Individuals with epilepsy experience seizures, during which neurons in the brain show abnormally heightened activity. It is common for epileptic individuals to report amnesia, or memory loss, for events which happened during the period of the seizure.
In many cases, the individuals also report anterograde amnesia for a short period after the seizure, which means that there is some disruption of the ability to store new information. The anterograde amnesia may last for a few minutes to a few hours after the seizure terminates. There may also be some retrograde amnesia, or memory loss for events which occurred before the seizure.
In rare cases, an individual may interact normally with his environment during a seizure, but later have no memory for the events which occurred during the seizure. This is known as a pure amnesic seizure or ictal amnesia. A person having a pure amnesic seizure doesn't show any outward symptoms (such as convulsion). The individual and his companions may be unaware that a seizure is occurring. For example, in one reported case, a man was able to continue playing cards while his seizure occurred, although he repeatedly asked his wife, "Why are we here?" Later, the man had no memory for the events which occurred during the seizure.
It is currently believed that pure amnesic seizures occur when the seizure is limited to the hippocampus, a brain structure important in new memory formation.
Article : "STORM IN THE BRAIN"
by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brain