How the brain compensates for sensory loss and points to its early evolutionary roots

January 20, 2016 by Avivit Delgoshen
Caenorhabditis elegans. Image: Wikipedia.

The human brain has the remarkable capacity to respond to sensory loss by boosting the remaining functioning senses. Through a compensation mechanism in the brain, known as cross-modal plasticity, some senses are enhanced following the loss of other sensory input, such as the improvement of hearing in people who are blind.

So far, this mechanism has been studied in humans and other mammals, under the assumption that it is a function of complex brains consisting of billions of cells, such as in humans. Now, a new international study led by researchers at The Hebrew University of Jerusalem, revealed that the brain's compensatory mechanism is a basic feature that also exists in less complex nervous systems. The study has also exposed the way the mechanism works in the brain through an inter-sensory signaling system.

The research, which was published in the journal PLOS Biology, was carried out jointly at the Institute for Medical Research Israel-Canada (IMRIC) at the Hebrew University's Faculty of Medicine, in collaboration with the MRC Laboratory for Molecular Biology in Cambridge, UK; and the Fred Hutchinson Cancer Research Center in Seattle, United States.

"One of the most fascinating capabilities of the brain is the ability to compensate for the loss of . We can learn a lot from how a relatively simple nervous system is able to exercise a brain function as sophisticated as this. In this research, we revealed an upper bound for the neural complexity required for a compensating mechanism like this, allowing us to examine and understand more easily how it works, all the way from the molecular level to the behavioral level," said Dr. Ithai Rabinowitch, who led the research during his work in the Department of Medical Neurobiology at the Hebrew University.

To better understand how cross-modal plasticity functions, the research team examined an organism with a substantially less complicated nervous system than is found in humans—the roundworm C. elegans. It is one millimeter long, feeds on bacteria, and its has only 302 neurons (compared to 100 billion in the ).

The researchers examined the relationship between the loss of the sense of touch and the possible enhancement of the sense of smell. To do this they focused on worms with a genetic mutation that eliminates their sense of touch.

They discovered that C. elegans mutants that cannot sense touch to the body exhibit an improved sense of smell. They were able to pinpoint this change in sensory performance to a change in strength of a specific synapse in the olfactory circuit.

"We were able to reverse these effects by artificially stimulating the touch neurons and by engineering a new synapse into the olfactory circuit," Dr. Rabinowitch explained. "We've still got a long way to go, but we can already think of future applications for treating unwanted side effects following the loss of sensory input."

This research adds to a series of studies investigating the role of neuropeptides in the brain's inter-sensory signaling, and expands the knowledge about the cellular and molecular processes underlying cross-modal plasticity. These results may also point to the ancient evolutionary roots of this compensation mechanism, now that it has been revealed in a much less developed system than our own.

Explore further: Brain plasticity after vision loss has an 'on-off switch'

More information: Ithai Rabinowitch et al. Neuropeptide-Driven Cross-Modal Plasticity following Sensory Loss in Caenorhabditis elegans, PLOS Biology (2016). DOI: 10.1371/journal.pbio.1002348

Related Stories

Brain plasticity after vision loss has an 'on-off switch'

August 12, 2015
KU Leuven biologists have discovered a molecular on-off switch that controls how a mouse brain responds to vision loss. When the switch is on, the loss of sight in one eye will be compensated by the other eye, but also by ...

For hearing parts of brain, deafness reorganizes sensory inputs, not behavioral function

May 10, 2011
– The part of the brain that uses hearing to determine sound location is reorganized in deaf animals to locate visual targets, according to a new study by a team of researchers from Virginia Commonwealth University and ...

Neuroscientists now can read the mind of a fly

December 4, 2015
Northwestern University neuroscientists now can read the mind of a fly. They have developed a clever new tool that lights up active conversations between neurons during a behavior or sensory experience, such as smelling a ...

Switching off brain circuit renders mice 'out of touch' with environment

May 21, 2015
The sense of touch is important but often taken for granted in daily life because it seems simple and automatic. New research suggests that the apparent simplicity of tactile sensation comes from a clever two-stage brain ...

Recommended for you

Scientists block evolution's molecular nerve pruning in rodents

July 27, 2017
Researchers investigating why some people suffer from motor disabilities report they may have dialed back evolution's clock a few ticks by blocking molecular pruning of sophisticated brain-to-limb nerve connections in maturing ...

In witnessing the brain's 'aha!' moment, scientists shed light on biology of consciousness

July 27, 2017
Columbia scientists have identified the brain's 'aha!' moment—that flash in time when you suddenly become aware of information, such as knowing the answer to a difficult question. Today's findings in humans, combined with ...

Social influences can override aggression in male mice, study shows

July 27, 2017
Stanford University School of Medicine investigators have identified a cluster of nerve cells in the male mouse's brain that, when activated, triggers territorial rage in a variety of situations. Activating the same cluster ...

Scientists become research subjects in after-hours brain-scanning project

July 27, 2017
A quest to analyze the unique features of individual human brains evolved into the so-called Midnight Scan Club, a group of scientists who had big ideas but almost no funding and little time to research the trillions of neural ...

Researchers reveal unusual chemistry of protein with role in neurodegenerative disorders

July 27, 2017
A common feature of neurodegenerative diseases is the formation of permanent tangles of insoluble proteins in cells. The beta-amyloid plaques found in people with Alzheimer's disease and the inclusion bodies in motor neurons ...

Mother's brain reward response to offspring reduced by substance addiction

July 27, 2017
Maternal addiction and its effects on children is a major public health problem, often leading to high rates of child abuse, neglect and foster care placement. In a study published today in the journal Human Brain Mapping, ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Jan 20, 2016
"We were able to reverse these effects by artificially stimulating the touch neurons and by engineering a new synapse into the olfactory circuit," Dr. Rabinowitch explained. "We've still got a long way to go, but we can already think of future applications for treating unwanted side effects following the loss of sensory input."

Why would the enhancement of the other senses be considered as an unwanted side effect? If I had lost a sense, I would definitely welcome a sharpening of the other senses!

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.