BrainCauses of TEA

We think that TEA is caused by problems in the temporal lobe of the brain. There are three reasons for this suggestion:

The role of the temporal lobe in the function of memory is well established. This region is known to be involved in consciously learning and recalling material; this is called declarative memory.

There are two forms of declarative memory:

We have found that TEA is linked to disturbances in the functioning of a particular area of the temporal lobe, called the medial temporal lobe; this is the inner part of the lobe which contains a number of important structures, in particular the hippocampus.


Above: A diagram showing the different structures of the medial temporal lobe and related brain regions

The Hippocampus

This plays an important role in memory, as demonstrated by the famous case of H.M, a 27 year old patient who was suffering from severe temporal lobe epilepsy. As treatment, doctors surgically removed a region of both his medial temporal lobes which included the hippocampus. The treatment was successful in stopping most of the seizures. However, H.M. experienced a disastrous side-effect from the surgery; he became unable to form new memories.

Damage to the hippocampus can produce both anterograde and retrograde amnesia but will not affect other aspects of memory, such as the ability to learn new skills (procedural memory) or to store information about meaning and facts (semantic memory).

The hippocampus is also believed to play an important role in storing information about the environmental (spatial) context of events that have happened in the past. Damage to this region is associated with difficulties in navigating through familiar places.

The Amygdala

This is often referred to as the "emotional brain" as it is believed to regulate a large number of emotional states. It is particularly associated with fear and anger.

The amygdala is also thought to be involved in emotional and autobiographical memory. It has the task of identifying the emotional significance of an event and making the event better remembered.

The Mammillary Bodies

These structures relay information from the amygdala and hippocampus to the thalamus. Damage here can impair memory.

The Olfactory Bulb

This controls the body's sense of smell and sends its signals back to the temporal lobes. It is involved in odour detection and discriminating between different smells. This structure also plays a role in emotional memory as distinctive smells are often associated with the memory of an event.