If my plastic brain (see my last two blogs) has been stamped with some ugly combat images, why not drop a couple of pleasant, high-adrenaline memories on top of the bad ones?

That’s the premise that X Sports 4 Vets is based on, and the program based out of Missoula, Mont., seems to be helping a number of vets.  You can learn more about the program at http://xsports4vets.org/

One form of therapy is whitewater rafting down the Lochsa River, a 20-mile stretch of wild and scenic river in western Idaho that boasts 25 class 3-4-and-5 rapids. I floated the Lochsa a few years ago, and it was a once-in-a-lifetime thrill for me.

“When I got out on the river, it was like team-building,” says Brandon Bryant, an Air Force vet. “It was exciting without the inherent danger of going out in the field.”

During five and a half years in the Air Force, Bryant fought the war from a cubicle in Las Vegas, where he was the co-pilot of a UAV (unmanned aerial vehicle) Predator.  “When we shot missiles, I was the one who guided them into the target,” he told me.

But the first deaths he witnessed were American soldiers returning from a mission in Iraq just after dawn.  “We saw something that looked like a buried IED (improvised explosive device) in the road, but we couldn’t stop them. The first vehicle went over it. Then the second went over it. It exploded, and everyone died,” he says. “I was 19 at the time and I felt guilty, as though I was responsible for the deaths of our military members. That’s when I knew I would never be the same again.”

In one sense, it was like being a bombardier in Vietnam. In another, it was a lot worse.

“We flew the Predator by satellite in Iraq and Afghanistan, gathering intelligence for a week or so unless our guys were under attack,” he says. “Then we found out where the bad guys were shooting from, and we would drop bombs on them.  I could see the aftermath of every strike.”

When Bryant returned home, he was diagnosed with 100 percent PTSD (post-traumatic stress disorder). He carried a lot of guilt and a lot of anger at people who had little regard for their own lives or the lives of others. And he isolated himself from most civilians, including his own family, who couldn’t understand what he’d been through.

That changed on the river.

“Being in combat, that adrenaline rush comes with worry,” says Bryant. “Deep in your gut, you’re not sure if something bad is going to happen until it’s all over. But out on the river, you know that if something bad happens, you’ve got a lot of guys around to help you. So there’s no risk of dying.”

I’m with Bryant to a point, but when I floated the Lochsa, I knew there was a risk of death. I felt we were challenging a huge natural element, something that was dangerous but not malevolent, something that could kill you but didn’t necessarily want to.

There was a lot of teamwork involved in pulling the oars together strongly so we could power the raft over a curl of boiling whitewater without it flipping backward and dumping us into the frigid water.

And when one of my friends, sitting in the seat directly in front of me, got washed into the river, I jumped to my feet, pushed an oar at him, pulled him over to the side of the raft, grabbed the shoulder pads of his life vest, lifted him as high as I could and then fell backward, dragging him on top of me into the raft. What a rush that was!

Adrenaline is a huge part of floating the Lochsa River, just as it’s a huge part of surviving combat. But we now know that adrenaline also plays a large role in enhancing memory for emotional events, so that voluntary exercise that involves an adrenaline rush may facilitate the “learning” of safety and the consolidation of new, positive memories.

Paul Gasser, a neuroscientist at Marquette University in Milwaukee, says that just the exercise from extreme sports reduces stress. “Exercise is at least as effective an antidepressant as any of the pharmaceutical treatments,” he told me recently.

Gasser and his colleagues have been tracking adrenaline and a hormone called cortisol in both humans and laboratory animals. Adrenaline is secreted into the bloodstream instantly by the adrenal gland during “fight-or-flight” situations because it enhances quick bursts of energy for survival purposes, heightened memory function, and a lower sensitivity to pain. Cortisol, an important stress hormone also secreted by the adrenal gland, acts more slowly to facilitate adaption and recovery after stress.