Researchers at the University of Virginia are looking into a reason why seizures can cause memory loss.
According to a release, the researchers, UVA Brain Institute Director Jaideep Kapur and postdoctoral fellow in neurology Anastasia Brodovskaya, found that seizures affect the same parts of the brain that are responsible for memory formation.
They were conducting a brain-mapping study at the time.
Across the country, one in 26 people will develop epilepsy at some point during their lives.
People who have epilepsy can have recurrent seizures or sudden periods of abnormal, excessive or synchronous neuronal activity in the brain.
The release says that people who experience mild seizures could also see brief losses of awareness and muscle twitches, while more severe episodes could last for several minutes, leading to injuries from falls and losing control of limbs.
Many people who have epilepsy also complain about having memory issues, such as retrograde amnesia, which means they cannot remember what happened just before the seizure.
While seizures can be caused by many things, such as abnormalities in the brain, genetic mutations, infections and autoimmune conditions, the root cause of a seizure is not currently known.
The most common form of epilepsy involves seizures that begin in the part of the brain that is right behind the ears, called the temporal lobe.
Memory issues in these instances may be caused by the seizure affecting the hippocampus, a part of the brain that is important for memory storage and processing.
The release says that while a person sleeps, the hippocampus transmits new information to another part of the brain called the cerebral cortex in order to consolidate it into new memories.
The researchers wanted to see if the electrical signals of seizures might follow the same routes in the brain as memory consolidation.
They believe the disruption of this pathway might cause memory loss.
The release says they used mice trained to navigate a T-shaped maze in order to reach a reward of sweetened condensed milk by learning how to alternate between the left and right arm of the maze in a specific pattern in order to reach the reward.
When the mice could get to the reward 80 percent of the time, the researchers said they had successfully consolidated the memory of how to navigate the maze.
The mice were then injected with a drug that caused seizures.
The next day, the researchers saw that the mice did not do well in the maze, much like they hadn’t learned how to navigate at all.
The release says this confirmed that a single seizure was enough for the mice to forget what they had learned just before the seizure.
The researchers then wanted to figure out why this happened, so they used genetically engineered mice whose neurons produce a red protein when activated.
They mapped these neurons as the mice learned how to get through the maze and during the induced seizures.
In looking at that data, the researchers found that learning and seizures activated the same pathways in the hippocampus and cortex.
The release says seizures can thus disrupt the memory consolidation process, resulting in amnesia.
However, memory impairments may not stem from issues in the hippocampus only, so future studies are needed on other regions of the brain to clarify how seizures cause memory loss.