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Samani NN, Proudlock FA, Siram V, Suraweera C, Hutchinson C, Nelson CP, Al-Uzri M, Gottlob I. Retinal Layer Abnormalities as Biomarkers of Schizophrenia. Schizophr Bull 2018; 44:876-885. [PMID: 29272501 PMCID: PMC6007436 DOI: 10.1093/schbul/sbx130] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Schizophrenia is associated with several brain deficits, as well as visual processing deficits, but clinically useful biomarkers are elusive. We hypothesized that retinal layer changes, noninvasively visualized using spectral-domain optical coherence tomography (SD-OCT), may represent a possible "window" to these abnormalities. METHODS A Leica EnvisuTM SD-OCT device was used to obtain high-resolution central foveal B-scans in both eyes of 35 patients with schizophrenia and 50 demographically matched controls. Manual retinal layer segmentation was performed to acquire individual and combined layer thickness measurements in 3 macular regions. Contrast sensitivity was measured at 3 spatial frequencies in a subgroup of each cohort. Differences were compared using adjusted linear models and significantly different layer measures in patients underwent Spearman Rank correlations with contrast sensitivity, quantified symptoms severity, disease duration, and antipsychotic medication dose. RESULTS Total retinal and photoreceptor complex thickness was reduced in all regions in patients (P < .0001). Segmentation revealed consistent thinning of the outer nuclear layer (P < .001) and inner segment layer (P < .05), as well as a pattern of parafoveal ganglion cell changes. Low spatial frequency contrast sensitivity was reduced in patients (P = .002) and correlated with temporal parafoveal ganglion cell complex thinning (R = .48, P = .01). Negative symptom severity was inversely correlated with foveal photoreceptor complex thickness (R = -.54, P = .001) and outer nuclear layer thickness (R = -.47, P = .005). CONCLUSIONS Our novel findings demonstrate considerable retinal layer abnormalities in schizophrenia that are related to clinical features and visual function. With time, SD-OCT could provide easily-measurable biomarkers to facilitate clinical assessment and further our understanding of the disease.
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Affiliation(s)
| | - Frank A Proudlock
- Ulverscroft Eye Unit, University of Leicester, Leicester, UK,Department of Neuroscience, Psychology and Behaviour, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, UK
| | - Vasantha Siram
- Leicestershire Partnership NHS Trust, Bradgate Unit, Glenfield Hospital, Leicester, UK
| | - Chathurie Suraweera
- Leicestershire Partnership NHS Trust, Bradgate Unit, Glenfield Hospital, Leicester, UK
| | - Claire Hutchinson
- Department of Neuroscience, Psychology and Behaviour, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, UK
| | - Christopher P Nelson
- NIHR Leicester Cardiovascular Biomedical Research Unit, Glenfield Hospital, Leicester, UK
| | - Mohammed Al-Uzri
- Leicestershire Partnership NHS Trust, Bradgate Unit, Glenfield Hospital, Leicester, UK,Adult Social and Epidemiological Psychiatry and Disability Research Group, Department of Health Sciences, University of Leicester, Leicester General Hospital, Leicester, UK
| | - Irene Gottlob
- Department of Neuroscience, Psychology and Behaviour, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, UK,To whom correspondence should be addressed; Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, PO Box 65, Leicester LE2 7LX, UK; tel: +44-116-252-3268, e-mail:
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Herzog MH, Brand A. Visual masking & schizophrenia. SCHIZOPHRENIA RESEARCH-COGNITION 2015; 2:64-71. [PMID: 29114454 PMCID: PMC5609636 DOI: 10.1016/j.scog.2015.04.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Revised: 03/30/2015] [Accepted: 04/07/2015] [Indexed: 11/28/2022]
Abstract
Visual masking is a frequently used tool in schizophrenia research. Visual masking has a very high sensitivity and specificity and masking paradigms have been proven to be endophenotypes. Whereas masking is a powerful technique to study schizophrenia, the underlying mechanisms are discussed controversially. For example, for more than 25 years, masking deficits of schizophrenia patients were mainly attributed to a deficient magno-cellular system (M-system). Here, we show that there is very little evidence that masking deficits are magno-cellular deficits. We will discuss the magno-cellular and other approaches in detail and highlight their pros and cons.
