This research was supported by grants from the Health Research Board, Dystonia Ireland, Science Foundation Ireland and the Irish Institute for Clinical Neuroscience.

The Medical Research Ethics Committee at St. Vincent&#39;s University Hospital, Dublin gave approval for the recruitment of patients with cervical dystonia, their siblings (unaffected by dystonia), and healthy controls, to participate in the protocol described below.

1. Hardware &#38; Software Solutions
Note: Two hardware options have been developed to display visual stimuli with precise inter-stimulus intervals. Both were designed and built in-house at the Trinity Centre for Bioengineering, Trinity College Dublin, and have been previously described5,16. Those wishing to replicate the exact hardware solutions used herein may request same by contacting the Trinity Centre for Bioengineering directly. Alternatively, a full set of instructions including 3D printing files for the headset, instructions for the accompanying Arduino microcontroller, etc. can be downloaded from http://www.dystoniaresearch.ie/temporal-discrimination-threshold/. The stimuli presented in the table top approach may be generated using custom programs in Presentation (e.g., Neurobehavioural Systems), installed on a desktop computer and programmed to control the light-emitting diodes (LED) via the parallel port of the computer. Alternatively, as described below, the table top LEDs may be controlled via an Arduino microcontroller. Both the Presentation code and Arduino files are also available to download from the above link.
<ol>
	<li>TDT hardware: Table-Top Method
	<ol>
		<li>Mark an &#39;X&#39;, as a fixation point, on a black mat or sheet placed on the table in front of the participant.</li>
		<li>Ask the participant to position themselves so that they are sitting directly in front of the fixation point.</li>
		<li>Place the yellow light-emitting diode (LED) pairs (5 mm diameter, 90 cd/m2 luminance), encased in a box, on the table in front of the participant.</li>
		<li>Orient the box such that the LEDs are vertically aligned and positioned 7 &#176; from the subject&#39;s center point on the left and right side, as needed.</li>
		<li>Conduct this experiment in a darkened room. A small amount of background luminance may be required to enable the operator to see enough to run the experiment.</li>
		<li>Instruct the participant to focus on the fixation point at all times and not to look directly at the flashing LEDs.</li>
		<li>Connect the microcontroller to the LED box and follow the on-screen instructions displayed on the liquid crystal display of the microcontroller box, e.g., select presentation method: &#39;random&#39; or &#39;staircase&#39;, and select mode: &#39;left top first&#39;, etc.</li>
		<li>Ask the participant to respond &#34;same&#34; or &#34;different&#34; following presentation of each stimulus pair, depending on whether they perceive the stimuli to be synchronous or asynchronous.</li>
		<li>Inform the participant when each trial is about to commence, by vocalizing the on-screen countdown from 5 - 0 s.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56310/56310fig1.jpg" /> 
Figure 1: (a) Schematic of the design of the headset. A pair of yellow LEDs (5 mm diameter),and the red fixation LED (3 mm diameter), are placed on the left and right side of the participant via a head-mounted unit and made visible by way of reflection in the mirrors in front of the user. (b) Schematic 3D model of the headset. The headset was developed from laser-sintered nylon plastic, weighs 0.70 kg, has a low transparency index and is black in color to minimize light penetrance. (a and b) are reproduced, with slight modification, from Butler et al.16 with permission from IOP Publishing. (c) The LED stimulus box for table-top presentation.
<ol start="2">
	<li>TDT Hardware: Portable TDT Headset
	<ol>
		<li>Conduct the experiment in any suitable location.</li>
		<li>Connect the microcontroller to the headset and follow the on-screen instructions displayed on the liquid crystal display of the microcontroller box, e.g., select presentation method: &#39;random&#39; or &#39;staircase&#39;, and mode: &#39;left top first&#39;, etc.</li>
		<li>Direct the participant to position themselves with their elbows on a table in front of them. Then, holding the device in their hands, direct them to gently press their face into the rubber sealant surrounding the eyepiece, thereby sealing out ambient light.</li>
		<li>Instruct the participant to focus on the red fixation LED at all times and not to look directly at the flashing LEDs.</li>
		<li>Ask the participant to respond &#34;same&#34; or &#34;different&#34; following presentation of each stimulus pair, depending on whether they perceive the stimuli to be synchronous or asynchronous.</li>
		<li>Inform the participant when each trial is about to commence, by vocalizing the on-screen countdown from 5 - 0 s.</li>
	</ol>
	</li>
</ol>
2. Stimulus Presentation
Note: Two approaches to stimulus presentation have been employed.
<ol>
	<li>Staircase method
	<ol>
		<li>Select &#39;staircase&#39; presentation; stimuli are presented every 5 s with the inter-stimulus interval starting at 0 and becoming progressively more asynchronous (increasing by 5 ms) each time.</li>
		<li>Select any of the four presentation modalities: (i) left top LED first (ii) left bottom LED first (iii) right top LED first, or (iv) right bottom LED first.</li>
		<li>Repeat step 2.1.2 so that each modality is run twice, resulting in a total of eight runs.</li>
		<li>Terminate the trial when a participant responds &#34;different&#34; for three consecutive pairs of stimuli.</li>
	</ol>
	</li>
	<li>Random Presentation Method
	<ol>
		<li>Select &#39;Random&#39; presentation; stimuli pairs are presented every 5 s. The inter-stimulus interval varies, in a randomized fashion, from 0-100 ms.</li>
