The Facts About the Article
An extra copy of the NR2B gene was inserted into mice. Mice with the insertion performed better than mice without the insertion on all of the tests used to evaluate the intelligence of mice. This disovery supported and helped link two existing hypothesis, Hebbs rule and LTP, about how memories are formed. In the conclusion of the article, the authors stated some future possibilites that may arise from this discovery. Fisrt they stated that this discovery may be helpful in treating diseases that affect memory. Second they suggested that this may be a way to genetically engineer smarter mammals.
The Popular Media's Portrayal of the Discovery
Magazines such as TIME, read the original article and created a headline about the future possibilities mentioned in the conclusion. On the September 13, 1999 cover of TIME, TIME aired the headline "IQ Gene" alongside a picture of a human baby staring at a piece of DNA. This headline was obviously devised to make readers think that the gene for human intelligence had been found and that this could lead to genetically engineering smarter humans. To the author's credit, after the first couple of paragraphs the article did give a realistic depiction of the biological pathways discovered from the experiement. The article also discussed the problems and hurdles that must be overcome before making smarter humans ever becomes a reality. However, the damge had already been done.
The Sientific Media's Portrayal of the Disovery
Articles in the scientific media focused more on
how the discovery helped further the understanding of how memories are
formed. These papers, such as an article by Bliss in Nature, focused
more on how Tsien's discovery pulled together two existing hypothesis on
how memories are formed, Hebbs rule and LTP (Bliss, 1999). Rather
than focusing on future possibilities, this article focused on what was
Another aticle in Nature did discuss the future possibilites mentioned in th original article. However, the author of this editorial (Editotial, 1999) pointed out all of the hurdles that had to be crossed before such a thing was even considered. This editorial pointed out that it wasn't even known if the same response would occur in humans. The author goes on to question whether the type of memory enhanced in Tsien's mice could even be considered an enhancement of intelligence. Also mentioned in the editorial are the many side effects that could result from improving memory and the fact that genetically engineering in humans will not only face many scientific hurdles but will also face many ethical hurdles.
The Bottom Line
The bottom line is that the popular
media create headlines that sell papers and not headlines that necessarily
portray the truth. Thus a word of caution, always be critical of
headlines. If you want the truth be sure to read the entire article
(more than the first couple of paragraphs) and look up other articles about
the original article in scientific journals.
Hebb's rule (1949) states that a memory forms when two adjacent neurons fire at the same time (Bliss, 1999). The simultaneous firing strengthens the connection between them (Bliss, 1999).
Long term potentiation (LTP) is a model that explains how a memory is formed according to Hebb's rule (Bliss, 1999). LTP occurss when nuerons in a pathway repeatedly fire thus strengthening the synapse between them (Tsien, 2000).
NR2B and its role in forming memories
The NR2B gene encodes for a subunit found in NMDA receptors( Bliss, 1999). The NMDA receptor forms a channel across a neuron's membrane (Bliss, 1999). When the NMDA is open calcium ions are allowed to enter the neuron cell which causes LTP (Bliss, 1999). The NMDA receptor will only open when two things occur within a short period of time (Bliss, 1999). One, a glutamate transmitter must bind to the NMDA receptor site (Bliss, 1999). Two, the neuron must be depolarized. In adult brains the NR2B subunit is replaced by the NR2A subunit (Bliss, 1999). It is believed that the NR2B subunit allows the NMDA receptor to stay open longer and thus increases LTP (Bliss, 1999). Increasing LTP increases the strength between neurons (Bliss, 1999). Memories are formed when the connection between two neurons are strengthened (Bliss, 1999).
Figure 1: Illustration of the human NR2 subunit of the NMDA receptor.
Image taken from the PDB web site.
To learn how to make a smart mouse click below.
For an illustration of how a neuron works click below.
Bliss, T.V.P. September 1999. Young receptors make smart mice. Nature. 401: 25-27.
Editorial. November 1999. A mouse's tale that grew in the telling. Nature neuroscience. 2(11):
Lemonick, Michael D. September 13, 1999. Smart Genes? Time. 54-58.
Tang, Ya Ping; Eiji Shimizu, Giles Dube, Claire Rampon, Geoffrey Kerchner, Min Zhuo, Liu
Guosong, Joe Tsien. September 1999. "Genetic enhancement of learning and memory in mice."
Nature. 401: 63-69.
Tsien, Joe. April 2000. Building a brainier mouse. Scientific American.
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