Summary: The poor colliculus, a brainstem place known for sound running, also plays a role in touch sensation by integrating sensory and audio signals. Pacinian corpuscles, very delicate skin mechanoreceptors, switch high-frequency vibrations to this mind area, exacerbating sensory experiences. This method explains phenomena like hearing music vibrate during a performance and demonstrates how adaptable the brain is to multisensory information processing is.
Important Information:
- Multisensory Integration: The poor colliculus processes both sensory and audio signals, enhancing sensory experience.
- Role of Pacinian Corpuscles: These mechanoreceptors are essential for detecting high-frequency motions and sending them to the head.
- Medical Possible: Insights could tell treatments for visual dysfunction in autism and severe neuropathy.
Origin: Harvard
Ludwig van Beethoven lost reading at the age of 28 and was deaf by the age of 44. While the cause of his hearing damage remains a matter of , academic debate and continued revision, one thing is clear: Despite his hearing loss, Beethoven never ceased to create music, good because he was able to sense the vibrations of music instruments and “hear” music through the sense of touch,  , researchers believe.
Researchers at Harvard Medical School’s review are now able to explain what caused Beethoven and other musicians to acquire an exquisitely delicate sense of touch after losing their reading.
The results, based on experiments in animals and reported Dec. 18 in , Cell, offer a enticing new idea into how and why the diminishment of one feeling augments the another.
They also give a surprising fresh perspective to how the mind and the body sync up to process multiple emotions simultaneously.
The study finds that the poor colliculus, which is primarily known for its part in noise control, is also involved in processing feel signals, including electrical vibrations that have been detected by nerve endings on the skin.
The team’s experiments reveal that the high-frequency mechanical vibrations picked up by Pacinian corpuscles, an extremely sensitive mechanoreceptor, are not exclusively directed to the somatosensory cortex, the area of the brain where bodily sensations are processed.
Instead, the study found, these signals are mainly routed from the body to the inferior colliculus in the midbrain.
This is a very unexpected finding that challenges the canonical view of how and where tactile sensations are processed in the brain, according to study senior author and author, David Ginty, the Edward R. and Anne G. Lefler Professor of Neurobiology.
We discover that a region in the inferior colliculus of the midbrain processes vibrations, whether it is mechanical vibrations that travel through the inner ear or mechanical vibrations that travel through the skin. When auditory and mechanical vibration signals converge in this brain region, they amplify the sensory experience, making it more salient”.
Organisms from all parts of the animal kingdom are able to sense and react to subtle changes in their surroundings, such as sensing and avoiding threats, which is essential for survival.
For instance, snakes can sense a predator’s and prey movements by lowering their jaws to the ground to pick up subtle vibrations.
The ability to sense vibrations is also essential for the development and refinement of more intricate adaptations, such as the brain’s neural rewiring that occurs after one sensation is lost in order to enhance another, such as the more pronounced sense of hearing that emerges after losing vision.
The neural rewiring that occurs after losing one sense is deemed particularly relevant in this latter context, according to researchers. These understandings may help to develop prosthetics that improve people with hearing loss ‘ ability to feel tactilely.
” Devices that transduce sounds into tactile vibrations within the Pacinian frequency range could provide individuals with greater capacity to perceive and experience sound”, said Ginty, who is also a , Howard Hughes Medical Institute , investigator.
” To enable sound-evoked mechanical vibrations of different frequencies across the hands, arms, feet, legs, and body, such devices could be placed around the body and in close proximity to Pacinian neurons.”
Exquisitely sensitive detectors of vibrations
The results demonstrate how crucially important a somatosensory system component is Pacinian neurons. Their extraordinary sensitivity is attributed to their distinctive and elaborate structure. Even the smallest mechanical vibrations can be detected by it.
A single nerve ending in the center of each Pacinian corpuscle is housed within layers of supporting lamellar cells. The lamellar cell membranes ‘ onion-like layers function as shock absorbers, allowing the Pacinian corpuscle to respond to high-frequency vibrations precisely and quickly while reducing low-frequency disturbances.
” Evolution has placed these receptors in different locations across the animal kingdom to suit different environments”, said study lead author , Erica Huey, research fellow in the , Ginty Lab.  ,
” In humans, these receptors are located deep within the skin of the fingertips and feet, while elephants, for example, have a high concentration in their feet and trunks”.
