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Ordás CM, Alonso-Frech F. The neural basis of somatosensory temporal discrimination threshold as a paradigm for time processing in the sub-second range: An updated review. Neurosci Biobehav Rev 2024; 156:105486. [PMID: 38040074 DOI: 10.1016/j.neubiorev.2023.105486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 11/20/2023] [Accepted: 11/27/2023] [Indexed: 12/03/2023]
Abstract
BACKGROUND AND OBJECTIVE The temporal aspect of somesthesia is a feature of any somatosensory process and a pre-requisite for the elaboration of proper behavior. Time processing in the milliseconds range is crucial for most of behaviors in everyday life. The somatosensory temporal discrimination threshold (STDT) is the ability to perceive two successive stimuli as separate in time, and deals with time processing in this temporal range. Herein, we focus on the physiology of STDT, on a background of the anatomophysiology of somesthesia and the neurobiological substrates of timing. METHODS A review of the literature through PubMed & Cochrane databases until March 2023 was performed with inclusion and exclusion criteria following PRISMA recommendations. RESULTS 1151 abstracts were identified. 4 duplicate records were discarded before screening. 957 abstracts were excluded because of redundancy, less relevant content or not English-written. 4 were added after revision. Eventually, 194 articles were included. CONCLUSIONS STDT encoding relies on intracortical inhibitory S1 function and is modulated by the basal ganglia-thalamic-cortical interplay through circuits involving the nigrostriatal dopaminergic pathway and probably the superior colliculus.
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Affiliation(s)
- Carlos M Ordás
- Universidad Rey Juan Carlos, Móstoles, Madrid, Spain; Department of Neurology, Hospital Rey Juan Carlos, Móstoles, Madrid, Spain.
| | - Fernando Alonso-Frech
- Department of Neurology, Hospital Clínico San Carlos, Universidad Complutense de Madrid, Spain
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2
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Rafee S, O'Riordan S, Reilly R, Hutchinson M. We Must Talk about Sex and Focal Dystonia. Mov Disord 2021; 36:604-608. [PMID: 33503303 DOI: 10.1002/mds.28454] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 11/10/2020] [Accepted: 11/30/2020] [Indexed: 01/28/2023] Open
Abstract
In a recent workshop on "Defining research priorities in dystonia,", there was absolutely no reference to sex as a factor in disease pathogenesis. In this viewpoint paper, we argue that the most distinctive aspects of adult onset isolated focal dystonia are the marked sex-related differences demonstrated by epidemiological, clinical, and laboratory studies in patients with adult onset dystonia, particularly in cervical dystonia, the most common presentation. We propose that the future focus of research should be on neurobiological mechanisms underlying the profound sexual dimorphism in this disorder. Targeting research into gamma aminobutyric acid (GABA)ergic function, which also shows similar sexual dimorphism, would be most productive in elucidating the pathogenesis of adult onset dystonia. © 2021 International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Shameer Rafee
- Department of Neurology, St. Vincent's University Hospital, Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
| | - Sean O'Riordan
- Department of Neurology, St. Vincent's University Hospital, Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
| | - Richard Reilly
- Trinity Centre for Bioengineering, Trinity College Dublin, Dublin, Ireland
| | - Michael Hutchinson
- Department of Neurology, St. Vincent's University Hospital, Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
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3
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Maguire F, Reilly RB, Simonyan K. Normal Temporal Discrimination in Musician's Dystonia Is Linked to Aberrant Sensorimotor Processing. Mov Disord 2020; 35:800-807. [PMID: 31930574 PMCID: PMC7818836 DOI: 10.1002/mds.27984] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 12/10/2019] [Accepted: 12/20/2019] [Indexed: 12/19/2022] Open
Abstract
OBJECTIVES Alterations in sensory discrimination are a prominent nonmotor feature of dystonia. Abnormal temporal discrimination in focal dystonia is considered to represent its mediational endophenotype, albeit unclear pathophysiological correlates. We examined the associations between the visual temporal discrimination threshold (TDT) and brain activity in patients with musician's dystonia, nonmusician's dystonia, and healthy controls. METHODS A total of 42 patients and 41 healthy controls participated in the study. Between-group differences in TDT z scores were computed using inferential statistics. Statistical associations of TDT z scores with clinical characteristics of dystonia and resting-state functional brain activity were examined using nonparametric rank correlations. RESULTS The TDT z scores of healthy controls were significantly different from those of patients with nonmusician's