Optogenetics switches off brain circuit of mice to study touch perception

May 26, 2015
Manipulating a two-stage brain circuit with light-driven optogenetic tools made laboratory mice "lose touch" with their surroundings.

Research at the RIKEN Brain Science Institute (Wako City, Japan) suggests that the apparent simplicity of tactile sensation comes from a clever two-stage brain circuit. By manipulating this circuit with light-driven optogenetic tools, the researchers made laboratory mice "lose touch" with their surroundings as their feet became unable to sense rough or smooth surfaces.

The study shows that the perception of touch relies on two signals, one from the skin to the brain and another within the brain itself. This second signal relays the first signal from a lower-level brain area to a higher one and then boomerangs it back to the lower level. The higher brain area is required for touch perception and its inactivation renders mice unable to use sensations in their footpads to discriminate different floor textures.

The research team, led by Dr. Masanori Murayama, observed the brains of mice after touching their paws and saw immediate activity in the sensory cortex—the brain area that receives signals from the skin. Unexpectedly, they recorded a second slower source of activity tens of milliseconds after the first.

"We investigated the source of this second activation and found that high-level motor cortex receives information from the sensory cortex and sends it back to the sensory cortex," Murayama explains. "This means that, for tactile perception, the flow of information from the skin to brain requires communication not only from the periphery to the brain, but also reverberation between two brain areas."

Mice were trained to distinguish rough and smooth surfaces with their feet. After temporarily switching off a second-order brain circuit with LED light, mice could no longer perceive the tactile information reaching their brains. (Credit: RIKEN)

While it was previously thought that one signal from the skin to the brain was sufficient to produce touch sensation, this study reveals that without the second signal, mice cannot feel or use the incoming sensory information, suggesting that they may not even perceive differences in texture. To investigate this idea, the researchers trained mice to distinguish two different floor textures, rough or smooth, by associating one of them with a food reward. When they prevented the second signal by shutting off the responsible neurons with light-activated optogenetics, the mice could not distinguish differences in floor texture.

"Our results show that a reverberant neural circuit from sensory cortex to higher motor cortex is required for the perception of touch," says lead researcher Satoshi Manita.

Murayama speculates that this two-stage circuit design may be a safety mechanism to ensure continuous accurate perception even when distracted by other senses, such as when feeling a steering wheel while concentrating on the road. "This form of perception, an external signal and its internal rebound, may extend to other senses, and we may find that communication between brain areas refines perception for more accurate and integrated behavior," he concludes.

Full details of the work appear in the journal Neuron; for more information, please visit http://dx.doi.org/10.1016/j.neuron.2015.05.006.

Follow us on Twitter, 'like' us on Facebook, connect with us on Google+, and join our group on LinkedIn

Sponsored Recommendations

Brain Computer Interface (BCI) electrode manufacturing

Jan. 31, 2025
Learn how an industry-leading Brain Computer Interface Electrode (BCI) manufacturer used precision laser micromachining to produce high-density neural microelectrode arrays.

Electro-Optic Sensor and System Performance Verification with Motion Systems

Jan. 31, 2025
To learn how to use motion control equipment for electro-optic sensor testing, click here to read our whitepaper!

How nanopositioning helped achieve fusion ignition

Jan. 31, 2025
In December 2022, the Lawrence Livermore National Laboratory's National Ignition Facility (NIF) achieved fusion ignition. Learn how Aerotech nanopositioning contributed to this...

Nanometer Scale Industrial Automation for Optical Device Manufacturing

Jan. 31, 2025
In optical device manufacturing, choosing automation technologies at the R&D level that are also suitable for production environments is critical to bringing new devices to market...

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!