Why evolutionarily ancient brain areas are important

November 30, 2011 in Neuroscience

Structures in the midbrain that developed early in evolution can be responsible for functions in newborns which in adults are taken over by the cerebral cortex. New evidence for this theory has been found in the visual system of monkeys by a team of researchers from the RUB. The scientists studied a reflex that stabilizes the image of a moving scene on the retina to prevent blur, the so-termed optokinetic nystagmus. They found that nuclei in the midbrain initially control this reflex and that signals from the cerebral cortex (neocortex) are only added later on. PD Dr. Claudia Distler-Hoffmann from the Department of General Zoology and Neurobiology and Prof. Dr. Klaus-Peter Hoffmann from the Department of Animal Physiology report in the Journal of Neuroscience.

To control sensorimotor functions (e.g. ), the is equipped with different areas in the neocortex, the evolutionarily youngest part of the cerebrum. "This raises the question, why older subcortical structures in the brain have not lost the functions that can also be controlled by the neocortex" says Hoffmann. The neocortex of primates is, however, not fully functional shortly after birth and therefore cannot control the optokinetic nystagmus. "This is most probably also the case with people" says Distler-Hoffmann. Nevertheless, this reflex works directly after birth.

The researchers examined what information controls the optokinetic nystagmus in the first weeks after birth. During the first two weeks, the reflex is controlled by signals from the retina, which are transmitted to two nuclei in the midbrain. The neocortex then adds its information and takes over during the first months of life. The optokinetic reflex, which was studied by the researchers also at the behavioural level, is almost identical under the control of the midbrain and the . It occurs, for example, when watching a moving scene. First the eyes follow the passing scene, then they move quickly in the opposite direction back to their original position. On this reflex, monkeys and humans build their slow eye tracking movements with which they keep "an eye" on moving objects.

The optokinetic nystagmus changes if the visual system does not develop normally. Lens aberrations, corneal opacity and strabismus affect the reflex. "These findings from research with primates are important for recognizing and treating maldevelopments in the visual system of infants and young children at an early stage" explains Distler-Hoffmann.

More information: C. Distler, K.-P. Hoffmann (2011): Visual pathway for the optokinetic reflex in infant macaque monkeys, Journal of Neuroscience, doi: 10.1523/JNEUROSCI.4302-11.2011

Journal reference: Journal of Neuroscience search and more info website

Provided by Ruhr-University Bochum

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kevinrtrs
Nov 30, 2011

Rank: 1 / 5 (2)
the neocortex, the evolutionarily youngest part of the cerebrum

Someone must have observed this development for billions of years for this assertion to be true. Is there such an observational record?
During the first two weeks, the reflex is controlled by signals from the retina, which are transmitted to two nuclei in the midbrain. The neocortex then adds its information and takes over during the first months of life.

Ask yourself how could such a complex control system develop through random blundering biological processes? Just consider what is involved and the mind boggles at the impossibilities involved for a random processes to achieve this.
kevinrtrs
Nov 30, 2011

Rank: 1 / 5 (2)
On this reflex, monkeys and humans build their slow eye tracking movements with which they keep "an eye" on moving objects.

Now what was the original creature doing to track objects whilst this movement was "evolving"? Presumably they could only "see" static objects. But then, how would they themself move among the static objects because movement is relative? How would they track their own progress amongst all the static things? How would they evade they predators or catch food whilst tracking of moving objects "evolved"? What stupendously lucky combination of just the right brain cells , nerve connections and eye muscles would have to be in place simultaneously to get it to work in the first place?
roboferret
Nov 30, 2011

Rank: 5 / 5 (1)

Someone must have observed this development for billions of years for this assertion to be true. Is there such an observational record?


Yes. Via the fossil record. The neocortex is not found in fossils in the lower strata. Which is a pretty big problem for you who claims they were all buried at roughly the same time.


Ask yourself how could such a complex control system develop through random blundering biological processes?

Selection.

Just consider what is involved and the mind boggles at the impossibilities involved for a random processes to achieve this

Your mind is easily boggled. Not our problem.
roboferret
Nov 30, 2011

Rank: 5 / 5 (1)
Now what was the original creature doing to track objects whilst this movement was "evolving"? Presumably they could only "see" static objects. But then, how would they themself move among the static objects because movement is relative?


The majority of animal species alive today don't have tracking eyes and seem to get along fine so your incredulity is moot. We don't need an "original creature".

The evolution of the eye is understood. The (tired) irreducible complexity argument you are trying to make has been thoroughly debunked. Many intermediate stages from light-sensitive patches through to eyes more sophisticated than ours have been studied in extant species.
aroc91
Nov 30, 2011

Rank: 5 / 5 (1)
Oh look, once again, kevin's trying to use the fatally flawed blind watchmaker analogy.
Tausch
Dec 01, 2011

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Mutual feedback contributes to embryonic development. Neurons need input (signals) independent of whether their sources (the senses) are functioning the same as if they were fully developed.
The cells forming future senses - if pathways are available from these cells to the neurons (the developing brain) - are simply these future senses cell's internal activity having nothing to do with the external stimuli that they will eventually pass on upon maturity to neurons after birth. 'Trial' or 'dry' runs for the sake of embryonic neuronal development.
The neocortex of primates is, however, not fully functional shortly after birth and therefore cannot control the optokinetic nystagmus... ...this reflex works directly after birth - Bochum University


A fully functional neocortex is not necessary. The reflex controlling the optokinetic nystagmus was 'primed' with 'trial' or 'dry' runs during fetal development to perfection - with little to do until the neocortex has full function.
Tausch
Dec 01, 2011

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You are asking why cells are mobile or immobile on their own accord. I don't know. Once cells became mobile on their own accord, we have learned to expect from Nature - with natural selection and evolution - that mobility leads to higher and higher forms of mobility until humans reflect the best of both types of cells that exist in Nature - mobile and immobile cells.

Both types of cells in humans have become preoccupied with the motion of Nature. Motion is what led to all the human senses. Whether from motion of the environment or one's own endowed mobility.
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cerebral cortex, journal of neuroscience, adult brain, neocortex, eye movements, neurobiology, retina, primates, visual system, reflex
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