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SUMMARY:A neural mechanism for decision-making\, or how I learned to stop 
 worrying and love the bound - Michael Shadlen\, Physiology and Biophysics 
 Department\, University of Washington
DTSTART:20061215T130000Z
DTEND:20061215T140000Z
UID:TALK5847@talks.cam.ac.uk
CONTACT:Cordula Becker
DESCRIPTION:With little sophistication\, the spike rates from sensory neur
 ons can be used to approximate useful statistics for decision-making. In t
 he context of deciding between two sensory hypotheses\, a simple differenc
 e in spike rate between sensory neurons with opposite selectivity is propo
 rtional to the log likelihood ratio in favor of one sensory interpretation
  over another. I will describe neural recording and stimulation experiment
 s that demonstrate the use of such a difference during decision-making in 
 a 2-alternative direction discrimination task. The accumulation of this di
 fference to threshold (aka\, “the bound”) explains the speed and accur
 acy of simple decisions. A new probabilistic classification task\, similar
  to the “weather prediction task” reveals a direct representation of l
 og probability in parietal cortex. And\, if time permits\, I will explain 
 how the brain uses elapsed time to decode such probability. Interestingly\
 , the neural computations that underlie such decision-making were anticipa
 ted during WWII by Alan Turing and Abraham Wald. Turing applied this tool 
 to break the German navy’s Enigma cipher\, while Wald invented the field
  of sequential analysis. In addition to mathematical elegance and winning 
 wars\, our experiments suggest that this computational strategy may lie at
  the core of higher brain function. 
LOCATION:Seminar Room (ground floor)\, Craik-Marshall Building
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