If a neural event is not deemed important, associated connections are flushed, leading to forgetting, but significant events trigger neurotransmitter release that alters cellular processes.

“And if nothing happens, if it just wasn't important at all, then it all just gets flushed. In one ear, out the other. You just forget it. But when something exciting happens, you get release of acetylcholine, norepinephrine. These things go into the brain. They bind to receptors. They change what's happening inside the cell.”