		<li>Select any of the four presentation modalities: (i) left top LED first (ii) left bottom LED first (iii) right top LED first, or (iv) right bottom LED first.</li>
		<li>Repeat step 2.2.2 so that each modality is run twice, resulting in a total of eight runs. 
		Note: Each run is the same length and will complete automatically.</li>
	</ol>
	</li>
</ol>
3. Data Analysis
<ol>
	<li>Single TDT value
	<ol>
		<li>Using the data from the staircase method, highlight the first of the final three &#34;different&#34; responses for each of the eight runs. These are the threshold values for each run.</li>
		<li>Calculate the temporal discrimination threshold (TDT) for each participant by taking the median of the thresholds from each of their eight runs; resulting in a single TDT value (in milliseconds) per individual.</li>
		<li>Calculate the Zscore for each participant. Define the Zscore as the difference between the participant&#39;s TDT, and the mean TDT from an age-matched control population (<img alt="Equaiton 1" src="/files/ftp_upload/56310/56310eq1.jpg" />, divided by the standard deviation of the TDT values for that control population <img alt="Equaiton 2" src="/files/ftp_upload/56310/56310eq2.jpg" />. 
		<img alt="Equaiton 3" src="/files/ftp_upload/56310/56310eq3.jpg" /></li>
		<li>Determine if the individual has a normal or abnormal TDT. A Zscore &#8805; 2.5 is deemed to reflect an abnormal TDT.</li>
	</ol>
	</li>
	<li>Distribution Analysis
	<ol>
		<li>Using the data from the staircase method, encode the response data such that &#39;0&#39; corresponds to &#34;same&#34; and &#39;1&#39; corresponds to &#34;different&#34;, Table 1.</li>
		<li>Download a free MATLAB.exe to perform the distribution analysis described below from http://www.dystoniaresearch.ie/temporal-discrimination-threshold/.&#160;See Butler et al.16 for a full description of this method. Alternatively, proceed as described below.</li>
		<li>Pad out the data to ensure all runs are the same length as the longest run. This is done by assuming all subsequent responses, following termination of a run, are &#34;different&#34;, Table 1(b).</li>
		<li>Average responses across trials for each participant, Table 1(c). This can be plotted as a function of stimulus asynchrony.</li>
		<li>Fit this averaged or representative data with a cumulative Gaussian function. The mean of this distribution represents the point at which participants are equally likely to respond &#8220;same&#8221; or &#8220;different&#8221;. This point is referred to as the &#8216;point of subjective equality&#8217; (PSE). The standard deviation of the Gaussian distribution, also referred to as the &#8216;just noticeable difference&#8217; (JND), indicates how sensitive participants are to changes in temporal asynchrony around their mean.</li>
		<li>Extend the analysis by submitting the data to a non-parametric bootstrapping procedure in order to estimate the 95% confidence intervals for the TDT and the PSE and JND of the psychometric, cumulative Gaussian function. To do this, generate new representative data sets by random sampling with replacement from the original responses, Table 1(b), for each time step. Calculate the TDT and fit a new psychometric function for each representative data set16.</li>
		<li>Calculate the goodness of fit, or deviance (D), for each participant using the log-likelihood ratio,16,17 
		<img alt="Equaiton 4" src="/files/ftp_upload/56310/56310eq4.jpg" /> 
		where K is the number of time points, ni is the number of repetitions at that time point, generally eight repetitions (four right and four left), yi is the observed proportion of asynchronous responses, pi is the proportion of asynchronous responses predicted by the fitted curve. A deviance value of 0 means a perfect fit.</li>
		<li>Plot the results. 
		Note: Data from the random presentation approach can be analyzed to determine the single or distributed TDT as described in section 3 above for data arising from the staircase presentation method. However, due to the random presentation order of inter-stimuli intervals, these data must first be ordered (from smallest to largest inter-stimulus interval), prior to commencing the analysis described above, Table 2. In addition, it is not necessary to pad the data following random presentation as, by default, all runs are of equal length.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Bradley, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temporal+discrimination+thresholds+in+adult-onset+primary+torsion+dystonia:+an+analysis+by+task+type+and+by+dystonia+phenotype.">Temporal discrimination thresholds in adult-onset primary torsion dystonia: an analysis by task type and by dystonia phenotype.</a> J Neurol. 259 (1), 77-82 (2012).</li><li>Hutchinson, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+endophenotype+and+the+phenotype:+temporal+discrimination+and+adult-onset+dystonia.">The endophenotype and the phenotype: temporal discrimination and adult-onset dystonia.</a> Mov Disord. 28 (13), 1766-1774 (2013).</li><li>Kimmich, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sporadic+adult+onset+primary+torsion+dystonia+is+a+genetic+disorder+by+the+temporal+discrimination+test.">Sporadic adult onset primary torsion dystonia is a genetic disorder by the temporal discrimination test.</a> Brain. 134 (Pt 9), 2656-2663 (2011).</li><li>Kimmich, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temporal+discrimination,+a+cervical+dystonia+endophenotype:+penetrance+and+functional+correlates.">Temporal discrimination, a cervical dystonia endophenotype: penetrance and functional correlates.</a> Mov Disord. 29 (6), 804-811 (2014).</li><li>Molloy, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+headset+method+for+measuring+the+visual+temporal+discrimination+threshold+in+cervical+dystonia.">A headset method for measuring the visual temporal discrimination threshold in cervical dystonia.</a> Tremor Other Hyperkinet Mov (N Y). 