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Backward Masking

The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform

Michael H. Herzog – 1st expert on this subject based on the ideXlab platform

  • Visual Backward Masking deficits in schizotypy
    , 2020
    Co-Authors: Céline Cappe, Christine Mohr, Daniela Herzig, Michael H. Herzog

    Abstract:

    Background: In visual Backward Masking, a target is followed by a mask impeding target perception. Visual Backward Masking is a potential endophenotype for schizophrenia because patients with schizophrenia and also their unaffected relatives show significant performance deficits compared to controls. If Backward Masking is an endophenotype, unaffected students with elevated schizotypal traits should also show relative Backward Masking impairments. In the past, research on endophenotypes has mostly focused on higher cognitive functions. For this reason, we also assessed performance in the widely used Wisconsin Card Sorting Test (WCST). Methods: We tested 40 healthy undergraduate students in the visual Backward Masking task and the WCST used in clinical studies before (Herzog et al., 2004; Chkonia et al., 2010). The visual Backward Masking paradigm is based on a two-step procedure. In the first step, we presented a visual target and determined the presentation time to reach 75% correct responses for each observer individually. With this step, we compensate for general, task-irrelevant effects. In the second step, this individual duration was used to assess the actual visual Backward Masking performance. Here, the target was followed by a Masking stimulus (5 or 25 element grating) after a blank period (ISI). All participants filled in a self-report schizotypy measure, i.e. the O-life questionnaire assessing schizotypy along three dimensions, i.e. positive schizotypy (unusual experience), cognitive disorganization, and negative schizotypy (introvertive anhedonia). Results: We observed that both visual Backward Masking and the total number of errors in the WCST were impaired for students with high scores on the cognitive disorganization dimension. No significant differences were found for introvertive anhedonia scores or unusual experience scores. Discussion: The present findings indicate that both tasks are potential endophenotypes along the schizophrenia spectrum. However, previous studies indicate that the Backward Masking task is more reliable than higher cognitive tasks (e.g. WCST) (Herzog et al., 2004; Chkonia et al., 2010). Because our findings were specific to cognitive disorganization, we suggest that this dimension is the most illness-relevant schizotypy dimension. Our results show further evidence that visual Backward Masking is a potential endophenotype for schizophrenia.

  • Electrophysiological Correlates of Visual Backward Masking in Schizotypy
    , 2020
    Co-Authors: Ophelie Favrod, Céline Cappe, Christine Mohr, Guillaume Sierro, Michael H. Herzog

    Abstract:

    Visual Backward Masking is strongly deteriorated in both schizophrenia and healthy students high as compared to low in cognitive disorganisation (CD; no relationship with positive or negative schizotypy). In patients, this deterioration was also reflected in reduced amplitudes of the EEG (global field power: GFP). Here, we investigated whether reduced GFP during visual Backward Masking is also evident in high as compared to low CD scorers. The results of the GFP analysis confirmed this assumption. We also found a late EEG component in high CD scorers which was absent in low CD scorers and patients. This might reflect compensation mechanisms that are affected in patients. CD might be a risk marker for psychosis, while positive and negative schizotypy may reflect healthy personality traits, at least when performance in this potential endophenotype of schizophrenia is considered. Underlying mechanisms for the current deficit could be diminished target processing.

  • electrophysiological correlates of visual Backward Masking in patients with first episode psychosis
    Psychiatry Research-neuroimaging, 2018
    Co-Authors: Ophelie Favrod, Michael H. Herzog, Maya Roinishvili, Andreas Brand, Janir R Da Cruz, Mariam Okruashvili, Tinatin Gamkrelidze, Patricia Figueiredo, Eka Chkonia

    Abstract:

    Abstract Visual Backward Masking is strongly impaired in patients with schizophrenia. Masking deficits have been proposed as potential endophenotypes of schizophrenia. Masking performance deficits manifest as strongly reduced amplitudes in the electroencephalogram (EEG). In order to fulfill the criteria of an endophenotype, Masking deficits should not vary substantially across time and should be present at the first psychotic event. To verify whether these conditions are met for visual Backward Masking, we tested patients with first episode psychosis (n = 21) in a longitudinal study. Patients were tested with visual Backward Masking and EEG three times every six months over a period of one year. We found that the EEG amplitudes of patients with first episode psychosis were higher as compared to those of patients with schizophrenia but lower as compared to those of unaffected controls. More interestingly, we found that the EEG amplitudes of patients with first episode psychosis remained stable over the course of one year. Since chronic schizophrenia patients have strongly reduced amplitudes, we speculate that the neural correlates of Masking deficits (EEG amplitudes) continue to decrease as the disease progresses.