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Affiliation(s)
- Michael H Herzog
- Laboratory of Psychophysics, Brain Mind Institute, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
| | - Andreas Brand
- Klinikum Bremen-Ost, Bremen, Germany.,Institute of Psychology and Cognition Research, University of Bremen, Germany
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Gracitelli CPB, Abe RY, Diniz-Filho A, Vaz-de-Lima FB, Paranhos A, Medeiros FA. Ophthalmology issues in schizophrenia. Curr Psychiatry Rep 2015; 17:28. [PMID: 25773224 PMCID: PMC4523638 DOI: 10.1007/s11920-015-0569-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Schizophrenia is a complex mental disorder associated with not only cognitive dysfunctions, such as memory and attention deficits, but also changes in basic sensory processing. Although most studies on schizophrenia have focused on disturbances in higher-order brain functions associated with the prefrontal cortex or frontal cortex, recent investigations have also reported abnormalities in low-level sensory processes, such as the visual system. At very early stages of the disease, schizophrenia patients frequently describe in detail symptoms of a disturbance in various aspects of visual perception that may lead to worse clinical symptoms and decrease in quality of life. Therefore, the aim of this review is to describe the various studies that have explored the visual issues in schizophrenia.
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Affiliation(s)
- Carolina P. B. Gracitelli
- Hamilton Glaucoma Center and Department of Ophthalmology, University of California, 9500 Gilman Drive, La Jolla, CA 92093-0946, USA; Department of Ophthalmology, Federal University of São Paulo, Botucatu Street, 821. Vila Clementino, São Paulo, SP 04023-062, Brazil
| | - Ricardo Y. Abe
- Hamilton Glaucoma Center and Department of Ophthalmology, University of California, 9500 Gilman Drive, La Jolla, CA 92093-0946, USA; ; Department of Ophthalmology, University of Campinas, Vital Brasil Street, 251, Cidade Universitária Zeferino Vaz, Campinas, SP 13083-970, Brazil
| | - Alberto Diniz-Filho
- Hamilton Glaucoma Center and Department of Ophthalmology, University of California, 9500 Gilman Drive, La Jolla, CA 92093-0946, USA; ; Department of Ophthalmology and Otorhinolaryngology, Federal University of Minas Gerais, Alfredo Balena Avenue, 190 Santa Efigenia, Belo Horizonte, MG 30130-100, Brazil
| | | | - Augusto Paranhos
- Department of Ophthalmology, Federal University of São Paulo, Botucatu Street, 821. Vila Clementino, São Paulo, SP 04023-062, Brazil;
| | - Felipe A. Medeiros
- Hamilton Glaucoma Center and Department of Ophthalmology, University of California, 9500 Gilman Drive, La Jolla, CA 92093-0946, USA;
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4
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On using very high temporal frequencies to isolate magnocellular contributions to psychophysical tasks. Neuropsychologia 2013; 51:1556-60. [PMID: 23702475 DOI: 10.1016/j.neuropsychologia.2013.05.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 04/27/2013] [Accepted: 05/10/2013] [Indexed: 11/24/2022]
Abstract
In connection with dyslexia several authors have sought to employ stimuli of very high temporal frequency to isolate magnocellular contributions to visual tasks. It is here pointed out that considerable evidence indicate that the ability to see the very highest temporal frequencies is limited by cortical mechanisms. This suggests that variations and abnormalities in this ability may reflect cortical factors rather than magnocellular ones. It is therefore difficult to rely upon very high temporal frequency stimuli to isolate contributions from the magnocellular system.
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5
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Herzog MH, Roinishvili M, Chkonia E, Brand A. Schizophrenia and visual backward masking: a general deficit of target enhancement. Front Psychol 2013; 4:254. [PMID: 23717290 PMCID: PMC3653113 DOI: 10.3389/fpsyg.2013.00254] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 04/16/2013] [Indexed: 02/04/2023] Open
Abstract
The obvious symptoms of schizophrenia are of cognitive and psychopathological nature. However, schizophrenia affects also visual processing which becomes particularly evident when stimuli are presented for short durations and are followed by a masking stimulus. Visual deficits are of great interest because they might be related to the genetic variations underlying the disease (endophenotype concept). Visual masking deficits are usually attributed to specific dysfunctions of the visual system such as a hypo- or hyper-active magnocellular system. Here, we propose that visual deficits are a manifestation of a general deficit related to the enhancement of weak neural signals as occurring in all other sorts of information processing. We summarize previous findings with the shine-through masking paradigm where a shortly presented vernier target is followed by a masking grating. The mask deteriorates visual processing of schizophrenic patients by almost an order of magnitude compared to healthy controls. We propose that these deficits are caused by dysfunctions of attention and the cholinergic system leading to weak neural activity corresponding to the vernier. High density electrophysiological recordings (EEG) show that indeed neural activity is strongly reduced in schizophrenic patients which we attribute to the lack of vernier enhancement. When only the masking grating is presented, EEG responses are roughly comparable between patients and control. Our hypothesis is supported by findings relating visual masking to genetic deviants of the nicotinic α7 receptor (CHRNA7).