4, 249 (2014).</li><li>Termsarasab, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+correlates+of+abnormal+sensory+discrimination+in+laryngeal+dystonia.">Neural correlates of abnormal sensory discrimination in laryngeal dystonia.</a> Neuroimage Clin. 10, 18-26 (2016).</li><li>Fiorio, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Defective+temporal+processing+of+sensory+stimuli+in+DYT1+mutation+carriers:+a+new+endophenotype+of+dystonia?.">Defective temporal processing of sensory stimuli in DYT1 mutation carriers: a new endophenotype of dystonia?.</a> Brain. 130 (1), 134-142 (2007).</li><li>Albanese, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phenomenology+and+classification+of+dystonia:+a+consensus+update.">Phenomenology and classification of dystonia: a consensus update.</a> Mov Disord. 28 (7), 863-873 (2013).</li><li>Nutt, J. G., Muenter, M. D., Aronson, A., Kurland, L. T., Melton, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epidemiology+of+focal+and+generalized+dystonia+in+Rochester,+Minnesota.">Epidemiology of focal and generalized dystonia in Rochester, Minnesota.</a> Mov Disord. 3 (3), 188-194 (1988).</li><li>Williams, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epidemiological,+clinical+and+genetic+aspects+of+adult+onset+isolated+focal+dystonia+in+Ireland.">Epidemiological, clinical and genetic aspects of adult onset isolated focal dystonia in Ireland.</a> Eur J Neurol. , (2016).</li><li>Bell, A. H., Munoz, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activity+in+the+superior+colliculus+reflects+dynamic+interactions+between+voluntary+and+involuntary+influences+on+orienting+behaviour.">Activity in the superior colliculus reflects dynamic interactions between voluntary and involuntary influences on orienting behaviour.</a> Eur J Neurosci. 28 (8), 1654-1660 (2008).</li><li>Hutchinson, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cervical+dystonia:+a+disorder+of+the+midbrain+network+for+covert+attentional+orienting.">Cervical dystonia: a disorder of the midbrain network for covert attentional orienting.</a> Front Neurol. 5, 54 (2014).</li><li>Williams, L. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Young+Women+do+it+Better:+Sexual+Dimorphism+in+Temporal+Discrimination.">Young Women do it Better: Sexual Dimorphism in Temporal Discrimination.</a> Front Neurol. 6, 258 (2015).</li><li>Butler, J. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Age-Related+Sexual+Dimorphism+in+Temporal+Discrimination+and+in+Adult-Onset+Dystonia+Suggests+GABAergic+Mechanisms.">Age-Related Sexual Dimorphism in Temporal Discrimination and in Adult-Onset Dystonia Suggests GABAergic Mechanisms.</a> Front Neurol. 6, 258 (2015).</li><li>Bradley, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temporal+discrimination+threshold:+VBM+evidence+for+an+endophenotype+in+adult+onset+primary+torsion+dystonia.">Temporal discrimination threshold: VBM evidence for an endophenotype in adult onset primary torsion dystonia.</a> Brain. 132 (Pt 9), 2327-2335 (2009).</li><li>Butler, J. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-parametric+bootstrapping+method+for+measuring+the+temporal+discrimination+threshold+for+movement+disorders.">Non-parametric bootstrapping method for measuring the temporal discrimination threshold for movement disorders.</a> J Neural Eng. 12 (4), 046026 (2015).</li><li>Wichmann, F. A., Hill, N. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+psychometric+function:+I.+Fitting,+sampling,+and+goodness+of+fit.">The psychometric function: I. Fitting, sampling, and goodness of fit.</a> Percept Psychophys. 63 (8), 1293-1313 (2001).</li><li>McGovern, E. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comparison+of+stimulus+presentation+methods+in+temporal+discrimination+testing.">A comparison of stimulus presentation methods in temporal discrimination testing.</a> Physiol Meas. 38 (2), N57-N64 (2017).</li><li>Scontrini, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Somatosensory+temporal+discrimination+in+patients+with+primary+focal+dystonia.">Somatosensory temporal discrimination in patients with primary focal dystonia.</a> J Neurol Neurosurg Psychiatry. 80 (12), 1315-1319 (2009).</li><li>Nardella, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inferior+parietal+lobule+encodes+visual+temporal+resolution+processes+contributing+to+the+critical+flicker+frequency+threshold+in+humans.">Inferior parietal lobule encodes visual temporal resolution processes contributing to the critical flicker frequency threshold in humans.</a> PLoS One. 9 (6), e98948 (2014).</li><li>Pastor, M. A., Macaluso, E., Day, B. L., Frackowiak, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Putaminal+activity+is+related+to+perceptual+certainty.">Putaminal activity is related to perceptual certainty.</a> Neuroimage. 41 (1), 123-129 (2008).</li><li>Isa, T., Hall, W. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exploring+the+superior+colliculus+in+vitro.">Exploring the superior colliculus in vitro.</a> J Neurophysiol. 102 (5), 2581-2593 (2009).</li><li>Isa, T., Endo, T., Saito, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+visuo-motor+pathway+in+the+local+circuit+of+the+rat+superior+colliculus.">The visuo-motor pathway in the local circuit of the rat superior colliculus.</a> J Neurosci. 18 (20), 8496-8504 (1998).</li><li>Kaneda, K., Isa, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GABAergic+mechanisms+for+shaping+transient+visual+responses+in+the+mouse+superior+colliculus.">GABAergic mechanisms for shaping transient visual responses in the mouse superior colliculus.</a> Neuroscience. 235, 129-140 (2013).</li><li>Ramos, V. F., Esquenazi, A., Villegas, M. A., Wu, T., Hallett, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temporal+discrimination+threshold+with+healthy+aging.">Temporal discrimination threshold with healthy aging.</a> Neurobiol Aging. 43, 174-179 (2016).</li></ol>

