A quadriplegic for the past 11 years, Julissa Santiago is the master of her own comfort. With the precision of a polite drill sergeant, she delivers instructions at bedtime for a series of minute body shifts and covers placed just so. And yet she still struggles to sleep.

"If I sleep for five hours, I'm lucky. My brain is constantly going, and it drains me," she says. In her wheelchair during the day, she occasionally experiences a sudden drop in blood pressure that is mentally discombobulating in its own way. These disruptions are deeply frustrating for the observant 35-year-old who soaks up information about her condition, types with her pinkie knuckle and hopes to one day tell her story.

Santiago's struggles are the focus of a study led by Donna Chen, a Ph.D. student in biomedical engineering, who is interested in the cognitive impacts of spinal cord injuries (SCI).

"People with spinal cord injuries commonly report shortened attention span and short-term memory difficulties," says Chen, who asks her study participants to perform simple recall and verbal dexterity tests and to respond to figures as they pop up on a computer screen.

While the causes are murky, key contributors may include problems with sleeping, lack of exercise, depression and anxiety, chronic pain and cardiovascular dysfunction. Chen adds, "Another theory posits that inflammatory signals travel to the brain as a secondary response to the trauma and these changes are associated with impairment."

While they're performing cognitive tasks, Chen scans their brains with functional near-infrared spectroscopy (fNIRS), which uses near-infrared light to measure the amount of oxygenated blood in regions of the brain associated with particular functions. Preliminary data revealed decreased functional brain connectivity in the sensorimotor networks, but also the prefrontal cortex, which controls executive functions, such as planning and organizing, and working memory.

Compared to able-bodied individuals, the differences in connectivity suggest reorganization of the brain's connections after injury, she notes. Similarly, seeing lower levels of oxygenated blood in a brain region may explain lower levels of cognitive performance in some people with SCI.

Chen's study of about 50 people is funded by the New Jersey Commission on Spinal Cord Research. Little is known about cognitive impairment in SCI patients, as most studies focus on motor disabilities below the site of the injury.

"There are a few studies that showed attention span and memory decline more rapidly with age in people with spinal cord injuries than people who are able-bodied. But those were mostly pencil and paper tests, which may be subjective. We want to give more quantitative answers."

She has noticed that people who had lots of physical therapy experienced smaller declines than less active people, and recommends that follow-up studies test the effects of exercise and other forms of rehabilitation on cognitive status.

"People active in rehabilitation seem to improve, but the data is not conclusive, as we don't currently monitor their brains as they exercise," she said. "But rehabilitation facilities and exercise programs are out of reach for many who can't get to them or afford them. The specialized equipment they use at them is expensive."

Her long-term goal, Chen says, is to facilitate the development of rehabilitation treatments for people with SCI, where they could accurately monitor their recovery by studying the effects of therapy over time.

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