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SUMMARY:Noise in the central nervous system - Aldo Faisal
DTSTART:20080507T130000Z
DTEND:20080507T140000Z
UID:TALK11518@talks.cam.ac.uk
CONTACT:Philip Sterne
DESCRIPTION:*Noise* — random disturbances of signals — pose a fundamen
 tal problem for information processing and affects all aspects of nervous-
 system function. However\, the nature\, amount and impact of noise in the 
 central nervous system have only recently been addressed in a quantitative
  manner by the use of\nstochastic models and simulations.\n\nHere\, I will
  focus on *action potentials*\, the fundamental signal used by neurons to 
 transmit information rapidly and reliably to other neurons along nerve fib
 ers (axons). \n\nI will show how conduction along such axons of our brains
  is affected by the probabilistic nature of voltage-gated ion channels\, "
 protein transitors" mediating the signal.  The key finding is that fluctua
 tions in these signalling proteins set a general lower limit to cell size.
  This limit operates above other biophysical limits to axon diameter and m
 atches anatomical data across the animal kingdom. \n\nAxons operating clos
 e to this limit\, as in our brains\,\nare affected by these molecular nois
 e sources\, as signals get corrupted in distance-dependent ways and modify
  information transmission at synapses. The combined effect of stochastical
 ly behaving ion channels produces two counterintuitive side-effects:\nFirs
 t\, the effect of noise decreases with increasing temperature. \nSecond\, 
 noise effects become dependent on the history of previous signalling event
 s.\n\nWhile\, these findings have direct implication to neuroscience\, the
  general nature of these mechanisms should apply to all cellular signallin
 g systems using noisy *protein switches* to propagate signals\, such as Ca
 ++ waves.
LOCATION:TCM Seminar Room\, Cavendish Laboratory\, Department of Physics
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