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Newbolds SF, Wenger MJ. Assessing the pattern electroretinogram as a proxy measure for dopamine in the context of iron deficiency. Nutr Neurosci 2024:1-12. [PMID: 38272898 DOI: 10.1080/1028415x.2024.2304943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2024]
Abstract
OBJECTIVES Animal studies have suggested that dietary iron deficiency (ID) negatively affects dopamine (DA) synthesis and re-uptake, which in turn negatively affects memory and cognition. This study was intended to assess whether the pattern electroretinogram (pattern ERG) could be used as an indirect measure of DA in college-age women with and without ID by determining the extent to which features of the ERG were sensitive to iron status and were related to other indirect measures of DA. METHODS The pattern ERG was measured in 21 iron deficient non-anemic (IDNA) and 21 iron sufficient (IS) women, who also performed a contrast detection and probabilistic selection task, both with concurrent electroencephalography (EEG). Both spontaneous and task-related blink rates were also measured. RESULTS The implicit times of the A- and B-waves were significantly longer for the IDNA than for the IS women. Both the amplitudes and implicit times of the A- and B-waves were significantly correlated with levels of serum ferritin (sFt). Only the amplitude of the A-wave was correlated with spontaneous blink rate. It was possible to accurately identify a woman's iron status solely on the basis of the implicit time of the B-wave. Finally, the implicit times of the ERG features mediated the relationship between iron levels and accuracy in the probabilistic selection task. CONCLUSIONS Results suggest the utility of the pattern ERG in testing the hypothesis that iron deficiency affects DA levels in humans and that this may be one of the mechanisms by which iron deficiency negatively affects cognition.
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Affiliation(s)
- Sarah F Newbolds
- Psychology and Cellular and Behavioral Neurobiology, The University of Oklahoma, Norman, OK, USA
| | - Michael J Wenger
- Psychology and Cellular and Behavioral Neurobiology, The University of Oklahoma, Norman, OK, USA
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2
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Constable PA, Lim JKH, Thompson DA. Retinal electrophysiology in central nervous system disorders. A review of human and mouse studies. Front Neurosci 2023; 17:1215097. [PMID: 37600004 PMCID: PMC10433210 DOI: 10.3389/fnins.2023.1215097] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 07/17/2023] [Indexed: 08/22/2023] Open
Abstract
The retina and brain share similar neurochemistry and neurodevelopmental origins, with the retina, often viewed as a "window to the brain." With retinal measures of structure and function becoming easier to obtain in clinical populations there is a growing interest in using retinal findings as potential biomarkers for disorders affecting the central nervous system. Functional retinal biomarkers, such as the electroretinogram, show promise in neurological disorders, despite having limitations imposed by the existence of overlapping genetic markers, clinical traits or the effects of medications that may reduce their specificity in some conditions. This narrative review summarizes the principal functional retinal findings in central nervous system disorders and related mouse models and provides a background to the main excitatory and inhibitory retinal neurotransmitters that have been implicated to explain the visual electrophysiological findings. These changes in retinal neurochemistry may contribute to our understanding of these conditions based on the findings of retinal electrophysiological tests such as the flash, pattern, multifocal electroretinograms, and electro-oculogram. It is likely that future applications of signal analysis and machine learning algorithms will offer new insights into the pathophysiology, classification, and progression of these clinical disorders including autism, attention deficit/hyperactivity disorder, bipolar disorder, schizophrenia, depression, Parkinson's, and Alzheimer's disease. New clinical applications of visual electrophysiology to this field may lead to earlier, more accurate diagnoses and better targeted therapeutic interventions benefiting individual patients and clinicians managing these individuals and their families.
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Affiliation(s)
- Paul A. Constable
- College of Nursing and Health Sciences, Caring Futures Institute, Flinders University, Adelaide, SA, Australia
| | - Jeremiah K. H. Lim
- Discipline of Optometry, School of Allied Health, University of Western Australia, Perth, WA, Australia
| | - Dorothy A. Thompson
- The Tony Kriss Visual Electrophysiology Unit, Clinical and Academic Department of Ophthalmology, Great Ormond Street Hospital for Children NHS Trust, London, United Kingdom
- UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
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4
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Chen YW, Huang YP, Wu PC, Chiang WY, Wang PH, Chen BY. The Functional Vision Protection Effect of Danshensu via Dopamine D1 Receptors: In Vivo Study. Nutrients 2021; 13:nu13030978. [PMID: 33803057 PMCID: PMC8002943 DOI: 10.3390/nu13030978] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 03/09/2021] [Accepted: 03/15/2021] [Indexed: 12/22/2022] Open
Abstract
Danshensu, a traditional herb-based active component (Salvia miltiorrhiza Bunge), has garnered attention, due to its safety, nutritional value, and antioxidant effects, along with cardiovascular-protective and neuroprotective abilities; however, its effect on the retinal tissues and functional vision has not been fully studied. The objective of this study was to analyze the protective effect of danshensu on retinal tissues and functional vision in vivo in a mouse model of light-induced retinal degeneration. High energy light-evoked visual damage was confirmed by the loss in structural tissue integrity in the retina accompanied by a decline in visual acuity and visual contrast sensitivity function (VCSF), whereas the retina tissue exhibited severe Müller cell gliosis. Although danshensu treatment did not particularly reduce light-evoked damage to the photoreceptors, it significantly prevented Müller cell gliosis. Danshensu exerted protective effects against light-evoked deterioration on low spatial frequency-based VCSF as determined by the behavioral optomotor reflex method. Additionally, the protective effect of danshensu on VCSF can be reversed and blocked by the injection of a dopamine D1 receptor antagonist (SCH 23390). This study demonstrated that the major functional vision promotional effect of danshensu in vivo was through the dopamine D1 receptors enhancement pathway, rather than the structural protection of the retinas.
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Affiliation(s)
- Yun-Wen Chen
- Department of Ophthalmology, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Kaohsiung 88301, Taiwan; (Y.-W.C.); (P.-C.W.); (W.-Y.C.)
| | - Yun-Ping Huang
- Department of Optometry, Chung Shan Medical University, Taichung 40201, Taiwan; (Y.-P.H.); (P.-H.W.)
| | - Pei-Chang Wu
- Department of Ophthalmology, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Kaohsiung 88301, Taiwan; (Y.-W.C.); (P.-C.W.); (W.-Y.C.)
| | - Wei-Yu Chiang
- Department of Ophthalmology, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Kaohsiung 88301, Taiwan; (Y.-W.C.); (P.-C.W.); (W.-Y.C.)
| | - Ping-Hsun Wang
- Department of Optometry, Chung Shan Medical University, Taichung 40201, Taiwan; (Y.-P.H.); (P.-H.W.)
| | - Bo-Yie Chen
- Department of Optometry, Chung Shan Medical University, Taichung 40201, Taiwan; (Y.-P.H.); (P.-H.W.)
- Department of Ophthalmology, Chung Shan Medical University Hospital, Taichung 40201, Taiwan
- Correspondence: ; Tel.: +886-4-2473-0022 (ext. 12319)
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5
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Retinal functioning and reward processing in schizophrenia. Schizophr Res 2020; 219:25-33. [PMID: 31280976 DOI: 10.1016/j.schres.2019.06.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 06/16/2019] [Accepted: 06/19/2019] [Indexed: 11/21/2022]
Abstract
Retinal responses to light, as measured by electroretinography (ERG), have been shown to be reduced in schizophrenia. Data from a prior ERG study in healthy humans indicated that activity of a retinal cell type affected in schizophrenia can be modified by the presence of a food reward. Therefore, we aimed to determine whether ERG amplitudes would be sensitive to the well-documented reward processing impairment in schizophrenia. Flash ERG data from 15 clinically stable people with schizophrenia or schizoaffective disorder and 15 healthy controls were collected under three conditions: baseline, anticipation of a food reward, and immediately after consuming the food reward. At the group level, data indicated that controls' ERG responses varied as a function of salience of the food reward (baseline vs. anticipation vs. consumption) whereas patients' ERG responses did not vary significantly across conditions. Correlations between ERG amplitudes and scores on measures of hedonic capacity (including motivation and pleasure negative symptom ratings for patients) indicated consistent relationships. These data suggest that flash ERG amplitudes may be a sensitive indicator of the integrity of reward processing mechanisms. However, several differences in the direction of findings between this and a prior study in controls point to the need for further investigation of the contributions of a number of key variables to the observed effects.