Rebecca B Beck, Eavan M Mc Govern, John Butler, Dorina Birsanu, Brendan Quinlivan, Ines Beiser, Shruti Narasimham have no funding sources, financial disclosures or conflict of interests to declare. Michael Hutchinson receives research grants from Dystonia Ireland, the Health Research Board of Ireland (CSA-2012-5), Foundation for Dystonia Research (Belgium) and the Irish Institute of Clinical Neuroscience. Sean O&#39;Riordan reports receiving a speaker&#39;s honorarium from Abbvie. Richard Reilly receives funding from Science Foundation Ireland, Enterprise Ireland and the Health Research Board of Ireland.

TDT Measurement and Analysis 
Two forms of apparatus (table-top and headset), two methods of stimulus presentation (staircase and random), and two approaches to data analysis (traditional and distribution) have been presented to illustrate how to measure and quantify a person&#39;s temporal discrimination ability. The portable headset provides a convenient hardware option that ensures consistency in distance and angles between the participant and the LED light sources while al...

Temporal discrimination describes a person&#39;s ability to discriminate, or perceive, rapid changes in their environment. The temporal discrimination threshold (TDT) is the shortest time interval at which an individual can perceive that two sequential sensory stimuli are asynchronous. Temporal discrimination has been shown to be abnormally prolonged in disorders affecting the basal ganglia, including dystonia1,2,3,4,5,6,7.
Dystonia is the third most common neurological movement disorder - after Parkinson&#39;s disease and Essential Tremor. It is characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements or postures8. Dystonia can affect any part of the body. When it affects one body part it is known as focal dystonia8. Dystonia affecting the neck muscles is known as cervical dystonia, and is the most common phenotype of adult onset idiopathic isolated focal dystonia.9,10 The pathogenesis of cervical dystonia remains unknown; it is considered to be a genetic disorder with autosomal dominant inheritance and markedly reduced penetrance. Environmental factors are also considered important in relation to disease penetrance and expression.
The superior colliculus, a sensorimotor structure situated in the dorsal midbrain, is important for the rapid detection of environmental stimuli in the process of covert attentional orienting2,11,12. Visual stimuli access the superior colliculus rapidly through the retino-tectal magnocellular pathway. The TDT is a simple, objective measure believed to represent the processing of visual (and other sensory stimuli) in the superficial layers of the superior colliculus. The TDT has been studied in individuals with cervical dystonia, their unaffected relatives and healthy control participants. Compared to age- and sex-matched control participants, an abnormal TDT has high sensitivity (97%, 36 of 37 patients) and specificity (98-100%) in cervical dystonia1. An abnormal TDT has been found in 50% of unaffected first-degree female relatives of patients with cervical dystonia (14 of 25, aged 48 years or older), demonstrating age- and sex-related penetrance with autosomal dominant inheritance13,14. An abnormal TDT in unaffected relatives of cervical dystonia patients (compared to relatives with normal TDTs) is associated with increased putaminal volume (by voxel-based morphometry)15 and reduced putaminal activity (by fMRI)4. The superior colliculus is considered a significant node in the neuronal network, which is dysfunctional in cervical dystonia12. The assessment of temporal discrimination is regarded as providing important clues as to the pathomechanisms underlying cervical dystonia.
The goal of this article is to present two methods for measuring and analyzing temporal discrimination, as well as demonstrating the application of this method to studying the pathophysiology of cervical dystonia.

