When people are recalling past traumas, brain scans show that the language center in the brain -- in fact, the entire left half of the brain where language and analytical skills reside -- loses power and shows less activity, but the right side shows increased activity. During a full-on flashback of a traumatic event, the language center (called Broca's area) goes almost entirely off-line, similar to what you might see in a stroke victim, and the person is often unable to speak at all until it passes. There's a chapter on this in "The Body Keeps the Score" with images of the brain scans, and you can actually see this visually.

I know we're not always talking about past traumas in therapy, but those things feel more present in the therapy room, and I do think it affects our ability to articulate. The more painful the subject, the less able we might be to find words. I hope therapists start to learn from the brain scan research that their clients are not necessarily being stubborn or unwilling when they can't describe emotions, they just don't have a fully operational language center. Using art or poetry seems like a good idea, because that's creative stuff that's more on the right side, and that side actually has more activity when past traumas are involved.