dystonia, but not of patients with musician's dystonia. Healthy controls showed a significant relationship between normal TDT levels and activity in the inferior parietal cortex. This relationship was lost in all patients. Instead, TDT z scores in musician's dystonia established additional correlations with activity in premotor, primary somatosensory, ventral extrastriate cortices, inferior occipital gyrus, precuneus, and cerebellum, whereas nonmusician's dystonia showed a trending correlation in the lingual gyrus extending to the cerebellar vermis. There were no significant relationships between TDT z scores and dystonia onset, duration, or severity. CONCLUSIONS TDT assessment as an endophenotypic marker may only be relevant to nonmusician forms of dystonia because of the lack of apparent alterations in musician's dystonia. Compensatory adaptation of neural circuitry responsible for TDT processing likely adjusted the TDT performance to the behaviorally normal levels in patients with musician's dystonia, but not nonmusician's dystonia. © 2020 International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Fiachra Maguire
- Trinity Centre for Bioengineering, Trinity College Dublin, University of Dublin, Dublin, Ireland
- Department of Otolaryngology–Head and Neck Surgery, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA
| | - Richard B. Reilly
- Trinity Centre for Bioengineering, Trinity College Dublin, University of Dublin, Dublin, Ireland
| | - Kristina Simonyan
- Trinity Centre for Bioengineering, Trinity College Dublin, University of Dublin, Dublin, Ireland
- Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts, USA
- Department of Otolaryngology–Head and Neck Surgery, Harvard Medical School, Boston, Massachusetts, USA
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4
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Beck RB, McGovern EM, Butler JS, Birsanu D, Quinlivan B, Beiser I, Narasimham S, O'Riordan S, Hutchinson M, Reilly RB. Measurement & Analysis of the Temporal Discrimination Threshold Applied to Cervical Dystonia. J Vis Exp 2018. [PMID: 29443021 DOI: 10.3791/56310] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The temporal discrimination threshold (TDT) is the shortest time interval at which an observer can discriminate two sequential stimuli as being asynchronous (typically 30-50 ms). It has been shown to be abnormal (prolonged) in neurological disorders, including cervical dystonia, a phenotype of adult onset idiopathic isolated focal dystonia. The TDT is a quantitative measure of the ability to perceive rapid changes in the environment and is considered indicative of the behavior of the visual neurons in the superior colliculus, a key node in covert attentional orienting. This article sets out methods for measuring the TDT (including two hardware options and two modes of stimuli presentation). We also explore two approaches of data analysis and TDT calculation. The application of the assessment of temporal discrimination to the understanding of the pathogenesis of cervical dystonia and adult onset idiopathic isolated focal dystonia is also discussed.
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Affiliation(s)
- Rebecca B Beck
- School of Engineering, Trinity College Dublin, The University of Dublin;
| | - Eavan M McGovern
- School of Engineering, Trinity College Dublin, The University of Dublin; Department of Neurology, St. Vincent's University Hospital; School of Medicine and Medical Sciences, University College Dublin
| | - John S Butler
- School of Mathematical Sciences, Dublin Institute of Technology
| | - Dorina Birsanu
- School of Engineering, Trinity College Dublin, The University of Dublin
| | - Brendan Quinlivan
- School of Engineering, Trinity College Dublin, The University of Dublin
| | - Ines Beiser
- School of Engineering, Trinity College Dublin, The University of Dublin; Department of Neurology, St. Vincent's University Hospital; School of Medicine and Medical Sciences, University College Dublin
| | - Shruti Narasimham
- School of Engineering, Trinity College Dublin, The University of Dublin
| | - Sean O'Riordan
- Department of Neurology, St. Vincent's University Hospital; School of Medicine and Medical Sciences, University College Dublin
| | - Michael Hutchinson
- Department of Neurology, St. Vincent's University Hospital; School of Medicine and Medical Sciences, University College Dublin
| | - Richard B Reilly
- School of Engineering, Trinity College Dublin, The University of Dublin; School of Medicine Trinity College Dublin, The University of Dublin
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5
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Conte A, McGovern EM, Narasimham S, Beck R, Killian O, O'Riordan S, Reilly RB, Hutchinson M. Temporal Discrimination: Mechanisms and Relevance to Adult-Onset Dystonia. Front Neurol 2017; 8:625. [PMID: 29234300 PMCID: PMC5712317 DOI: 10.3389/fneur.2017.00625] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 11/07/2017] [Indexed: 12/05/2022] Open
Abstract
