Dynamics of Brains Showing Adaptability and Stability
In the realm of neural wonders, adaptation is the star performer. Neuroscience investigator Mark Harnett of MIT's McGovern Institute for Brain Research explains, "Brains have learned to navigate the landscape of balancing between stability and flexibility, so you can learn new stuff and still have long-term memories." In the August 27 issue of Cell Reports, Harnett's research team sheds light on how individual neurons achieve this vital duality.
By studying pyramidal neurons in the brain's sensory cortex, they uncover that stability and adaptability coexist in these cells. When a young animal is absorbing visual information, most synapses are highly adaptable, ready to modulate their strength. Yet, some of these synapses lose their flexibility when the animals are less than a month old, preserving a delicate equilibrium.
Postdoc Courtney Yaeger soon discovered a group of remarkable, unusually stable synapses, clustered along a narrow region of the pyramidal cells. Meticulously tracing their connections revealed that they primarily received primary visual information from the dorsal lateral geniculate nucleus (dLGN) in the thalamus.
Examining these synapses further, Yaeger found several distinctions from other synapses on the same cells. For instance, when stimulating the apical oblique dendrite domain, each synapse responded equally, without any interaction with its neighbors. Furthermore, limited presence of a certain neurotransmitter receptor, the NMDA receptor, was another striking difference. These discoveries initially puzzled the team, as NMDA receptors are generally known for their key role in learning and memory.
However, upon stimulating the apical oblique synapses, the team found that their strength did not change despite electrical stimulation—a direct consequence of the receptor scarcity. This stability makes sense, as these connections convey primary visual information that the brain learns to recognize fundamental features like shapes and lines.
As expected, these stable synapses do not undergo activity-dependent plasticity, a remarkable testament to their steadfastness. Yaeger asserts, "You don't want those to undergo plasticity. Imagine forgetting what a vertical line looks like while you're sleeping. That would be catastrophic."
By investigating this phenomenon in mice of various ages, the team determined that the stabilization of these synapses occurs around the time young mice open their eyes, thus relying on visual experiences to hardwire these essential visual feature recognitions.
The team's findings offer valuable insights into the brain's ability to balance stability and adaptability. Moreover, their research could inspire artificial intelligence developers to design more efficient neural networks that retain information while allowing flexible learning, a challenge currently encountered in AI systems called "catastrophic forgetting." Harnett's research team is now exploring potential solutions for this problem, drawing inspiration from the workings of real brains.
- The research, published in the August 27 issue of Cell Reports, delves into the learning process of individual neurons in the brain's sensory cortex.
- In their study, Harnett's research team found that some synapses in pyramidal cells exhibit a unique stability, which helps maintain a delicate equilibrium between learning new information and retaining long-term memories.
- This discovery in the field of neuroscience has potential implications for education-and-self-development and health-and-wellness, as it sheds light on the mental mechanisms that enable learning.
- The team's findings could contribute to the development of more efficient artificial intelligence systems, addressing the challenge of retaining information while allowing flexible learning, a problem known as "catastrophic forgetting."
