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Secrets of learning revealed: How our brains make and retrieve memories

A recent study led by Dr. Tomás Ryan from Trinity College Dublin and his team of neuroscientists has uncovered new insights into the brain’s learning mechanisms. The study, published in the journal Current Biology, reveals that learning involves the formation of new connectivity patterns between specific engram cells in various brain regions.

Our brains are constantly adapting and changing, incorporating new information from our daily experiences. This continuous process of learning and memory formation has long intrigued scientists. 

Memory engram cells 

Dr. Ryan’s research focuses on understanding how these experiences modify our neurons, allowing us to create new memories. The key to this process lies in identifying the ‘engram,’ which is the change in the brain that stores a memory.

“Memory engram cells are groups of brain cells that, activated by specific experiences, change themselves to incorporate and thereby hold information in our brain,” explained lead author Clara Ortega-de San Luis, a Postdoctoral Research Fellow in the Ryan Lab. 

“Reactivation of these ‘building blocks’ of memories triggers the recall of the specific experiences associated with them. The question is, how do engrams store meaningful information about the world?”

Focus of the study

To explore this question, the researchers employed a learning paradigm in which animals learned to identify and associate different contexts that are similar to each other. 

The experts utilized genetic techniques to label two distinct populations of engram cells in the brain for two discrete memories. They then monitored the formation of new connections between these engram cells as learning occurred.

Optogenetics, a technique that controls brain cell activity with light, was used to demonstrate the necessity of these newly formed connections for learning. 

New insights into learning

The study identified a molecular mechanism involving a specific protein in the synapse that regulates the connectivity between engram cells.

This research provides direct evidence that changes in synaptic wiring connectivity between engram cells are a likely mechanism for memory storage in the brain.

Study significance 

Commenting on the significance of these findings, Dr. Ryan said: “Understanding the cellular mechanisms that allow learning to occur helps us to comprehend not only how we form new memories or modify those pre-existent ones but also advance our knowledge towards disentangling how the brain works and the mechanisms needed for it to process thoughts and information.”

“In 21st-century neuroscience, many of us like to think memories are being stored in engram cells, or their sub-components. This study argues that rather than looking for information within or at cells, we should search for information between cells, and that learning may work by altering the wiring diagram of the brain – less like a computer and more like a developing sculpture. In other words, the engram is not in the cell; the cell is in the engram,” he concluded.

Learning, memory and engram cells

Engram cells, as discussed previously, are often referred to as memory traces. They are a fundamental concept in understanding how the brain encodes, stores, and retrieves memories.

Scientists identify these cells as the physical embodiment of memories within the brain’s neural network. When we learn something new, specific patterns of brain activity occur, leading to changes in certain neurons, which become engram cells.

Formation of engram cells

The formation of engram cells begins with learning or experiencing something new. This process, known as encoding, involves various brain regions, particularly the hippocampus for declarative memories and the amygdala for emotional memories.

During encoding, synaptic connections between neurons strengthen, making these neurons more likely to fire together in the future. This phenomenon, based on the principle “neurons that fire together, wire together,” underlies the formation of engram cells.

Engram cells and memory storage

Once formed, engram cells play a crucial role in memory storage and recall. They represent the physical and chemical changes in the brain that correspond to a specific memory. When we try to recall a memory, the brain reactivates the same pattern of neural activity that was present during the encoding of the memory, effectively ‘lighting up’ the engram cells associated with that memory.

Engram cells and learning

Learning involves the continuous formation and reformation of engram cells. Each new piece of information or skill we acquire results in the creation of new engram cells or the modification of existing ones. This dynamic nature of engram cells is key to their role in learning. They are not static but rather adapt and change as we continue to learn and as our memories evolve over time.

In summary, engram cells are at the heart of the learning process and memory formation. They represent the brain’s remarkable ability to encode, store, and recall vast amounts of information. Understanding how engram cells work not only unravels the mysteries of memory but also opens up potential avenues for treating memory-related disorders.

Learning, memory and sleep

Sleep is another crucial component in both learning and memory. This relationship that has been extensively researched and documented in various scientific studies.

Active role of sleep in learning

Enhancing Cognitive Abilities: Sleep actively improves cognitive abilities essential for learning. It boosts attention and focus, enabling more efficient processing and absorption of new information. By refreshing the mind, sleep prepares individuals for new learning experiences.

Facilitating Memory Consolidation: One of the most crucial functions of sleep in learning is memory consolidation. During sleep, the brain actively transfers new information from short-term to long-term memory, a process essential for learning retention.

How different sleep stages aid memory

REM Sleep: This stage is pivotal for consolidating declarative memories, like facts and figures. Here, the brain actively integrates new information with existing knowledge, enhancing understanding and recall.

Non-REM Sleep: The deeper stages of non-REM sleep are vital for procedural memory, involving skills and tasks. This stage strengthens neural connections, solidifying new skills learned during the day.

Sleep’s role in synaptic plasticity

Synaptic plasticity, the brain’s ability to strengthen or weaken synaptic connections, is vital for learning and memory. Sleep actively fosters this plasticity, allowing the brain to reorganize and optimize neural pathways based on new experiences and learnings.

Impact of sleep deprivation

Sleep deprivation actively hampers learning and memory. It impairs the brain’s ability to focus, process information, and engage in the critical process of memory consolidation. Chronic lack of sleep can lead to long-term deficits in learning and memory retention.

Using sleep to enhance learning and memory

Maintain Regular Sleep Patterns: Consistent sleep schedules support the brain’s natural rhythms, enhancing learning and memory processes.

Create a Conducive Sleep Environment: A comfortable, distraction-free sleep environment actively promotes deeper, more restorative sleep.

Prioritize Sleep Hygiene: Practices like limiting caffeine and screen time before bed can significantly improve sleep quality, directly benefiting learning and memory.

In summary, the active involvement of sleep in learning and memory is undeniable. By facilitating memory consolidation, enhancing cognitive functions, and supporting synaptic plasticity, sleep proves to be a cornerstone of effective learning and robust memory. Recognizing and prioritizing sleep is, therefore, essential for anyone looking to maximize their learning potential and cognitive health.


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