Temporal discrimination is the ability to determine that two sequential sensory stimuli are separated in time. For any individual, the temporal discrimination threshold (TDT) is the minimum interval at which paired sequential stimuli are perceived as being asynchronous; this can be assessed, with high test–retest and inter-rater reliability, using a simple psychophysical test. Temporal discrimination is disordered in a number of basal ganglia diseases including adult-onset dystonia, of which the two most common phenotypes are cervical dystonia and blepharospasm. The causes of adult-onset focal dystonia are unknown; genetic, epigenetic, and environmental factors are relevant. Abnormal TDTs in adult-onset dystonia are associated with structural and neurophysiological changes considered to reflect defective inhibitory interneuronal processing within a network which includes the superior colliculus, basal ganglia, and primary somatosensory cortex. It is hypothesized that abnormal temporal discrimination is a mediational endophenotype and, when present in unaffected relatives of patients with adult-onset dystonia, indicates non-manifesting gene carriage. Using the mediational endophenotype concept, etiological factors in adult-onset dystonia may be examined including (i) the role of environmental exposures in disease penetrance and expression; (ii) sexual dimorphism in sex ratios at age of onset; (iii) the pathogenesis of non-motor symptoms of adult-onset dystonia; and (iv) subcortical mechanisms in disease pathogenesis.
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Affiliation(s)
- Antonella Conte
- Department of Neurology and Psychiatry, Sapienza, University of Rome, Rome, Italy.,IRCCS Neuromed, Pozzilli, Isernia, Italy
| | - Eavan M McGovern
- Department of Neurology, St Vincent's University Hospital Dublin, Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
| | - Shruti Narasimham
- Trinity Centre for Bioengineering, Trinity College, The University of Dublin, Dublin, Ireland.,School of Medicine, Trinity College, The University of Dublin, Dublin, Ireland.,School of Engineering, Trinity College, The University of Dublin, Dublin, Ireland
| | - Rebecca Beck
- Trinity Centre for Bioengineering, Trinity College, The University of Dublin, Dublin, Ireland.,School of Medicine, Trinity College, The University of Dublin, Dublin, Ireland.,School of Engineering, Trinity College, The University of Dublin, Dublin, Ireland
| | - Owen Killian
- Trinity Centre for Bioengineering, Trinity College, The University of Dublin, Dublin, Ireland.,School of Medicine, Trinity College, The University of Dublin, Dublin, Ireland.,School of Engineering, Trinity College, The University of Dublin, Dublin, Ireland
| | - Sean O'Riordan
- Department of Neurology, St Vincent's University Hospital Dublin, Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
| | - Richard B Reilly
- Trinity Centre for Bioengineering, Trinity College, The University of Dublin, Dublin, Ireland.,School of Medicine, Trinity College, The University of Dublin, Dublin, Ireland.,School of Engineering, Trinity College, The University of Dublin, Dublin, Ireland
| | - Michael Hutchinson
- Department of Neurology, St Vincent's University Hospital Dublin, Dublin, Ireland.,School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
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6
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Sadnicka A, Daum C, Cordivari C, Bhatia KP, Rothwell JC, Manohar S, Edwards MJ. Mind the gap: temporal discrimination and dystonia. Eur J Neurol 2017; 24:796-806. [PMID: 28544409 DOI: 10.1111/ene.13293] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 03/06/2017] [Indexed: 02/05/2023]
Abstract
BACKGROUND AND PURPOSE One of the most widely studied perceptual measures of sensory dysfunction in dystonia is the temporal discrimination threshold (TDT) (the shortest interval at which subjects can perceive that there are two stimuli rather than one). However the elevated thresholds described may be due to a number of potential mechanisms as current paradigms test not only temporal discrimination but also extraneous sensory and decision-making parameters. In this study two paradigms designed to better quantify temporal processing are presented and a decision-making model is used to assess the influence of decision strategy. METHODS 22 patients with cervical dystonia and 22 age-matched controls completed two tasks (i) temporal resolution (a randomized, automated version of existing TDT paradigms) and (ii) interval discrimination (rating the length of two consecutive intervals). RESULTS In the temporal resolution task patients had delayed (P = 0.021) and more variable (P = 0.013) response times but equivalent discrimination thresholds. Modelling these effects suggested this was due to an increased perceptual decision boundary in dystonia with patients requiring greater evidence before committing to decisions (P = 0.020). Patient performance on the interval discrimination task was normal. CONCLUSIONS Our work suggests that previously observed abnormalities in TDT may not be due to a selective sensory deficit of temporal processing as decision-making itself is abnormal in cervical dystonia.
