Received: by alpheratz.cpm.aca.mmu.ac.uk id FAA10938 (8.6.9/5.3[ref pg@gmsl.co.uk] for cpm.aca.mmu.ac.uk from fmb-majordomo@mmu.ac.uk); Tue, 31 Oct 2000 05:11:49 GMT Date: Tue, 31 Oct 2000 16:07:31 +1100 From: John Wilkins <wilkins@wehi.EDU.AU> Subject: Neuronal competition To: memetics@mmu.ac.uk Message-ID: <MailDrop1.2d7k-PPC.1001031160731@mac463.wehi.edu.au> X-Authenticated: <wilkins@wehiz.wehi.edu.au> Content-Type: TEXT/PLAIN; CHARSET=US-ASCII Sender: fmb-majordomo@mmu.ac.uk Precedence: bulk Reply-To: memetics@mmu.ac.uk
While I'm on the kick of posting references, here's another that seemed
relevant to memes - the way the brain develops has close analogies to
the way populations evolve.
Development of Nerve Connections under the Control of Neurotrophic
Factors: Parallels with Consumer-Resource Systems in Population Biology
Arjen van Ooyen 1 and David J. Willshaw
Journal of Theoretical Biology (2000) 206: 195-210.
Abstract
The development of connections between neurons and their target cells
involves competition between axons for target-derived neurotrophic
factors. Although the notion of competition is commonly used in
neurobiology, the process is not well understood, and only a few formal
models exist. In population biology, in contrast, the concept of
competition is well developed and has been studied by means of many
formal models of consumer-resource systems. Here we show that a recently
formulated model of axonal competition can be rewritten as a general
consumer-resource system. This allows neurobiological phenomena to be
interpreted in population biological terms and, conversely, results from
population biology to be applied to neurobiology. Using findings from
population biology, we study two extensions of our axonal competition
model. In the first extension, the spatial dimension of the target is
explicitly taken into account. We show that distance between axons on
their target mitigates competition and permits the coexistence of axons.
The model can account for the fact that, in many types of neurons, a
positive correlation exists between the size of the dendritic tree and
the number of innervating axons surviving into adulthood. In the second
extension, axons are allowed to respond to more than one neurotrophic
factor. We show that this permits competitive exclusion among axons of
one type, while at the same time there is coexistence with axons of
another type innervating the same target. The model offers an
explanation for the innervation pattern found on cerebellar Purkinje
cells, where climbing fibres compete with each other until only a single
one remains, which coexists with parallel fibre input to the same
Purkinje cell.
--John Wilkins, Head, Graphic Production The Walter and Eliza Hall Institute of Medical Research Melbourne, Australia <mailto:wilkins@WEHI.EDU.AU> <http://www.users.bigpond.com/thewilkins/darwiniana.html> Homo homini aut deus aut lupus - Erasmus of Rotterdam
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