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Romeo A, Supèr H. Spiking model of fixational eye movements and figure-ground segmentation. NETWORK (BRISTOL, ENGLAND) 2022; 33:143-166. [PMID: 35613078 DOI: 10.1080/0954898x.2022.2073393] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 03/25/2022] [Accepted: 04/28/2022] [Indexed: 06/15/2023]
Abstract
We present a model connecting eye movements and cortical state. Its structure includes simulated retinal images, motion detection, feature detectors and layers of spiking neurons. The designed scheme shows how the effect of micro-saccadic scale eye movements can lead to successful figure segregation in a figure-ground paradigm, by inducing changes in the neural dynamics through the time evolution of the inhibition range.
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Affiliation(s)
- August Romeo
- Vision and Control of Action Group, Department of Cognition, Development and Educational Psychology, University of Barcelona, Barcelona, Spain
| | - Hans Supèr
- Vision and Control of Action Group, Department of Cognition, Development and Educational Psychology, University of Barcelona, Barcelona, Spain
- Institute of Neurosciences of the University of Barcelona (UBNeuro), Barcelona, Spain
- Institut de Recerca Sant Joan de Déu (IRSJD), Barcelona, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
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2
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Vergence eye movements during figure-ground perception. Conscious Cogn 2021; 92:103138. [PMID: 34022640 DOI: 10.1016/j.concog.2021.103138] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 04/19/2021] [Accepted: 04/20/2021] [Indexed: 11/24/2022]
Abstract
Figure-ground, that is the segmentation of visual information into objects and their surrounding backgrounds, provides structure for visual attention. Recent evidence shows a novel role of vergence eye movements in visual attention. In the present work, vergence responses during figure-ground segregation tasks are psychophysically investigated. We show that during a figure-ground detection task, subjects convergence their eyes. Vergence eye movements are larger in figure trials than in ground trials. In detected figures trials, vergence are stronger than in trials where the figure went unnoticed. Moreover in figure trials, vergence responses are stronger to low-contrast figures than to high-contrast figures. We argue that these discriminative vergence responses have a role in figure-ground.
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Early recurrence enables figure border ownership. Vision Res 2021; 186:23-33. [PMID: 34023589 DOI: 10.1016/j.visres.2021.04.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 04/23/2021] [Accepted: 04/28/2021] [Indexed: 11/19/2022]
Abstract
Rubin's face-vase illusion demonstrates how one can switch back and forth between two different interpretations depending on how the figure outlines are assigned. In the primate visual system, assigning ownership along figure borders is encoded by neurons called the border ownership (BO) cells. Studies show that the responses of these neurons not only depend on the local features within their receptive fields, but also on contextual information. Despite two decades of studies on BO neurons, the ownership assignment mechanism in the brain is still unknown. Here, we propose a hierarchical recurrent model grounded on the hypothesis that neurons in the dorsal stream provide the context required for ownership assignment. Our proposed model incorporates early recurrence from the dorsal pathway as well as lateral modulations within the ventral stream. While dorsal modulations initiate the response difference to figure on either side of the border, lateral modulations enhance the difference. We found responses of our dorsally-modulated BO cells, similar to their biological counterparts, are invariant to size, position and solid/outlined figures. Moreover, our model BO cells exhibit comparable levels of reliability in the ownership signal to biological BO neurons. We found dorsal modulations result in high levels of accuracy and robustness for BO assignments in complex scenes compared to previous models based on ventral feedback. Finally, our experiments with illusory contours suggest that BO encoding could explain the perception of such contours in higher processing stages in the brain.
