<div dir="ltr"><div class="gmail_quote"><div dir="ltr"><div style="font-size:small">Dear colleagues,</div><div style="font-size:small"><br></div><div style="font-size:small">I would like to bring to your attention a recent paper of ours entitled "NEURAL MODELLING OF ANTISACCADE PERFORMANCE OF HEALTHY CONTROLS AND EARLY HUNTINGTON'S DISEASE PATIENTS" published in Chaos journal.</div><div style="font-size:small"> <br></div><div style="font-size:small">Questions, comments, criticism are most welcome. A brief <span class="gmail_default" style="font-size:small">description of our research work and its find</span>ings follow:<span class="gmail_default" style="font-size:small"></span></div><div style="font-size:small"><span class="gmail_default" style="font-size:small"><br></span></div><div style="font-size:small"><span class="gmail_default" style="font-size:small">
<font size="2"><span style="font-family:arial,sans-serif"><span style="left: 120.04px; top: 168.239px; transform: scaleX(0.883781);">Antisaccade task, a </span><span style="left: 265.433px; top: 168.239px; transform: scaleX(0.90927);">behavioral response inhibition </span><span style="left: 491.483px; top: 168.239px; transform: scaleX(0.897591);">paradigm, involves suppressi</span><span style="left: 704.517px; top: 168.239px; transform: scaleX(0.926098);">on of the reflex to look </span><span style="left: 120.04px; top: 189.239px; transform: scaleX(0.887779);">towards a newly presented target (error prosaccade response) and instead directs the eyes to a position </span><span style="left: 120.04px; top: 210.237px; transform: scaleX(0.905992);">diametrically opposite to target’s position (correct antisaccade response). Failure to suppress th</span><span style="left: 823.567px; top: 210.239px; transform: scaleX(0.899831);">e error </span><span style="left: 120.04px; top: 231.439px; transform: scaleX(0.86344);">prosaccade response r</span><span style="left: 281.833px; top: 231.439px; transform: scaleX(0.920656);">esults in a direction error.</span><span style="left: 476.283px; top: 231.437px; transform: scaleX(0.879487);"> Τwo processes </span><span style="left: 590.117px; top: 231.439px; transform: scaleX(0.922654);">usually </span><span style="left: 647.917px; top: 231.439px; transform: scaleX(0.911844);">take place during this </span><span style="left: 811.567px; top: 231.439px; transform: scaleX(0.876);">task</span><span style="left: 841.167px; top: 231.439px; transform: scaleX(0.945799);">: (1) </span><span style="left: 120.04px; top: 252.439px; transform: scaleX(0.875365);">suppression of an error prosaccade towards the peripheral stimulus, and (2) generation of an antisaccade </span><span style="left: 120.04px; top: 273.639px; transform: scaleX(0.918616);">to the diametrically opposite directio</span><span style="left: 388.883px; top: 273.639px; transform: scaleX(0.9);">n.</span><span style="left: 406.883px; top: 273.639px; transform: scaleX(0.881498);"> Participants have been observed to express any of the f</span><span style="left: 807.367px; top: 273.639px; transform: scaleX(0.971202);">ollowing </span><span style="left: 120.04px; top: 294.639px; transform: scaleX(0.876505);">three eye movement behaviors during a trial: (1) Participant f</span><span style="left: 593.717px; top: 294.639px; transform: scaleX(0.993201);">ail</span><span style="left: 612.117px; top: 294.639px;">s</span><span style="left: 626.317px; top: 294.639px; transform: scaleX(0.847492);"> to suppress the error prosaccade </span><span style="left: 120.04px; top: 315.639px; transform: scaleX(0.908142);">result</span><span style="left: 160.84px; top: 315.639px; transform: scaleX(0.960195);">ing</span><span style="left: 190.233px; top: 315.639px; transform: scaleX(0.9206);">in a direction error</span><span style="left: 331.683px; top: 315.639px; transform: scaleX(0.910277);">, (2) Participant makes an antisaccade, or (3) Participant </span><span style="left: 760.767px; top: 315.639px; transform: scaleX(0.867154);">makes an error </span><span style="left: 120.04px; top: 337.039px; transform: scaleX(0.883454);">prosaccade and corrects with a corrected an</span><span style="left: 439.883px; top: 337.039px; transform: scaleX(0.890415);">tisaccade in the same trial</span><span style="left: 629.517px; top: 337.039px;">.</span>
