We have developed techniques to discriminate the action potentials of separate neurons. Then, the activity across these 6 electrodes was recorded in response to separate stimulation of four different vibrissae. It is evident that activity spreads across the cortex from one column to its neighbor. In this rat, all except two whiskers were clipped a few days before the experiment. We find that the cortical representation of the intact whiskers has expanded.
Neurons appear to code stimuli in a language where the relative timing of events is important.
That is, two neurons firing action potentials at the same instant is a different message from two neurons firing at separate moments. By placing many electrodes in the brain, we can record activity from many neurons simultaneously. This figure shows the degree of synchrony in the firing of two neurons. Each action potential is time-stamped, and the two neurons activities are plotted together. Each plot shows the response of the neuron pair to a different stimulus.