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Fornaciai M, Park J. Early Numerosity Encoding in Visual Cortex Is Not Sufficient for the Representation of Numerical Magnitude. J Cogn Neurosci 2018; 30:1788-1802. [DOI: 10.1162/jocn_a_01320] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Recent studies have demonstrated that the numerosity of visually presented dot arrays is represented in low-level visual cortex extremely early in latency. However, whether or not such an early neural signature reflects the perceptual representation of numerosity remains unknown. Alternatively, such a signature may indicate the raw sensory representation of the dot-array stimulus before becoming the perceived representation of numerosity. Here, we addressed this question by using the connectedness illusion, whereby arrays with pairwise connected dots are perceived to be less numerous compared with arrays containing isolated dots. Using EEG and fMRI in two independent experiments, we measured neural responses to dot-array stimuli comprising 16 or 32 dots, either isolated or pairwise connected. The effect of connectedness, which reflects the segmentation of the visual stimulus into perceptual units, was observed in the neural activity after 150 msec post stimulus onset in the EEG experiment and in area V3 in the fMRI experiment using a multivariate pattern analysis. In contrast, earlier neural activity before 100 msec and in area V2 was strictly modulated by numerosity regardless of connectedness, suggesting that this early activity reflects the sensory representation of a dot array before perceptual segmentation. Our findings thus demonstrate that the neural representation for numerosity in early visual cortex is not sufficient for visual number perception and suggest that the perceptual encoding of numerosity occurs at or after the segmentation process that takes place later in area V3.
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Acerbo MJ, Lazareva OF. Pharmacological manipulation of GABA activity in nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS) impairs figure-ground discrimination in pigeons: Running head: SP/IPS in figure-ground segregation. Behav Brain Res 2018; 344:1-8. [PMID: 29408282 DOI: 10.1016/j.bbr.2018.01.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 01/09/2018] [Accepted: 01/30/2018] [Indexed: 11/18/2022]
Abstract
Figure-ground segregation is a fundamental visual ability that allows an organism to separate an object from its background. Our earlier research has shown that nucleus rotundus (Rt), a thalamic nucleus processing visual information in pigeons, together with its inhibitory complex, nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS), are critically involved in figure-ground discrimination (Acerbo et al., 2012; Scully et al., 2014). Here, we further investigated the role of SP/IPS by conducting bilateral microinjections of GABAergic receptor antagonist and agonists (bicuculline and muscimol, respectively) and non-NMDA glutamate receptor antagonist (CNQX) after the pigeons mastered figure-ground discrimination task. We used two doses of each drug (bicuculline: 0.1 mM and 0.05 mM; muscimol: 4.4 mM and 8.8 mM; CNQX: 2.15 mM and 4.6 mM) in a within-subject design, and alternated drug injections with baseline (ACSF). The order of injections was randomized across birds to reduce potential carryover effects. We found that a low dose of bicuculline produced a decrement on figure trials but not on background trials, whereas a high dose impaired performance on background trials but not on figure trials. Muscimol produced an equivalent, dose-dependent impairment on both types of trials. Finally, CNQX had no consistent effect at either dose. Together, these results further confirm our earlier hypothesis that inhibitory projections from SP to Rt modulate figure-ground discrimination, and suggest that the Rt and the SP/IPS provide a plausible substrate that could perform figure-ground segregation in avian brain.
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Sole Puig M, Pallarés JM, Perez Zapata L, Puigcerver L, Cañete J, Supèr H. Attentional Selection Accompanied by Eye Vergence as Revealed by Event-Related Brain Potentials. PLoS One 2016; 11:e0167646. [PMID: 27973591 PMCID: PMC5156422 DOI: 10.1371/journal.pone.0167646] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 11/17/2016] [Indexed: 11/18/2022] Open
Abstract
Neural mechanisms of attention allow selective sensory information processing. Top-down deployment of visual-spatial attention is conveyed by cortical feedback connections from frontal regions to lower sensory areas modulating late stimulus responses. A recent study reported the occurrence of small eye vergence during orienting top-down attention. Here we assessed a possible link between vergence and attention by comparing visual event related potentials (vERPs) to a cue stimulus that induced attention to shift towards the target location to the vERPs to a no-cue stimulus that did not trigger orienting attention. The results replicate the findings of eye vergence responses during orienting attention and show that the strength and time of eye vergence coincide with the onset and strength of the vERPs when subjects oriented attention. Our findings therefore support the idea that eye vergence relates to and possibly has a role in attentional selection.
