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The Brain as Hologram 23

to the first, is bathed in laser light and the light is bounced off the
himself suddenly flooded with memories from his past. At first he is 
mirror and onto the film after it has been developed,a bright pointof
puzzled, but then, slowly, after much effort on his part, he remembers 
light will appear on the film. The brighter and sharper the point of
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 light the greater the degree of similarity between the first and second

had similar experiences—a whiff of a particular food being prepared, objects. If the two objects are completely dissimilar, no point of light

or a glimpse of some long-forgotten object—that suddenly evoke some will appear. By placing a light-sensitive photocell behind the holo-

scene out of our past.
graphic film, one can actually use the setup as a mechanical recogni-
The holographic idea offers a further analogy for the associative tion system.

tendencies of memory. This is illustrated by yet another kind of holo- A similar technique known as interference holography may also

graphic recording technique. First, the light of a single laser beam is explain how we can recognize both the familiar and unfamiliar fea-

bounced off two objects simultaneously, say an easy chair and a smok- tures of an image such as the face of someone we have not seen for

ing pipe. The light bounced off each object is then allowed to collide, many years. In this technique an object is viewed through a piece of

and the resulting interference pattern is captured on film. Then, when- holographic film containing its image. When this is done, any feature

ever the easy chair is illuminated with laser light and the light that of the object that has changed since its image was originally recorded

reflects off the easy chair is passed through the film, a three-dimen- will reflect light differently. An individual looking through the film is

sional image of the pipe will appear. Conversely, whenever the same instantly aware of both how the object has changed and how it has

is done with the pipe, a hologram of the easy chair appears. So, if our remained the same. The technique is so sensitive that even the pres-

brains function holographically, a similar process may be responsible sure of a finger on a block of granite shows up immediately, and the

for the way certain objects evoke specific memories from our past.
process has been found to have practical applications in the materials-

testing industry.


At first glance our ability to recognize familiar things may not seem 
In 1972, Harvard vision researchers Daniel Pollen and Michael Trac- 
so unusual, but brain researchers have long realized it is quite a 
tenberg proposed that the holographic brain theory may explain why 
complex ability. For example, the absolute certainty we feel when we 
some people possess photographic memories (also known as eidetic 
spot a familiar face in a crowd of several hundred people is not just 
memories}. Typically, individuals with photographic memories will 
a subjective emotion, but appears to be caused by an extremely fast 
spend a few moments scanning the scene they wish to memorize. 
and reliable form of information processing in our brain.
When they want to see the scene again, they "project" a mental image 

In a 1970 article in the British science magazine Nature, physicist of it, either with their eyes closed or as they gaze at a blank wall or 

Pieter van Heerden proposed that a type of holography known as screen. In a study of one such individual, a Harvard art history profes- 

recognition holography offers a way of understanding this ability.* 
sor named Elizabeth, Pollen and Tractenberg found that the mental 
In recognition holography a holographic image of an object is recorded 
images she projected were so real to her that when she read an image 
in the usual manner, save that the laser beam is bounced off a special 
of a page from Goethe's Faust her eyes moved as if she were reading 
kind of mirror known as a focusing mirror before it is allowed to 
a real page.
strike the unexposed film. If a second object, similar but not identical
Noting that the image stored in a fragment of holographic film gets 

hazier as the fragment gets smaller, Pollen and Tractenberg suggest 
*Van Heerden, a researcher at the Polaroid Research Laboratories in Cambridge, Massachu- 
setts, actually proposed his own version of a holographic theory of memory in 1963, but his that perhaps such individualshave more vivid memories because they 

work went relatively unnoticed.
somehow have access to very large regions of their memory holo-

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