Understanding Long-term Memory
Long term memory is the brain’s ability to store and retrieve information over extended periods, from days to an entire lifetime. It includes memories for facts and events, learned skills, personal experiences, and the knowledge that shapes who we are.
But long term memory is not a single system. It involves multiple brain regions working together, different types of memory serving different purposes, and a process of consolidation that can be strengthened or disrupted. Understanding how it works has practical implications for learning, for managing cognitive challenges, and for anyone who wants to remember more of what matters.
Dr Sarah Rudebeck, senior clinical neuropsychologist and Recallify co-founder, completed her PhD in memory disorders and amnesia at Oxford University. The information below reflects current understanding in cognitive neuroscience and clinical practice.
How Long Term Memory Works
Scientists describe long term memory formation in three stages: encoding, storage, and retrieval. Problems at any stage can affect how well we remember.
Encoding
Encoding is the process of converting sensory information into a form the brain can store. Not everything we experience gets encoded. Attention plays a critical role: if you are distracted or not actively engaged, information is far less likely to make it into long term memory.
Research by Fergus Craik and Robert Lockhart established that the depth at which we process information determines how well we remember it. Shallow processing (such as noticing how a word looks) produces weaker memories than deep processing (such as thinking about what a word means and how it connects to things you already know). This is known as the levels of processing framework, and it explains why simply re-reading notes is one of the least effective ways to learn, while actively engaging with material produces much stronger recall.
Storage
Once encoded, memories are not immediately stable. They go through a process called consolidation, during which the brain strengthens and reorganises the neural connections that represent the memory.
The hippocampus plays a central role in this process. It acts as a temporary holding area, binding together the different elements of an experience (what you saw, heard, felt, and thought) into a coherent memory. Over time, through a process that depends heavily on sleep, these memories are gradually transferred to the neocortex for long term storage.
This is one reason sleep is so important for memory. During deep sleep (slow wave sleep), the hippocampus replays recent experiences, strengthening the neural pathways that will form lasting memories. Research by Matthew Walker at UC Berkeley has shown that even one night of poor sleep can reduce the ability to form new long term memories by up to 40%.
Retrieval
Retrieval is the process of accessing stored memories when you need them. A memory may be stored perfectly well but still feel inaccessible if the right retrieval cue is not present. Familiar smells, sounds, locations, and emotional states can all act as cues that trigger recall.
This is also where active recall and spaced repetition become important. Each time you actively retrieve a memory rather than passively re-read it, you strengthen the retrieval pathway. A landmark study by Roediger and Karpicke (2006) found that students who practised retrieval remembered 50% more material a week later than students who simply reviewed their notes.
Types of Long Term Memory
Long term memory is not one single system. It divides into several distinct types, each serving a different function and relying on different brain structures.
Explicit (Declarative) Memory
Explicit memory is what most people think of when they think about “remembering.” It involves the conscious recall of facts and experiences, and it depends heavily on the hippocampus.
Episodic memory stores personal experiences and events. Your memory of what you had for dinner last night, your first day at a new job, or a conversation with a friend are all episodic memories. They are tied to a specific time and place.
Semantic memory stores general knowledge and facts that are not tied to a particular experience. Knowing that London is the capital of the UK, that water boils at 100°C, or what the word “hippocampus” means are all semantic memories. Over time, episodic memories can become semantic: you may remember that Paris is in France without remembering the specific moment you learned it.
Implicit (Non-Declarative) Memory
Implicit memory operates without conscious awareness. You do not need to deliberately “remember” how to ride a bike, type on a keyboard, or walk. These are stored as procedural memories and are primarily managed by the cerebellum and basal ganglia rather than the hippocampus.
This distinction matters clinically. People with hippocampal damage (for example, after certain types of brain injury or in early stage dementia) may lose the ability to form new episodic memories while retaining their procedural skills. This is why someone with mild cognitive impairment might struggle to remember a recent conversation but still be able to drive, cook, or play a musical instrument.
Short Term Memory vs Long Term Memory
These two systems are often confused, but they work quite differently.
Short term memory (also called working memory) holds a small amount of information for a brief period, typically around 20 to 30 seconds unless actively maintained through rehearsal. Its capacity is limited, often cited as roughly 7 items (plus or minus 2), based on George Miller’s classic 1956 research.
Long term memory, by contrast, has effectively unlimited capacity and can store information for a lifetime. The transfer from short term to long term memory depends on consolidation, which in turn depends on attention, repetition, emotional significance, and sleep.