Michael F Green – 2nd expert on this subject based on the ideXlab platform

  • event related gamma activity in schizophrenia patients during a visual Backward Masking task
    American Journal of Psychiatry, 2005
    Co-Authors: Jonathan K Wynn, Keith H Nuechterlein, Gregory A Light, Bruno G Breitmeyer, Michael F Green

    Abstract:

    OBJECTIVE: Schizophrenia patients experience deficits in many aspects of cognition and perception. Abnormalities in gamma activity may underlie some of these deficits, including rapid processing of visual stimuli. This study examined event-related gamma range activity during a visual BackwardMasking task in schizophrenia patients and normal comparison subjects. METHOD: Event-related gamma activity was recorded in 15 normal comparison subjects and 32 schizophrenia patients. Participants had event-related gamma activity recorded while viewing 60 unmasked visual targets and 240 trials of visual Backward Masking. Effects of group, accuracy (correct versus incorrect), stimulus-onset asynchrony, and regional activity (left versus right hemisphere, anterior versus posterior regions) were assessed. RESULTS: Schizophrenia patients had significantly reduced gamma activity in relation to comparison subjects during the BackwardMasking task. Normal comparison subjects showed significantly greater gamma activity in t…

  • Regional Brain Activity Associated with Visual Backward Masking
    Journal of Cognitive Neuroscience, 2005
    Co-Authors: Michael F Green, Keith H Nuechterlein, David Glahn, Stephen A. Engel, Fred Sabb, Magda Strojwas, Mark S. Cohen

    Abstract:

    In visual Backward Masking, the visibility of a briefly presented visual target is disrupted by a mask that is presented shortly thereafter. The goal of the current study was to identify regions in the human cortex that may provide the neural basis of visual Masking. We searched for areas whose activity correlated with perception as we systematically varied the strength of Masking. A total of 13 subjects performed a Backward Masking task during functional magnetic resonance imaging. Target and mask were presented at three delay intervals (34, 68, and 102 msec) and behavioral measures confirmed that the targets were more visible at longer Masking intervals. Two sets of regions of interest were identified: Distinct regions in the visual cortex (V1/V2, LO, hMT+) were segregated using scans to localize visual processing drawn from the existing literature. Additional cortical regions were selected in a data-driven approach based on their activity during the Backward Masking task. For each set, we determined the regions whose magnitude of activation increased at longer Masking intervals. Nine of the subjects provided valid behavioral performance data on the visual Masking task and imaging data from these subjects were used for subsequent analysis. The scans of visual processing areas identified four regions, including: early visual areas (V1 and V2), the motion-sensitive regions in the lateral occipital (LO) lobe (hMT+), and two components (dorsal and ventral) of the object-sensitive region, LO. Of these, the ventral and dorsal LO regions were sensitive to the strength of the mask. For the data-driven approach, six regions were identified on the basis of a difference map in which all Masking intervals were contrasted with rest. These included the inferior parietal, anterior cingulate, precentral, insula, thalamic, and occipital areas. The predicted effects of more activity with weaker Masking were seen in the thalamus, inferior parietal, and anterior cingulate. This study isolated three types of visual processing areas. The first included regions that subserve key stages of vision (including object and motion processing). The second type responded to the presentation of briefly presented visual stimuli, regardless of Masking interval. The third type (selected from the first two) included regions sensitive to the interval between the target and mask. These latter regions (including ventral LO, inferior parietal, anterior cingulate, and thalamus) may form the neural substrate of Backward Masking.

  • Backward Masking performance as an indicator of vulnerability to schizophrenia
    Acta Psychiatrica Scandinavica, 1999
    Co-Authors: Michael F Green, Keith H Nuechterlein

    Abstract:

    : Several types of design have been used to identify neurocognitive measures that indicate vulnerability to schizophrenia rather than the presence of the illness. These designs include studies of first-degree relatives of patients, studies of patients in symptomatic remission, and studies of subjects who are considered to be prone to psychosis. The Backward Masking procedure is one promising indicator of vulnerability to schizophrenia. Backward Masking is a procedure in which identification of an initial stimulus (the target) is disrupted by a later stimulus (the mask). Schizophrenic patients show performance deficits on Backward Masking. Unaffected siblings of patients, remitted patients, and individuals prone to psychosis also show performance deficits on Backward Masking. This pattern of results suggests that Backward Masking is a promising indicator of vulnerability to schizophrenia. It provides an alternative phenotype for schizophrenia that is separate from the disorder. The composite nature of Masking procedures helps investigators to parse a performance deficit into its smallest meaningful elements and relate them to vulnerability to schizophrenia.