In fact, research has demonstrated that elephants can sense minute seismic vibrations through the skin of their trunk and the pads of their feet. However,  , until recently, scientists haven’t been able to record the activity of Pacinian neurons in an awake, freely moving animal, making it challenging to get the full picture of how sensitive these neurons truly are and what stimuli trigger their activation.
Prior research led by Josef Turecek, a postdoctoral researcher at the Ginty Lab, demonstrated that Pacinian neurons can detect mechanical vibrations as subtle as those produced by a finger moving across a surface even from meters away.
The new study builds on previous research to understand how the brain processes and transmits signals from Pacinian corpuscles. Using a mechanical stimulator, the researchers recorded the activity of neurons in brain regions involved in sensory processing while simultaneously applying mechanical vibrations at varying frequencies to the limbs of mice or the platform they were standing on.
The researchers found that neurons in the ventral posterolateral nucleus of the thalamus (VPL), a relay station for sensory information before it enters the somatosensory cortex, were more sensitive to low-frequency vibrations when they compared the responses of neurons located in two distinct brain regions. In contrast, neurons in the lateral cortex of the inferior colliculus responded preferentially to high-frequency vibrations.
The team studied genetically modified mice that lack either the Pacinian corpuscles or the Meissner corpuscles to examine the relationship between the two brain regions ‘ responses to high- and low-frequency vibrations.
In mice lacking Pacinian corpuscles, inferior colliculus neurons showed a marked decrease in their response to high-frequency vibrations, which suggests that this region’s neurons are involved in the transmission of high-frequency vibrations.
When the researchers subjected the mice to white noise rather than mechanical vibrations, they observed neurons in the inferior colliculus also responding, suggesting that this region processes both auditory and somatosensory stimuli.
” In fact, we observed that neurons in the inferior colliculus responded more strongly to combined tactile-auditory stimulation than to either one alone,” said Ginty.
According to Ginty, this fusion of sound and touch in the inferior colliculus of the midbrain helps explain how we can both perceive and feel the music at a concert, making the experience more profound.
From an evolutionary standpoint, this phenomenon is likely essential for survival, and knowing more about it can help develop treatments for conditions like autism and chronic neuropathy, where dysfunction leads to hypersensitivity to touch.
In upcoming studies, the researchers are also interested in finding out whether these findings reveal a link between the brain’s capacity for adaptation, and whether this includes studying whether organisms become more sensitive to vibration sensing as a compensatory mechanism for hearing loss.
Authorship, funding, disclosures
Additional authors include Josef Turecek, Michelle M. Delisle, Ofer Mazor, Gabriel E. Romero, Malvika Dua, Zoe K. Sarafis, Alexis Hobble, Kevin T. Booth, Lisa V. Goodrich, and David P. Corey.
The work was supported by a HHMI Hannah Gray fellowship, NEI P30 Core Grant for Vision Research #EY012196, NIH grants F31 NS097344 and R35 5R35NS097344-05, the Edward R. and , Anne G. Lefler Center for Neurodegenerative Disorders, and the , Hock E. Tan and K. Lisa Yang Center for Autism Research.
About this news about sensory neuroscience research
Author: Ekaterina Pesheva
Source: Harvard
Contact: Ekaterina Pesheva – Harvard
Image: The image is credited to Neuroscience News
Original Research: Open access.
David Ginty and colleagues ‘” The auditory midbrain is responsible for sensing tactile vibration..” Cell
Abstract
The auditory midbrain is responsible for sensing tactile vibration.
Vibrations are ubiquitous in nature, shaping behavior across the animal kingdom. Mechanical vibrations that occur in mammals are detected by mechanoreceptors in the skin and deep tissues and processed by the somatosensory system, while sound waves that travel through air are captured by the cochlea and encoded in the auditory system.
Here, we report that mechanical vibrations detected by the body’s Pacinian corpuscle neurons, which are distinguished by their ability to entrain to high-frequency ( 40–1, 000 , Hz ) environmental vibrations, are prominently encoded by neurons in the lateral cortex of the inferior colliculus (LCIC ) of the midbrain.
Most LCIC neurons, however, respond more strongly to coincident tactile-auditory stimulation and receive convergent Pacinian and auditory input than to either modality alone.
Moreover, the LCIC is required for behavioral responses to high-frequency mechanical vibrations. Thus, the auditory midbrain is used to mediate behavior by capturing environmental vibrations that Pacinian corpuscles have captured.
