Understanding How Your Brain Forms New Memories: Neuroscientists Reveal Underlying 'Rules' for Neuronal Encoding

Every day, our brains are engaged in the remarkable task of learning and memory formation. From taking up a new hobby, trying out a recipe, to staying updated with global news, our brains are constantly storing new information that can last for years or even decades. But how does this process of memory encoding actually work?

Recent research published in the journal Science sheds light on some of the fundamental 'rules' that govern how neurons learn and encode new experiences. The human brain is composed of billions of nerve cells, or neurons, which communicate via electrical pulses. These electrical signals travel across connections called synapses, where neurons are linked. Each neuron can receive thousands of inputs through dendrites—branching extensions—integrating this information in the neuron's main body, ultimately generating electrical signals that represent various pieces of information.

Historically, neuroscientists believed that learning and memory were primarily driven by changes in synaptic strength — a process called synaptic plasticity. As we encounter new information, specific synaptic connections are reinforced or weakened, creating neural representations that encode our experiences. However, a key question remains: what rules determine which synapses change during learning?

To explore this, scientists monitored the activity of individual synapses in mice engaged in a learning task—pressing a lever after hearing a sound to obtain water. They genetically encoded biosensors into the neurons, allowing real-time observation of synaptic activity. Interestingly, they found that not all synapses on the same neuron follow identical learning rules. Some synapses adhered to the classic Hebbian principle—'fire together, wire together'—where simultaneous activity strengthens connections. Others, however, behaved differently, with their synaptic changes being independent of the neuron's overall activity.

This discovery suggests that neurons utilize multiple learning strategies simultaneously, applying different rules to different sets of synapses. Such a multi-rule approach allows neurons to fine-tune the various inputs they receive, enhancing their capacity to encode complex information more efficiently. It also enables neurons to perform multiple functions in parallel, broadening our understanding of neural plasticity.

Understanding these diverse synaptic rules has profound implications. Since many brain disorders, including neurodegenerative and psychiatric conditions, involve dysfunctional synapses, insights into normal synaptic plasticity could inform new treatment approaches. For instance, conditions like depression, which may involve weakened synaptic connections, could benefit from therapies targeting synaptic strengthening mechanisms.

Furthermore, the findings have potential impacts on artificial intelligence. Current AI models, inspired by the brain, use uniform learning rules that lack biological plausibility. Incorporating multiple learning principles, as observed in the brain, could lead to more realistic and efficient neural network algorithms.

While these discoveries open exciting avenues, there remains much to explore. Scientists are still unraveling why neurons employ different rules at various synapses and how this diversity enhances brain function. Continued research aims to deepen our understanding of these processes, ultimately paving the way for innovative therapies and smarter AI systems.

This ongoing research provides critical insights into the fundamental mechanisms of learning and memory, highlighting the incredible adaptability of the brain.