How many inputs are needed to excite/saturate a neuron

Douglas Fitts dfitts at
Fri Feb 26 01:00:27 EST 1993

In article <TAL.93Feb25224725 at> tal at (Doron Tal) writes:
>On the one hand, anatomical evidence suggests that a neuron has, on
>average, on the order of THOUSANDS of neurons impinging on it.  On the
>other hand, physiological evidence shows that only a few epsps are
>needed to generate an action potential - which would imply that ONE
>cell is sufficient for exciting the postsynaptic neuron.
>Can anyone explain this disparity between anatomy and physiology?
>Some hypotheses:
>1. most of the thousands of synapses on a neuron are inactive
>2. a neuron that has thousands of inputs has an extremely large and
>finely-tuned range
>If we knew what the range of a neuron is, on average, then we'd be
>able to tell between the two above hypotheses.
3. Lots of the synapses are inhibitory.


Doug Fitts
dfitts at

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