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Harper L, Spencer E, Davidson C, Hutchinson CV. Selectively reduced contrast sensitivity in high schizotypy. Exp Brain Res 2020; 238:51-62. [PMID: 31781821 PMCID: PMC6957544 DOI: 10.1007/s00221-019-05695-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2019] [Accepted: 11/15/2019] [Indexed: 11/30/2022]
Abstract
Deficits in the ability to encode small differences in contrast between adjacent parts of an image (contrast sensitivity) are well documented in schizophrenic patients. In the present study, we sought to determine whether contrast sensitivity deficits reported in schizophrenic patients are also evident in those who exhibit high schizotypy scores in a typical (i.e., non-schizophrenic) population. Using the O-Life Questionnaire, we determined the effects of schizotypy on spatial (0.5, 2 and 8 c/deg) and spatiotemporal (0.5 and 8 c/deg at 0.5 and 8 Hz) contrast sensitivity in 73 young (18-26 years), majority female (n = 68) participants. We found differences in contrast sensitivity that were spatial, spatiotemporal and O-Life subscale specific. Spatial contrast sensitivity was significantly lower in high, compared to low schizotypes at low spatial frequencies (0.5 c/deg) in those who scored highly on the Unusual Experiences and Cognitive Disorganisation O-Life subscales. For moving stimuli, individuals with high scores on the Unusual Experiences subscale exhibited lower spatiotemporal contrast sensitivity for 0.5 and 8 c/deg patterns drifting at 8 Hz. Although the effects reported here were relatively small, this is the first report of reduced contrast sensitivity in schizotypy.
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Affiliation(s)
- Lauren Harper
- Department of Neuroscience, Psychology and Behaviour, College of Life Sciences, University of Leicester, Leicester, UK
| | - Emily Spencer
- Department of Neuroscience, Psychology and Behaviour, College of Life Sciences, University of Leicester, Leicester, UK
| | - Colin Davidson
- School of Pharmacy and Biomedical Sciences, Faculty of Clinical and Biomedical Sciences, University of Central Lancashire, Preston, UK
| | - Claire V Hutchinson
- Department of Neuroscience, Psychology and Behaviour, College of Life Sciences, University of Leicester, Leicester, UK.
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7
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Parisi V, Barbano L, Di Renzo A, Coppola G, Ziccardi L. Neuroenhancement and neuroprotection by oral solution citicoline in non-arteritic ischemic optic neuropathy as a model of neurodegeneration: A randomized pilot study. PLoS One 2019; 14:e0220435. [PMID: 31348806 PMCID: PMC6660126 DOI: 10.1371/journal.pone.0220435] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 07/05/2019] [Indexed: 12/02/2022] Open
Abstract
PURPOSE To evaluate whether treatment with Citicoline in oral solution (OS-Citicoline) would increase visual function, retinal ganglion cells (RGCs) function, and neural conduction along visual pathways (neuroenhancement), and/or induce preservation of RGCs fibers' loss (neuroprotection) in non-arteritic ischemic optic neuropathy (NAION), a human model of neurodegeneration. METHODS Thirty-six patients with NAION and 20 age-matched controls were enrolled. Nineteen NAION patients received 500 mg/day of OS-Citicoline for a 6-month period followed by 3-month of wash-out (NC Group); 17 NAION patients were not treated (NN Group) from baseline to 9 months. In all subjects at baseline, and in NC and NN eyes at 6 and 9 months of follow-up, we assessed Visual Acuity (VA), Pattern Electroretinogram (PERG), Visual Evoked Potentials (VEP), retinal nerve fiber layer thickness (RNFL-T), and Humphrey 24-2 visual field mean deviation (HFA MD). Mean differences were statistically evaluated with ANOVA between Groups, and linear correlations were analysed with Pearson's test. RESULTS At 6 months, significant differences between groups for all parameters were observed (ANOVA, p<0.01). In NC eyes, VA increased, PERG responses increased, VEP recordings improved and were significantly correlated with increases in HFA MD (p<0.01), and RNFL-T was unmodified or improved. In contrast, in NN eyes, VA, PERG, VEP responses, RNFL-T, and HFA MD were further worsened. Significant differences were still present at 9-month follow-up in the NN Group and after 3 months of OS-Citicoline wash-out in NC eyes. CONCLUSIONS OS-Citicoline treatment induced neuroenhancement (improvement in RGCs function and neural conduction along visual pathways related to improvement of visual field defects) and neuroprotection (unmodified or improved RNFL morphological condition) in a human model of NAION involving fast RGCs degeneration. TRIAL REGISTRATION ClinicalTrials.gov NCT03758118.
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Affiliation(s)
| | | | | | - Gianluca Coppola
- Department of Medico-Surgical Sciences and Biotechnologies, Sapienza University of Rome—Polo Pontino, Latina, Italy
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8
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Zhang Y, Phan E, Wildsoet CF. Retinal Defocus and Form-Deprivation Exposure Duration Affects RPE BMP Gene Expression. Sci Rep 2019; 9:7332. [PMID: 31089149 PMCID: PMC6517395 DOI: 10.1038/s41598-019-43574-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 04/23/2019] [Indexed: 11/09/2022] Open
Abstract
In the context of ocular development and eye growth regulation, retinal defocus and/or image contrast appear key variables although the nature of the signal(s) relayed from the retina to the sclera remains poorly understood. Nonetheless, under optimal visual conditions, eye length is brought into alignment with its optical power to achieve approximate emmetropia, through appropriate adjustment to eye growth. The retinal pigment epithelium (RPE), which lies between the retina and choroid/sclera, appears to play a crucial role in this process. In the investigations reported here, we used a chick model system to assess the threshold duration of exposure to lens-imposed defocus and form-deprivation necessary for conversion of evoked retinal signals into changes in BMP gene expression in the RPE. Our study provides evidence for the following: 1) close-loop, optical defocus-guided (negative and positive lenses) bidirectional BMP gene expression regulation, 2) open-loop, form-deprivation (diffusers)-induced down-regulation of BMP gene expression, and 3) early, transient up-regulation of BMP gene expression in response to both types of lens and diffuser applications. The critical exposure for accurately encoding retinal images as biological signals at the level of the RPE is in the order of minutes to hours, depending on the nature of the visual manipulations.
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Affiliation(s)
- Yan Zhang
- School of Optometry, University of California, Berkeley, Berkeley, CA, USA.
| | - Eileen Phan
- School of Optometry, University of California, Berkeley, Berkeley, CA, USA
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9
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Lee H, Scott J, Griffiths H, Self JE, Lotery A. Oral levodopa rescues retinal morphology and visual function in a murine model of human albinism. Pigment Cell Melanoma Res 2019; 32:657-671. [PMID: 30851223 PMCID: PMC6766973 DOI: 10.1111/pcmr.12782] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 02/07/2019] [Accepted: 03/04/2019] [Indexed: 01/10/2023]
Abstract
Albinism is a group of disorders characterized by pigment deficiency and abnormal retinal development. Despite being a common cause for visual impairment worldwide, there is a paucity of treatments and patients typically suffer lifelong visual disability. Residual plasticity of the developing retina in young children with albinism has been demonstrated, suggesting a post-natal window for therapeutic rescue. L-3, 4 dihydroxyphenylalanine (L-DOPA), a key signalling molecule which is essential for normal retinal development, is known to be deficient in albinism. In this study, we demonstrate for the first time that post-natal L-DOPA supplementation can rescue retinal development, morphology and visual function in a murine model of human albinism, but only if administered from birth or 15 days post-natal age.
