Page 120 - The Memory Program How to Prevent Memory Loss and Enhance Memory Power

Page 109

rarer. A history of head injury with loss of consciousness increases the risk of memory loss later in
life, presumably by lowering the brain's cognitive reserve capacity against age-related memory loss.

Two widely quoted cases of structural brain damage have taught us a great deal about the seat of
memory in the brain.

A Tamping Iron Went Through His Brain

Phineas Gage was a stalwart foreman working the railroad in Burlington, Vermont, in 1848. A
misfired explosive blew a long tamping iron, which is like a crowbar, into his skull and through the
other side. To everyone's astonishment, he was only stunned, got up, took a cart into town, and
walked into a doctor's office for treatment. How could this be? The answer is simple. If the centers in
the base of the brain (just above the neck) that control the heart and breathing are not affected, and
there isn't undue mechanical pressure on other brain structures, the patient can indeed survive.
Phineas Gage's injury affected the frontal lobes, and he developed a “disinhibition” syndrome with
irritability and childlike capricious behavior that persisted for several decades after the injury. He
constantly changed his plans and could not manage to complete even the simplest tasks. Despite the
enormous size of his brain injury, many aspects of his memory remained fairly intact. This helped
doctors realize that memory resides primarily in some region that was not destroyed by Gage's
injury. However, the fact that he did have some deficits in recall showed that the frontal lobes are
important, though perhaps not primary, for memory functions.

The Story of H.M.

This brings us to the 1950s and the story of H.M., who had surgical removal of large parts of both
temporal lobes, including the hippocampus and neighboring amygdala, to treat uncontrollable
epilepsy. His epileptic seizures stopped, but the cure may have been worse than the disease. He
developed a profound defect in short-term or episodic memory, a type of severe amnesia. To this
day, he cannot remember anything said to him barely a minute earlier, or recall having met a person
a few moments ago. Remarkably, his recognition memory, which is distributed in many brain
regions, including the frontal lobes, remains intact. Therefore, he can still choose the right answer,
which he seems to have completely “forgotten,” from a multiple-choice option. This startling
discrepancy in his memory test