JIM LEHRER: Finally tonight, veterans coping with brain injuries they received fighting in Iraq. A version of this report aired earlier on "California Connected," a program produced by PBS stations in that state. The reporter is Lisa McRee.
STAFF SGT. JAY WILKERSON, Injured War Veteran: I've heard so many great things about going to Iraq and helping the people and the government there, so I thought it was a great opportunity to do something great.
LISA MCREE, NewsHour Correspondent: His name is Staff Sergeant Jay Wilkerson, and today his greatest challenge is picking up a paper clip.
STAFF SGT. JAY WILKERSON: The feeling, it's slowly coming back. And there's two nerves that go through your thumb the operational therapist told me that need to attach.
LISA MCREE: The same year she became an American citizen, Claudia Carreon joined the Army National Guard.
SPC. CLAUDIA CARREON, Injured War Veteran: I had the opportunity to come to this country, and I wanted to say thank you to this country for opening their doors to me and my family. I don't remember how the accident happened, but somehow my knees got hurt.
LISA MCREE: And while Claudia and Jay's injuries may look manageable, down the hall it's a different story. It's been six months since Frank Sandoval's brain was damaged by an explosion in Iraq.
MICHELLE SANDOVAL, Wife of Injured War Veteran: He joined the military shortly after 9/11.
FRANK SANDOVAL, Injured War Veteran: I miss you.
MICHELLE SANDOVAL: I miss you, too, baby.
He wanted to make a change. He wanted to be something important.
LISA MCREE: Michelle is Frank's wife.
MICHELLE SANDOVAL: We've been married going on four years. Of course, we have our beautiful daughter. Frankie's such a strong person, and him being here is one thing that I know is going to be OK, because he's making such a big improvement.
LISA MCREE: Here is Ward 7-D of the Palo Alto V.A. Hospital, one of four polytrauma units in the United States.
HARRIET ZEINER, Neuropsychologist, Veterans Administration: It's set up to receive individuals who have received multiple wounds, multiple system damage.
LISA MCREE: Dr. Harriet Zeiner is a clinical neuropsychologist.
HARRIET ZEINER: You may notice some of the patients here are wearing helmets, and that's because part of their injuries have actually destroyed some of the bone. And all that's there is some skin. So they wear the helmet until such time as surgeons can make a prosthetic skull and replace it.
LISA MCREE: In a matter of weeks, that will happen for Frank, and his head will again have a normal shape. But elsewhere on the ward, there are injuries less visible that are nonetheless devastating.
It's not an obvious injury.
HARRIET ZEINER: No, they look like everyone else. They look like themselves.
LISA MCREE: It is the signature injury of this war: TBI, traumatic brain injury.
HARRIET ZEINER: A traumatic brain injury is an injury to brain tissue, which is extremely soft stuff. It has the consistency of, like, Jell-O left at room temperature. It's so soft that, when they do surgery on the brain, they don't use knives. They use little suction pipettes.
LISA MCREE: And the reason brain injury has become the signature injury has a lot to do with the signature weapon of this war: the improvised explosive device.
U.S. SERVICEMAN: Get up! Get up!
HARRIET ZEINER: There's a concussive force that moves through them. When this moves back and forth, it hits the boney part inside your skull. That's where a lot of damage occurs from these improvised explosive devices.
STAFF SGT. JAY WILKERSON: I've suffered a traumatic brain injury in Baghdad, Iraq. It's something that most people, if they're not in the medical field, they're not aware of the phases of it. But if I didn't have on this neck brace and I was walking around normally, you wouldn't know anything's wrong.
DOCTOR: We'll make a copy of it, and then we'll give it back to you.
LISA MCREE: But even if you can't see the damage, you can see the symptoms.
HARRIET ZEINER: They're slowed in their information processing. So they're focusing very hard to listen to you one-on-one. They're sort of 45 RPMs in a 78-RPM world.
DOCTOR: It's a long journey.
SPC. CLAUDIA CARREON: No, no, say that -- you're speaking too fast.
DOCTOR: OK, the journey to the center of your heart...
INJURED VETERANS: The journey to the center of your heart is like the journey to the center of the Earth.
SPC. CLAUDIA CARREON: You guys are speaking too fast for me.
DOCTOR: The journey to the center...
SPC. CLAUDIA CARREON: One at a time, please. One at a time. One, one.
HARRIET ZEINER: You see a lot of irritability. And it's not because there's an irritable center in the brain that gets released; it's because life gets so hard that you're frustrated, and you're using up all your energy, and you're overwhelmed. You're over-stimulated.
LISA MCREE: Even alone in her room, Claudia's frustration remains, because in her case, the greatest injury she sustained was to the part of the brain that allows her to remember.