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Affiliation(s)
- A Sadnicka
- Sobell Department for Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, UK
| | - C Daum
- Sobell Department for Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, UK
| | - C Cordivari
- Sobell Department for Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, UK
| | - K P Bhatia
- Sobell Department for Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, UK
| | - J C Rothwell
- Sobell Department for Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, UK
| | - S Manohar
- Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - M J Edwards
- Institute of Cardiovascular and Cell Sciences, St George's University, London, UK
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7
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Abstract
The evolutionary success of Homo sapiens is attributed to the following two factors: the upright body posture (which freed our hands and allowed unconstrained operation of various objects) and intensive development of the frontal lobes, mainly the Broca area of the brain. Underlining the uniqueness of the human brain, we often forget about the fact that the frontal lobes – the most developed part of the brain – are at the same time our greatest weakness, exposed to the action of damaging factors in our evolving environment. Is depression the cost of evolution?
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Affiliation(s)
- Piotr Gałecki
- Department of Adult Psychiatry, Medical University of Łódź, Łódź, Poland
| | - Monika Talarowska
- Department of Adult Psychiatry, Medical University of Łódź, Łódź, Poland
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8
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Mc Govern EM, O'Connor E, Beiser I, Williams L, Butler JS, Quinlivan B, Narasimham S, Beck R, Reilly RB, O'Riordan S, Hutchinson M. Menstrual cycle and the temporal discrimination threshold. Physiol Meas 2017; 38:N65-N72. [PMID: 28099161 DOI: 10.1088/1361-6579/38/2/n65] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The temporal discrimination threshold (TDT) is a proposed pre-clinical biomarker (endophenotype) for adult onset isolated focal dystonia (AOIFD). Age- and sex-related effects on temporal discrimination demonstrate that women, before the age of 40 years, have faster temporal discrimination than men but their TDTs worsen with age at almost three times the rate of men. Thus after 40 years the TDT in women is progressively worse than in men. AOIFD is an increasingly female-predominant disorder after the age of 40; it is not clear whether this age-related sexually-dimorphic difference observed for both the TDT and sex ratio at disease onset in AOIFD is a hormonal or chromosomal effect. The aim of this study was to examine temporal discrimination at weekly intervals during two consecutive menstrual cycles in 14 healthy female volunteers to determine whether physiological hormonal changes affected temporal discrimination. We observed no significant differences in weekly temporal discrimination threshold values during the menstrual cycles and no significant correlation with the menstrual cycle stage. This observed stability of temporal discrimination during cyclical hormonal change raises interesting questions concerning the age-related sexually-dimorphic decline observed in temporal discrimination. Our findings pave the way for future studies exploring potential pathomechanisms for this age-related deterioration.
