Researchers from New York University (NY, USA) have discovered a correlation between cross-hemispheric cerebral activity and a delayed response time in concussion patients. The study, presented recently at the Radiological Society of North America Annual Meeting (1–6 December, Chicago, IL, USA), suggests that damage from concussion may alter the way information is transmitted between the two halves of the brain.
Previous research has demonstrated that mild traumatic brain injury can cause damage to the corpus callosum. Until now, very little has been known about the effect this has on cognitive function.
This study involved 36 patients with recent concussion and 27 healthy controls. Researchers studied the corpus callosum of each individual using an MRI technique measuring water diffusion to view the brain’s signal-carrying white matter.
In order to measure any difference in clinical status, researchers combined the MRI findings alongside a test called an interhemispheric speed of processing task to evaluate how well the two brain hemispheres communicate with each other. Participants were told to focus their gaze on the letter X displayed on a screen in front of them. Three-letter words flashed either side of the X and participants were told to say those words as quickly as possible.
The team discovered there to be a significant difference in reaction time of the concussion patients compared with the control group. “There is a definite and reproducible delay in reaction time to the words presented to the left of the X compared with words presented to the right visual field,” reported Melanie Wegener (New York University), co-author of the study.
“This shows it takes time for information to cross the corpus callosum from one hemisphere to the other, which is measured by the difference in response time between words presented to different sides of our visual field.”
The researchers postulated the delay to be a result of language function being typically located in the left hemisphere. This means that information presented to the left visual field is transmitted to the right visual cortex, which then crosses over the corpus callosum in order to reach the language center. However, information presented to the right visual cortex does not need to cross the corpus callosum.
The team observed that performance on the test correlated with the results of the MRI. Among the controls, reaction time was associated with several diffusion measures across the splenium, which is located between the right visual cortex and the left language center. No such correlation was observed among concussion patients.
“This information could ultimately help with treatment in patients who have mild traumatic brain injury,” commented Wegener. “For instance, patients could undergo MRI immediately after a concussion to see if they experienced any clinically important white matter injury and thus may benefit from early intervention.”
“Another thing we can do is use MRI to look at patients’ brains during treatment and monitor the microstructure to see if there is a treatment-related response,” Wegener concluded.