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Affiliation(s)
- Michael H Herzog
- Laboratory of Psychophysics, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland
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Koychev I, El-Deredy W, Mukherjee T, Haenschel C, Deakin JFW. Core dysfunction in schizophrenia: electrophysiology trait biomarkers. Acta Psychiatr Scand 2012; 126:59-71. [PMID: 22384856 DOI: 10.1111/j.1600-0447.2012.01849.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Core symptoms of schizophrenia, particularly in the cognitive domain are hypothesized to be due to an abnormality in neural connectivity. Biomarkers of connectivity may therefore be a promising tool in exploring the aetiology of schizophrenia. We used electrophysiological methods to demonstrate abnormal visual information processing during in patients performing a simple cognitive task. METHOD Electrophysiological recordings were acquired from 20 chronically ill, medicated patients diagnosed with either schizophrenia or schizo-affective disorder and 20 healthy volunteers while they conducted a working memory (WM) task. RESULTS The patient group had significantly lower accuracy on the WM task and a trend for slower responses. An early visual evoked response potential was reduced in patients. Analysis of the electroencephalographic oscillations showed a decreased phase-locking factor (in the theta, beta and gamma bands) and signal power (theta frequency band). The beta and gamma oscillatory abnormalities were confined to two sets of correlated fronto and occipital electrodes. CONCLUSION The findings of event-related potential and oscillatory abnormalities in patients with schizophrenia confirm the sensitivity of early visual information processing measurements for identification of schizophrenia phenotype. The fronto-occipital distribution of the oscillatory abnormalities replicates our findings from a schizotypal sample and implicates a possible top-down dysfunction as a vulnerability trait.
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Affiliation(s)
- I Koychev
- Neuroscience and Psychiatry Unit, The University of Manchester, UK.
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7
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Skottun BC, Skoyles JR. Visually evoked potentials, NMDA receptors and the magnocellular system in schizophrenia. Acta Neuropsychiatr 2012; 24:50-5. [PMID: 25288459 DOI: 10.1111/j.1601-5215.2011.00611.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Background: It has been claimed that schizophrenia can be linked to the magnocellular system by way of N-methyl-d-aspartate (NMDA) receptors. The present report examines this claim.Methods: A review is made of relevant research literature.Results: The NMDA studies that have been referenced to connect visual deficits in schizophrenia to the magnocellular system are based on the cat, a species whose visual system is fundamentally different from that of primates. The cat visual system cannot easily be divided into magno- and a parvocellular portions.Conclusions: Owing to the substantial differences between the visual systems of cats and primates, it is difficult to link sensory abnormalities in schizophrenia specifically to the magnocellular system based on data from the cat.
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Affiliation(s)
| | - John R Skoyles
- Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), University College London, London, UK
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SKOTTUN BERNTC, SKOYLES JOHNR. THE TIME COURSE OF VISUAL BACKWARD MASKING DEFICITS IN SCHIZOPHRENIA. J Integr Neurosci 2011; 10:33-45. [DOI: 10.1142/s0219635211002609] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2010] [Accepted: 01/24/2011] [Indexed: 11/18/2022] Open
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9
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Skottun BC, Skoyles JR. On identifying magnocellular and parvocellular responses on the basis of contrast-response functions. Schizophr Bull 2011; 37:23-6. [PMID: 20929967 PMCID: PMC3004196 DOI: 10.1093/schbul/sbq114] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
It has been proposed that magnocellular and parvocellular sensitivity in schizophrenic individuals can be assessed using steady-state visually evoked potentials (VEPs) to either low-contrast stimuli or stimuli whose contrast is modulated around a high contrast "pedestal" (Green MF, Butler PD, Chen Y, et al. Schizophr Bull. 2009;35:163-181). This suggestion faces 2 difficulties: (1) To use low-contrast stimuli to activate the magnocellular system is inconsistent with lesion studies that have shown that under many conditions, the parvocellular system responds to the lowest contrasts and (2) To rely on contrast-response relationships to identify magnocellular and parvocellular responses is difficult because other neurons exist in the visual system that have contrast-response relationships similar to those of magnocellular and parvocellular cells.
