Black box revisited: a technique for estimating postsynaptic potentials in neurons.

Our understanding of the operation of the brain depends on knowledge of its wiring. Currently, the wiring of the human brain is estimated by counting the number of neuron discharges that occur at specific times following a stimulus. There is now strong evidence that this approach generates significant errors. Recently, the accuracy of this 'count' method has been compared directly with an alternative 'rate' method in rat brain slices. The results confirmed that the count method generates significant errors that are minimized by the rate method, because the rate of discharge of a neuron accurately displays its excitability at the time of discharge. Therefore, it is now crucial that the rate method be used to reassess previous estimates of the characteristics of wiring in the brain.