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</o:shapelayout></xml><![endif]--></head><body lang=SL link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Vabimo vas na 14. predavanje iz sklopa "Kolokviji na IJS" v letu 2013/14, ki bo <b><span style='color:red'>v sredo, 02. aprila 2014, ob 13. uri </span></b><span style='color:red'>v Veliki predavalnici Instituta »Jožef Stefan«</span> na Jamovi cesti 39 v Ljubljani. Napovednik predavanja najdete tudi na naslovu <a href="http://www.ijs.si/ijsw/Koledar_prireditev">http://www.ijs.si/ijsw/Koledar_prireditev</a>, posnetke preteklih predavanj<span style='color:blue'> </span>pa na <a href="http://videolectures.net/kolokviji_ijs">http://videolectures.net/kolokviji_ijs</a>. <o:p></o:p></p><p class=MsoNormal style='margin-bottom:12.0pt'>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<o:p></o:p></p><p class=MsoNormal><b><span style='mso-fareast-language:ZH-CN'>Prof. dr. Gašper Tkačik<o:p></o:p></span></b></p><p class=MsoNormal><i><span style='mso-fareast-language:ZH-CN'>Institute of Science and Technology Austria, Dunaj, Avstrija<o:p></o:p></span></i></p><p class=MsoNormal><b><span style='font-size:14.0pt'><o:p> </o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:14.0pt'>Kritično obnašanje v mrežah pravih nevronov<o:p></o:p></span></b></p><p class=MsoNormal style='text-align:justify'><span style='font-size:11.0pt;font-family:"Arial","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt;text-align:justify'>Vzorci hkratne aktivnosti v populaciji mrežničnih ganglijskih celic vsebujejo popolno informacijo o vizualnem svetu in s tem postavljajo meje tega, kar lahko z možgani izvemo o okolici. Na ravni posameznega pulza smo analizirali eksperimentalno zabeleženo simultano aktivnost več kot sto tovrstnih nevronov iz interagirajoče populacije, ki se odziva na karseda stvarne dražljaje. Skonstruirali smo natančne modele porazdelitve stanj aktivnosti mreže, zasnovane na načelu maksimalne entropije. Konstrukcija, ki je v bistvu enaka kot pri inverznem spinskem steklu, je razkrila močno frustracijo parske sklopitve med nevroni. Ta vodi do grobe energijske ploskve z mnogo lokalnimi ekstremi, do močnih kolektivnih interakcij v podskupinah nevronov kljub šibkim individualnim parskim korelacijam in do skupne porazdelitve aktivnosti z zelo širokim dinamičnim razponom z značilno Zipfovo potenčno odvisnostjo, močnimi odmiki od “tipičnosti” in vrsto znakov kritičnega obnašanja. Sklepamo, da je delovanje v kritični točki dinamična lastnost sistema, in predlagamo eksperimente, s katerimi bi to hipotezo lahko preverili.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt;text-align:justify'>Predavanje bo v angleščini.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt'><b><span style='font-family:"Calibri","sans-serif";color:red'>Lepo vabljeni!</span></b><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><span style='font-size:12.0pt;font-family:"Times New Roman","serif";mso-fareast-language:SL'><br clear=all style='page-break-before:always'></span><p class=MsoNormal><span style='color:black'>We invite you to the 14th Institute colloquium in the academic year 2013/14. The colloquium will be held <b>on Wednesday April 02, 2014 at 1 PM</b> in <b>the main Institute</b></span><b><span style='color:#1F497D'> </span><span style='color:black'>lecture hall</span></b><span style='color:black'>, Jamova 39, Ljubljana. To read the abstract click </span><span style='color:#1F497D'><a href="http://www.ijs.si/ijsw/Koledar_prireditev">http://www.ijs.si/ijsw/Koledar_prireditev</a>. </span><span style='color:black'>Past colloquia are posted on</span><span style='color:#1F497D'> <a href="http://videolectures.net/kolokviji_ijs">http://videolectures.net/kolokviji_ijs</a>.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'>********************************************<b><o:p></o:p></b></p><p class=MsoNormal><b>prof. dr. Gašper Tkačik<o:p></o:p></b></p><p class=MsoNormal><i>Institute of Science and Technology Austria, Vienna, Austria<o:p></o:p></i></p><p class=MsoNormal><b><span style='font-size:16.0pt;mso-fareast-language:ZH-CN'><o:p> </o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:16.0pt'>Critical behavior in networks of real neurons<o:p></o:p></span></b></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The patterns of joint activity in a population of retinal ganglion cells encode the complete information about the visual world, and thus place limits on what could be learned about the environment by the brain. We analyze the recorded simultaneous activity of more than a hundred such neurons from an interacting population responding to naturalistic stimuli, at the single spike level, by constructing accurate maximum entropy models for the distribution of network activity states. This – essentially an inverse spin glass – construction reveals strong frustration in the pairwise couplings between the neurons that results in a rugged energy landscape with many local extrema; strong collective interactions in subgroups of neurons despite weak individual pairwise correlations; and a joint distribution of activity that has an extremely wide dynamic range characterized by a Zipf-like power law, strong deviations from typicality, and a number of signatures of critical behavior. We hypothesize that this tuning to a critical operating point might be a dynamic property of the system and suggest experiments to test this hypothesis.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Cordially invited!<o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div></body></html>