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Affiliation(s)
- Helena Lee
- Clinical and Experimental Sciences, Faculty of Medicine, Sir Henry Wellcome Laboratories, Southampton University Hospital, University of Southampton, Southampton, UK.,Eye Unit, University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Jennifer Scott
- Clinical and Experimental Sciences, Faculty of Medicine, Sir Henry Wellcome Laboratories, Southampton University Hospital, University of Southampton, Southampton, UK
| | - Helen Griffiths
- Clinical and Experimental Sciences, Faculty of Medicine, Sir Henry Wellcome Laboratories, Southampton University Hospital, University of Southampton, Southampton, UK
| | - Jay E Self
- Clinical and Experimental Sciences, Faculty of Medicine, Sir Henry Wellcome Laboratories, Southampton University Hospital, University of Southampton, Southampton, UK.,Eye Unit, University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Andrew Lotery
- Clinical and Experimental Sciences, Faculty of Medicine, Sir Henry Wellcome Laboratories, Southampton University Hospital, University of Southampton, Southampton, UK.,Eye Unit, University Hospital Southampton NHS Foundation Trust, Southampton, UK
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10
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Guo L, Normando EM, Shah PA, De Groef L, Cordeiro MF. Oculo-visual abnormalities in Parkinson's disease: Possible value as biomarkers. Mov Disord 2018; 33:1390-1406. [DOI: 10.1002/mds.27454] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 05/16/2018] [Accepted: 05/18/2018] [Indexed: 12/16/2022] Open
Affiliation(s)
- Li Guo
- Glaucoma and Retinal Degenerative Disease Research Group, Institute of Ophthalmology; University College London; London UK
| | - Eduardo M. Normando
- Glaucoma and Retinal Degenerative Disease Research Group, Institute of Ophthalmology; University College London; London UK
- Western Eye Hospital, Imperial College Healthcare National Health Service Trust; London UK
- Imperial College Ophthalmology Research Group, Department of Surgery and Cancer, Imperial College London; London UK
| | - Parth Arvind Shah
- Glaucoma and Retinal Degenerative Disease Research Group, Institute of Ophthalmology; University College London; London UK
| | - Lies De Groef
- Glaucoma and Retinal Degenerative Disease Research Group, Institute of Ophthalmology; University College London; London UK
- Neural Circuit Development and Regeneration Research Group, Department of Biology; University of Leuven; Leuven Belgium
| | - M. Francesca Cordeiro
- Glaucoma and Retinal Degenerative Disease Research Group, Institute of Ophthalmology; University College London; London UK
- Western Eye Hospital, Imperial College Healthcare National Health Service Trust; London UK
- Imperial College Ophthalmology Research Group, Department of Surgery and Cancer, Imperial College London; London UK
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11
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Mikulskaya E, Martin FH. Contrast sensitivity and motion discrimination in cannabis users. Psychopharmacology (Berl) 2018; 235:2459-2469. [PMID: 29909427 DOI: 10.1007/s00213-018-4944-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 06/05/2018] [Indexed: 01/09/2023]
Abstract
RATIONALE Cannabis use impairs visual attention; however, it is unclear whether cannabis use also impairs low level visual processing or whether low level visual deficits can be related to lower dopaminergic functioning found in cannabis users. OBJECTIVES To investigate whether spatiotemporal contrast sensitivity and motion discrimination under normal and low luminance conditions differ in cannabis users and non-users. METHODS Control (n = 20) and cannabis (n = 21) participants completed a visual acuity test, a saliva test and self-report measures. Spatial and temporal contrast thresholds, motion coherence thresholds for translational and radial motion and the spontaneous eye blink rate were then collected. RESULTS Cannabis users showed decreased spatial contrast sensitivity under low luminance conditions and increased motion coherence thresholds under all luminance levels tested compared to non-users. No differences in temporal contrast sensitivity were found between the groups. Frequency of cannabis use correlated significantly and negatively with contrast sensitivity, both spatial and temporal, in the cannabis group and higher motion coherence thresholds for radial motion were also associated with more frequent cannabis use in this group. The eye blink rate was significantly lower in cannabis users compared to non-users. CONCLUSIONS The present study shows that cannabis use is associated with deficits in low level visual processing. Such deficits are suggested to relate to lower dopamine, in a similar manner as in clinical populations. The implications for driving safety under reduced visibility (e.g. night) in abstaining cannabis users are discussed.
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Affiliation(s)
- Elena Mikulskaya
- School of Psychology, University of Newcastle, Ourimbah, NSW, 2258, Australia.,TIEI, Russian Federation, Tula University, Tula, Russia
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12
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Mantovani S, Smith SS, Gordon R, O'Sullivan JD. An overview of sleep and circadian dysfunction in Parkinson's disease. J Sleep Res 2018; 27:e12673. [PMID: 29493044 DOI: 10.1111/jsr.12673] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 01/15/2018] [Accepted: 01/15/2018] [Indexed: 12/18/2022]
Abstract
Sleep and circadian alterations are amongst the very first symptoms experienced in Parkinson's disease, and sleep alterations are present in the majority of patients with overt clinical manifestation of Parkinson's disease. However, the magnitude of sleep and circadian dysfunction in Parkinson's disease, and its influence on the pathophysiology of Parkinson's disease remains often unclear and a matter of debate. In particular, the confounding influences of dopaminergic therapy on sleep and circadian dysfunction are a major challenge, and need to be more carefully addressed in clinical studies. The scope of this narrative review is to summarise the current knowledge around both sleep and circadian alterations in Parkinson's disease. We provide an overview on the frequency of excessive daytime sleepiness, insomnia, restless legs, obstructive apnea and nocturia in Parkinson's disease, as well as addressing sleep structure, rapid eye movement sleep behaviour disorder and circadian features in Parkinson's disease. Sleep and circadian disorders have been linked to pathological conditions that are often co-morbid in Parkinson's disease, including cognitive decline, memory impairment and neurodegeneration. Therefore, targeting sleep and circadian alterations could be one of the earliest and most promising opportunities to slow disease progression. We hope that this review will contribute to advance the discussion and inform new research efforts to progress our knowledge in this field.
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Affiliation(s)
- Susanna Mantovani
- Faculty of Medicine, The University of Queensland, UQ Centre for Clinical Research, Herston, QLD, Australia.,Wesley Medical Research, Auchenflower, QLD, Australia.,Department of Neurology, Royal Brisbane and Women's Hospital, Herston, QLD, Australia
| | - Simon S Smith
- Institute for Social Science Research (ISSR), The University of Queensland, Indooroopilly, Australia
| | - Richard Gordon
- Faculty of Medicine, The University of Queensland, UQ Centre for Clinical Research, Herston, QLD, Australia.,Wesley Medical Research, Auchenflower, QLD, Australia
| | - John D O'Sullivan
- Faculty of Medicine, The University of Queensland, UQ Centre for Clinical Research, Herston, QLD, Australia.,Wesley Medical Research, Auchenflower, QLD, Australia.,Department of Neurology, Royal Brisbane and Women's Hospital, Herston, QLD, Australia
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13
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Leinonen H, Tanila H. Vision in laboratory rodents-Tools to measure it and implications for behavioral research. Behav Brain Res 2017; 352:172-182. [PMID: 28760697 DOI: 10.1016/j.bbr.2017.07.040] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/17/2017] [Accepted: 07/27/2017] [Indexed: 02/09/2023]
Abstract
Mice and rats are nocturnal mammals and their vision is specialized for detection of motion and contrast in dim light conditions. These species possess a large proportion of UV-sensitive cones in their retinas and the majority of their optic nerve axons target superior colliculus rather than visual cortex. Therefore, it was a widely held belief that laboratory rodents hardly utilize vision during day-time behavior. This dogma is being questioned as accumulating evidence suggests that laboratory rodents are able to perform complex visual functions, such as perceiving subjective contours, and that declined vision may affect their performance in many behavioral tasks. For instance, genetic engineering may have unexpected consequences on vision as mouse models of Alzheimer's and Huntington's diseases have declined visual function. Rodent vision can be tested in numerous ways using operant training or reflex-based behavioral tasks, or alternatively using electrophysiological recordings. In this article, we will first provide a summary of visual system and explain its characteristics unique to rodents. Then, we present well-established techniques to test rodent vision, with an emphasis on pattern vision: visual water test, optomotor reflex test, pattern electroretinography and pattern visual evoked potentials. Finally, we highlight the importance of visual phenotyping in rodents. As the number of genetically engineered rodent models and volume of behavioral testing increase simultaneously, the possibility of visual dysfunctions needs to be addressed. Neglect in this matter potentially leads to crude biases in the field of neuroscience and beyond.