Céline Cappe – 3rd expert on this subject based on the ideXlab platform

  • Visual Backward Masking deficits in schizotypy
    , 2020
    Co-Authors: Céline Cappe, Christine Mohr, Daniela Herzig, Michael H. Herzog

    Abstract:

    Background: In visual Backward Masking, a target is followed by a mask impeding target perception. Visual Backward Masking is a potential endophenotype for schizophrenia because patients with schizophrenia and also their unaffected relatives show significant performance deficits compared to controls. If Backward Masking is an endophenotype, unaffected students with elevated schizotypal traits should also show relative Backward Masking impairments. In the past, research on endophenotypes has mostly focused on higher cognitive functions. For this reason, we also assessed performance in the widely used Wisconsin Card Sorting Test (WCST). Methods: We tested 40 healthy undergraduate students in the visual Backward Masking task and the WCST used in clinical studies before (Herzog et al., 2004; Chkonia et al., 2010). The visual Backward Masking paradigm is based on a two-step procedure. In the first step, we presented a visual target and determined the presentation time to reach 75% correct responses for each observer individually. With this step, we compensate for general, task-irrelevant effects. In the second step, this individual duration was used to assess the actual visual Backward Masking performance. Here, the target was followed by a Masking stimulus (5 or 25 element grating) after a blank period (ISI). All participants filled in a self-report schizotypy measure, i.e. the O-life questionnaire assessing schizotypy along three dimensions, i.e. positive schizotypy (unusual experience), cognitive disorganization, and negative schizotypy (introvertive anhedonia). Results: We observed that both visual Backward Masking and the total number of errors in the WCST were impaired for students with high scores on the cognitive disorganization dimension. No significant differences were found for introvertive anhedonia scores or unusual experience scores. Discussion: The present findings indicate that both tasks are potential endophenotypes along the schizophrenia spectrum. However, previous studies indicate that the Backward Masking task is more reliable than higher cognitive tasks (e.g. WCST) (Herzog et al., 2004; Chkonia et al., 2010). Because our findings were specific to cognitive disorganization, we suggest that this dimension is the most illness-relevant schizotypy dimension. Our results show further evidence that visual Backward Masking is a potential endophenotype for schizophrenia.

  • Electrophysiological Correlates of Visual Backward Masking in Schizotypy
    , 2020
    Co-Authors: Ophelie Favrod, Céline Cappe, Christine Mohr, Guillaume Sierro, Michael H. Herzog

    Abstract:

    Visual Backward Masking is strongly deteriorated in both schizophrenia and healthy students high as compared to low in cognitive disorganisation (CD; no relationship with positive or negative schizotypy). In patients, this deterioration was also reflected in reduced amplitudes of the EEG (global field power: GFP). Here, we investigated whether reduced GFP during visual Backward Masking is also evident in high as compared to low CD scorers. The results of the GFP analysis confirmed this assumption. We also found a late EEG component in high CD scorers which was absent in low CD scorers and patients. This might reflect compensation mechanisms that are affected in patients. CD might be a risk marker for psychosis, while positive and negative schizotypy may reflect healthy personality traits, at least when performance in this potential endophenotype of schizophrenia is considered. Underlying mechanisms for the current deficit could be diminished target processing.

  • electrophysiological correlates of visual Backward Masking in high schizotypic personality traits participants
    Psychiatry Research-neuroimaging, 2017
    Co-Authors: Ophelie Favrod, Céline Cappe, Michael H. Herzog, Christine Mohr, Guillaume Sierro, Maya Roinishvili, Eka Chkonia

    Abstract:

    Visual Backward Masking is strongly deteriorated in patients with schizophrenia. Masking deficits are associated with strongly reduced amplitudes of the global field power in the EEG. Healthy participants who scored high in cognitive disorganization (a schizotypic trait) were impaired in Backward Masking compared to participants who scored low. Here, we show that the global field power is also reduced in healthy participants scoring high (n=25) as compared to low (n=20) in cognitive disorganization, though quantitatively less pronounced than in patients (n=10). These results point to similar mechanisms underlying visual Backward Masking deficits along the schizophrenia spectrum.