Summary: Neurons in the motor cortex of rats fall into two categories, those that are externally focused and relay information to other parts of the body, and those that are internally focused. When inhibition is increased, the externally focused neurons switch to internally focused cells.
Source: University of Arkansas
A study conducted by University of Arkansas researchers reveals that neurons in the motor cortex of the brain exhibit an unexpected division of labor, a finding that could help scientists understand how the brain controls the body and provide insight on certain neurological disorders.
The researchers studied the neurons in the motor cortex of rats and found that they fall into two groups: “externally focused” neurons that communicate with and control different parts of the body and “internally focused” neurons that only communicate with each other and don’t send signals to other parts of the body. The researchers also found that when they increased inhibition of neurons in the motor cortex, the externally focused neurons switched to internally focused.
“Alterations in inhibitory signaling are implicated in numerous brain disorders,” explained Woodrow Shew, associate professor of physics.
“When we increased inhibition in the motor cortex, those neurons responsible for controlling the body become more internally oriented. This means that the signals that are sent to the muscles from the motor cortex might be corrupted by the ‘messy’ internal signals that are normally not present.”
Rett Syndrome, a rare but severe neurological disorder, is one of the brain disorders associated with an increase in inhibition. Shew plans to further research the implications of these findings for Rett Syndrome.
Shew, along with U of A graduate students Patrick Kells, Leila Fakhraei and Jingwen Li and postdoctoral researcher Shree Hair Gautam, published their results in Nature Communications.
University of Arkansas
Woodrow Shew – University of Arkansas
The image is credited to University Relations.
Original Research: Open access.
“Strong neuron-to-body coupling implies weak neuron-to-neuron coupling in motor cortex”
Patrick A. Kells, Shree Hari Gautam, Leila Fakhraei, Jingwen Li & Woodrow L. Shew. Nature Communications volume 10, Article number: 1575 (2019)5. doi:10.1038/s41467-019-09478-2
Strong neuron-to-body coupling implies weak neuron-to-neuron coupling in motor cortex
Cortical neurons can be strongly or weakly coupled to the network in which they are embedded, firing in sync with the majority or firing independently. Both these scenarios have potential computational advantages in motor cortex. Commands to the body might be more robustly conveyed by a strongly coupled population, whereas a motor code with greater information capacity could be implemented by neurons that fire more independently. Which of these scenarios prevails? Here we measure neuron-to-body coupling and neuron-to-population coupling for neurons in motor cortex of freely moving rats. We find that neurons with high and low population coupling coexist, and that population coupling was tunable by manipulating inhibitory signaling. Importantly, neurons with different population coupling tend to serve different functional roles. Those with strong population coupling are not involved with body movement. In contrast, neurons with high neuron-to-body coupling are weakly coupled to other neurons in the cortical population.