What if everything you’ve ever experienced –– from that first cup of coffee in the morning to your greatest achievement –– was stuck in your head forever? Although not all of our memories are retained indefinitely, learning and memory allow us to hold on to the experiences that shape who we are. 

Learning and remembering may feel like second nature to us, but below the surface, our brains are working overtime to keep information available. They generate, store, and retrieve information through a network of neurons — nerve cells that allow electrical signals to be relayed to different parts of your body and specialized regions in the brain. From quick facts to deeply ingrained habits, learning is a complex process.

Forming and storing memories

Memory formation and retention involve multiple processes that help us encode, store, and retrieve information. The hippocampus, a seahorse-shaped structure near the base of your brain, plays a key role in forming new memories by reinforcing short-term experiences into long-term memories. 

Long-term memories are formed through the constant reactivation and strengthening of the neural connections associated with original experiences. When you learn, your brain forms connections between neurons, which grow stronger with repetition and practice. This ability, called neuroplasticity, allows the brain to reorganize itself in response to new information, demonstrating why repeated engagement helps us remember certain facts and processes over time.

Some of these memories stay with us in long-term memory, which, as the name suggests, is where information is stored for a long time, perhaps a lifetime. These memories include moments like how to ride a bike or the joy associated with a favourite song. 

However, not all memories are built to last. Short-term memory, often called working memory, assists us in holding and managing a small amount of information, like a series of numbers in a math problem or a stranger’s name, for short periods of time. 

Information stored in the working memory fades rapidly unless it is actively maintained by the prefrontal cortex, the anterior part of the brain responsible for thinking, planning, making decisions, and controlling behaviour. The way the hippocampus decides what to retain in long-term memory is influenced by attention, emotional significance, and repetition. 

The concept of memory consolidation, first proposed by the German psychologist Georg Elias Müller and his student Alfons Pilzecker in 1900, is the process by which temporary, labile information transfers from short-term to a more permanent long-term memory. 

This is where sleep plays a crucial role. As studies have shown, during deep sleep, the brain consolidates memories by strengthening connections between brain cells, where messages are passed using chemical signals. It also replays recent events, helping to solidify memories so they become more deeply embedded in memory and easier to recall. In essence, short-term and long-term memory work hand-in-hand, allowing us to retain vital information and recall it when we need it most.

Interestingly, emotions are an important aspect of the learning and memory process. In a 2007 Mind, Brain, and Education paper, researchers Mary Helen Immordino-Yang and Antonio Damasio asserted that emotions aren’t separate from thinking; rather, they’re highly correlated with the way we learn and remember. 

When something triggers strong emotions, be it happiness or fear, the emotional centre of the brain, called the amygdala, enhances hippocampus activity. This partnership causes emotional experiences to last longer in our memory compared to other everyday, emotionally insignificant moments.

From theory to practice

Understanding the processes of memory and learning has far-reaching applications in many different fields. For instance, in medicine, there is strong evidence that drugs like nucleoside reverse transcriptase inhibitors (NRTIs) –– used to treat HIV by blocking viral replication –– can reduce the risk of Alzheimer’s disease. 

One side effect of NRTIs is that they inhibit receptors that are involved in pathological brain inflammation. This type of inflammation is linked with memory loss and learning disabilities, so by suppressing these inflammatory effects, NRTIs could potentially avert harm to the brain’s ability to retain and develop long-term memories. 

Dr. Reina Bendayan of the Leslie Dan Faculty of Pharmacy at U of T has conducted extensive research on the potential of antiretroviral drugs –– medications used to treat infections caused by retroviruses, particularly HIV –– like NRTIs to cross the blood-brain barrier and influence the central nervous system. The blood-brain barrier is a selectively permeable membrane of tightly attached cells that regulate the exchange of substances to maintain the stable environment of the central nervous system. The barrier permits essential nutrients into the brain and keeps out toxins and pathogens. 

Dr. Bendayan’s work provides critical details on how antiretroviral drugs could potentially influence neuroinflammation as well as cognitive impairments, and thus become potential medicines to treat memory-related illnesses like Alzheimer’s.

The human memory system is also shaping the design of artificial intelligence (AI). Among the researchers contributing to this field is Dr. Blake Richards, who holds a Bachelor of Science in Cognitive Science and AI from U of T. He is working on developing AI systems inspired by human learning mechanisms, such as memory consolidation while sleeping. 

These researchers seek to address problems like “catastrophic forgetting,” where AI systems eventually forget previously acquired knowledge when learning new information. Simulation of human memory in AI systems helps address the issue of catastrophic forgetting by imitating how the brain preserves and recalls information over time without overriding previous knowledge. By modelling AI systems on the working memory of the human brain, scientists aim to develop machines with self-learning and reasoning capabilities, linking human and machine intelligence. 

As researchers uncover the mechanisms behind learning and memory, new possibilities open for treating cognitive disorders and enhancing educational practices. Through neuroplasticity, our brains continuously modify neural connections based on new knowledge and experiences, forming the neurological basis of our identity. This neuroplastic capability facilitates cognitive development, learning acquisition, and adaptive responses to environmental demands.