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Affiliation(s)
- Eavan M Mc Govern
- Department of Neurology, St. Vincent's University Hospital, Dublin, Ireland. School of Medicine and Medical Sciences, University College Dublin, Dublin, Ireland. Trinity Centre for Bioengineering, Dublin, Ireland
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9
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Mc Govern EM, Butler JS, Beiser I, Williams L, Quinlivan B, Narasiham S, Beck R, O'Riordan S, Reilly RB, Hutchinson M. A comparison of stimulus presentation methods in temporal discrimination testing. Physiol Meas 2017; 38:N57-N64. [PMID: 28099169 DOI: 10.1088/1361-6579/38/2/n57] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The temporal discrimination threshold (TDT) is the shortest time interval at which an individual detects two stimuli to be asynchronous (normal = 30-50 ms). It has been shown to be abnormal in patients with disorders affecting the basal ganglia including adult onset idiopathic focal dystonia (AOIFD). Up to 97% of patients have an abnormal TDT with age- and sex-related penetrance in unaffected relatives, demonstrating an autosomal dominant inheritance pattern. These findings support the use of the TDT as a pre-clinical biomarker for AOIFD. The usual stimulus presentation method involves the presentation of progressively asynchronous stimuli; when three sequential stimuli are reported asynchronous is taken as a participant's TDT. To investigate the robustness of the 'staircase' method of presentation, we introduced a method of randomised presentation order to explore any potential 'learning effect' that may be associated with this existing method. The aim of this study was to investigate differences in temporal discrimination using two methods of stimulus presentation. Thirty healthy volunteers were recruited to the study (mean age 33.73 ± 3.4 years). Visual and tactile TDT testing using a staircase and randomised method of presentation order was carried out in a single session. There was a strong relationship between the staircase and random method for TDT values. This observed consistency between testing methods suggests that the existing experimental approach is a robust method of recording an individual's TDT. In addition, our newly devised randomised paradigm is a reproducible and more efficient method for data acquisition in the clinic setting. However, the two presentation methods yield different absolute TDT results and either of the two methods should be used uniformly in all participants in any one particular study.
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Affiliation(s)
- Eavan M Mc Govern
- Department of Neurology, St. Vincent's University Hospital, Dublin, Ireland. School of Medicine and Medical Sciences, University College Dublin, Dublin, Ireland. Trinity Centre for Bioengineering, Dublin, Ireland
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10
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Williams L, McGovern E, Kimmich O, Molloy A, Beiser I, Butler JS, Molloy F, Logan P, Healy DG, Lynch T, Walsh R, Cassidy L, Moriarty P, Moore H, McSwiney T, Walsh C, O'Riordan S, Hutchinson M. Epidemiological, clinical and genetic aspects of adult onset isolated focal dystonia in Ireland. Eur J Neurol 2016; 24:73-81. [DOI: 10.1111/ene.13133] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 08/09/2016] [Indexed: 02/06/2023]
Affiliation(s)
- L. Williams
- Department of Neurology; St Vincent's University Hospital; Dublin Ireland
- School of Medicine and Medical Sciences; University College Dublin; Dublin Ireland
| | - E. McGovern
- Department of Neurology; St Vincent's University Hospital; Dublin Ireland
- School of Medicine and Medical Sciences; University College Dublin; Dublin Ireland
| | - O. Kimmich
- Department of Neurology; St Vincent's University Hospital; Dublin Ireland
- School of Medicine and Medical Sciences; University College Dublin; Dublin Ireland
| | - A. Molloy
- Department of Neurology; St Vincent's University Hospital; Dublin Ireland
- School of Medicine and Medical Sciences; University College Dublin; Dublin Ireland
| | - I. Beiser
- Department of Neurology; St Vincent's University Hospital; Dublin Ireland
- School of Medicine and Medical Sciences; University College Dublin; Dublin Ireland
| | - J. S. Butler
- Trinity Centre for Bioengineering; Dublin and School of Mathematical Sciences; Dublin Institute of Technology; Dublin Ireland
| | | | - P. Logan
- Beaumont Hospital; Dublin Ireland
| | | | - T. Lynch
- Mater Misericordiae University Hospital; Dublin Ireland
| | - R. Walsh
- Adelaide and Meath Hospital; Dublin Ireland
| | - L. Cassidy
- Royal Victoria Eye and Ear Hospital; Dublin Ireland
| | - P. Moriarty
