30 September 2009

The Self-Organising Brain

...the brain of a newborn itself seems to organise its own development. The electrical activity of the waking brain triggers the series of events... _SD
We are not born knowing how to improvise jazz riffs on the saxophone. A newborn child is not able to prove mathematical theorems or argue political economics. But the infant child is born with the potential to do those things. How does the brain bootstrap upon itself to create the sophisticated organ of thought, action, and communication that adult humans possess?
Chaos brews in the brains of newborns: the nerve cells are still bound only loosely to each other. Under the leadership of Academy Research Fellow Sari Lauri, a team of researchers at the University of Helsinki has been studying for years how a neural network capable of processing information effectively is created out of chaos. The team has now found a new kind of mechanism that adjusts the functional development of nerve cell contacts.

The results were published in early September as the leading article of the Journal of Neuroscience.

The work carried out by Lauri's team and its partners at the Viikki campus sheds light on a development path that results in some of the large number of early synapses becoming stronger. The researchers found out that the BDNF growth factor of nerve cells triggers a functional chain which promotes the release of the neurotransmitter glutamate. BDNF enables the release of glutamate by prohibiting the function of kainate receptors which slow down the development of the preforms of the synapses. The activity of the kainate receptors restricts the release of glutamate and the development of synapses into functional nerve cell contacts. _SD
Until brain cells begin communicating via bioelectric signalling, true organisation of the brain cannot take place. The "waking brain" triggers the bioelectric signalling. What creates the "waking brain?"
During early phases of brain development gene expression and postranslational modifications of gene expression are controlled by biochemical signals which are produced in a cellular microenvironment. Later in brain development there is a difference from the development of other organs because electrical signals are added to biochemical messengers as a further signaling in the self-organizing between genes and their respective environments. It must be considered that these electrical signals are capable in influencing gene expression and postranslational modifications. Electrical signals are transported by neuronal processes over distances and with highly topological selectively. This enlarges the range and complexity of the "environment" available to self-organization process. The "environment" relevant to brain self-organization includes all domains with which the evolving brain is capable to interact and from which it receives messages. The same electrical signals which convey messages are used by the brain as information carriers for computational process .... results in the replacement of sensory stimuli by self-organization activity patterns that are contingent on past experience, present motivational state and expectancy of the future. _Turbes1993
Something has to "wake up" the developing brain to initiate this highly complex process of autopoietic development. While the child remains warm and wet within the womb, it has little reason to wake. But when squeezed and thrust into the cold and open brightness, little eyes instinctively open in reaction to the disturbance. This tiny opening sets up a chain of events leading to the jazz riff or the discovery of a new scientific principle.

Far from being a mere local phenomenon, clusters of nerves organise themselves both locally and over distances within the brain, and between the brain and peripheral organs of the body. How is it done?
A considerable amount of evidence and theory suggests that transient, short-lived phase-coupled oscillations within and between specialized areas of the brain provide a mechanism for neural integration. The idea is that these oscillations are coupled or “bound” together into a coherent network when people attend to a stimulus, perceive, remember, think and act. __ScottKelso
In the brain, traditional biochemical signaling and transduction is combined with neuroelectrical stimulation in a complex brew of cognitive magic. Current understanding of the brain is not yet at a fine enough resolution to trace back to first principles of how mind emerges from brain. But we are getting there.

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