Some 400,000 current and former American soldiers suffer from traumatic brain injuries, which can cause memory loss, lack of concentration, depression, anxiety attacks and other problems. In some cases symptoms last only weeks or months; sometimes they persist indefinitely.

Finding any sort of treatment, much less a cure, has not been easy. But some neuroscientists now see great potential in techniques of manipulating the brain’s “neuroplasticity,” its propensity to rearrange its neuronal structure in response to behavior and stimuli.

Earlier this year, the Department of Defense awarded a $2 million grant to Brain Plasticity Inc. to study the effectiveness of Posit Science software in restoring memory and attention in victims of traumatic brain injury, or TBI. Posit Science, based in San Francisco, is one of several companies, including Nintendo and Luminosity, that sell brain health software products to consumers.

If the Posit Science software is proved effective, it could become one of the first medical applications of an approach to brain improvement that remains controversial. Such software could potentially help TBI patients and also those who have been determined to have autism, Parkinson’s disease, schizophrenia and other psychiatric and neurological diseases.

“This is the beginning of a revolution,” said Michael Merzenich, the co-founder and chief scientist of Posit Science; the president of Brain Plasticity; and a celebrated University of California, San Francisco, neuroscientist who pioneered the idea of neuroplasticity.

The Posit Science software, sold commercially under the names Brain Fitness Program and InSight, is supposed to strengthen memory, attention, language skills and visual-spatial abilities in aging adults. Studies of it have shown improvement in those areas, but critics like P. Murali Doraiswamy, a Duke University psychiatrist, are not convinced that those gains translate into long-term benefits that can be generalized to daily challenges like remembering where the car is parked.

“There is a big gap between the claims and the evidence,” said Doraiswamy, who said he doubted whether short-term improvements in memory would last longer than the three-month period most studies test.

“If they were a drug,” he said of the software, “they would have been pulled from the market.”

Whether the computer-game-like software can be harnessed to improve overall mental acuity in those with brain damage from trauma to the head is an even bigger question.

“It is theoretically reasonable,” said Gary Abrams, director of neurorehabilitation at UCSF and head of the TBI support clinic at the San Francisco VA Medical Center. “But will it actually work to help veterans? I can’t talk to that.”

The idea of neuroplasticity dates to the 1980s, when the conventional scientific wisdom held that once people reached adulthood, their brains were hard-wired and would remain that way for life. Merzenich did not think that was true, and eventually his research showed that the brains of primates continued to change well into maturity.

By the mid-2000s, Merzenich and his colleagues at the university had brought much of the neuroscience field around to the idea that brain change, or plasticity, was the rule rather than the exception.