For people with conditions that affect working memory, such as ADHD or acquired brain injury, the challenge is often getting information into long term memory in the first place. External tools that capture information in the moment, such as voice recordings, transcriptions, and automatic summaries, can bridge this gap by reducing the load on working memory. This is one of the core principles behind memory support tools.
When Long Term Memory Is Affected
Long term memory can be disrupted by a wide range of conditions:
Acquired brain injury (stroke, traumatic brain injury, brain tumour, brain infection) can damage the hippocampus or the connections between brain regions involved in memory. The specific pattern of memory difficulty depends on which areas are affected. Read about how Recallify supports people navigating the challenges of acquired brain injury.
Neurological conditions such as multiple sclerosis, Parkinson’s disease, and epilepsy can affect memory through damage to neural pathways, cognitive fatigue, or medication side effects.
Mild cognitive impairment (MCI) and early stage dementia involve a gradual decline in the ability to form and retrieve long term memories. Understanding MCI is an important step in seeking support early.
ADHD primarily affects working memory and attention, which in turn makes encoding into long term memory less reliable. It is not that long term memory itself is damaged, but that information is less likely to be encoded in the first place due to attentional difficulties. Practical ADHD strategies can help.
Normal ageing brings gradual changes in memory, particularly for episodic memory (remembering specific events) and for the speed of retrieval. Semantic memory and procedural memory tend to be well preserved into older age.
How to Strengthen Long Term Memory
The most effective approaches are those supported by research in cognitive psychology and neuroscience.
Retrieval practice (active recall): Testing yourself on material is significantly more effective than re-reading or highlighting. Each act of retrieval strengthens the memory trace. This is one of the most robustly supported findings in memory research. Learn more about active recall and spaced repetition.
Spaced repetition: Reviewing information at increasing intervals (for example, after one day, then three days, then a week) produces much stronger long term retention than massed practice (cramming). The spacing effect was first described by Hermann Ebbinghaus in 1885 and has been replicated consistently since.
Sleep: As described above, sleep is essential for memory consolidation. Prioritising consistent, adequate sleep is one of the simplest ways to support long term memory.
Elaborative encoding: Connecting new information to things you already know produces deeper encoding and stronger memories. Asking “how does this relate to what I already know?” while learning is a practical way to apply this.
Reducing cognitive load: When working memory is overloaded, encoding suffers. Breaking information into smaller pieces, using external aids (notes, recordings, summaries), and reducing distractions during learning all help. For people with cognitive challenges, tools like Recallify can capture information in the moment through voice recording and AI transcription, so that nothing is lost even when attention or energy is limited.
Conclusion
Long term memory is a dynamic and complex process involving multiple brain regions and mechanisms. Understanding how it works can help us adopt practices that enhance our ability to remember and learn. By taking care of our brain through healthy habits, we can improve our long-term memory and overall cognitive health. In particular, knowing about long-term memory brain mechanisms can help us make sense of why some memories stay vivid for decades while others fade more quickly.
iOS App
Get Recallify from the App Store to boost your memory, learning, and task management.
Android App
Get Recallify from Google Play to boost your memory, learning, and task management.
Frequently Asked Questions
What is long term memory?
Long term memory is the brain’s system for storing information over extended periods, from days to a lifetime. It includes memories for facts, personal experiences, and learned skills.
How does long term memory work?
It works through three stages: encoding (taking information in), storage (consolidating and maintaining it, primarily through the hippocampus and neocortex), and retrieval (accessing it when needed).
How long does long term memory last?
There is no fixed limit. Some long term memories, particularly those with strong emotional associations or those that have been retrieved repeatedly, can last a lifetime. Others may fade if they are not revisited or reinforced.
What is the difference between short term and long term memory?
Short term memory holds small amounts of information for seconds to minutes. Long term memory stores information indefinitely with effectively unlimited capacity. The transfer between the two depends on consolidation, which requires attention, repetition, and sleep.
How can I improve my long term memory?
The strategies with the strongest evidence are retrieval practice (testing yourself rather than re-reading), spaced repetition (reviewing at increasing intervals), adequate sleep, and elaborative encoding (connecting new information to existing knowledge). Active recall and spaced repetition are particularly well supported by research.
Can long term memory be affected by brain injury or neurological conditions?
Yes. Conditions such as acquired brain injury, MS, epilepsy, MCI, and dementia can all affect different aspects of long term memory. The specific pattern depends on which brain regions are involved. Recallify’s memory support tools are designed to help people manage these challenges in daily life.