Attentional modulation of perceptual organisation in schizophrenia

Kéri, Szabolcs; Kelemen, Ogúz; Benedek, György

doi:10.1080/13546800902757936

Cited by 18 publications

(21 citation statements)

References 16 publications

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“…We opted to present the stimulus on every trial rather than use a two-interval forced choice since qualitatively the same results arise in the two cases (Keri, Kelemen, et al, 2005), and since the former allows for a shorter experiment. A 1-up, 3-down staircase determined the threshold, the amount of contrast needed to detect the stimulus with 79.4% accuracy (Keri et al, 2009; Keri, Kelemen, et al, 2005; Keri, Kiss, et al, 2005; Must et al, 2004). Specifically, in the event of one incorrect response (miss), the contrast between the background and the central Gabor increased by 0.1 log units (26%) and in the event of three consecutive correct responses (hit), the contrast decreased by the same amount.…”

Section: Methodsmentioning

confidence: 99%

“…The problem is that the individual elements in clinical CG studies are Gabor patches—that is, oriented sinusoidal luminance gratings multiplied with a circularly symmetric Gaussian kernel—and the carrier frequencies were almost always below 8.3 cycles/deg. In some cases, the SF was 6.7 cycles/deg (Keri, Kelemen, & Benedek, 2009; Keri, Kelemen, Benedek, & Janka, 2005; Keri, Kiss, Kelemen, Benedek, & Janka, 2005; Must, Janka, Benedek, & Keri, 2004); in other cases, it was 5 cycles/deg (Kozma-Wiebe et al, 2006; Silverstein et al, 2009; Silverstein, Kovacs, Corry, & Valone, 2000), and in still other cases, it was less than 4 cycles/deg (Robol et al, 2013; Schallmo, Sponheim, & Olman, 2013). It is thus entirely possible that the reason that patients perform poorly in grouping tasks owes not to an integration deficit per se , but to a problem in detecting or accurately representing the elements integrated.…”

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confidence: 96%

“…That is, patients would tolerate less noise when integrating contours (Keane, Silverstein, et al, 2012; Kozma-Wiebe et al, 2006; Silverstein et al, 2000), benefit less from collinear flankers when detecting a central target (Keri et al, 2009; Keri, Kelemen, et al, 2005; Keri, Kiss, et al, 2005; Must et al, 2004), and benefit less from Gestalt grouping when discerning global shape (Keane et al, 2014). More tenuously, we hypothesized that CG dysfunction would be improved by increasing the peak spatial frequency or reducing the lower spatial frequency amplitude of the integrated elements.…”

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confidence: 99%

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Multiple forms of contour grouping deficits in schizophrenia: What is the role of spatial frequency?

et al. 2014

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Schizophrenia patients poorly perceive Kanizsa figures and integrate co-aligned contour elements (Gabors). They also poorly process low spatial frequencies (SFs), which presumably reflects dysfunction along the dorsal pathway. Can contour grouping deficits be explained in terms of the spatial frequency content of the display elements? To address the question, we tested patients and matched controls on three contour grouping paradigms in which the SF composition was modulated. In the Kanizsa task, subjects discriminated quartets of sectored circles (“pac-men”) that either formed or did not form Kanizsa shapes (illusory and fragmented conditions, respectively). In contour integration, subjects identified the screen quadrant thought to contain a closed chain of co-circular Gabors. In collinear facilitation, subjects attempted to detect a central low-contrast element flanked by collinear or orthogonal high-contrast elements, and facilitation corresponded to the amount by which collinear flankers reduced contrast thresholds. We varied SF by modifying the element features in the Kanizsa task and by scaling the entire stimulus display in the remaining tasks (SFs ranging from 4–12 cycles/deg). Irrespective of SF, patients were worse at discriminating illusory, but not fragmented shapes. Contrary to our hypothesis, collinear facilitation and contour integration were abnormal in the clinical group only for the higher SF (>=10 c/deg). Tasks correlated with clinical variables, such as conceptual disorganization, general symptoms, and levels of functioning. In schizophrenia, three forms of contour grouping impairments prominently arise and cannot be attributed to poor low SF processing. Neurobiological and clinical implications are discussed.