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Affiliation(s)
- Maria Sole Puig
- Dept of Cognition, Development and Educational Psychology, University of Barcelona, Barcelona, Spain
| | - Josep Marco Pallarés
- Dept of Cognition, Development and Educational Psychology, University of Barcelona, Barcelona, Spain
- Neuroscience Inst, University of Barcelona, Barcelona, Spain
- Pediatric Research Inst, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Laura Perez Zapata
- Dept of Cognition, Development and Educational Psychology, University of Barcelona, Barcelona, Spain
| | - Laura Puigcerver
- Pediatric Research Inst, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Josep Cañete
- Mental Health Dept, Consorci Sanitari del Maresme, Mataro, Spain
| | - Hans Supèr
- Dept of Cognition, Development and Educational Psychology, University of Barcelona, Barcelona, Spain
- Neuroscience Inst, University of Barcelona, Barcelona, Spain
- Pediatric Research Inst, Hospital Sant Joan de Déu, Barcelona, Spain
- ICREA, Pg. Lluís Companys, Barcelona, Spain
- * E-mail:
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Romeo A, Supèr H. Global oscillation regime change by gated inhibition. Neural Netw 2016; 82:76-83. [PMID: 27479874 DOI: 10.1016/j.neunet.2016.06.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 06/06/2016] [Accepted: 06/26/2016] [Indexed: 10/21/2022]
Abstract
The role of sensory inputs in the modelling of synchrony regimes is exhibited by means of networks of spiking cells where the relative strength of the inhibitory interaction is controlled by the activation of a linear unit working as a gating variable. Adaptation to stimulus size is determined by the value of a changing length scale, modelled by the time-varying radius of a circular receptive field. In this set-up, 'consolidation' time intervals relevant to attentional effects are shown to depend on the dynamics governing the evolution of the introduced length scale.
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Affiliation(s)
- August Romeo
- Department of Cognition, Development and Educational Psychology, Faculty of Psychology, University of Barcelona, Spain
| | - Hans Supèr
- Department of Cognition, Development and Educational Psychology, Faculty of Psychology, University of Barcelona, Spain; Institute of Neurosciences, Faculty of Psychology, University of Barcelona, Spain; Catalan Institution for Research and Advanced Studies (ICREA), Spain.
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Layton OW, Mingolla E, Yazdanbakhsh A. Neural dynamics of feedforward and feedback processing in figure-ground segregation. Front Psychol 2014; 5:972. [PMID: 25346703 PMCID: PMC4193330 DOI: 10.3389/fpsyg.2014.00972] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 08/15/2014] [Indexed: 11/13/2022] Open
Abstract
Determining whether a region belongs to the interior or exterior of a shape (figure-ground segregation) is a core competency of the primate brain, yet the underlying mechanisms are not well understood. Many models assume that figure-ground segregation occurs by assembling progressively more complex representations through feedforward connections, with feedback playing only a modulatory role. We present a dynamical model of figure-ground segregation in the primate ventral stream wherein feedback plays a crucial role in disambiguating a figure's interior and exterior. We introduce a processing strategy whereby jitter in RF center locations and variation in RF sizes is exploited to enhance and suppress neural activity inside and outside of figures, respectively. Feedforward projections emanate from units that model cells in V4 known to respond to the curvature of boundary contours (curved contour cells), and feedback projections from units predicted to exist in IT that strategically group neurons with different RF sizes and RF center locations (teardrop cells). Neurons (convex cells) that preferentially respond when centered on a figure dynamically balance feedforward (bottom-up) information and feedback from higher visual areas. The activation is enhanced when an interior portion of a figure is in the RF via feedback from units that detect closure in the boundary contours of a figure. Our model produces maximal activity along the medial axis of well-known figures with and without concavities, and inside algorithmically generated shapes. Our results suggest that the dynamic balancing of feedforward signals with the specific feedback mechanisms proposed by the model is crucial for figure-ground segregation.
