Scientists from Fujita Health University have conducted a study that challenges the traditional view of how the brain processes sensory information during movement. It has long been believed that the primary motor cortex is responsible for modulating sensory experiences during movement. However, the researchers discovered that other regions beyond the primary motor cortex actually have a significant influence on the primary sensory cortex.
The human brain is widely regarded as the most complex organ in the body, and understanding how it processes sensory information and how this information interacts with motor control has been a topic of interest for neuroscientists for over a century. Fortunately, advanced laboratory tools and techniques now allow researchers to use animal models, like mice, to investigate these complex mechanisms.
Previous studies conducted on anesthetized mice in the 20th century suggested that sensory inputs primarily define neuronal activity in the primary sensory cortices. However, more recent studies involving awake mice have revealed that spontaneous behaviors, such as exploratory motion and whisking, actually regulate the activity of sensory responses in the primary sensory cortices. In other words, body movements significantly impact sensations at the neuronal level, but the underlying mechanisms are not fully understood.
To bridge this knowledge gap, a research team from Japan focused on investigating the primary somatosensory barrel cortex (S1), which is responsible for processing tactile input from the whiskers in mice. Led by Professor Takayuki Yamashita from Fujita Health University and Dr. Masahiro Kawatani from Nagoya University, the researchers conducted a study published in The Journal of Neuroscience.
The S1 region receives input from several other areas, including the secondary somatosensory cortex (S2), the primary motor cortex (M1), and the sensory thalamus (TLM). To understand how these regions modulate activity in S1, the researchers used optogenetics, a technique that controls the activities of specific neuronal populations using light. They introduced a light-sensitive protein called eOPN3 into the M1, S2, and TLM regions of the mice.
By selectively inhibiting different signal inputs going to S1 using light, the researchers observed the effect on neuronal activity in S1 while the mice performed spontaneous whisking. Surprisingly, they found that only signal inputs from S2 and TLM to S1, not from M1 to S1, modulated neuronal activity during whisking. The pathway from S2 to S1 appeared to convey information about the motion state of the whiskers, while the TLM-to-S1 pathway relayed information related to the phase of spontaneous whisking.
These findings challenge the conventional understanding that neuronal activity in sensory cortices is primarily modulated by motor cortices during movement. According to Professor Yamashita, these results provoke a reconsideration of the role of motor-sensory projections in sensorimotor integration and reveal a new function for S2-to-S1 projections.
Understanding how different brain regions modulate activities in response to movement could have significant implications in various fields. This research could potentially revolutionize areas such as artificial intelligence, prosthetics, and brain-computer interfaces. By gaining a better understanding of these neural mechanisms, it may be possible to develop AI systems that mimic human sensory-motor integration and create more intuitive prosthetics and interfaces for individuals with disabilities.
In conclusion, this study provides new insights into the complex workings of the brain and opens avenues for further research on the connection between body motion and sensory perception. As scientists continue to unravel the mysteries of the human brain, studies like this offer crucial clues in the quest to understand this intricate organ.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
