Amnesia and Memory

Decades of research underscores our lack of understanding

Today, I’d like to talk to you about Henry Gustav Molaison (H.M.), born on 26th February 1926. He would have been 88 years old this year and he is one of the most celebrated figures in medical history. He is the corner stone in our understanding of the human brain and memory formation. He was not a doctor but a patient.

H.M. was in a bicycle accident at the age of 7. Unfortunately (or fortunately depending on how you look at it), helmets were not very common back then. The resulting traumatic brain injury (TBI) he sustained sent him into an ever worsening tailspin of uncontrolled seizures.

At first, the seizures where occasional and partial, he was able to recover from them quickly and have some semblance of a childhood. However, by the age of 16, the problem had blossomed into a fully blown grand mal (The worst type of seizure like the one shown in the movies) which is a form of epilepsy characterized by tonic-clonic seizures — features a loss of consciousness and violent muscle contractions. They strike without warning and incapacitate the person for hours in a day.

This situation persisted for another 9 years until a brave Surgeon by the name of William Scoville did a rather radical procedure to try and help the now long suffering patient (H.M).

Using his understanding of the human brain, EEGs and quite a bit of brilliant deductive reasoning, Scoville was able to localize parts of the damaged brain that seemed to be giving rise to these seizures. He localized the seizure generator to two parts of the brain called the right and left medial temporal lobes (MTLs). In this landmark surgery carried out on the 25th of August 1953 at the now famous Hartford Hospital, parts of Henry’s brain were removed (the damaged parts which caused the seizures).

The surgery was ultimately found to be successful in the days and weeks after recovering. Mr. Molaison’s seizures became less and less frequent as observed by the hospital staff.

Henry, on the other hand, never really remembered the improvement. After the surgery, Henry’s memory of his childhood and young adulthood were vivid and detailed. However, he couldn’t remember anything that was new.

He remembered the bicycle accident; he couldn’t remember what he’d had for breakfast on August 27th. The surgery and the curious case of H.M has given medical science a key piece of information about the brain. Forming memory is an active process and different parts of the brain do different things. It looked like the MTL’s were related to the formation of new memories.

Fast forward more than 60 years, and the brain is still quite a mystery, concepts and cases of amnesia (memory loss) are well documented and strides have been made in understanding how memories are stored in the brain and what diseases can affect them. It has been a slow going learning and development process.

To understand amnesia a bit, it’s useful to know the causes and the types.

The most common causes of amnesia are things like:

• TBI
• Infections of the Brain (Encephalitis, etc)
• Psychological causes (Stress, Trauma, Abuse, Etc)

Amnesia can be broadly classified into categories according to their type:

A. Anterograde Amnesia: One remembers the past but new memories are not registered

B. Retrograde Amnesia: One forgets portions of the past but new memories form well enough. (Remember the condition of the main protagonist in ‘Bourne Identity’?)

C. Post Traumatic Amnesia: Just like the name suggests, this is associated with TBIs where memory loss is inconsistent, for a while the patient may have both anterograde and retrograde amnesia. The silver lining here is that this kind of memory loss is usually temporary, as the brain heals and the memories return.

D. Dissociative Amnesia: This is the type normally associated with great psychological trauma or strain.

E. There are various other types of amnesia in the ‘Others’ category which also include:

• Drug Induced Amnesia (Valium abusers)
• Korsakoff Syndrome (Alcoholics who don’t get enough Vitamin B)

The size and variety of specific conditions that come in the ‘Others” category just goes to show how little we know about the basic principles of how the brain works.

The treatment of amnesia is always about finding the cause. If the Amnesia is due to an injury, help it heal, if it is stress related then de-stress.

A great majority of people who have suffered from amnesia get a lot better and ultimately regain all of their memories. Most will be able to live comfortable lives, even with some broken memory loss. Treatments like Cognitive Behavioral Therapy, Occupational Therapy etc., are shown to help speed up and even enhance recovery.