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Affiliation(s)
- Oliver W Layton
- The Perception and Action Lab, Department of Cognitive Science, Rensselaer Polytechnic Institute Troy, NY, USA ; Vision Lab, Center for Computational Neuroscience and Neural Technology, Boston University Boston, MA, USA
| | - Ennio Mingolla
- Computational Vision Laboratory, Department of Speech-Language Pathology and Audiology, Northeastern University Boston, MA, USA
| | - Arash Yazdanbakhsh
- Vision Lab, Center for Computational Neuroscience and Neural Technology, Boston University Boston, MA, USA
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Romeo A, Supèr H. A feed-forward spiking model of shape-coding by IT cells. Front Psychol 2014; 5:481. [PMID: 24904494 PMCID: PMC4034053 DOI: 10.3389/fpsyg.2014.00481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 05/02/2014] [Indexed: 11/24/2022] Open
Abstract
The ability to recognize a shape is linked to figure-ground (FG) organization. Cell preferences appear to be correlated across contrast-polarity reversals and mirror reversals of polygon displays, but not so much across FG reversals. Here we present a network structure which explains both shape-coding by simulated IT cells and suppression of responses to FG reversed stimuli. In our model FG segregation is achieved before shape discrimination, which is itself evidenced by the difference in spiking onsets of a pair of output cells. The studied example also includes feature extraction and illustrates a classification of binary images depending on the dominance of vertical or horizontal borders.
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Affiliation(s)
- August Romeo
- Department of Basic Psychology, Faculty of Psychology, University of Barcelona Barcelona, Spain
| | - Hans Supèr
- Department of Basic Psychology, Faculty of Psychology, University of Barcelona Barcelona, Spain ; Institute for Brain, Cognition and Behavior (IR3C) Barcelona, Spain ; Catalan Institution for Research and Advanced Studies (ICREA) Barcelona, Spain
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Romeo A, Puig MS, Zapata LP, Lopez-Moliner J, Supèr H. Stimulus detection after interruption of the feedforward response in a backward masking paradigm. Cogn Neurodyn 2013; 6:459-66. [PMID: 24082965 DOI: 10.1007/s11571-012-9193-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Revised: 01/11/2012] [Accepted: 01/31/2012] [Indexed: 11/28/2022] Open
Abstract
In backward masking, a target stimulus is rendered invisible by the presentation of a second stimulus, the mask. When the mask is effective, neural responses to the target are suppressed. Nevertheless, weak target responses sometimes may produce a behavioural response. It remains unclear whether the reduced target response is a purely feedforward response or that it includes recurrent activity. Using a feedforward neural network of biological plausible spiking neurons, we tested whether a transient spike burst is sufficient for face categorization. After training the network, the system achieved face/non-face categorization for sets of grayscale images. In a backward masking paradigm, the transient burst response was cut off thereby reducing the feedforward target response. Despite the suppressed feedforward responses stimulus classification remained robust. Thus according to our model data stimulus detection is possible with purely, suppressed feedforward responses.
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Affiliation(s)
- August Romeo
- Department of Basic Psychology, Faculty of Psychology, University of Barcelona (UB), Pg. Vall d' Hebron 171, 08035 Barcelona, Spain
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Markov NT, Kennedy H. The importance of being hierarchical. Curr Opin Neurobiol 2013; 23:187-94. [DOI: 10.1016/j.conb.2012.12.008] [Citation(s) in RCA: 121] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 12/07/2012] [Accepted: 12/30/2012] [Indexed: 11/28/2022]
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Romeo A, Arall M, Supèr H. Noise destroys feedback enhanced figure-ground segmentation but not feedforward figure-ground segmentation. Front Physiol 2012; 3:274. [PMID: 22934028 PMCID: PMC3429048 DOI: 10.3389/fphys.2012.00274] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 06/26/2012] [Indexed: 11/30/2022] Open
Abstract
Figure-ground (FG) segmentation is the separation of visual information into background and foreground objects. In the visual cortex, FG responses are observed in the late stimulus response period, when neurons fire in tonic mode, and are accompanied by a switch in cortical state. When such a switch does not occur, FG segmentation fails. Currently, it is not known what happens in the brain on such occasions. A biologically plausible feedforward spiking neuron model was previously devised that performed FG segmentation successfully. After incorporating feedback the FG signal was enhanced, which was accompanied by a change in spiking regime. In a feedforward model neurons respond in a bursting mode whereas in the feedback model neurons fired in tonic mode. It is known that bursts can overcome noise, while tonic firing appears to be much more sensitive to noise. In the present study, we try to elucidate how the presence of noise can impair FG segmentation, and to what extent the feedforward and feedback pathways can overcome noise. We show that noise specifically destroys the feedback enhanced FG segmentation and leaves the feedforward FG segmentation largely intact. Our results predict that noise produces failure in FG perception.