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Affiliation(s)
| | - John R. Skoyles
- Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), University College London, London, UK,Centre for Philosophy of Natural and Social Science (CPNSS), London School of Economics, London, UK,To whom correspondence should be addressed; tel: +44 (0)20-7679-4325, e-mail address:
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Brittain PJ, Surguladze S, McKendrick AM, Ffytche DH. Backward and forward visual masking in schizophrenia and its relation to global motion and global form perception. Schizophr Res 2010; 124:134-41. [PMID: 20685082 DOI: 10.1016/j.schres.2010.07.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2010] [Revised: 04/28/2010] [Accepted: 07/09/2010] [Indexed: 10/19/2022]
Abstract
Whilst visual backward masking deficits in schizophrenia have been reliably reported and may reveal magnocellular dysfunction, forward masking, which may rely more heavily on the parvocellular system, has been under investigated. In a group of 64 schizophrenia patients and 65 matched controls we undertook a visual masking paradigm containing both conditions, together with tests of 'global motion' and 'global form' perception, two 'down-stream' visual tasks reflecting later processing linked to magnocellular and parvocellular function respectively. In the patient group, a significant but small deficit on the masking task, equivalent across forward and backward conditions was seen. Correlations between the masking and motion/form tasks supported the predominant theoretical framework describing the neural processes involved in masking. Performance on the motion and form tasks was differentiated by a trend-level motion processing deficit but near-normal form processing. The results suggest an 'early visual' processing deficit in both magno- and parvocellular systems but one which is only transferred to 'down-stream' processing areas with predominantly magnocellular input.
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Affiliation(s)
- P J Brittain
- Affective Neuroscience Group, Section of Cognitive Neuropsychiatry, King's College London, Institute of Psychiatry, 16 De Crespigny Park, London SE5 8AF, UK.
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Lalor EC, Foxe JJ. Reply to Skottun & Skoyles. On interpreting responses to low contrast stimuli in terms of magnocellular activity – A few remarks. Vision Res 2010. [DOI: 10.1016/j.visres.2009.12.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Skottun BC, Skoyles JR. Are masking abnormalities in schizophrenia specific to type-B masking? World J Biol Psychiatry 2010; 10:798-808. [PMID: 19707956 DOI: 10.1080/15622970903051944] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The abnormal visual masking in those with schizophrenia, it has been proposed, arises from a deficiency in their magnocellular system. Two kinds of masking exist: Type-A and Type-B. Type-A masking is characterized by the masking being strongest when target and mask are presented simultaneously. Type-B masking is characterized by a non-monotonic masking curve, i.e. the masking is largest when the mask is presented at some time after the target. The proposed link between masking and magnocellular activity applies mainly to Type-B masking. Thus, a magnocellular deficiency, if it exists, should effect Type-B masking more prominently than Type-A masking. Here we review the relevant literature. The majority of studies of masking in those with schizophrenia, it is found, have examined only Type-A masking. These find substantial evidence for abnormal masking. Where Type-B masking has been obtained, evidence also exists for abnormalities. However, the abnormal masking in these cases is largely unrelated to the defining characteristic of Type-B masking (i.e. to the non-monotonic masking function). It is concluded that the evidence for linking masking abnormalities in schizophrenia specifically to Type-B masking is weak. This undermines the proposal that masking abnormalities in schizophrenia have a magnocellular origin.
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On interpreting responses to low contrast stimuli in terms of magnocellular activity - a few remarks. Vision Res 2010; 50:989-90; author reply 991-4. [PMID: 20116393 DOI: 10.1016/j.visres.2009.04.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 03/30/2009] [Accepted: 04/07/2009] [Indexed: 11/23/2022]
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Skottun BC, Skoyles JR. On using Vernier acuity to assess magnocellular sensitivity. Brain Cogn 2009; 72:165-6; discussion 167-8. [PMID: 19646804 DOI: 10.1016/j.bandc.2009.07.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Accepted: 07/01/2009] [Indexed: 11/18/2022]
Abstract
A recent study [Keri, S., & Benedek, G. (2009). Visual pathway deficit in female fragile x premutation carriers: A potential endophenotype. Brain and Cognition, 69, 291-295] has found Vernier acuity deficiencies together with contrast sensitivity defects consistent with a magnocellular deficit in female fragile x premutation carriers. This may appear to support the notion that Vernier acuity may serve as a test of magnocellular sensitivity. However, Vernier acuity deficiencies have been reported in other conditions (e.g., schizophrenia, amblyopia and cortical visual impairment) where there is little evidence for magnocellular deficits. The observation that Vernier acuity deficiencies can occur without magnocellular deficits indicates that Vernier acuity is not a reliable test of magnocellular sensitivity.
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