Nav: Home

Newly discovered role for climbing fibers: Conveying a sensory snapshot to the cerebellum

March 27, 2019

As we go about our daily lives, we are constantly bombarded by a steady stream of sensory information. Take a typical morning routine for example- roused from sleep by a shrill alarm, the strong aroma of freshly brewed coffee, and the brake lights and traffic horns of rush hour. In the course of a single day, we experience thousands of different cues across all senses.

Despite the numerous chaotic cues we encounter, our brains do a remarkable job assembling and processing them; allowing us to make sense of the world around us. This processing can take shape in very noticeable ways, such as our vision and hearing, but also occurs more subtly and unexpectedly. For instance, when learning a new movement, our brain is constantly keeping track of the sensory cues around us. This sensory snapshot helps to instruct and guide motor learning so that when we encounter the same context again, we'll be more likely to perform the movement in better way.

Though there is a wealth knowledge supporting the idea that sensory cues benefit motor learning, the precise brain circuitry and mechanisms tying these two together has been debated in recent years. Shedding new light on this topic, a recently published paper in Neuron from the lab of Dr. Jason Christie, Research Group Leader at the Max Planck Florida Institute for Neuroscience (MPFI), has revealed that a special input pathway into the cerebellum seems to hold the key to coding sensory information.

The cerebellum is a unique structure within the brain that plays a critically important role in motor coordination and learning that improves movements. By receiving many inputs from various regions of the brain, the cerebellum integrates and sends refined information out through a single neuron type called a Purkinje cell. One significant input to the Purkinje cells, are long-range projections called climbing fibers.

"Climbing fibers are very well-known and extensively studied in the field." describes Dr. Michael Gaffield, Research Fellow in the Christie Lab and first author of the publication. "These fibers form long-range connections with the cerebellum and are thought to deliver instructive motor signals and relay sensory information. But in the past few years it's been suggested that local circuits within the cerebellum, such as parallel fibers or molecular layer interneurons, may also play a part in coding of sensory information."

To investigate, the team used two-photon calcium imaging to monitor the activity of Purkinje cells within the cerebellum of mice while presenting various sensory stimuli (auditory, visual and somatosensory). They then isolated and assessed changes in Purkinje cell activity that directly corresponded to the timing of each individual stimulus and climbing fiber input.

"Within each Purkinje cell, we saw a consistent enhancement of activity whenever a sensory stimulus was presented. But the enhancement wasn't the exact same across all three sensory types, it varied depending on the type of stimulus presented" explains Gaffield.

Next MPFI scientists examined if other cell types besides climbing fibers, contributed directly to the sensory enhanced activity seen in the Purkinje cells. Using the techniques of optogenetic inactivation (suppression of neural activity using light) and chemogenetic inhibition (suppression of neural activity using drugs), the team was able to inhibit individual cell types in the local cerebellar circuitry. Despite altering the local activity, no change occurred to the sensory enhanced activity of the Purkinje cells. However, by inhibiting climbing fiber activity directly, the enhancement was abolished; indicating that climbing fibers alone are responsible for conveying sensory information to the cerebellum.

Taking their investigation a step further, the Christie lab pioneered a novel technique allowing them to monitor the activity of climbing fiber axonal projections themselves. They discovered that when presenting sensory stimuli, the graded changes in the presynaptic activity of climbing fibers was accurately represented in the Purkinje cells; stronger activity in the climbing fiber was precisely mirrored by stronger activity in the Purkinje cells they connect with.

"Our results actually came as a bit of a surprise" notes Dr. Christie. "Traditionally it was thought that sensory signals arriving in the cerebellum were integrated and processed by Purkinje cells using local connections. Our findings demonstrate that Purkinje cells are merely reflecting what the climbing is doing. This means that a more distal region of the brain is doing the actual processing of sensory information and simply relaying it to the cerebellum. "

"Since Purkinje cell activity is critically important for motor learning, we are now in the process looking at sensory-derived activity during more complex motor behaviors" describes Dr. Christie. "Hopefully we will be able to uncover the neural mechanisms that underlie the climbing fiber's unique ability to convey sensory information and how learning benefits from this coding scheme."

Max Planck Florida Institute for Neuroscience

Related Brain Articles:

Transplanting human nerve cells into a mouse brain reveals how they wire into brain circuits
A team of researchers led by Pierre Vanderhaeghen and Vincent Bonin (VIB-KU Leuven, Université libre de Bruxelles and NERF) showed how human nerve cells can develop at their own pace, and form highly precise connections with the surrounding mouse brain cells.
Brain scans reveal how the human brain compensates when one hemisphere is removed
Researchers studying six adults who had one of their brain hemispheres removed during childhood to reduce epileptic seizures found that the remaining half of the brain formed unusually strong connections between different functional brain networks, which potentially help the body to function as if the brain were intact.
Alcohol byproduct contributes to brain chemistry changes in specific brain regions
Study of mouse models provides clear implications for new targets to treat alcohol use disorder and fetal alcohol syndrome.
Scientists predict the areas of the brain to stimulate transitions between different brain states
Using a computer model of the brain, Gustavo Deco, director of the Center for Brain and Cognition, and Josephine Cruzat, a member of his team, together with a group of international collaborators, have developed an innovative method published in Proceedings of the National Academy of Sciences on Sept.
BRAIN Initiative tool may transform how scientists study brain structure and function
Researchers have developed a high-tech support system that can keep a large mammalian brain from rapidly decomposing in the hours after death, enabling study of certain molecular and cellular functions.
Wiring diagram of the brain provides a clearer picture of brain scan data
In a study published today in the journal BRAIN, neuroscientists led by Michael D.
Blue Brain Project releases first-ever digital 3D brain cell atlas
The Blue Brain Cell Atlas is like ''going from hand-drawn maps to Google Earth'' -- providing previously unavailable information on major cell types, numbers and positions in all 737 brain regions.
Landmark study reveals no benefit to costly and risky brain cooling after brain injury
A landmark study, led by Monash University researchers, has definitively found that the practice of cooling the body and brain in patients who have recently received a severe traumatic brain injury, has no impact on the patient's long-term outcome.
Brain cells called astrocytes have unexpected role in brain 'plasticity'
Researchers from the Salk Institute have shown that astrocytes -- long-overlooked supportive cells in the brain -- help to enable the brain's plasticity, a new role for astrocytes that was not previously known.
Largest brain study of 62,454 scans identifies drivers of brain aging
In the largest known brain imaging study, scientists from Amen Clinics (Costa Mesa, CA), Google, John's Hopkins University, University of California, Los Angeles and the University of California, San Francisco evaluated 62,454 brain SPECT (single photon emission computed tomography) scans of more than 30,000 individuals from 9 months old to 105 years of age to investigate factors that accelerate brain aging.
More Brain News and Brain Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

There's so much we've yet to explore–from outer space to the deep ocean to our own brains. This hour, Manoush goes on a journey through those uncharted places, led by TED Science Curator David Biello.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

Dispatch 2: Every Day is Ignaz Semmelweis Day
It began with a tweet: "EVERY DAY IS IGNAZ SEMMELWEIS DAY." Carl Zimmer – tweet author, acclaimed science writer and friend of the show – tells the story of a mysterious, deadly illness that struck 19th century Vienna, and the ill-fated hero who uncovered its cure ... and gave us our best weapon (so far) against the current global pandemic. This episode was reported and produced with help from Bethel Habte and Latif Nasser. Support Radiolab today at