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Affiliation(s)
- August Romeo
- Faculty of Psychology, Department of Basic Psychology, Universitat de Barcelona Barcelona, Spain
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Supèr H, Romeo A. Masking of figure-ground texture and single targets by surround inhibition: a computational spiking model. PLoS One 2012; 7:e31773. [PMID: 22393370 PMCID: PMC3290529 DOI: 10.1371/journal.pone.0031773] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Accepted: 01/17/2012] [Indexed: 01/10/2023] Open
Abstract
A visual stimulus can be made invisible, i.e. masked, by the presentation of a second stimulus. In the sensory cortex, neural responses to a masked stimulus are suppressed, yet how this suppression comes about is still debated. Inhibitory models explain masking by asserting that the mask exerts an inhibitory influence on the responses of a neuron evoked by the target. However, other models argue that the masking interferes with recurrent or reentrant processing. Using computer modeling, we show that surround inhibition evoked by ON and OFF responses to the mask suppresses the responses to a briefly presented stimulus in forward and backward masking paradigms. Our model results resemble several previously described psychophysical and neurophysiological findings in perceptual masking experiments and are in line with earlier theoretical descriptions of masking. We suggest that precise spatiotemporal influence of surround inhibition is relevant for visual detection.
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Affiliation(s)
- Hans Supèr
- Institute for Brain, Cognition and Behavior, Barcelona, Spain.
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Magnée MJCM, Lamme VAF, de Sain-van der Velden MGM, Vorstman JAS, Kemner C. Proline and COMT status affect visual connectivity in children with 22q11.2 deletion syndrome. PLoS One 2011; 6:e25882. [PMID: 21998713 PMCID: PMC3187802 DOI: 10.1371/journal.pone.0025882] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 09/12/2011] [Indexed: 11/17/2022] Open
Abstract
Background Individuals with the 22q11.2 deletion syndrome (22q11DS) are at increased risk for schizophrenia and Autism Spectrum Disorders (ASDs). Given the prevalence of visual processing deficits in these three disorders, a causal relationship between genes in the deleted region of chromosome 22 and visual processing is likely. Therefore, 22q11DS may represent a unique model to understand the neurobiology of visual processing deficits related with ASD and psychosis. Methodology We measured Event-Related Potentials (ERPs) during a texture segregation task in 58 children with 22q11DS and 100 age-matched controls. The C1 component was used to index afferent activity of visual cortex area V1; the texture negativity wave provided a measure for the integrity of recurrent connections in the visual cortical system. COMT genotype and plasma proline levels were assessed in 22q11DS individuals. Principal Findings Children with 22q11DS showed enhanced feedforward activity starting from 70 ms after visual presentation. ERP activity related to visual feedback activity was reduced in the 22q11DS group, which was seen as less texture negativity around 150 ms post presentation. Within the 22q11DS group we further demonstrated an association between high plasma proline levels and aberrant feedback/feedforward ratios, which was moderated by the COMT158 genotype. Conclusions These findings confirm the presence of early visual processing deficits in 22q11DS. We discuss these in terms of dysfunctional synaptic plasticity in early visual processing areas, possibly associated with deviant dopaminergic and glutamatergic transmission. As such, our findings may serve as a promising biomarker related to the development of schizophrenia among 22q11DS individuals.
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Affiliation(s)
- Maurice J C M Magnée
- Rudolf Magnus Institute of Neuroscience, Department of Child and Adolescent Psychiatry, University Medical Center Utrecht, Utrecht, The Netherlands.
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