SPC. CLAUDIA CARREON: It's a daily struggle. I have to write everything down every day, everything that I do, everything that happened. And if I don't do it, at the end of the day or during the day, the next day I might not remember.
LISA MCREE: And it's not just the everyday events of her life she loses; it's the people in it, as well.
SPC. CLAUDIA CARREON: People that are close to me, I have to have pictures of them, otherwise I stop seeing them for about a week or two, their image will be gone.
LISA MCREE: Even the image of her own child.
SPC. CLAUDIA CARREON: To the best of my recollection, I have never been pregnant. I don't know what it is to be pregnant. I don't know what it is to give birth, and basically I don't know what it is to have a child.
All that I know is that I have a baby. She is my daughter. She is two years old. I talk to her every day. She says, "Mommy," because she sees pictures of me, but I don't know. I don't know.
I do not have the feeling in the relationship between a mother and a daughter. How is it possible that I forget such a great event in my life, when it's something that nobody will never, never forget?
HARRIET ZEINER: You know, 20 percent of the people who have been injured are women who had head injuries. And I actually think some of the head injuries and some of the traumas that occur are experienced somewhat differently by women than by men.
Men certainly hate the loss of memory, the loss of information. Women experience it as a change in their ability to relate. And that, again, is what I meant by the wound internally, the wound in who you want to be in this life.
LISA MCREE: But that's not to say the ability to relate doesn't matter to men, too. Just ask Jay.
How does it feel when you realized that the person you didn't recognize was actually your own brother?
STAFF SGT. JAY WILKERSON: It felt weird. I cried. And he told me, if you feel like crying, you go ahead and cry, because you're still a man if you cry. You know, because I always thought crying was -- a soldier wasn't supposed to cry. But I couldn't help it; I cried because I felt like I've lost too much memory.
LISA MCREE: If we saw each other tomorrow, you may or may not remember our conversation.
STAFF SGT. JAY WILKERSON: I'm hoping that I will remember, but to be very truthful and honest, I don't really know if I will remember even having this conversation tomorrow.
LISA MCREE: And there's another cause of brain injury that's also unique to this war.
HARRIET ZEINER: About half of the injuries are motor vehicle accidents, and I was very surprised by that. When you're driving in Baghdad, from the minute you leave the compound, you're told to floor it, because that basically makes you a quicker target for snipers, for IEDs that are remotely detonated.
LISA MCREE: And even though Claudia can be taught how to drive again, her devastating brain injury makes that harder than it sounds.
DOCTOR: Please turn on the radio. Please slide your climate control to the right.
LISA MCREE: And the driving simulator isn't Claudia's only high-tech helper. Because her injury destroyed her ability to remember, she's being trained on a personal data assistant, a PDA, to help her remember everything from when to take her medication to the names and faces of her family members.
HARRIET ZEINER: Let's look at today's appointments, OK? You've got yours?
It's a memory prosthesis. A prosthesis is something like a brace like she's wearing on her knee right now to help support the knee. Well, this is a support for her memory.
For example, if you're going to do something on Saturday...
SPC. CLAUDIA CARREON: Basically, this is my memory. It's just that my memory is not in my head any more; it's in my hands.
LISA MCREE: And traumatic brain injury is not just a problem for soldiers like Claudia who've come home.
HARRIET ZEINER: We're getting calls from the military on these military conference calls that there are people who are being exposed to five and six blasts now.
LISA MCREE: Dr. Zeiner says the military is now realizing it's got a big problem on the battlefield.
HARRIET ZEINER: The military's concern is: Are they still battle-ready? Can they follow orders? Can they protect their buddies?
We tell sergeants, if you have someone who is operating pretty well and suddenly they're starting to look like a screw-up, they're starting to look changed and different in some way, you suspect that something has happened, and it's time to get that person screened.
LISA MCREE: In fact, that is exactly what happened with Claudia.
SPC. CLAUDIA CARREON: She was significantly injured, but they thought it was her knees and her back. No one recognized that she had a head injury. And so she is one of those people who had a stellar record before and now suddenly was seen as, "You're not following orders. You're lazy. You're screwing up." And she was actually demoted.
LISA MCREE: And the number of brain-injured victims like Claudia may be grossly underestimated.
So we know we have hundreds, but we could have thousands?
HARRIET ZEINER: We have thousands. We have thousands of people who don't know that they are brain-injured. And we think what's happening is that a truck goes over, an IED goes off, and one guy or two guys are really seriously injured.
And so the system goes right into play for them. They're MedEvaced. They're taken care of. But the other five guys in the truck were thrown against the walls, and they had a blast effect. They just pick up and they go.
LISA MCREE: While the V.A. estimates it's treated some 800 soldiers for TBI, Zeiner says the real number of victims could be 10 times that.
JIM LEHRER: Since that report was produced, Specialist Claudia Carreon and Sergeant Frank Sandoval have returned home.