanism of visual completion.
    Journal of Vision 10/2015; 15(14)(6):1–10. DOI:10.1167/15.14.6 · 2.39 Impact Factor
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    • "The reduced activity in lower visual areas may also be due to cortical feedback from higher visual areas that represent the figure. Specifically, V1 activity has been shown to decrease when object elements can be grouped into coherent shapes, and this is accompanied by increased activity in the LOC (Murray, Wylie, et al., 2002). It is suggested that when areas such as the LOC can " explain " a visual stimulus, concurrent activity in lower areas decreases because higher-level predictions match and therefore discount the incoming sensory information. "
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    ABSTRACT: When an object moves behind a bush, for example, its visible fragments are revealed at different times and locations across the visual field. Nonetheless, a whole moving object is perceived. Unlike traditional modal and amodal completion mechanisms known to support spatial form integration when all parts of a stimulus are simultaneously visible, relatively little is known about the neural substrates of the spatiotemporal form integration (STFI) processes involved in generating coherent object representations from a succession visible fragments. We use fMRI to identify brain regions involved in two mechanisms supporting the representation of stationary and rigidly rotating objects whose form features are shown in succession: STFI and position updating. STFI allows past and present form cues to be integrated over space and time into a coherent object even when the object is not visible in any given frame. STFI can occur whether or not the object is moving. Position updating allows us to perceive a moving object, whether rigidly rotating or translating, even when its form features are revealed at different times and locations in space. Our results suggest that STFI is mediated by visual regions beyond V1 and V2. Moreover, although widespread cortical activation has been observed for other motion percepts derived solely from form-based analyses [Tse, P. U. Neural correlates of transformational apparent motion. Neuroimage, 31, 766-773, 2006; Krekelberg, B., Vatakis, A., & Kourtzi, Z. Implied motion from form in the human visual cortex. Journal of Neurophysiology, 94, 4373-4386, 2005], increased responses for the position updating that lead to rigidly rotating object representations were only observed in visual areas KO and possibly hMT+, indicating that this is a distinct and highly specialized type of processing.
    Journal of Cognitive Neuroscience 10/2015; 27(11):2158-2173. DOI:10.1162/jocn_a_00850 · 4.09 Impact Factor
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