K/r-Selection Applied to the CNS

• K-Selection and r-Selection: Profound or Trivial? by James Brody, 6/28/97
  
  

I checked Wilson's definitions again and found I drifted from his concepts. R-selection is a function of unstable environments. Rapid discovery, rapid occupancy, rapid redeployment are needed for survival. The gambit seems to be that of "use it up before it disappears." (Sounds like this could apply to locusts, rats, and many humans.)

K-selection is supposed to be a function of stable environments that give a species the opportunity to reproduce to the environmental limits. Once carrying capacity (K) is approached, it's important to live in patterns that allow efficient, sustained energy use and reuse. There are usually fewer offspring but given more training, and more in competition with each other for the same resources. K-selection appears to be more "rule-bound," associated with a greater investment in social skills, hierarchies, coalitions, and pair-bonding.

It seems that K/r can also be applied to our CNS configuration. We have many patterns of neural organization; K/r fit the poles of one continuum.

The r-selection brain (Warning! This is contrived!) consists of many, finer fibers, supplying diffuse information. Lateral inhibition is not a conspicuous feature in these systems; recruitment phenomena (in which successive stimuli eventually exceed some threshold and trigger massive approach or escape) seem more common as do nets of closely connected fibers. Deep, diffuse pain and temperature are commonly processed by these systems; they seem to characterized the reticular system as well.

The K-selection brain consists of larger fibers that go to discrete areas and supply more focused information. High density of innervation is associated with making fine discriminations in the visual, auditory, or tactile domains. Given a high density of innervation, it is likely that one stimulus will impact on several receptors. Thus, lateral inhibition (suppressor effects between adjacent receptors) is common and allows contrast effects for the detection of boundaries and movement.

The K/r model thus applies to size of fibers (size of individuals), mate selection (many, non-exclusive connections), phylogenetic age (the r-systems seem to be older whereas the myelinated systems appear newer), presence of altruism or competition (recruitment vs inhibitory effects), and stability of the environment (highly detailed connections are made and easily disrupted by trauma). Because of the newness of myelinated systems, one might expect them to be more dependent on earlier strata and thus, represent a greater degree of parental investment!

Told you it was contrived. The prior exercise reinforces my intuition that K/r-selection is either one of the more subtle and powerful or the more useless concepts in sociobiology and evolutionary psychology.

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