Wednesday, July 15, 2009

The "biology" of neuroplasticity

Let’s take a closer look at the "biology" of neuroplasticity to understand how these principles work.

The neuron

Neurons are the core components of the brain. A neuron has three parts – the dendrites, axon and cell body. The information flows along the neuron in one direction from the dendrites to the axon, via the cell body. Axons are often compared with wires, they carry electrical impulses at high speeds towards the dendrites or other neurones.

A neuron can receive excitatory signals and inhibitory signals. When it receives excitatory signals the neuron will fire off signals. When it receives inhibitory signals it becomes less likely to fire. The axons do not touch the other neurons, they are separated by a microscopic space called synapse. When the electrical signal arrives at the end of the axon it releases a neurotransmitter into synapses.

The neuron
A neurotransmitter is a chemical messenger that floats over the dendrite of the adjacent neuron, exciting it or inhibiting it. The alterations occur at the synapse level, strengthening or wakening the number of connections between the neurons. We call this process neurons “rewiring” or neurons “rewire” themselves.

"What Fire together Wire Together"

The neurons form strong connections to one another, when they are activated at the same moment. When an axon of a cell is near enough to excite cell of another neuron and repeatedly takes part in firing it, growth process or metabolic change takes place in one or both cells increasing the efficiency of one or both cells. This is often paraphrased as "Neurons that fire together wire together." It is commonly referred to as Hebb's Law ("")

Activity could produce changes in the structure of the brain

One of the first proofs that the brain can be modified through activity and stimulation came as a result of Mark Rosenzweig’s studies. In 1960, Mark Rosenzweig, a professor of psychology at the University of California at Berkeley, published findings showing that rats raised in enriched environments had heavier brains. His experiments showed that stimulation lead the brain to grow (Hirsh, Golinkoff, Eyer, 2003, 27). Therefore Rosenzweig was able to demonstrate that animals raised in enriched environments – surrounded by other animals, objects to explore, toys and running wells learn better than the identical animals that the animals that have not been exposed to these kind of stimuli.
Studies have shown that while completing an activity, the neurons in a center of a certain area of the brain that performs the activity are most committed to the task, while those on the border are less committed. Adjacent brain areas compete with each other to “recruit” these border neurons. Daily activities will determine who wins and will cause the map expansion of the brain area. The map expansion occurs at the boundaries between brain areas as a result of repeated activity. (Doidge 2007, 207). At the same time neuronal structure of the brain can be modified by experience and brain stimulation can lead to brain growth. The stimulating environment not only that is beneficial to development, but also will cause the brain to grow.

Marian Cleeves Diamond, a professor of anatomy and the first woman on the science faculty at Berkely in her book Enriching Heredity, speaks about the anatomy of the brain and how this can be changed by the environment. A stimulating environment will increases the cortical growth. Increases in cortical growth as a consequence of stimulating environmental can occur at every age, however the cerebral cortex is growing most rapidly in the first the first ten years, this being one of the reasons why it is very important to provide children with experiences through education and stimulating environments. Cognitively rich mental and physical activities will stimulate and exercise the brain. Learning a new skill such as dancing, play an instrument, learn a new language, through concentration, exercise will stimulate the neurons and preserve the brain’s balance system.

Plasticity is competitive

If we stop exercising certain mental skills the brain map allocated for that skill is turned over to the skills we practice instead. Plasticity is competitive. The more we practice an activity the more we make sure that its brain space is not lost to another. This has been demonstrated through sensory reassignment experiments that have demonstrated that when one sense is blocked, the cortex is deprived of receiving normal impulses and will start to receive impulses from other senses. At the same time, bad habits are difficult to unlearn. When we learn a bad habit, when we repeat the behaviour this takes claims more control of that map and prevents us from using that part of the brain for “good” habits. (Doidge 2007, 60)

1. Wikipedia, "Hebbian theory." Wikipedia Encyclopedia. Web.6 Jul 2009.
2. Doidge, Norman. The Brain that Changes Itself. 2007. New York: Penguin Group , 2007. Print.
3. Kathy Hirsh-Pasek, Roberta Michnick Golinkoff, Diane E. Eyer. 2003 Einstein never used flash cards: How Our Children Really Learn. Rodale Books, 2003. Print
4. Diamond, Marian Cleeves. Enriching Heredity: Impact of the Environment on Brain Development. 1988.Free Press, 1988. Print
5. Diamond, Marian Cleeves. "The Brain. Use It or Lose It ." Mindshift Connection 1(1998): Print.

No comments:

Post a Comment