Important to keep in mind that the brain isn't one neuron; small effects amplify across many. Cortical neurons don't spike that often. They spend most of the time teetering on the spiking edge, oscillating and contributing to the electric fields. Like Humpty Dumpty, a small push can tip them over.

It also important to keep in mind that a large proportion of neurons are astrocytes. They do not spike but have membrane potentials that spread electrical influences