<table><tbody><tr><td>TDT head set</td><td>Can be supplied by Trinity Centre for Bioengineering, Trinity College Dublin.&amp;nbsp; Alternatively full instructions are available for free download from http://www.dystoniaresearch.ie/temporal-discrimination-threshold/</td><td>1</td><td>A custom-built, portable device for the presentation of visual stimuli.</td></tr><tr><td>TDT table top LED box</td><td>Can be supplied by Trinity Centre for Bioengineering, Trinity College Dublin.&amp;nbsp; Alternatively full instructions are available for free download from http://www.dystoniaresearch.ie/temporal-discrimination-threshold/</td><td>2</td><td>A custom-built, table-top device for the presentation of visual stimuli.</td></tr><tr><td>Microcontroller</td><td>Can be supplied by Trinity Centre for Bioengineering, Trinity College Dublin.&amp;nbsp; Alternatively full instructions are available for free download from http://www.dystoniaresearch.ie/temporal-discrimination-threshold/</td><td>3</td><td>A custom-built microcontroller for the delivery of visual stimuli in staircase or random order, with precise inter-stimulus intervals.</td></tr></tbody></table>

measurement &amp; analysis of the temporal discrimination threshold applied to cervical dystonia

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.

Examples of filled score sheets are provided in Tables 1 and 2, where these respectively represent results following staircase and random stimulus presentation methods. The thresholds for each run (the timing of the first of three stimulus pairs deemed to be &#39;different&#39;), are highlighted. In the case of Table 1, the TDT is calculated as 25 ms (i.e., the median of 40, 25, 25, 25, 45, 25, 40, 10 ms). These ...

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Measurement & Analysis of the Temporal Discrimination Threshold Applied to Cervical Dystonia

Methods for the measurement and analysis of the temporal discrimination threshold are presented, and its application to the study of the pathogenesis of cervical dystonia are discussed.

Measurement &amp; Analysis of the Temporal Discrimination Threshold Applied to Cervical Dystonia

The temporal discrimination threshold (TDT) is the shortest time interval at which an observer can discriminate two sequential stimuli as being ...

measurement-analysis-temporal-discrimination-threshold-applied-to

Research

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9.7K Views.  Trinity College Dublin, The University of Dublin. Methoden voor de meting en analyse van de temporele discriminatie drempel worden gepresenteerd, en de toepassing ervan op de studie van de pathogenese van cervicale dystonie worden besproken.

Video: Measurement & Analysis of the Temporal Discrimination Threshold Applied to Cervical Dystonia

Corticospinal Excitability Modulation During Action Observation

This study used the transcranial magnetic stimulation/motor evoked potential (TMS/MEP) technique to pinpoint when the automatic tendency to mirror someone else's action becomes anticipatory simulation of a complementary act. TMS was delivered to the left primary motor cortex corresponding to the hand to induce the highest level of MEP activity from the abductor digiti minimi (ADM; the muscle serving little finger abduction) as well as the first dorsal interosseus (FDI; the muscle serving index finger flexion/extension) muscles. A neuronavigation system was used to maintain the position of the TMS coil, and electromyographic (EMG) activity was recorded from the right ADM and FDI muscles. Producing original data with regard to motor resonance, the combined TMS/MEP technique has taken research on the perception-action coupling mechanism a step further. Specifically, it has answered the questions of how and when observing another person's actions produces motor facilitation in an onlooker's corresponding muscles and in what way corticospinal excitability is modulated in social contexts.

Single-pulse transcranial magnetic stimulation over the primary motor cortex, neuronavigation, and registration of electromyographic activity of hand muscles were used in this study to explore corticospinal excitability while participants were observing action sequences.

This study used the transcranial magnetic stimulation/motor evoked potential (TMS/MEP) technique to pinpoint when the automatic tendency to mirror someone ...

