Joshua Frey occasionally hears the voice of his best friend -- a fellow Marine who was killed in Iraq in 2004.
It's one of his many symptoms brought on by post-traumatic stress disorder, or PTSD, that Frey is trying to overcome using a new virtual reality therapy for troops returning from Iraq. The three-year, $4 million experiment is being run by the Pentagon's Office of Naval Research.
A July 2004 study published in The New England Journal of Medicine reported that about 17 percent of troops returning from Iraq suffer from PTSD-related symptoms.
The 28-year-old Frey agreed to take part in the treatment after flashbacks and nightmares replayed the horrors of war so frequently that he had difficulty functioning once he got home.
He says feelings of anxiety, guilt, and depression are often overwhelming and take a toll on his marriage. And pain from a shoulder wound brings back memories of the day Frey was shot during a firefight, while trying to help rescue his best friend, Joshua Dickenson.
"It's so hard for me because I have so much stuff going on in my head and I break down and I cry, and I just get emotional and I just don't know what to do sometimes," he said.
So once a week, Frey has agreed to meet with Dr. James Spira at the Naval Medical Center in San Diego for therapy sessions. But instead of just talking about his experiences in Iraq, Frey puts on special goggles to relive them inside of a realistic videogame-like simulation that re-creates the sights, sounds -- and soon -- the smells of the battlefield. It's called exposure therapy.
Inside the virtual world, Frey sees a generic Middle Eastern desert city that could easily double for Baghdad. It is quiet at first. Sensors attached to his fingers and body display heart rate, breathing and other information on a monitor for Spira to see how his patient is responding.
When he's sure Frey is doing all right, Spira begins clicking his mouse to gradually add ambient noises like distant gunshots and jets flying overhead. Frey's breathing becomes shallow. His heart rate increases. Next, he begins to hear accented voices shouting at him, saying things like "Go home cowboy!" The sounds of explosions and machine guns get louder as a Blackhawk helicopter swoops in for a landing in the middle of the street.
"This isn't real," Spira reassures Frey. "Just reminders from the past. You can let those thoughts be further away, more distant. They will still come, but you don't have to pay attention to them. You can say to yourself, 'these are just memories.' "
The virtual reality world, Spira said, "triggers those thoughts, those feelings, those earlier reactions they had. What we're trying to do now is train them to have different reactions to those same stimulus and reminders."
For Frey, who served with the 3rd Marines 1st Battalion, the thoughts and feelings are still vivid. He says he was always on edge in Iraq from the constant threat of mortar attacks, roadside bombs and sniper fire.
"There never was a really secure place," he said, thinking it couldn't get much worse.
Then came Dec. 12, 2004.
Frey says the morning had been relatively quiet when a gunbattle suddenly broke out between insurgents and Marines in the city of Fallujah. Dickenson was shot in the head during the firefight and died. Frey, responding to a call of a man down, was hit a few minutes later.