After a stroke, which occurs when blood flow to the brain is disrupted, females tend to have a more difficult physical recovery than males. They often experience worse standing balance, slower walking speeds, and higher levels of fatigue. The specific reasons why these recovery differences exist between the sexes are not yet fully understood.
This research used a technique called Functional Near-Infrared Spectroscopy, or fNIRS, to study brain activity. fNIRS is a non-invasive method that uses light to measure changes in blood oxygen levels in the brain. When a part of the brain is working harder, it uses more oxygen, and fNIRS can detect this change. The size of the fNIRS signal, called its amplitude, can show how much cognitive effort is needed to perform a task. It can also help track how rehabilitation affects brain function.
The goal of this small study, known as a case series, was to gather detailed data on brain activity in the prefrontal cortex of females who were in a hospital for stroke rehabilitation. The prefrontal cortex is the front part of the brain responsible for complex thinking, planning, and controlling actions. The researchers wanted to see how this brain area was activated while the women performed tasks involving movement and sensation in their lower limbs.
The study involved four female participants who had recently experienced a subcortical ischemic stroke. This is a common type of stroke caused by a blockage in a blood vessel deep within the brain, below the outer layer. The participants were evaluated when they were first admitted to the inpatient stroke rehabilitation unit and again when they were discharged.
These evaluations included standard clinical tests to measure physical impairment, balance, walking ability, and fatigue. The women also underwent fNIRS scans while performing five specific tasks: standing still, standing in a more difficult semi-tandem position (with one foot slightly in front of the other), and performing three different ankle movement tasks while lying on their backs.
By the time they were discharged, all four women showed improvements in their physical condition. On average, their motor skills improved, their balance scores increased significantly, their walking speed got faster, and they could walk a longer distance in two minutes.
The fNIRS scans revealed a pattern in brain activity. At the beginning of the study, the women's brains showed higher levels of activity (larger fNIRS amplitudes) when performing the three ankle tasks while lying down. This suggests these simple tasks required a lot of cognitive effort. By the time of their discharge, the brain activity during these same tasks had decreased. For the two more complex standing tasks, the changes in brain activity were less consistent among the participants. Results for fatigue were mixed; two women reported feeling less fatigue at discharge, while the other two reported small increases in fatigue.
The study's findings suggest that for these female stroke patients, there may be a relationship between their physical improvements and a decrease in the brain effort required for simple tasks performed while lying down. The more demanding standing tasks seemed to produce more diverse brain activity responses. This research demonstrates that fNIRS can be used to collect brain activation data from female patients in a hospital stroke unit. It also indicates that a standard inpatient rehabilitation program appears to influence the level of brain activity required to perform certain motor tasks.