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Affiliation(s)
- Henri Leinonen
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, P.O. Box 1627, Neulaniementie 2, 70211 Kuopio, Finland.
| | - Heikki Tanila
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, P.O. Box 1627, Neulaniementie 2, 70211 Kuopio, Finland
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Abstract
This chapter describes the visual problems likely to be encountered in Parkinson's disease (PD) and whether such signs are useful in differentiating the parkinsonian syndromes. Visual dysfunction in PD may involve visual acuity, contrast sensitivity, color discrimination, pupil reactivity, saccadic and pursuit eye movements, motion perception, visual fields, and visual processing speeds. In addition, disturbance of visuospatial orientation, facial recognition problems, rapid eye movement (REM) sleep behavior disorder, and chronic visual hallucinations may be present. Problems affecting pupil reactivity, stereopsis, pursuit eye movement, and visuomotor adaptation, when accompanied by REM sleep behavior disorder, could be early features of PD. Dementia associated with PD is associated with enhanced eye movement problems, visuospatial deficits, and visual hallucinations. Visual dysfunction may be a useful diagnostic feature in differentiating PD from other parkinsonian symptoms, visual hallucinations, visuospatial dysfunction, and variation in saccadic eye movement problems being particularly useful discriminating features.
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15
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Dopamine promotes NMDA receptor hypofunction in the retina through D 1 receptor-mediated Csk activation, Src inhibition and decrease of GluN2B phosphorylation. Sci Rep 2017; 7:40912. [PMID: 28098256 PMCID: PMC5241882 DOI: 10.1038/srep40912] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 12/12/2016] [Indexed: 11/21/2022] Open
Abstract
Dopamine and glutamate are critical neurotransmitters involved in light-induced synaptic activity in the retina. In brain neurons, dopamine D1 receptors (D1Rs) and the cytosolic protein tyrosine kinase Src can, independently, modulate the behavior of NMDA-type glutamate receptors (NMDARs). Here we studied the interplay between D1Rs, Src and NMDARs in retinal neurons. We reveal that dopamine-mediated D1R stimulation provoked NMDAR hypofunction in retinal neurons by attenuating NMDA-gated currents, by preventing NMDA-elicited calcium mobilization and by decreasing the phosphorylation of NMDAR subunit GluN2B. This dopamine effect was dependent on upregulation of the canonical D1R/adenylyl cyclase/cAMP/PKA pathway, of PKA-induced activation of C-terminal Src kinase (Csk) and of Src inhibition. Accordingly, knocking down Csk or overexpressing a Csk phosphoresistant Src mutant abrogated the dopamine-induced NMDAR hypofunction. Overall, the interplay between dopamine and NMDAR hypofunction, through the D1R/Csk/Src/GluN2B pathway, might impact on light-regulated synaptic activity in retinal neurons.
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Abstract
Although visual processing impairments are common in schizophrenia, it is not clear to what extent these originate in the eye vs. the brain. This review highlights potential contributions, from the retina and other structures of the eye, to visual processing impairments in schizophrenia and high-risk states. A second goal is to evaluate the status of retinal abnormalities as biomarkers for schizophrenia. The review was motivated by known retinal changes in other disorders (e.g., Parkinson’s disease, multiple sclerosis), and their relationships to perceptual and cognitive impairments, and disease progression therein. The evidence reviewed suggests two major conclusions. One is that there are multiple structural and functional disturbances of the eye in schizophrenia, all of which could be factors in the visual disturbances of patients. These include retinal venule widening, retinal nerve fiber layer thinning, dopaminergic abnormalities, abnormal ouput of retinal cells as measured by electroretinography (ERG), maculopathies and retinopathies, cataracts, poor acuity, and strabismus. Some of these are likely to be illness-related, whereas others may be due to medication or comorbid conditions. The second conclusion is that certain retinal findings can serve as biomarkers of neural pathology, and disease progression, in schizophrenia. The strongest evidence for this to date involves findings of widened retinal venules, thinning of the retinal nerve fiber layer, and abnormal ERG amplitudes. These data suggest that a greater understanding of the contribution of retinal and other ocular pathology to the visual and cognitive disturbances of schizophrenia is warranted, and that retinal changes have untapped clinical utility.
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Abstract
This review describes the oculo-visual problems likely to be encountered in Parkinson's disease (PD) with special reference to three questions: (1) are there visual symptoms characteristic of the prodromal phase of PD, (2) is PD dementia associated with specific visual changes, and (3) can visual symptoms help in the differential diagnosis of the parkinsonian syndromes, viz. PD, progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB), multiple system atrophy (MSA), and corticobasal degeneration (CBD)? Oculo-visual dysfunction in PD can involve visual acuity, dynamic contrast sensitivity, colour discrimination, pupil reactivity, eye movement, motion perception, and visual processing speeds. In addition, disturbance of visuo-spatial orientation, facial recognition problems, and chronic visual hallucinations may be present. Prodromal features of PD may include autonomic system dysfunction potentially affecting pupil reactivity, abnormal colour vision, abnormal stereopsis associated with postural instability, defects in smooth pursuit eye movements, and deficits in visuo-motor adaptation, especially when accompanied by idiopathic rapid eye movement (REM) sleep behaviour disorder. PD dementia is associated with the exacerbation of many oculo-visual problems but those involving eye movements, visuo-spatial function, and visual hallucinations are most characteristic. Useful diagnostic features in differentiating the parkinsonian symptoms are the presence of visual hallucinations, visuo-spatial problems, and variation in saccadic eye movement dysfunction.
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Visual contrast sensitivity in major depressive disorder. J Psychosom Res 2013; 75:83-6. [PMID: 23751244 DOI: 10.1016/j.jpsychores.2013.03.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 03/12/2013] [Accepted: 03/15/2013] [Indexed: 11/23/2022]
Abstract
OBJECTIVE Through the eyes of those depressed, the world may appear dull and gray. Visual contrast sensitivity has recently been reported to be lower in depressed patients compared to healthy controls. We aimed to examine the consistency of this finding and to explore the underlying retinal electrophysiology. METHODS Twenty subjects with major depressive disorder and 20 matched healthy controls were studied. Pattern electroretinogram (PERG) and subjective visual contrast test were used to assess visual contrast sensitivity. Full-field electroretinography (ffERG) was additionally used to assess retinal neurophysiology. Depression was diagnosed based on the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) and depression severity was measured using standard psychometric scales. RESULTS Visual contrast sensitivity was significantly lower in depressed patients compared to controls based on the Landolt C visual contrast test, but no difference was found between groups using PERG and ffERG. Greater severity of depressive symptoms correlated (r=0.49, p=0.001) with poorer visual contrast sensitivity. CONCLUSIONS Depressed subjects had reduced visual contrast discrimination performance, but this finding could not be consistently determined using PERG. The neurobiological link between major depressive disorder and visual contrast sensitivity warrants further investigation.
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Bubl E, Dörr M, Philipsen A, Ebert D, Bach M, van Elst LT. Retinal contrast transfer functions in adults with and without ADHD. PLoS One 2013; 8:e61728. [PMID: 23658697 PMCID: PMC3642133 DOI: 10.1371/journal.pone.0061728] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Accepted: 03/13/2013] [Indexed: 11/19/2022] Open
Abstract
In previous studies, we found a strong reduction in contrast perception and retinal contrast gain in patients with major depression, which normalized after remission of depression. We also identified a possible role of the dopaminergic system in this effect, because visual contrast perception depends on dopaminergic neurotransmission. Dopamine is also known to play an important role in the pathogenesis of attention deficit hyperactivity disorder (ADHD). Therefore, in order to explore the specificity of retinal contrast gain as a marker of depression in comparison with other psychiatric diseases, we recorded the pattern electroretinogram (PERG) in patients with ADHD. Twenty patients diagnosed with ADHD and 20 matched healthy subjects were studied. Visual pattern electroretinograms were recorded from both eyes. The contrast gain of the patients with attention deficit disorder (ADD) did not differ from the control group, nor did the contrast gain of any ADHD subgroup (predominantly inattentive or combined patients). In the healthy subjects, a significant correlation between depression score and contrast gain was found. As the contrast gain in an earlier study clearly separated the patients with depression from the controls, we assume that retinal contrast gain might be a specific marker in depression.
