Hey, absent-minded professional: Your favorite gadget could sap your ability to remember.

Only a few years ago, Michael Schell had a memory that put people to shame. The CEO for RW3 LLC, a New York-based expatriate cultural online training organization, had almost every important phone number, calling-card code, and PIN - hundreds of them - committed to memory. He also knew his entire schedule for the week without glancing at a calendar. "I could recall all the information instantly," he says.

Then he bought a personal digital assistant (PDA) and began storing all the data in it. "Now I can't recall my wife's cellphone number, and I find myself increasingly relying on the device to serve as my memory," he admits. "If you lose or damage the device, you can find yourself in big trouble."

These days, Schell isn't the only one worried about losing his mind. Amid a deluge of personal information - phone numbers, e-mail addresses, birthdays, passwords, PINs, credit-card numbers and expiration dates, government and employee ID numbers, and more -people increasingly rely on computers, PDAs, and cellphones to store data and auto-dial calls. The same people often find this same data disappearing from their brains.

That's leading some scientists to question whether gadgets undermine our memories and change the way we think. "Our brains have only a certain amount of memory capacity, and we have to pick and choose what we commit to memory,"­ says Dr. Gary Small, director of the UCLA Center on Aging and author of The Memory Prescription: Dr. Gary Small's 14-Day Plan to Keep Your Brain and Body Young. "There's no question that these devices make our lives easier and allow us to retrieve information more quickly. The question is, Does it worsen brainpower or lead to negative results?"

Over the years, studies have shown that there's a "use it or lose it" element to memory. Within the brain, neurons and synapses that aren't used will disconnect from one another. Although humans are capable of remarkable feats of memory - including learning numerous foreign languages and recalling hundreds of thousands of chess moves - they are also capable of forgetting all that information …or misplacing the car keys.

"It's like muscle tone. If you don't exercise, you get flabby,"observes Alan S. Brown, a professor of psychology at Southern Methodist University. He's worried about the trend toward storing information in silicon rather than in gray matter. "When it comes to memory, the mind gets rusty and capacity fades without practice," he explains.

The problem is growing worse. His research indicates that only 7.1 percent of those venturing online use a different password for each of their accounts, and many rely on easy-to-remember names, including those of their pets and spouses, to protect their data. "In many cases, people feel overwhelmed by all the things they have to remember, so they try to simplify things, even when it is not in their best interest," Brown says. "Passwords are the last frontier of flexing our memory muscle, and most of us are failing."

Other studies support Brown's notion that we're losing our memories bit by bit. For example, a few years ago, researchers from Hokkaido University in Japan examined 150 young adults between the ages of 20 and 35 and found that more than one in 10 suffered from serious memory problems. Among the causes: growing reliance on computers, electronic organizers, and automobile navigation systems. Researcher Toshiyuki Sawaguchi, who headed the study, described the problem as a "type of brain dysfunction."