This study is relevant to the study of visual cognition and to the
innateness debate.
Ian Jobling
---------- Forwarded Message ----------
Date: Thursday, November 16, 2000, 7:45 PM +0000
From: Ian Pitchford <ian.pitchford@scientist.com>
To: evolutionary-psychology@egroups.com
Subject: [evol-psych] Brain wiring is largely inborn
> FOR RELEASE: 16 NOVEMBER 2000 AT 14:00 ET US
> Duke University
> http://www.duke.edu/
>
> Study indicates that brain wiring is largely inborn
>
> DURHAM, N.C. – Neurobiologists at Duke University Medical Center mapping
> the developing visual systems of newborn ferrets have discovered evidence
> challenging the long-held view that the brain's circuitry is largely
> wired by experience. Rather, they contend, much of the circuitry is
> inborn, with experience acting merely to preserve and enhance existing
> connections.
>
> The finding, published in the Nov. 17 Science, calls into question a
> fundamental tenet of brain development – that early sensory stimulation is
> critical to the basic wiring of the brain.
>
> Reporting the studies are graduate student Justin Crowley and Howard
> Hughes Medical Institute investigator Lawrence Katz. Besides Howard
> Hughes Medical Institute, their work also was supported by the National
> Institutes of Health.
>
> Crowley and Katz studied newborn ferrets because the animals' visual
> wiring is the equivalent of that of other mammals still in the fetal
> stage. The researchers' objective was to detect "ocular dominance
> columns" in a visual area of the brain called the visual cortex. The
> presence of these alternating stripe-like columns of nerve fibers
> constitutes evidence that the visual system has established a basic
> component of the adult visual circuit, forming groups of nerve cells in
> the visual cortex that respond to input from one eye or the other.
>
> The scientists used an innovative surgical technique that allowed them to
> inject tracer dye more precisely in order to reveal the neural
> connections from the eye within the cortex. They first reported use of
> the tracer technique to reveal ocular dominance columns in adult ferrets
> in a December 1999 article in Nature Neuroscience.
>
> The latest studies clearly revealed the presence of columns in the newborn
> animals' brains earlier than ever suspected, Katz said, and the
> scientists' measurements showed that in size, spacing and arrangement the
> columns closely resembled those previously found in adult animals.
>
> Importantly, when the researchers traced the columns in newborn ferrets
> that received visual information from only one eye, those animals still
> showed normal development of the columns. This finding confirmed that the
> columns did not require information from the eyes to develop normally.
>
> "For about three decades, ocular dominance columns have served as
> something of a Rosetta Stone for understanding how brain circuits are
> wired, and in particular for understanding the role of neural activity
> and experience in constructing them," said Katz. "The prevailing idea has
> been that activity is critical for establishing brain circuits.
>
> "Until now, the concept has been that neural connections in young animals
> were not specified very accurately, and that experience and environment
> were needed to refine initially crude connections, by a process of
> elimination, into the adult pattern," Katz said.
>
> "The critical finding in our study was that this is not the case. Rather,
> we found that these columns were present as early as we looked for them,
> and they are basically as well formed as structures in an adult.
>
> "This finding, in a way, addresses the whole question of nature versus
> nurture," said Katz. "It questions the notion that the young animal and
> its neural connections are either a ‘blank slate' or a poorly specified
> version of the adult's. Rather, our findings suggest that the brain of an
> animal or human starts life with a pretty good idea of what to expect –
> that it possesses an initial template of circuitry representing a
> ‘best-guess' of what experiences the animal will encounter. If normal
> experience ensues, this template is preserved and enhanced. But if the
> animal encounters something different during a critical period
> immediately after birth, there's some possibility of altering these
> connections."
>
> Added Crowley, "The assumption that activity was important in initially
> constructing these circuits was based on good data from animals on the
> remodeling of circuits by visual experience during the critical period.
> These data led investigators to believe that the influences on wiring
> connections during this later period were the same ones that wired them
> during establishment of the circuitry. It was a good guess, but not
> necessarily a correct one."
>
> According to Katz, the findings emphasize the importance of current
> scientific efforts to discover the intricate molecular cues that guide
> the initial wiring of the brain.
>
> "While until now many scientists had searched for the mechanism by which
> activity drives neuronal competition to form certain brain structures,
> we're now offering evidence that it may not be competition at all.
> Rather, neurons in developing animals may initially form connections
> based on molecular labels. We believe that the search for these guidance
> molecules is critical to understanding the initial stages of brain
> wiring."
>
>
> ###
> Note to editors: An image showing the researchers can be downloaded from
> http://photo1.dukenews.duke.edu. After 5 p.m. Tuesday, the image will be
> in the subdirectory Duke News Service, and the file name will be
> ferret.jpg. Lawrence Katz may be contacted at (919) 681-6225, e-mail
> larry@neuro.duke.edu.
> http://www.eurekalert.org/releases/duke-sit111300.html
>
>
>
>
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