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Section: Methodsmentioning

confidence: 99%

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confidence: 96%

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confidence: 99%

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Multiple forms of contour grouping deficits in schizophrenia: What is the role of spatial frequency?

et al. 2014

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“…Compared to controls, patients demonstrate reduced facilitatory effects of collinear flankers on detection of a target at short target-flanker distances (Kéri et al, 2005). They also show lack of attentional modulation of this effect (Kéri et al, 2009), which is a further example of the reduced effects of modulatory amplification. Such patients also need more of the contours to be present to identify objects, so that is further evidence of impaired disambiguation (Doniger, et al, 2002).…”

Section: Contextual Disambiguationmentioning

confidence: 98%

On the functions, mechanisms, and malfunctions of intracortical contextual modulation

Phillips

Clark

Silverstein

2015

Neuroscience & Biobehavioral Reviews

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A broad neuron-centric conception of contextual modulation is reviewed and re-assessed in the light of recent neurobiological studies of amplification, suppression, and synchronization. Behavioural and computational studies of perceptual and higher cognitive functions that depend on these processes are outlined, and evidence that those functions and their neuronal mechanisms are impaired in schizophrenia is summarized. Finally, we compare and assess the long-term biological functions of contextual modulation at the level of computational theory as formalized by the theories of coherent infomax and free energy reduction. We conclude that those theories, together with the many empirical findings reviewed, show how contextual modulation at the neuronal level enables the cortex to flexibly adapt the use of its knowledge to current circumstances by amplifying and grouping relevant activities and by suppressing irrelevant activities.

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“…Research on the neurobiology of these impairments suggests that they involve reduced binding of visual features in areas of the occipital lobe with large receptive fields (e.g., V4 and lateral occipital complex) [9,18] , involving weakened synchronization of neuronal oscillations within the γ-band [19] . While in some cases, reduced perceptual organization appears to be independent of attention [20] , in other cases there are clear effects of reduced effects of expectation on the structuring of the visual field [13] , suggesting poor integration of top-down signals and of gain (from attention) with sensory input.…”

Section: Perceptual Fragmentationmentioning

confidence: 99%

Space and Objects: On the Phenomenology and Cognitive Neuroscience of Anomalous Perception in Schizophrenia (Ancillary Article to EAWE Domain 1)

2017

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Background/Aims: Perception of space and objects is a traditional focus within phenomenology, and disturbances in these aspects of perception among people with schizophrenia have long been discussed within phenomenological psychiatry. Despite this, there has been little empirical work on the causes and effects of most of these perceptual alterations in people with schizophrenia. Progress towards this goal can be accelerated by the use of EAWE (Examination of Anomalous World Experience), an interview-based tool to elicit, categorize, and quantify abnormal perceptual and other experiential phenomena. Methods: In this brief paper, we review the main types of disturbances in space and object perception in schizophrenia - as described by phenomenologists, clinicians from other theoretical orientations, and experimental psychopathologists - as a first step in a research agenda to achieve a better integration of the clinical and experimental literatures. Results/Conclusion: This review indicates that in some cases the cognitive and neurobiological mechanisms of altered space and object perception in schizophrenia are relatively well understood, while in other cases there exist only plausible hypotheses. In still other cases, however, almost nothing is known. Moreover, a fundamental hypothesis of phenomenological psychiatry - that perceptual changes are related to disturbances in the sense of self - has yet to be investigated actively. From this context, we offer suggestions for future research and suggest general research designs that may be useful for advancing progress in this area.

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Attentional modulation of perceptual organisation in schizophrenia

Abstract: These results suggest that lateral connections are impaired in early visual cortex of schizophrenia patients. This deficit cannot be restored by top-down attentional modulation of target-flanker interactions.

Cited by 18 publications

References 16 publications

Multiple forms of contour grouping deficits in schizophrenia: What is the role of spatial frequency?

Multiple forms of contour grouping deficits in schizophrenia: What is the role of spatial frequency?

On the functions, mechanisms, and malfunctions of intracortical contextual modulation

Space and Objects: On the Phenomenology and Cognitive Neuroscience of Anomalous Perception in Schizophrenia (Ancillary Article to EAWE Domain 1)

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