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Affiliation(s)
- Emanuel Bubl
- Department of Psychiatry and Psychotherapy, Albert-Ludwigs-University of Freiburg, Freiburg, Germany
| | - Michael Dörr
- Department of Psychiatry and Psychotherapy, Albert-Ludwigs-University of Freiburg, Freiburg, Germany
| | - Alexandra Philipsen
- Department of Psychiatry and Psychotherapy, Albert-Ludwigs-University of Freiburg, Freiburg, Germany
| | - Dieter Ebert
- Department of Psychiatry and Psychotherapy, Albert-Ludwigs-University of Freiburg, Freiburg, Germany
| | - Michael Bach
- University Eye Hospital, Albert-Ludwigs-University of Freiburg, Freiburg, Germany
| | - Ludger Tebartz van Elst
- Department of Psychiatry and Psychotherapy, Albert-Ludwigs-University of Freiburg, Freiburg, Germany
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Blue-yellow colour vision impairment and cognitive deficits in occasional and dependent stimulant users. Int J Neuropsychopharmacol 2013; 16:535-47. [PMID: 22704223 DOI: 10.1017/s1461145712000624] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Specific blue-yellow colour vision impairment has been reported in dependent cocaine users and it was postulated that drug-induced changes in retinal dopamine neurotransmission are responsible. However, it is unclear whether these changes are confined to chronic cocaine users, whether they are specific for dopaminergic stimulants such as cocaine and amphetamine and whether they are related to cognitive functions such as working memory, encoding and consolidation. In 47 occasional and 29 dependent cocaine users, 23 MDMA (commonly known as 'ecstasy') users and 47 stimulant-naive controls, colour vision discrimination was measured with the Lanthony Desaturated Panel D-15 Test and memory performance with the Auditory Verbal Learning Test. Both occasional and dependent cocaine users showed higher colour confusion indices than controls. Users of the serotonergic stimulant MDMA (26%), occasional (30%) and dependent cocaine users (34%) exhibited more frequent blue-yellow colour vision disorders compared to controls (9%). Inferior performance of MDMA users was caused by a subgroup with high amphetamine co-use (55%), while MDMA use alone was not associated with decreased blue-yellow discrimination (0%). Cognitive performance was worse in cocaine users with colour vision disorder compared to users and controls with intact colour vision and both colour vision impairment and cognitive deficits were related to cocaine use. Occasional cocaine and amphetamine use might induce blue-yellow colour vision impairment, whereas the serotonergic stimulant MDMA does not impair colour vision. The association between colour vision impairment and cognitive deficits in cocaine users may reflect that retinal and cerebral dopamine alterations are linked to a certain degree.
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Foveal vision is impaired in Parkinson's disease. Parkinsonism Relat Disord 2013; 19:1-14. [DOI: 10.1016/j.parkreldis.2012.07.012] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Revised: 07/16/2012] [Accepted: 07/21/2012] [Indexed: 11/23/2022]
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Bozkurt H, Ayaydın H, Adak İ, Zoroğlu SS. Risperidone-induced paroxysmal perceptual alteration in a child with autism. J Child Adolesc Psychopharmacol 2012; 22:470-1. [PMID: 23234592 DOI: 10.1089/cap.2012.0053] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Hasan Bozkurt
- Istanbul Medical Faculty, Department of Child and Adolescent Psychiatry, Istanbul University, Istanbul, Turkey
| | - Hamza Ayaydın
- Istanbul Medical Faculty, Department of Child and Adolescent Psychiatry, Istanbul University, Istanbul, Turkey
| | - İbrahim Adak
- Istanbul Medical Faculty, Department of Child and Adolescent Psychiatry, Istanbul University, Istanbul, Turkey
| | - S. Salih Zoroğlu
- Istanbul Medical Faculty, Department of Child and Adolescent Psychiatry, Istanbul University, Istanbul, Turkey
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Alexander GE. Biology of Parkinson's disease: pathogenesis and pathophysiology of a multisystem neurodegenerative disorder. DIALOGUES IN CLINICAL NEUROSCIENCE 2012. [PMID: 22033559 PMCID: PMC3181806 DOI: 10.31887/dcns.2004.6.3/galexander] [Citation(s) in RCA: 272] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Parkinson's disease (PD) is the second most common movement disorder. The characteristic motor impairments - bradykinesia, rigidity, and resting tremor - result from degenerative loss of midbrain dopamine (DA) neurons in the substantia nigra, and are responsive to symptomatic treatment with dopaminergic medications and functional neurosurgery. PD is also the second most common neurodegenerative disorder. Viewed from this perspective, PD is a disorder of multiple functional systems, not simply the motor system, and of multiple neurotransmitter systems, not merely that of DA. The characteristic pathology - intraneuronal Lewy body inclusions and reduced numbers of surviving neurons - is similar in each of the targeted neuron groups, suggesting a common neurodegenerative process. Pathological and experimental studies indicate that oxidative stress, proteolytic stress, and inflammation figure prominently in the pathogenesis of PD. Yet, whether any of these mechanisms plays a causal role in human PD is unknown, because to date we have no proven neuroprotective therapies that slow or reverse disease progression in patients with PD. We are beginning to understand the pathophysiology of motor dysfunction in PD, but its etiopathogenesis as a neurodegenerative disorder remains poorly understood.
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Affiliation(s)
- Garrett E Alexander
- Department of Neurology, Emory University School of Medicine, Atlanta, Ga, USA
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25
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Jackson CR, Ruan GX, Aseem F, Abey J, Gamble K, Stanwood G, Palmiter RD, Iuvone PM, McMahon DG. Retinal dopamine mediates multiple dimensions of light-adapted vision. J Neurosci 2012; 32:9359-68. [PMID: 22764243 PMCID: PMC3400466 DOI: 10.1523/jneurosci.0711-12.2012] [Citation(s) in RCA: 184] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 05/14/2012] [Accepted: 05/19/2012] [Indexed: 11/21/2022] Open
Abstract
Dopamine is a key neuromodulator in the retina and brain that supports motor, cognitive, and visual function. Here, we developed a mouse model on a C57 background in which expression of the rate-limiting enzyme for dopamine synthesis, tyrosine hydroxylase, is specifically disrupted in the retina. This model enabled assessment of the overall role of retinal dopamine in vision using electrophysiological (electroretinogram), psychophysical (optokinetic tracking), and pharmacological techniques. Significant disruptions were observed in high-resolution, light-adapted vision caused by specific deficits in light responses, contrast sensitivity, acuity, and circadian rhythms in this retinal dopamine-depleted mouse model. These global effects of retinal dopamine on vision are driven by the differential actions of dopamine D1 and D4 receptors on specific retinal functions and appear to be due to the ongoing bioavailability of dopamine rather than developmental effects. Together, our data indicate that dopamine is necessary for the circadian nature of light-adapted vision as well as optimal contrast detection and acuity.
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Affiliation(s)
- Chad R. Jackson
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235
| | - Guo-Xiang Ruan
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235
| | - Fazila Aseem
- Departments of Ophthalmology and Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Jane Abey
- Departments of Ophthalmology and Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Karen Gamble
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama-Birmingham, Birmingham, Alabama 35294-0017
| | - Greg Stanwood
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, and
| | - Richard D. Palmiter
- Howard Hughes Medical Institute and Department of Biochemistry, University of Washington, Seattle, Washington 98195
| | - P. Michael Iuvone
- Departments of Ophthalmology and Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Douglas G. McMahon
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235
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Rohani M, Langroodi AS, Ghourchian S, Falavarjani KG, SoUdi R, Shahidi G. Retinal nerve changes in patients with tremor dominant and akinetic rigid Parkinson's disease. Neurol Sci 2012; 34:689-93. [PMID: 22661077 DOI: 10.1007/s10072-012-1125-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 05/22/2012] [Indexed: 11/28/2022]
Abstract
Parkinson disease is a multisystem neurodegenerative disease which involves not only basal ganglia and extrapyramidal system but also many other neurologic systems such as retinal ganglion cells. Optical coherence tomography (OCT) is a non-invasive method for assessment of retinal nerve fiber layer (RNFL) thickness and its changes in different diseases. To evaluate the RNFL thickness in patients with Parkinson disease (PD), we performed OCT in patients with PD and compared it with a control group. From October 2010 to July 2011, 27 PD patients (54 eyes) and 25 healthy persons (50 eyes) were entered to this analytical cross-sectional study according to the defined criteria. PD patients were categorized into two groups "akinetic rigid (AR) and tremor dominant (TD)". RNFL was divided into four quadrants and was assessed by OCT. Afterwards; the data were analyzed by bivariate and multivariate models. The RNFL thickness in PD was significantly lower than the control group. Also, the thicknesses of inferior and nasal quadrants of RNFL in TD group were significantly more than AR group. According to these findings, OCT can be used as a sensitive and objective marker for assessment of early neurodegenerative changes of PD and early initiation of neuroprotective treatments. Future studies with adequate sample sizes are recommended to investigate interactions between age, distribution of the disease and type of PD as well as the effects of individual factors.
