The relevance of animals used in experiments to study human concussion has been called into question by a recent study.1
In an attempt to mimic injuries in humans, concussion experiments using animals usually involve surgical damage to the brain or severe blows to the head. But because animals are unable to explain how they are feeling, researchers have to rely on visible changes in the brain to study the impact of concussion and potential treatments. Conversely, in human patients the diagnosis of concussion relies heavily on self-reported symptoms such as nausea and headaches to determine how severe the injury is and how to proceed, “revealing a clear disconnect” between the two situations.
In an attempt to combine the two approaches, scientists in the USA glued a metal disc onto the skulls of 31 rats before dropping a weight onto the disc to damage the brain. One day later, the animals were subjected to various behavioural tests of learning, memory, movement and emotional functions that are often evaluated when diagnosing concussion in patients. The rats were forced to walk on rotating rods, swim in inescapable pools of water and navigate mazes over a period of seven days before they were killed and their brains dissected. The researchers discovered that while clear brain damage was visible in all of the rats, none of them behaved any differently to a group of healthy rats that underwent the same behaviour tests.
These results clearly show that human concussion cannot be studied in animals. Even with visible brain damage, the rats displayed no symptoms of concussion. The authors admit that animal concussion experiments are too simplistic and do not take into account the highly varied nature of human concussion. Frustratingly, instead of encouraging the use of more human-relevant studies, the authors conclude by suggesting ways in which the animal studies can be improved.
1. Elucidating the severity of preclinical traumatic brain injury models: a role for functional assessment? (2014). Neurosurgery, 74(4): 382-394. Original article can be found here: http://www.ncbi.nlm.nih.gov/pubmed/24448183