Behavior

Measurement of Vibration Detection Threshold and Tactile Spatial Acuity in Human Subjects

Tests that allow the precise determination of psychophysical thresholds for vibration and grating orientation provide valuable information about mechanosensory function that are relevant for clinical diagnosis as well as for basic research. Here, we describe two psychophysical tests designed to determine the vibration detection threshold (automated system) and tactile spatial acuity (handheld device). Both procedures implement a two-interval forced-choice and a transformed-rule up and down experimental paradigm. These tests have been used to obtain mechanosensory profiles for individuals from distinct human cohorts such as twins or people with sensorineural deafness.

Here, we present protocols to determine vibration detection thresholds and tactile acuity using psychophysical methods in man.

Tests that allow the precise determination of psychophysical thresholds for vibration and grating orientation provide valuable information about ...

Psychophysically-anchored, Robust Thresholding in Studying Pain-related Lateralization of Oscillatory Prestimulus Activity

In perceptual studies, it is often important to objectively assess the equality of delivered stimulation across participants or to quantify the intra-individual sensation magnitude that is evoked by stimulation over multiple trials. This requires a robust mapping of stimulus magnitude to perceived intensity and is commonly achieved by psychophysical estimation methods such as the staircase procedure. Newer, more efficient procedures like the QUEST algorithm fit a psychophysical function to the data in real time while at the same time maximizing the efficiency of data collection. A robust estimate of the threshold intensity between painful and nonpainful perceptions can then be used to reduce the influence of variations in sensory input in subsequent analyses of oscillatory brain activity. By stimulating at a constant threshold intensity determined by an adaptive estimation procedure, the variance in the ratings can be directly attributed to perceptual processes. Oscillatory activity can then be contrasted between &#34;pain&#34; and &#34;no-pain&#34; trials directly, yielding activity that closely relates to perceptual classification processes in nociception.

Psychophysical methods such as the QUEST estimation procedure can efficiently yield robust estimates of the stimulation intensity at which nonpainful sensations transition into painful sensations. By stimulating repeatedly at the threshold intensity, the variability in rating responses can directly be attributed to perceptual classifications in subsequent analyses.

In perceptual studies, it is often important to objectively assess the equality of delivered stimulation across participants or to quantify the ...

A Standardized Method for Measurement of Elbow Kinesthesia

Proprioception is an important component of controlled movement. The threshold to detection of passive movement (TDPM) is a commonly used method for quantifying the proprioceptive submodality of kinesthesia in research settings. The TDPM paradigm has been found to be valid and reliable; however, the equipment and methods used for TDPM vary between studies. In particular, the research laboratory apparatuses for producing passive movement of an extremity are often custom designed by individual laboratories or inaccessible due to high cost. There is a need for a standardized, valid, and reliable method for measuring TDPM using readily available equipment. The purpose of this protocol is to provide a standardized method for measurement of TDPM at the elbow that is economical, easy to administer, and that produces quantitative results for measurement purposes in research-based settings. This method was tested on 20 healthy adults without neurological impairment, and eight adults with chronic stroke. The results obtained suggest this method is a reliable way to quantify elbow TDPM in healthy adults, and provides initial support for validity. Researchers seeking a balance between equipment affordability and measurement precision are most likely to find this protocol of benefit.

Here, we present a standardized method for measurement of elbow passive kinesthesia using the threshold to detection of passive movement (TDPM) that is appropriate for a research setting.

Proprioception is an important component of controlled movement. The threshold to detection of passive movement (TDPM) is a commonly used method for ...

Investigating Oculomotor Responses in Visual Duration Perception Tasks

Eye Movements in Visual Duration Perception: Disentangling Stimulus from Time in Predecisional Processes

Eye-tracking methods may allow the online monitoring of cognitive processing during visual duration perception tasks, where participants are asked to estimate, discriminate, or compare time intervals defined by visual events like flashing circles. However, and to our knowledge, attempts to validate this possibility have remained inconclusive so far, and results remain focused on offline behavioral decisions made after stimulus appearance. This paper presents an eye-tracking protocol for exploring the cognitive processes preceding behavioral responses in an interval comparison task, where participants viewed two consecutive intervals and had to decide whether it speeded up (first interval longer than second) or slowed down (second interval longer). 
Our main concern was disentangling oculomotor responses to the visual stimulus itself from correlates of duration related to judgments. To achieve this, we defined three consecutive time windows based on critical events: baseline onset, the onset of the first interval, the onset of the second interval, and the end of the stimulus. We then extracted traditional oculomotor measures for each (number of fixations, pupil size) and focused on time-window-related changes to separate the responses to the visual stimulus from those related to interval comparison per se. As we show in the illustrative results, eye-tracking data showed significant differences that were consistent with behavioral results, raising hypotheses on the mechanisms engaged. This protocol is embryonic and will require many improvements, but it represents an important step forward in the current state of art.

