The Holographic Universe (3 page)

Pribram's thinking was
further solidified by his and other researchers’ inability to duplicate
Penfield's findings when stimulating brains other than those of epileptics.
Even Penfield himself was unable to duplicate his results in nonepileptic
patients.

Despite the growing
evidence that memories were distributed, Pribram was still at a loss as to how
the brain might accomplish such a seemingly magical feat. Then in the mid-1960s
an article he read in
Scientific American
describing the first
construction of a hologram hit him like a thunderbolt. Not only was the concept
of holography dazzling, but it provided a solution to the puzzle with which he
had been wrestling.

To understand why
Pribram was so excited, it is necessary to understand a little more about
holograms. One of the things that makes holography possible is a phenomenon
known as interference. Interference is the crisscrossing pattern that occurs
when two or more waves, such as waves of water, ripple through each other. For
example, if you drop a pebble into a pond, it will produce a series of
concentric waves that expands outward. If you drop two pebbles into a pond, you
will get two sets of waves that expand and pass through one another. The
complex arrangement of crests and troughs that results from such collisions is
known as an interference pattern.

Any wavelike phenomena
can create an interference pattern, including light and radio waves. Because
laser light is an extremely pure, coherent form of light, it is especially good
at creating interference patterns. It provides, in essence, the perfect pebble
and the perfect pond. As a result, it wasn't until the invention of the laser
that holograms, as we know them today, became possible.

A hologram is produced
when a single laser light is split into two separate beams. The first beam is
bounced off the object to be photographed. Then the second beam is allowed to
collide with the reflected light of the first. When this happens they create an
interference pattern which is then recorded on a piece of film.

To the naked eye the
image on the film looks nothing at all like the object photographed. In fact,
it even looks a little like the concentric rings that form when a handful of
pebbles is tossed into a pond. But as soon as another laser beam (or in some
instances just a bright light source) is shined through the film, a
three-dimensional image of the original object reappears. The
three-dimensionality of such images is often eerily convincing. You can
actually walk around a holographic projection and view it from different angles
as you would a real object. However, if you reach out and try to touch it, your
hand will waft right through it and you will discover there is really nothing
there.

Three-dimensionality is
not the only remarkable aspect of holograms. If a piece of holographic film
containing the image of an apple is cut in half and then illuminated by a
laser, each half mil still be found to contain the entire image of the apple!
Even if the halves are divided again and then again, an entire apple can still
be reconstructed from each small portion of the film (although the images will
get hazier as the portions get smaller). Unlike normal photographs, every small
fragment of a piece of holographic film contains all the information recorded
in the whole.

This was precisely the
feature that got Pribram so excited, for it offered at last a way of
understanding how memories could be distributed rather than localized in the
brain. If it was possible for every portion of a piece of holographic film to
contain all the information necessary to create a whole image, then it seemed
equally possible for every part of the brain to contain all of the information
necessary to recall a whole memory.

Vision Also Is
Holographic

Memory is not the only
thing the brain may process holographically. Another of Lashley's discoveries
was that the visual centers of the brain were also surprisingly resistant to
surgical excision. Even after removing as much as 90 percent of a rat's visual
cortex (the part of the brain that receives and interprets what the eye sees),
he found it could still perform tasks requiring complex visual skills.
Similarly, research conducted by Pribram revealed that as much as 98 percent of
a cat's optic nerves can be severed without seriously impairing its ability to
perform complex visual tasks.

Such a situation was
tantamount to believing that a movie audience could still enjoy a motion
picture even after 90 percent of the movie screen was missing, and his
experiments presented once again a serious challenge to the standard
understanding of how vision works. According to the leading theory of the day,
there was a one-to-one correspondence between the image the eye sees and the
way that image is represented in the brain. In other words, when we look at a
square, it was believed the electrical activity in our visual cortex also
possesses the form of a square.

Although findings such
as Lashley's seemed to deal a deathblow to this idea, Pribram was not
satisfied. While he was at Yale he devised a series of experiments to resolve
the matter and spent the next seven years carefully measuring the electrical
activity in the brains of monkeys while they performed various visual tasks. He
discovered that not only did no such one-to-one correspondence exist, but there
wasn't even a discernible pattern to the sequence in which the electrodes
fired. He wrote of his findings, “These experimental results are incompatible
with a view that a photographic-like image becomes projected onto the cortical
surface.”

Once again the
resistance the visual cortex displayed toward surgical excision suggested that,
like memory, vision was also distributed, and after Pribram became aware of holography
he began to wonder if it, too, was holographic. The “whole in every part”
nature of a hologram certainly seemed to explain how so much of the visual
cortex could be removed without affecting the ability to perform visual tasks.
If the brain was processing images by employing some kind of internal hologram,
even a very small piece of the hologram could still reconstruct the whole of
what the eyes were seeing. It also explained the lack of any one-to-one
correspondence between the external world and the brain's electrical activity.
Again, if the brain was using holographic principles to process visual
information, there would be no more one-to-one correspondence between
electrical activity and images seen than there was between the meaningless swirl
of interference patterns on a piece of holographic film and the image the film
encoded.