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<font size="2"><span style="font-family:arial,sans-serif"><span>The current accepted dogma in the antisaccade task is that a third top</span><span>-</span><span>down inhibitory signal is needed </span><span>to suppress the error prosaccade in favor of the antisaccade. In </span><span>line with this dogma past modelling </span><span>studies of the antisac</span><span>cade task in health and Huntington disease (HD) required the presence of a third </span><span>STOP decision signal to suppress in trials the erroneous response. These models although they provided </span><span>a successful m</span><span>echanistic view of decision making in the antisaccade task</span><span>, they failed to capture all </span><span>aspects of antisaccade performance.</span><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span>Our research work described in our paper offers an alternative view, which succeeds for the first time </span><span>to:</span><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span>1. </span><span>Capture all aspects of the</span><span> antisaccade performance of both healthy controls and earl</span><span>y HD </span><span>patients</span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span></span><span>2. </span><span>Offer a mechanistic view of processes taking place in the antisaccade paradigm</span><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span>3. </span><span>Decipher the mechanisms which give rise to the observed slowed and more variable antisaccade </span><span>latencies an</span><span>d increased error rates in HD patients relative to healthy</span><span>controls. </span><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span>The model shows </span><span>that </span><span>th</span><span>e </span><span>poor HD antisaccade </span><span>performance is </span><span>not due to </span><span>a deficit in the top</span><span>-</span><span>down </span><span>inhibitory control of the erroneous response</span><span>as many speculated, </span><span>but instead </span><span>is a product</span><span>of a </span><span>competition between </span><span>two different neuronal populatio</span><span>ns each coding for a different decision signal: one </span><span>coding for </span><span>the erroneous prosaccade </span><span>decision </span><span>and </span><span>the other one for </span><span>antisaccade </span><span>decision</span><span>. <br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span></span><span>The model accurately reproduces</span><span></span><span> the error rates, </span><span>respons</span><span>e latencies and latency distributions of</span><span> antisaccade</span><span>s</span><span>, err</span><span>or prosaccade</span><span>s </span><span>and corrected antisaccade</span><span>s </span><span>of </span><span>both </span><span>healthy </span><span>controls </span><span>and </span><span>HD </span><span>participants. </span><span>Our model </span><span></span><span>show</span><span>s</span><span> that the increased variability in the antisaccade and corrected antisaccade </span><span>RT </span><span>distributions of </span><span>HD </span><span>participants are due to a </span><span>slower and </span><span>nois</span><span>ier</span><span> acc</span><span>umulation of info</span><span>rmation (μ and σ), </span><span>but the HD patients’ </span><span>confidence level required before commitment to a particular course</span><span> of action is not </span><span>affected by the disease</span><span>. </span><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span>Our results have m</span><span>ajor implications in clinical and pharmaceutical research. </span><span>Furthermore, </span><span>our</span><span> results illustrate the benefits of tightly integrating psychophysical studies with </span><span>computational neural model</span><span>l</span><span>ing, because the two methods complement each other and they may provid</span><span>e </span><span>together a strong basis for hypothesis generation and theory testing r</span><span>egarding the neural basis of </span><span>decision making in health and in disease.</span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span><br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span>Kind regards,</span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span>Vassilis Cutsuridis<br></span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span>University of Lincoln</span></span></font></div><div style="font-size:small"><font size="2"><span style="font-family:arial,sans-serif"><span>UK<br></span></span></font>
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