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Affiliation(s)
- Mohammad Rohani
- Department of Neurology, Tehran University of Medical Sciences, Tehran, Iran
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27
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Visusminderung nach Pipamperon-Therapie. Ophthalmologe 2011; 108:763-5. [DOI: 10.1007/s00347-011-2349-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Armstrong RA. Visual symptoms in Parkinson's disease. PARKINSON'S DISEASE 2011; 2011:908306. [PMID: 21687773 PMCID: PMC3109513 DOI: 10.4061/2011/908306] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 02/21/2011] [Accepted: 03/24/2011] [Indexed: 11/20/2022]
Abstract
Parkinson's disease (PD) is a common disorder of middle-aged and elderly people in which degeneration of the extrapyramidal motor system causes significant movement problems. In some patients, however, there are additional disturbances in sensory systems including loss of the sense of smell and auditory and/or visual problems. This paper is a general overview of the visual problems likely to be encountered in PD. Changes in vision in PD may result from alterations in visual acuity, contrast sensitivity, colour discrimination, pupil reactivity, eye movements, motion perception, visual field sensitivity, and visual processing speeds. Slower visual processing speeds can also lead to a decline in visual perception especially for rapidly changing visual stimuli. In addition, there may be disturbances of visuospatial orientation, facial recognition problems, and chronic visual hallucinations. Some of the treatments used in PD may also have adverse ocular reactions. The pattern electroretinogram (PERG) is useful in evaluating retinal dopamine mechanisms and in monitoring dopamine therapies in PD. If visual problems are present, they can have an important effect on the quality of life of the patient, which can be improved by accurate diagnosis and where possible, correction of such defects.
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Affiliation(s)
- R. A. Armstrong
- Department of Vision Sciences, Aston University, Birmingham B4 7ET, UK
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Kent BW, Weinstein ZA, Passarelli V, Chen Y, Siever LJ. Deficient visual sensitivity in schizotypal personality disorder. Schizophr Res 2011; 127:144-50. [PMID: 20541911 PMCID: PMC2965789 DOI: 10.1016/j.schres.2010.05.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Revised: 05/03/2010] [Accepted: 05/05/2010] [Indexed: 01/07/2023]
Abstract
Schizotypal personality disorder is a personality disorder in the schizophrenia spectrum, sharing genetic and neurobiologic characteristics with schizophrenia. Visual contrast detection, found to be abnormal in chronic schizophrenia, was investigated in schizotypal personality disorder (SPD). Since dopamine in the retina enhances visual contrast detection and SPD patients have relatively reduced dopaminergic activity in the brain compared to schizophrenia patients, it was hypothesized that SPD patients would have decreased to normal contrast sensitivity. Twenty-one subjects with DSM-IV diagnosed SPD, 18 healthy controls, and 12 subjects with a personality disorder unrelated to schizophrenia (OPD) were evaluated for contrast detection using a sinusoidal grating presented at varying temporal frequencies. Subjects also were evaluated neuropsychologically using several standardized neurocognitive tests. A significant effect of subject group was found on the contrast detection threshold (p<0.01) with a significant difference between the SPD group and the healthy control group but not between the OPD group and the healthy control group. The SPD group had higher contrast detection thresholds at all temporal frequencies tested. Correlations were found between contrast detection and performance on the Trail-Making, N-Back, and CPT tasks in SPD patients. These results, based upon a paradigm reflecting dopamine activity in the early visual system, highlight the differences as well as similarities between SPD and schizophrenia with regard to the dopamine system in schizophrenia spectrum (Siever and Davis, 2004).
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Affiliation(s)
- Brendon W. Kent
- Department of Psychiatry, Mount Sinai School of Medicine, New York, New York
| | | | - Vincent Passarelli
- Department of Psychiatry, Mount Sinai School of Medicine, New York, New York
| | - Yue Chen
- Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, Massachusetts
| | - Larry J. Siever
- Department of Psychiatry, Mount Sinai School of Medicine, New York, New York,VISN3 Mental Illness Research Education and Clinical Center, Bronx, New York,Psychiatry Program, James J. Peters Veterans Affairs Medical Center, Bronx, New York
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Oh YS, Kim JS, Chung SW, Song IU, Kim YD, Kim YI, Lee KS. Color vision in Parkinson’s disease and essential tremor. Eur J Neurol 2010; 18:577-83. [DOI: 10.1111/j.1468-1331.2010.03206.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
BACKGROUND Reduced dopaminergic transmission has been implicated in the pathophysiology of major depression. Furthermore, dopaminergic neurotransmission plays an important role in the physiology of visual contrast sensitivity (CS). To test the hypothesis that altered dopaminergic neurotransmission plays a role in major depression we measured contrast sensitivity in patients with major depression and in healthy control subjects. METHODS Twenty-eight patients diagnosed with major depressive disorder were compared to 21 age-matched control subjects on their ability to detect a Gabor target with slightly elevated luminance contrast embedded in seven equi-contrast distracters. RESULTS Contrast discrimination thresholds were significantly elevated in unmedicated and medicated patients with major depression compared to control subjects, at all pedestal contrast levels tested. CONCLUSIONS Contrast discrimination performance is reduced in depressive patients and might reflect a state of altered dopaminergic neurotransmission.
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Affiliation(s)
- Emanuel Bubl
- Department of Psychiatry and Psychotherapy, Albert-Ludwigs-Universität, Freiburg, Germany
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Ezzati A, Khadjevand F, Zandvakili A, Abbassian A. Higher-level motion detection deficit in Parkinson's disease. Brain Res 2010; 1320:143-51. [DOI: 10.1016/j.brainres.2010.01.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2009] [Revised: 01/04/2010] [Accepted: 01/10/2010] [Indexed: 11/17/2022]
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Khadjevand F, Shahzadi S, Abbassian A. Reduction of negative afterimage duration in Parkinson's disease patients: a possible role for dopaminergic deficiency in the retinal Interplexiform cell layer. Vision Res 2009; 50:279-83. [PMID: 20004214 DOI: 10.1016/j.visres.2009.09.026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 09/16/2009] [Accepted: 09/17/2009] [Indexed: 11/18/2022]
Abstract
Dopaminergic deficiency may affect Parkinson's disease patients (PD) in the central as well as the peripheral tissues. In the retina, the neuromodulatory role of the dopaminergic Interplexiform cell layer (IP) plays a major role in the retinal light adaptation and may account for the duration of the negative afterimage. Here we present results showing a significant reduction of negative afterimage duration in PD patients. This supports the hypothesis that the retinal dopaminergic system may be the main cause for the long duration of negative afterimage. We suggest that the observed reduction of afterimage duration is due to possible dopaminergic deficiency in patients with Parkinson's disease.
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Affiliation(s)
- Fatemeh Khadjevand
- School of Cognitive Sciences (SCS), Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5746, Iran.
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Retinopathy in Parkinson disease. J Neural Transm (Vienna) 2009; 116:1493-501. [DOI: 10.1007/s00702-009-0292-z] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2009] [Accepted: 08/02/2009] [Indexed: 10/20/2022]
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Peters S, Schweibold G, Przuntek H, Müller T. Loss of visual acuity under dopamine substitution therapy. Neuroophthalmology 2009. [DOI: 10.1076/0165-8107(200008)2411-vft273] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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Harris J. Vision in Parkinson’s disease: what are the deficits and what are their origins? Neuroophthalmology 2009. [DOI: 10.1076/noph.19.3.113.7896] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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Abstract
As a more complete picture of the clinical phenotype of Parkinson's disease emerges, non-motor symptoms have become increasingly studied. Prominent among these non-motor phenomena are mood disturbance, cognitive decline and dementia, sleep disorders, hyposmia and autonomic failure. In addition, visual symptoms are common, ranging from complaints of dry eyes and reading difficulties, through to perceptual disturbances (feelings of presence and passage) and complex visual hallucinations. Such visual symptoms are a considerable cause of morbidity in Parkinson's disease and, with respect to visual hallucinations, are an important predictor of cognitive decline as well as institutional care and mortality. Evidence exists of visual dysfunction at several levels of the visual pathway in Parkinson's disease. This includes psychophysical, electrophysiological and morphological evidence of disruption of retinal structure and function, in addition to disorders of 'higher' (cortical) visual processing. In this review, we will draw together work from animal and human studies in an attempt to provide an insight into how Parkinson's disease affects the retina and how these changes might contribute to the visual symptoms experienced by patients.
