The idea that the adult brain changes with experience was once a radical idea, but it is now well accepted that certain areas—say, the motor cortex, when learning a new physical skill—can grow new neurons or create stronger connections.
Now scientists report that the brain is even more mutable than suspected. Thanks to an unconventional research technique, neuroscientists have found the first physical proof that new experiences and information have wide-ranging effects throughout both hemispheres of the brain, rather than just creating connections in one discrete area.
The story begins in the hippocampus, the area of the brain associated with short-term memory. In the past, researchers have electrically stimulated slices of disembodied hippocampus and seen how stimulation changes the structure of nearby neurons. But the new study took a different tack. Led by Santiago Canals, a biological cyberneticist currently at the Institute of Neurosciences in Alicante, Spain, the team set aside the dissected hippocampi in favor of a more true-to-life approach. After implanting electrodes in live rats, the group used a combination of functional MRI, electroencephalography (EEG) and microstimulation—triggering nerve cells with small doses of electric current—to trace in real time what happened to neuronal structures in the rats’ brains when neurons in the hippocampus were stimulated. In contrast to studying the slices, this method allowed the scientists to see what happened in the hippocampus in context with what was going on all over the brain—like comparing a 2-D drawing of a bedroom with a 3-D rendering of the whole house.
“We have learned that what we call neuronal plasticity isn’t exclusive to individual synapses or even the neurons where they contact but rather occurs throughout the functional network in which synapses and neurons are embedded,” Canals says. “Those networks are absent in brain slices, so they couldn’t be studied before.”
By showing how activity in the hippocampus causes widespread changes in brain structure, Canals says the findings could explain why new memories are at first dependent on the hippocampus but can eventually be recalled without triggering that part of the brain at all.
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Add CommentDoes anyone know if, since the brain structure has changed, has the DNA or RNA changed as well? This effect might be a great way to study the epigenome.
Reply | Report Abuse | Link to thisPsychologist Donald Hebb's dictum, "neurons that fire together, wire together" was a 1948 insight helping to begin query into possible types of plasticity.
Reply | Report Abuse | Link to thisModern hippocampus studies used that area because it appears most active in development and migration of new neurons in various species.
Numerous exciting questions remain all over the map.
Among them:
Why and through what mechanisms do new human behaviors and habits take about the classic 21 days to supplant older patterns of thought and physical coordinations (or lack thereof)?
The involvement of cerebellum in physical learning, and indications of involvement in emotions, also seems to be, like the hippocampus, a temporary circuit before being abandoned to motor/sensory cortical areas. Conscious effort may indicate participation of some of the initial circuits, or it may be involved in the pressure of neuronal/dendritic change. Are there studies (fMRI or other) of learning which can be reported here?
Consciousness itself is poorly and often mistakenly defined. While it is certainly an emergent phenomenon (see for instance such work as Michael Gazzaniga's and other studies of impaired human brains), can intentional learning be studied at these cellular and circuitry levels?
We know that exogenous chemicals mimic neurotransmitters and modulators. The worldwide dependence on caffeine, nicotine, and alcohol, among lesser-used brain stimulators and pacifiers is a possible evolutionary problem. We already know that the human brain appears to have diminished in size over some periods, due to what?
What factors (think of how testosterone production is impaired in those who supplement it) are involved in the use or lack of use of various neurotransmitter analogues?
What psychological activities might stimulate or impair growth?
How is a self formed, and what areas and transmitter circuits can be recognized as recruited?
How are mirror neurons wired to such circuits?
Just how malleable is a self? What effects do beliefs, new realizations, experiences have on the apparent reshuffling of experience to change personality, open or close minds?
We realize that trauma, whether psychological or physical, has effects on learning, on perception, on emotion.
The brains of mammals are clearly structured as emotional organs. We can consciously ignore information due to our perceptions of source, type, etc. The creation of global theories of the world based on memory, thoughts, biases, is a characteristic needing tracing. Such questions need neuronal answer.
Increasingly, if reluctantly, there seems to be a growing awareness that nothing in existence stands alone. The components of any system both contribute to and are dependent on their environment - a change in one cannot but impact on the system of which it is a part and will subsequently itself be affected by the change it itself induced. This is the nature of Wholeness and in that respect all systems are components of the Universe.
Reply | Report Abuse | Link to thisA functional organ of the sophistication of the brain, the ultimate human sense organ, would be significantly failing in its function were it not to be aware of changes occurring within it or indeed within the body to which it is intimately and interactively communicating - a functional system in its own right, a unit of wholeness within Wholeness itself.
This is the reality of Condition of Existence the core principle of evolution.