To stop a thought, the brain uses inhibitory neurons to prevent excitatory neurons from passing information from one to another.

“The inhibitory neurons are like a priest saying, ‘Don’t do it,'” Calvetti said. The “priest neurons” block information by releasing gamma aminobutyric acid, commonly called GABA, which counteracts the effect of the neurotransmitter glutamate by excitatory neurons…

All together, “It’s a surprising expense to keep inhibition on,” he said.