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Affiliation(s)
- Neil K Archibald
- Clinical Research Fellow, Clinical Ageing Research Unit, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, NE4 5PL, UK.
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Compromised circadian function in Parkinson's disease: Enucleation augments disease severity in the unilateral model. Behav Brain Res 2008; 193:37-47. [DOI: 10.1016/j.bbr.2008.04.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2008] [Revised: 04/16/2008] [Accepted: 04/19/2008] [Indexed: 11/23/2022]
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Abstract
Paroxysmal perceptual alteration is the brief and recurrent episodes of perceptual alterations that have been reported to occur occasionally with the use of antipsychotics. We report a case of paroxysmal perceptual alteration that occurred with exposure to typical antipsychotics wherein the frequency and duration of occurrence decreased after the substitution of antipsychotic with olanzapine. It seems that patterns on the surfaces are perceived vividly, which is specific of paroxysmal perceptual alteration.
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Parisi V, Coppola G, Ziccardi L, Gallinaro G, Falsini B. Cytidine-5'-diphosphocholine (Citicoline): a pilot study in patients with non-arteritic ischaemic optic neuropathy. Eur J Neurol 2008; 15:465-74. [PMID: 18325025 DOI: 10.1111/j.1468-1331.2008.02099.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND AND PURPOSE Our work evaluates visual function before and after treatment with cytidine-5-diphosphocholine (Citicoline) in patients with non-arteritic ischaemic optic neuropathy (NION). METHODS Twenty-six patients in which at least 6 months elapsed from NION, were randomly divided into two age-similar groups: 14 patients had Citicoline (Cebrolux-Tubilux, Italy, 1600 mg/diem for 60 days, followed by a 120-day period of wash out, days 60-180) (T-NION); 12 patients had no treatment during the same period (NT-NION). At day 180, in T-NION a second period of treatment (days 181-240) followed by a wash-out (days 241-360) was performed. Fourteen age-matched healthy subjects provided normative data. In all patients, pattern-electroretinogram (PERG), visual evoked potentials (VEPs) and visual acuity (VA) measurements were performed at baseline and at days 60 and 180. In T-NION, further measurements were achieved at days 240 and 360. RESULTS At baseline, NT-NION and T-NION patients showed abnormal PERGs and VEPs, and reduced VA, compared to controls. At the end of treatment (days 60 and 240), T-NION patients showed improvement (P < 0.01) of PERGs, VEPs parameters and VA, compared to pre-treatment values. After wash out, functional improvements persisted compared to baseline. No changes in NT-NION patients were observed. CONCLUSIONS Our results suggest a beneficial effect of oral Citicoline in NION.
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Affiliation(s)
- V Parisi
- Department of Neurophysiology of Vision and Neurophthalmology, G.B. Bietti Eye Foundation-IRCCS, Rome, Italy.
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Brandies R, Yehuda S. The possible role of retinal dopaminergic system in visual performance. Neurosci Biobehav Rev 2007; 32:611-56. [PMID: 18061262 DOI: 10.1016/j.neubiorev.2007.09.004] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2007] [Revised: 09/23/2007] [Accepted: 09/28/2007] [Indexed: 10/22/2022]
Abstract
It is a well-known fact that the retina is one of the tissues in the body, which is richest in dopamine (DA), yet the role of this system in various visual functions remains unclear. We have identified 13 types of DA retinal pathologies, and 15 visual functions. The pathologies were arranged in this review on a net grid, where one axis was "age" (i.e., from infancy to old age) and the other axis the level of retinal DA (i.e., from DA deficiency to DA excess, from Parkinson disorder to Schizophrenia). The available data on visual dysfunction(s) is critically presented for each of the DA pathologies. Special effort was made to evaluate whether the site of DA malfunction in the different DA pathologies and visual function is at retinal level or in higher brain centers. The mapping of DA and visual pathologies demonstrate the pivot role of retinal DA in mediating visual functions and also indicate the "missing links" in our understanding of the mechanisms underlying these relationships.
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Affiliation(s)
- R Brandies
- Department of Pharmacology, Israel Institute for Biological Research, P.O. Box 19, Ness Ziona 74100, Israel
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Righi S, Viggiano MP, Paganini M, Ramat S, Marini P. Recognition of category-related visual stimuli in Parkinson's disease: Before and after pharmacological treatment. Neuropsychologia 2007; 45:2931-41. [PMID: 17662314 DOI: 10.1016/j.neuropsychologia.2007.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2006] [Revised: 06/01/2007] [Accepted: 06/08/2007] [Indexed: 11/25/2022]
Abstract
Visual-sensory dysfunctions and semantic processing impairments are widely reported in Parkinson's disease (PD) research. The present study investigated the category-specific deficit in object recognition as a function of both the semantic category and spatial frequency content of stimuli. In the first experiment, the role of dopamine in object-recognition processing was assessed by comparing PD drug naïve (PD-DN), PD receiving levodopa treatment (PD-LD), and control subjects. Experiment 2 consisted of a retest session for PD drug naïve subjects after a period of pharmacological treatment. All participants completed an identification task which displayed animals and tools at nine levels of filtering. Each object was revealed in a sequence of frames whereby the object was presented at increasingly less-filtered images up to a complete version of the image. Results indicate an impaired identification pattern for PD-DN subjects solely for animal category stimuli. This differential pharmacological therapy effect was also confirmed at retest (experiment 2). Thus, our data suggest that dopaminergic loss has a specific role in category-specific impairment. Two possible hypotheses are discussed that may account for the defective recognition of semantically different objects in PD.
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Affiliation(s)
- S Righi
- Dipartimento di Psicologia, Università degli Studi di Firenze, Via s. Niccolò 93, 50125 Firenze, Italy.
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Belekhova MG, Kenigfest NB, Gapanovich SO, Rio JP, Peperant J. Neurochemical organization of reptilian thalamus. Comparative analysis of amniote optical centers. J EVOL BIOCHEM PHYS+ 2006. [DOI: 10.1134/s0022093006060019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Banaschewski T, Ruppert S, Tannock R, Albrecht B, Becker A, Uebel H, Sergeant JA, Rothenberger A. Colour perception in ADHD. J Child Psychol Psychiatry 2006; 47:568-72. [PMID: 16712633 DOI: 10.1111/j.1469-7610.2005.01540.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Attention-deficit/hyperactivity disorder (ADHD) is associated with unexplained impairments on speeded naming of coloured stimuli. These deficits may reflect hypofunctioning retinal dopaminergic mechanisms impairing particularly blue-yellow colour discrimination. Colour perception and rapid colour naming ability were investigated in 14 children with ADHD and 13 healthy peers matched for age, gender, and IQ, using the Farnsworth-Munsell 100 Hue Test (FMT) and the Stroop-Colour-Word test. Children with ADHD committed more errors on the FMT, particularly on discrimination of colours along the blue-yellow axis, and were slower on Stroop subtests involving colour naming. However, the latter deficit was accounted for similarly by blue-yellow and red-green discrimination abilities. Blue-yellow colour perception problems in ADHD contribute to but do not fully explain the observed slowed colour naming.
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Uchida H, Suzuki T, Yamazawa R, Tomita M, Nemoto T, Kimura Y, Watanabe K, Imasaka Y, Kashima H. Reducing the dose of antipsychotic agents ameliorates visual hypersensitivity attack: an ideal treatment option in terms of the adverse effect. J Clin Psychopharmacol 2006; 26:50-5. [PMID: 16415706 DOI: 10.1097/01.jcp.0000195384.04008.25] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
There are sporadic reports of antipsychotic-induced visual hypersensitivity attack (VHA). VHA is characterized by hypersensitivity of perception mainly in the visual modality and sometimes accompanied by an oculogyric crisis. However, some researchers regard VHA as a schizophrenia symptom. To determine whether VHA is an adverse effect of antipsychotic agents, we examined the effect of dose reduction on VHA. This was an open-label 36-week study. We randomized 34 patients with VHA to a reduced-dose group and a fixed-dose group. Primary outcome measures were the frequency and duration of VHA, assessed with patients' self-reports, and the Clinical Global Impressions (CGI). Assessment also included the Drug-induced Extrapyramidal Symptoms Scale for extrapyramidal symptoms, the Positive and Negative Syndrome Scale (PANSS) for schizophrenia, and the CGI for other diagnoses. Data were collected from August 2000 to April 2005 at 4 psychiatric hospitals in Tokyo.VHA diminished in 16 patients (94.1%) in the reduced-dose group in the CGI score, the frequency (number of episodes per week), and the duration of the episodes (from 4.06 to 1.77, P < 0.001; from 2.59 to 0.82, P = 0.001; and from 1.92 to 0.66 hours, P = 0.007, respectively), but there were no changes in the fixed-dose group. There were no changes in the underlying illness as measured by the PANSS in both groups. Reducing the dose of antipsychotic agents ameliorates VHA and represents the ideal treatment option for patients with VHA.
