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--></style></head><body><div><span title="spike66@att.net">spike</span><span class="detail"> <spike66@att.net></span> , 1/5/2014 6:23 PM:<br><blockquote class="mcnt mori" style="margin:0 0 0 .8ex;border-left:2px blue solid;padding-left:1ex;"><div class="mcnt"><div class="mcntWordSection1"><p class="mcntMsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;"> </span><span style="color: rgb(31, 73, 125); font-family: Calibri, sans-serif; font-size: 11pt;"> </span></p><p class="mcntMsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;">Consider the above calculation. We have about 1E11 brain cells (I think that is the standard estimate, do correct me if I err.) If the above calculation of 4E15 is correct, then the average brain cell would need to fire 4E4 times per second. The standard estimate I have heard is a typical brain cell fires at about 200 Hz, for a 2E13 rate.</span></p></div></div></blockquote></div><div><br></div><div>Yup. 1E11 is the standard guess, with 86 billion neurons the latest number I heard (the cortex seems to be slightly less numerous than we previously thought, while there are 4 times as many neurons in the cerebellum as in the cortex). Firing rates vary *a lot* but for most neurons it is usually way below 200 Hz; most of the activity is below 40 Hz. At any time only a fraction are in "up-states" where they fire bursts. So quadrillions of firings is likely a bit of an overstatement. <br></div><div><br></div><div>Still. *Lots* of action potentials. </div><div><br></div><br><br>Anders Sandberg, Future of Humanity Institute Philosophy Faculty of Oxford University</body></html>