- Royal Victoria Eye and Ear Hospital; Dublin Ireland
| | - H. Moore
- Cork University Hospital; Cork Ireland
| | | | - C. Walsh
- Departments of Statistics; Trinity College Dublin; University of Limerick; Limerick Ireland
| | - S. O'Riordan
- Department of Neurology; St Vincent's University Hospital; Dublin Ireland
- School of Medicine and Medical Sciences; University College Dublin; Dublin Ireland
| | - M. Hutchinson
- Department of Neurology; St Vincent's University Hospital; Dublin Ireland
- School of Medicine and Medical Sciences; University College Dublin; Dublin Ireland
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11
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Butler JS, Beiser IM, Williams L, McGovern E, Molloy F, Lynch T, Healy DG, Moore H, Walsh R, Reilly RB, O'Riordan S, Walsh C, Hutchinson M. Age-Related Sexual Dimorphism in Temporal Discrimination and in Adult-Onset Dystonia Suggests GABAergic Mechanisms. Front Neurol 2015; 6:258. [PMID: 26696957 PMCID: PMC4677337 DOI: 10.3389/fneur.2015.00258] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 11/23/2015] [Indexed: 12/04/2022] Open
Abstract
Background Adult-onset isolated focal dystonia (AOIFD) presenting in early adult life is more frequent in men, whereas in middle age it is female predominant. Temporal discrimination, an endophenotype of adult-onset idiopathic isolated focal dystonia, shows evidence of sexual dimorphism in healthy participants. Objectives We assessed the distinctive features of age-related sexual dimorphism of (i) sex ratios in dystonia phenotypes and (ii) sexual dimorphism in temporal discrimination in unaffected relatives of cervical dystonia patients. Methods We performed (i) a meta-regression analysis of the proportion of men in published cohorts of phenotypes of adult-onset dystonia in relation to their mean age of onset and (ii) an analysis of temporal discrimination thresholds in 220 unaffected first-degree relatives (125 women) of cervical dystonia patients. Results In 53 studies of dystonia phenotypes, the proportion of men showed a highly significant negative association with mean age of onset (p < 0.0001, pseudo-R2 = 59.6%), with increasing female predominance from 40 years of age. Age of onset and phenotype together explained 92.8% of the variance in proportion of men. Temporal discrimination in relatives under the age of 35 years is faster in women than men but the age-related rate of deterioration in women is twice that of men; after 45 years of age, men have faster temporal discrimination than women. Conclusion Temporal discrimination in unaffected relatives of cervical dystonia patients and sex ratios in adult-onset dystonia phenotypes show similar patterns of age-related sexual dimorphism. Such age-related sexual dimorphism in temporal discrimination and adult-onset focal dystonia may reflect common underlying mechanisms. Cerebral GABA levels have been reported to show similar age-related sexual dimorphism in healthy participants and may be the mechanism underlying the observed age-related sexual dimorphism in temporal discrimination and the sex ratios in AOIFD.
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Affiliation(s)
- John S Butler
- Trinity Centre for Bioengineering, School of Engineering, Trinity College Dublin , Dublin , Ireland
| | - Ines M Beiser
- Department of Neurology, St. Vincent's University Hospital , Dublin , Ireland ; School of Medicine and Medical Sciences, University College Dublin , Dublin , Ireland
| | - Laura Williams
- Department of Neurology, St. Vincent's University Hospital , Dublin , Ireland ; School of Medicine and Medical Sciences, University College Dublin , Dublin , Ireland
| | - Eavan McGovern
- Department of Neurology, St. Vincent's University Hospital , Dublin , Ireland ; School of Medicine and Medical Sciences, University College Dublin , Dublin , Ireland
| | | | - Tim Lynch
- Dublin Neurological Institute, Mater Misericordiae University Hospital , Dublin , Ireland
| | | | | | | | - Richard B Reilly
- Trinity Centre for Bioengineering, School of Engineering, Trinity College Dublin , Dublin , Ireland ; School of Medicine, Trinity College Dublin , Dublin , Ireland
| | - Seán O'Riordan
- Department of Neurology, St. Vincent's University Hospital , Dublin , Ireland ; School of Medicine and Medical Sciences, University College Dublin , Dublin , Ireland
| | - Cathal Walsh
- Department of Statistics, Trinity College Dublin , Dublin , Ireland ; Department of Mathematics and Statistics, University of Limerick , Limerick , Ireland
| | - Michael Hutchinson
- Department of Neurology, St. Vincent's University Hospital , Dublin , Ireland ; School of Medicine and Medical Sciences, University College Dublin , Dublin , Ireland
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