Of mice and men and intelligence genes

Philip L Ferguson PLF13 at SPAMstudent.canterbury.ac.nz
Fri Sep 3 21:31:07 MDT 1999

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LM Commentary:

Of mice and men

Researchers may have used genetics to improve the memory of mice, but it is
nonsense to talk of an 'intelligence gene', argues Dr Stuart Derbyshire

Teams of researchers from Princeton University, New Jersey, and another
from the University of Tokyo have discovered improved memory and learning
ability in two strains of genetically modified mice. The results have
caused much excitement, with some commentators talking about an
'intelligence gene' - raising the possibility of enhancing the normal
intelligence of 'other mammals', including humans.

But while this work is undoubtedly a step towards enhancement of some of
the basic information-processing capacities that all mammals share, it is
still a long stretch from these studies to a facilitation of human memory,
let alone intelligence.

Memory in humans and all other mammals is intricately tied in with a piece
of the brain called the hippocampus. If you were to be so unlucky as to
lose your hippocampus on both sides of your brain, you would never again be
able to place an event into long-term memory. Memories never develop beyond
the moment of hippocampal destruction and the patient forever lives in the
past and immediate present.

Knowing this important site for memory, researchers have turned their
attention towards the mechanisms of the hippocampus. This is what the
current studies investigated. It is known that information is shuffled
around and maintained inside the hippocampus dependent upon the properties
of receptors (sites at which actions take place) and their interaction with
neurotransmitters (chemicals that allow communication between receptor
sites). The important receptor is NMDA and the important neurotransmitter
is glutamate. When NMDA binds to glutamate a current is evoked which opens
a channel allowing calcium ions to enter the cell. This is the magical
moment when the cells of the hippocampus talk in harmony and strengthen
their connections, known technically as long-term potentiation (LTP) and
more commonly as the beginning of memory. The researchers in Tokyo hoped to
improve the memory of mice through the increase of an NMDA subtype that has
an extended LTP - while the researchers at Princeton deleted the genetic
code for a non-NMDA hippocampal receptor that inhibits LTP, thereby
inadvertently extending overall LTP.

Both groups demonstrated improved memory in their transgenic strains
through a standard behavioural test. The mice were released into a shallow
pool of water and swam around until stumbling across a hidden platform and
standing on it. This was done on multiple occasions and the time taken to
reach the platform was recorded. All the mice reached the platform more
quickly on later trials, indicating learning. The transgenic mice, however,
performed better than the normal mice, showing further improved learning
due to the genetic manipulation.

So will we be able to create humans with super memories? Perhaps. I have no
doubt that humans and mice share important properties relating to the
hippocampus and its basic function. But even so, memory in mice and memory
in humans are far removed. Simple associative learning - discovering that A
follows B, etc - is an aspect of memory and, if you are a mouse surviving
from one moment to the next, it might be terrific to have your associative
learning enhanced. But humans do not survive in this manner - we have
developed ourselves and our society and can operate on a more general,
abstract level. Being able to understand connections between A and B might
be a prerequisite for abstract memories but that does not mean a better
recognition of concrete relationships will improve abstract memory. It
might even be detrimental. Humans use memory in a transformative manner to
go beyond simple relationships and to develop abstract connections.

The ability to draw abstract relationships and pursue meaningful goals is
the hallmark of human intelligence that is sorely lacking in the mouse
world - even in the newly created super mouse world. In the mouse, memory
is merely an extension of their basic biological function with zero
intelligent content. Our intelligence remains under the influence of basic
information-processing skills (as evidenced by its severe compromising when
processing is lost to dementia), but intelligence is more than the simple
additive effects of processing environmental associations. For humans,
memory is not a natural extension of biology but is a part of the
transformation and interweaving of innate biological processes into higher
intelligent function.

The transformation of our biological information-processing capacity, which
we share with mice, takes place in the sociocultural world, which we do not
share with mice. During development, formal schooling and other cultural
interventions, the subordination of biological instinct to volitional
control is nurtured and encouraged. Memory ceases to be slavishly dictated
by internal and external events and becomes a tool that can be used in the
pursuit of reasoned goals. A genetic and neural influence can remain, but
the cause of intelligence lies outside of genetics and pharmacology.

Dr Stuart Derbyshire is head of neuro-imaging at the Neuroenteric Disease
Program, University of California in Los Angeles

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