Author Spotlight: Exploring the Link Between Time Perception of Visual Stimuli and Reading Skills

We present a protocol that employs eye tracking to monitor eye movements during an interval comparison (duration perception) task based on visual events. The aim is to provide a preliminary guide to separate oculomotor responses to duration perception tasks (comparison or discrimination of time intervals) from responses to the stimulus itself.

Eye-tracking methods may allow the online monitoring of cognitive processing during visual duration perception tasks, where participants are asked to ...

Real-Time Mouse Eye Squint Detection for Migraine Pain Tracking Using DeepLabCut

An Automated Squint Method for Time-syncing Behavior and Brain Dynamics in Mouse Pain Studies

Spontaneous pain has been challenging to track in real time and quantify in a way that prevents human bias. This is especially true for metrics of head pain, as in disorders such as migraine. Eye squint has emerged as a continuous variable metric that can be measured over time and is effective for predicting pain states in such assays. This paper provides a protocol for the use of DeepLabCut (DLC) to automate and quantify eye squint (Euclidean distance between eyelids) in restrained mice with freely rotating head motions. This protocol enables unbiased quantification of eye squint to be paired with and compared directly against mechanistic measures such as neurophysiology. We provide an assessment of AI training parameters necessary for achieving success as defined by discriminating squint and non-squint periods. We demonstrate an ability to reliably track and differentiate squint in a CGRP-induced migraine-like phenotype at a sub second resolution.

Author Spotlight: Deciphering Electrical Networks Behind Complex Brain Activities and Disorders

This protocol provides a method for tracking automated eye squint in rodents over time in a manner compatible with time-locking to neurophysiological measures. This protocol is expected to be useful to researchers studying mechanisms of pain disorders such as migraine.

Spontaneous pain has been challenging to track in real time and quantify in a way that prevents human bias. This is especially true for metrics of head ...

Implantation of Osmotic Pumps and Induction of Stress to Establish a Symptomatic, Pharmacological Mouse Model for DYT/PARK-ATP1A3 Dystonia

Genetically modified mouse models face limitations, especially when studying movement disorders, where most of the available transgenic rodent models do not present a motor phenotype resembling the clinical aspects of the human disease. Pharmacological mouse models allow for a more direct study of the pathomechanisms and their effect on the behavioral phenotype. Osmotic pumps connected to brain cannulas open up the possibility of creating pharmacological mouse models via local and chronic drug delivery. For the hereditary movement disorder of rapid-onset dystonia-parkinsonism, the loss-of-function mutation in the &#945;3-subunit of the Na+/K+-ATPase can be simulated by a highly specific blockade via the glycoside ouabain. In order to locally block the &#945;3-subunit in the basal ganglia and the cerebellum, which are the two brain structures believed to be heavily involved in the pathogenesis of rapid-onset dystonia-parkinsonism, a bilateral cannula is stereotaxically implanted into the striatum and an additional single cannula is introduced into the cerebellum. The cannulas are connected via vinyl tubing to two osmotic pumps, which are subcutaneously implanted on the back of the animals and allow for the chronic and precise delivery of ouabain. The pharmacological mouse model for rapid-onset dystonia-parkinsonism carries the additional advantage of recapitulating the clinical and pathological features of asymptomatic and symptomatic mutation carriers. Just like mutation carriers of rapid-onset dystonia parkinsonism, the ouabain-perfused mice develop dystonia-like movements only after additional exposure to stress. We demonstrate a mild stress paradigm and introduce two modified scoring systems for the assessment of a motor phenotype.

We provide a protocol to generate a pharmacological DYT/PARK-ATP1A3 dystonia mouse model via implantation of cannulas into basal ganglia and cerebellum connected to osmotic pumps. We describe the induction of dystonia-like movements via application of a motor challenge and the characterization of the phenotype via behavioral scoring systems.

Genetically modified mouse models face limitations, especially when studying movement disorders, where most of the available transgenic rodent models do ...

Induction and Assessment of Levodopa-induced Dyskinesias in a Rat Model of Parkinson's Disease

Levodopa (L-DOPA) remains the gold-standard therapy used to treat Parkinson&#39;s disease (PD) motor symptoms. However, unwanted involuntary movements known as L-DOPA-induced dyskinesias (LIDs) develop with prolonged use of this dopamine precursor.&#160;It is estimated that the incidence of LIDs escalates to approximately 90% of individuals with PD within 10&#8211;15 years of treatment. Understanding the mechanisms of this malady and developing both novel and effective anti-dyskinesia treatments requires consistent and accurate modeling for pre-clinical testing of therapeutic interventions. A detailed method for reliable induction and comprehensive rating of LIDs following 6-OHDA-induced nigral lesioning in a rat model of PD is presented here. Dependable LID assessment in rats provides a powerful tool that can be readily utilized across laboratories to test emerging therapies focused on reducing or eliminating this common treatment-induced burden for individuals with PD.