The only question that
remained was what wavelike phenomenon the brain might be using to create such
internal holograms. As soon as Pribram considered the question he thought of a
possible answer. It was known that the electrical communications that take
place between the brain's nerve cells, or neurons, do not occur alone. Neurons
possess branches like little trees, and when an electrical message reaches the
end of one of these branches it radiates outward as does the ripple in a pond.
Because neurons are packed together so densely, these expanding ripples of
electricity—also a wavelike phenomenon—are constantly crisscrossing one
another. When Pribram remembered this he realized that they were most assuredly
creating an almost endless and kaleidoscopic array of interference patterns,
and these in turn might be what give the brain its holographic properties. “The
hologram was there all the time in the wave-front nature of brain-cell
connectivity,” observed Pribram. “We simply hadn't had the wit to realize it.”

Other Puzzles
Explained by the Holographic Brain Model

Pribram published his
first article on the possible holographic nature of the brain in 1966, and
continued to expand and refine his ideas during the next several years. As he
did, and as other researchers became aware of his theory, it was quickly
realized that the distributed nature of memory and vision is not the only
neurophysiological puzzle the holographic model can explain.

THE VASTNESS OF
OUR MEMORY

Holography also explains
how our brains can store so many memories in so little space. The brilliant
Hungarian-born physicist and mathematician John von Neumann once calculated
that over the course of the average human lifetime, the brain stores something
on the order of 2.8 × 10
²⁰
(280,000,000,000,000,000,000) bits of
information. This is a staggering amount of information, and brain researchers
have long struggled to come up with a mechanism that explains such a vast
capability.

Interestingly, holograms
also possess a fantastic capacity for information storage. By changing the
angle at which the two lasers strike a piece of photographic film, it is
possible to record many different images on the same surface. Any image thus
recorded can be retrieved simply by illuminating the film with a laser beam
possessing the same angle as the original two beams. By employing this method
researchers have calculated that a one-inch-square of film can store the same
amount of information contained in fifty Bibles!

OUR ABILITY TO
BOTH RECALL AND FORGET

Pieces of holographic
film containing multiple images, such as those described above, also provide a
way of understanding our ability to both recall and forget. When such a piece
of film is held in a laser beam and tilted back and forth, the various images
it contains appear and disappear in a glittering stream. It has been suggested
that our ability to remember is analogous to shining a laser beam on such a
piece of film and calling up a particular image. Similarly, when we are unable
to recall something, this may be equivalent to shining various beams on a piece
of multiple-image film, but failing to find the right angle to call up the
image/memory for which we are searching.

ASSOCIATIVE
MEMORY

In Proust's
Swann ‘s
Way
a sip of tea and a bite of a small scallop-shaped cake known as a
petite
madeleine
cause the narrator to find himself suddenly flooded with memories
from his past At first he is puzzled, but then, slowly, after much effort on
his part, he remembers that his aunt used to give him tea and madeleines when
he was a little boy, and it is this association that has stirred his memory. We
have all had similar experiences—a whiff of a particular food being prepared,
or a glimpse of some long-forgotten object—that suddenly evoke some scene out
of our past.

The holographic idea
offers a further analogy for the associative tendencies of memory. This is
illustrated by yet another kind of holographic recording technique. First, the
light of a single laser beam is bounced off two objects simultaneously, say an
easy chair and a smoking pipe. The light bounced off each object is then
allowed to collide, and the resulting interference pattern is captured on film.
Then, whenever the easy chair is illuminated with laser light and the light
that reflects off the easy chair is passed through the film, a
three-dimensional image of the pipe will appear. Conversely, whenever the same
is done with the pipe, a hologram of the easy chair appears. So, if our brains
function holographically, a similar process may be responsible for the way
certain objects evoke specific memories from our past.

OUR ABILITY TO
RECOGNIZE FAMILIAR THINGS

At first glance our
ability to recognize familiar things may not seem so unusual, but brain
researchers have long realized it is quite a complex ability. For example, the
absolute certainty we feel when we spot a familiar face in a crowd of several
hundred people is not just a subjective emotion, but appears to be caused by an
extremely fast and reliable form of information processing in our brain.

In a 1970 article in the
British science magazine
Nature
, physicist Pieter van Heerden proposed
that a type of holography known as
recognition holography
offers a way
of understanding this ability.
^*
In recognition
holography a holographic image of an object is recorded in the usual manner,
save that the laser beam is bounced off a special kind of mirror known as a
focusing
mirror
before it is allowed to strike the unexposed film. If a second
object similar but not identical to the first, is bathed in laser light and the
light is bounced off the mirror and onto the film after it has been developed,
a bright point of light will appear on the film. The brighter and sharper the
point of light, the greater the degree of similarity between the first and
second objects. If the two objects are completely dissimilar, no point of light
will appear. By placing a light-sensitive photocell behind the holographic
film, one can actually use the setup as a mechanical recognition system.

A similar technique
known as
interference holography
may also explain how we can recognize
both the familiar and unfamiliar features of an image such as the face of
someone we have not seen for many years. In this technique an object is viewed
through a piece of holographic film containing its image. When this is done,
any feature of the object that has changed since its image was originally
recorded will reflect light differently. An individual looking through the film
is instantly aware of both how the object has changed and how it has remained
the same. The technique is so sensitive that even the pressure of a finger on a
block of granite shows up immediately, and the process has been found to have
practical applications in the materials-testing industry.