Ever since people began trying to summit Mount Everest, climbers have become
aware of subtle changes in their mental state as they ascend the mountain—and their brains gradually receive less oxygen. This year, we have set about
trying to measure changes in the mental abilities of four people as they climb
to ever higher altitudes.
Our premise is that the higher you go, the slower you think, and
the more difficult it is to think a problem through. To quantify this, we have
put together a small battery of tests that the climbers will take at
predetermined stops along the route to the summit. In March, we tested the
climbers at sea level to establish their "baseline"—or how they function
under normal conditions. Different versions of the same tests will be given to
the climbers as they ascend. To prevent the climbers from relying on the effect
of practice or memory to help them respond, they do not know in advance what
specific questions will be asked.
One change we expect to see in the climbers as they ascend is that they
will not be able to remember things easily, and that it will be more
difficult for them to get the words out of their mouths. In order to see
if this is true, they will be asked to listen to sentences, which will be read
to them via radio from Base Camp, and then try to repeat them word for word.
We will be timing how long they take to repeat the sentences, and counting the
number of errors.
Another test will look at the ability to solve simple verbal puzzles.
A typical question will be, "If John is taller than Tom, who is shorter?" This
puzzle is fairly simple to analyze at sea level, but as the climbers reach
higher altitudes, we expect to see them struggling to come up with the correct
answer, or perhaps even answering incorrectly. Again, this will be measured by
how long it takes them to respond, and by whether or not they respond
Another area we will look at is the speed with which they process
information. To examine this cognitive ability, the climbers will read simple
statements to which they will have to answer 'true' or 'false' via radio.
Typical statements are "Rats are built in factories," or "Desks wear clothes,"
or "Ants are insects." Some of these statements are patently absurd when you
think about them at sea level, but at altitude we may find that the climbers
have to think twice before they can respond, or again, that they may respond
We will also be looking at how well the climbers can pay attention, through a
special sound test. The climbers will be asked to listen to a tape which plays
a series of sounds, some of which are high, and some of which are low. The
climbers must count the number of low tones, while ignoring the high ones.
One test which the climbers and others find very difficult is the Stroop test.
It is a test of one's mental flexibility. In this test, you have to make yourself inhibit, or stop one
response, and say something else. In one such test, the climbers will see
words with the names of colors, but the actual words will be different from the
color in which they are written. For example, the word 'blue' will be written in
green ink. The climbers will have to say the color they see, and disregard the
word they read. This is much harder than it sounds, and we expect to see the
climbers' mental flexibility decrease with altitude.
Although we hope to obtain some very interesting data from these tests, four
climbers is not a large enough sample to answer the question of whether
judgment is compromised at very high altitude. However, we will begin to gain
new insight from these neuro-behavioral tests as to whether it takes longer to
think and evaluate information, how that changes with increasing altitude, and
how it can vary from one person to another.
We also have to keep in mind, however, that some of the changes we will see in
the ability to process information might be due to effects other than lack of
oxygen. The climbers may also be affected by lack of sleep, general physical
fatigue, diet, climate, or any number of other variables.
We are all waiting eagerly to see what our data will look like. Will we
see the changes we expect from sea level to the top of the mountain? Will
there be a measurable difference between the climbers' ability with and without
oxygen at the summit? Will we get some surprises? Will we see
some results we don't expect, such as improvements in some cognitive abilities,
and deterioration in others? All of these questions reveal that very little is
known about altitude's effect on the brain and one's ability to problem-solve
in mentally taxing situations.
Gail Rosenbaum is the Associate Director and Supervising Psychometrist
at the Neuropsychology Laboratory at Harborview Medical Center in
Seattle. She has worked in a clinical setting for many years doing
psychometric testing to evaluate brain function. Besides being involved in a
previous high altitude study, she has been involved in AIDS research and is
currently working on a study looking at the neuropsychological effects
of dental amalgam in children in Portugal.
Photos: (1) MRI of Ed Viestur's brain; (2) Howard Donner and Gail Rosenbaum test
David Carter (center) at sea level; (3) Howard Carter uses stopwatch to time David Carter;
(4) David Carter reads the Stroop Test.