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Affiliation(s)
- Hiroyuki Uchida
- Department of Neuro-Psychiatry, School of Medicine, Keio University, Tokyo, Japan.
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Tannock R, Banaschewski T, Gold D. Color naming deficits and attention-deficit/hyperactivity disorder: a retinal dopaminergic hypothesis. BEHAVIORAL AND BRAIN FUNCTIONS : BBF 2006; 2:4. [PMID: 16441891 PMCID: PMC1403787 DOI: 10.1186/1744-9081-2-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Accepted: 01/27/2006] [Indexed: 11/24/2022]
Abstract
BACKGROUND Individuals with Attention-Deficit/Hyperactive Disorder (ADHD) have unexplained difficulties on tasks requiring speeded processing of colored stimuli. Color vision mechanisms, particularly short-wavelength (blue-yellow) pathways, are highly sensitive to various diseases, toxins and drugs that alter dopaminergic neurotransmission. Thus, slow color processing might reflect subtle impairments in the perceptual encoding stage of stimulus color, which arise from hypodopaminergic functioning. PRESENTATION OF HYPOTHESES 1) Color perception of blue-yellow (but not red-green) stimuli is impaired in ADHD as a result of deficient retinal dopamine; 2) Impairments in the blue-yellow color mechanism in ADHD contribute to poor performance on speeded color naming tasks that include a substantial proportion of blue-yellow stimuli; and 3) Methylphenidate increases central dopamine and is also believed to increase retinal dopamine, thereby normalizing blue-yellow color perception, which in turn improves performance on the speeded color naming tasks. TESTING THE HYPOTHESIS Requires three approaches, including:1) direct assessment of color perception in individuals with ADHD to determine whether blue-yellow color perception is selectively impaired; 2) determination of relationship between performance on neuropsychological tasks requiring speeded color processing and color perception; and 3) randomized, controlled pharmacological intervention with stimulant medication to examine the effects of enhancing central dopamine on color perception and task performance IMPLICATIONS OF HYPOTHESIS If substantiated, the findings of color perception problems would necessitate a re-consideration of current neuropsychological models of attention-deficit/hyperactivity disorder, guide psycho-education, academic instruction, and require consideration of stimulus color in many of the widely used neuropsychological tests.
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Affiliation(s)
- Rosemary Tannock
- The University of Toronto, Toronto, Canada: Brain and Behaviour Research Program, The Hospital for Sick Children, Toronto, Canada
- Centre for Advanced Study at the Norwegian Academy of Science and Letters 2004–2005, Norway
| | - Tobias Banaschewski
- Child and Adolescent Psychiatry, University of Göttingen, Germany
- Centre for Advanced Study at the Norwegian Academy of Science and Letters 2004–2005, Norway
| | - David Gold
- The University of Western Ontario, London, Canada
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Cuenca N, Herrero MT, Angulo A, de Juan E, Martínez-Navarrete GC, López S, Barcia C, Martín-Nieto J. Morphological impairments in retinal neurons of the scotopic visual pathway in a monkey model of Parkinson's disease. J Comp Neurol 2005; 493:261-73. [PMID: 16255027 DOI: 10.1002/cne.20761] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Physiological abnormalities resulting from death of dopaminergic neurons of the central nervous system in Parkinson's disease also extend to the retina, resulting in impaired visual functions. In both parkinsonian patients and animal models, low levels of dopamine and loss of dopaminergic cells in the retina have been reported. However, the morphology and connectivity of their postsynaptic neurons, the amacrine cells, have not been analyzed. Here we report, with macaques chronically treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as a model of Parkinson's disease, that morphological impairments in dopaminergic retinal neurons and their plexus in the inner retina are accompanied by an immunoreactivity decrease in gamma-aminobutyric acidergic and glycinergic amacrine cells. Especially deteriorated were AII amacrine cells, the main neuronal subtype postsynaptic to dopaminergic cells, which exhibited a marked loss of lobular appendages and dendritic processes. Concomitantly, electrical synapses among AII cells, as well as chemical synapses between these and rod bipolar cells, were highly deteriorated in parkinsonian monkeys. These results highlight that the scotopic visual pathway is severely impaired in the parkinsonian condition and provide a morphological basis for a number of abnormalities found in electrophysiological and psychophysical trials in Parkinson's disease patients and animal models.
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Affiliation(s)
- Nicolás Cuenca
- Departamento de Biotecnología, Facultad de Ciencias, Universidad de Alicante, Campus San Vicente del Raspeig, Spain.
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Chapter 25 Visual dysfunction in disorders with altered dopaminergic neurotransmission. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/s1567-4231(09)70222-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Schmid KL, Wildsoet CF. Inhibitory effects of apomorphine and atropine and their combination on myopia in chicks. Optom Vis Sci 2004; 81:137-47. [PMID: 15127933 DOI: 10.1097/00006324-200402000-00012] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE The inhibitory effect of apomorphine on form-deprivation myopia implies a role for dopaminergic pathways in eye growth; however, the effect of apomorphine on lens-induced changes has not been studied. Our study filled this deficiency. After establishing that apomorphine inhibited lens-induced myopia, we investigated whether apomorphine and atropine acted sequentially via the same control pathway or via different parallel pathways. METHODS This study, conducted in 8-day-old chicks, was comprised of two parts: (1) a comparative study of apomorphine's effect on lens-induced myopia (-15 D), form-deprivation myopia (diffusers), and lens-induced hyperopia (+15 D) and (2) a study of the interacting effects of apomorphine and atropine on lens-induced myopia and form-deprivation myopia. In the first part, dH2O and six apomorphine doses (8 pmole to 800 nmole in log10 steps) were given as 10-microL intravitreal injections in combination with the above visual treatments. Apomorphine was used alone or given with atropine in the second part, which included four drug treatment groups: (1) control (dH2O); (2) 80 pmole of apomorphine; (3) 18 nmole of atropine; and (4) apomorphine + atropine. Additional dH2O injections were used to equalize the number of injections across groups. After 4.5 days of treatment, refractive errors and axial ocular dimensions were measured. RESULTS The myopic shifts and axial elongation typical of lens-induced myopia (-15 D lens wear) were inhibited to maxima of 43% (4.5 D) and 52% (0.17 mm) by apomorphine, which, in contrast, enhanced lens-induced hyperopia (refractive error: 114%, 1.55 D; axial length: 134%, 0.16 mm). Inhibitory effects of apomorphine on lens-induced myopia were observed at doses > or = 80 pmole, whereas the doses required to enhance lens-induced hyperopia were 2 log10 units higher. Only a weak inhibitory effect of apomorphine on form-deprivation myopia was observed. Although both apomorphine and atropine inhibited lens-induced myopia, atropine was slightly more effective for the doses compared (refractive error, 53% cf. 32%), and the effect of the combination was not significantly greater than that of atropine alone (refractive error, 59% cf. 53%). CONCLUSIONS Apomorphine inhibits both types of experimental myopia, which implies the involvement of dopaminergic mechanisms in both phenomena; likewise, cholinergic mechanisms are indicated by the inhibitory effects of atropine on both lens-induced myopia and form-deprivation myopia. We speculate that apomorphine and atropine act at different sites on a common control pathway because the combined effect of apomorphine and atropine was no more than atropine alone.
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Affiliation(s)
- Katrina L Schmid
- School of Optometry, Queensland University of Technology, and Vision Touch and Hearing Research Centre, School of Biomedical Science, University of Queensland, Brisbane, Australia.
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