Old brains, new tricks: Rewiring the elderly

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  • Published: Jun 1, 2012
  • Author: David Bradley
  • Channels: MRI Spectroscopy
thumbnail image: Old brains, new tricks: Rewiring the elderly

Adolescence is not the end

Conventional wisdom has it that after major

Can we rewire seniors?

Conventional wisdom has it that after major "rewiring" work during adolescence, the connections between neurones and groups of neurons remain fixed as we get older. However, evidence is emerging from a variety of sources to suggest that even the aged adult brain has plenty of plasticity and can adapt to accommodate novel sensory experiences.

Marcel Oberlaender of the Max Planck Florida Institute (MPFI) and Randy Bruno and Alejandro Ramirez of the Department of Neuroscience and the Kavli Institute for Brain Science at Columbia University, in New York, USA, publish details in the journal Neuron this month. They also report how their study shows that this "rewiring" involves fibres that supply the primary input to the cerebral cortex, the part of the brain that is responsible for sensory perception, motor control and cognition at least in elderly laboratory rats.

The team examined the brains of older rats, focusing on a region known as the thalamus, which processes and delivers information obtained from sensory organs to the cerebral cortex. Previously, researchers had assumed that connections between the thalamus and the cortex stop changing by the time mammals reach early adulthood. However, this did not seem to be the case in the present study. Rats are largely nocturnal and so they rely on their sensitive whiskers rather than vision to investigate and navigate their environment. The "whisker centres" of the rat's brain is, the researchers say, an ideal model for studying brain plasticity. A quick trim will prevent the rats from receiving the usual sensory input and perhaps stimulate extensive rewiring between the thalamus and cortex would occur.

Examination of the trimmed rats showed them to have altered axons, the nerve fibres along which information is conveyed from one neuron to several others. There were no axonal changes in the untrimmed animals. The rats were by rodent standards elderly animals, but despite this the changes were marked despite their age. The researchers also note that the rewiring seems to happen rapidly over the course of just a few days.

"We've shown that the structure of the rodent brain is in constant flux, and that this rewiring is shaped by sensory experience and interaction with the environment," explains Oberlaender. "These changes seem to be life-long and may pertain to other sensory systems and species, including people. Our findings open the possibility of new avenues of research on development of the aging brain using quantitative anatomical studies combined with non-invasive imaging technologies suitable for humans, such as functional magnetic resonance imaging (fMRI)."

"This study overturns decades-old beliefs that most of the brain is hard-wired before a critical period that ends when one is a young adult," explains neuroscientist Oberlaender. "By changing the nature of sensory experience, we were able to demonstrate that the brain can rewire, even at an advanced age. This may suggest that if one stops learning and experiencing new things as one ages, a substantial number of connections within the brain may be lost."

We ultimately want to understand how the brain is able to adapt to an ever-changing world," Bruno told us. "The most familiar aspect of that question for all of us, scientist or not, is learning and memory. Where in the brain is new experience stored? How is that information encoded (what is the nature of the memory trace or "engram")? The less familiar, but equally important, aspect of this issue is how does the brain deal with traumatic experience (e.g., the loss of a limb or sensory organ)? If we know where and how such changes occur, can medical science do something to ameliorate the loss or even repair the system?"

"Sensory Experience Restructures Thalamocortical Axons during Adulthood", Neuron, 2012, 74, 648-655; DOI: 10.1016/j.neuron.2012.03.022

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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