This article describes methods to induce and evaluate levodopa-induced dyskinesias in a rat model of Parkinson&#39;s disease. The protocol offers detailed information regarding the intensity and frequency of a range of dyskinetic behaviors, both dystonic and hyperkinetic, providing a reliable tool to test treatments targeting this unmet medical need.

Levodopa (L-DOPA) remains the gold-standard therapy used to treat Parkinson&#39;s disease (PD) motor symptoms. However, unwanted involuntary movements ...

Measuring Contralateral Silent Period Induced by Single-Pulse Transcranial Magnetic Stimulation to Investigate M1 Corticospinal Inhibition

Contralateral silent period (cSP) is a period of suppression in the background electrical muscle activity captured by electromyography (EMG) after a motor evoked potential (MEP). To obtain this, an MEP is elicited by a suprathreshold transcranial magnetic stimulation (TMS) pulse delivered to the primary motor cortex (M1) of the target muscle selected, while the participant provides a standardized voluntary target muscle contraction. The cSP is a result of inhibitory mechanisms that occur after the MEP; it provides a broad temporal assessment of spinal inhibition in its initial ~50 ms, and cortical inhibition after. Researchers have tried to better understand the neurobiological mechanism behind the cSP to validate it as a potential diagnostic, surrogate, and predictive biomarker for different neuropsychiatric diseases. Therefore, this article describes a method to measure M1 cSP of lower and upper limbs, including a selection of target muscle, electrode placement, coil positioning, method of measuring voluntary contraction stimulation, intensity setup, and data analysis to obtain a representative result. It has the educational objective of giving a visual guideline in performing a feasible, reliable, and reproducible cSP protocol for lower and upper limbs and discussing practical challenges of this technique.

Contralateral silent period (cSP) assessment is a promising biomarker to index cortical excitability and treatment response. We demonstrate a protocol to assess cSP intended for studying M1 corticospinal inhibition of upper and lower limbs.

Contralateral silent period (cSP) is a period of suppression in the background electrical muscle activity captured by electromyography (EMG) after a motor ...

Open-Source Real-Time Closed-Loop Electrical Threshold Tracking for Translational Pain Research

Nociceptors are a class of primary afferent neurons that signal potentially harmful noxious stimuli. An increase in nociceptor excitability occurs in acute and chronic pain conditions. This produces abnormal ongoing activity or reduced activation thresholds to noxious stimuli. Identifying the cause of this increased excitability is required for the development and validation of mechanism-based treatments. Single-neuron electrical threshold tracking can quantify nociceptor excitability. Therefore, we have developed an application to allow such measurements and demonstrate its use in humans and rodents. APTrack provides real-time data visualization and action potential identification using a temporal raster plot. Algorithms detect action potentials by threshold crossing and monitor their latency after electrical stimulation. The plugin then modulates the electrical stimulation amplitude using an up-down method to estimate the electrical threshold of the nociceptors. The software was built upon the Open Ephys system (V0.54) and coded in C++ using the JUCE framework. It runs on Windows, Linux, and Mac operating systems. The open-source code is available (<a data-saferedirecturl="https://www.google.com/url?q=https://github.com/Microneurography/APTrack&amp;source=gmail&amp;ust=1680789829274000&amp;usg=AOvVaw0nMk9J_EI2jUn8SlmC5JJm" href="https://github.com/Microneurography/APTrack" target="_blank">https://github.com/Microneurography/APTrack</a>). The electrophysiological recordings were taken from nociceptors in both a mouse skin-nerve preparation using the teased fiber method in the saphenous nerve and in healthy human volunteers using microneurography in the superficial peroneal nerve. Nociceptors were classified by their response to thermal and mechanical stimuli, as well as by monitoring the activity-dependent slowing of the conduction velocity. The software facilitated the experiment by simplifying the action potential identification through the temporal raster plot. We demonstrate real-time closed-loop electrical threshold tracking of single-neuron action potentials during&#160;in vivo&#160;human microneurography, for the first time, and during&#160;ex vivo&#160;mouse electrophysiological recordings of C-fibers and A&#948;-fibers. We establish proof of principle by showing that the electrical threshold of a human heat-sensitive C-fiber nociceptor is reduced by heating the receptive field. This plugin enables the electrical threshold tracking of single-neuron action potentials and allows the quantification of changes in nociceptor excitability.

APTrack is a software plugin developed for the Open Ephys platform that enables real-time data visualization and the closed-loop electrical threshold tracking of neuronal action potentials. We have successfully used this in microneurography for human C-fiber nociceptors and mouse C-fiber and A&#948;-fiber nociceptors.

Nociceptors are a class of primary afferent neurons that signal potentially harmful noxious stimuli. An increase in nociceptor excitability occurs in ...

Measurement & Analysis of the Temporal Discrimination Threshold Applied to Cervical Dystonia

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