Peak performance is not limited to our bodies. Our brains possess an incredible cognitive capacity to learn, grow, and drive us to our goals. Like many other consequences of the aging process, this capacity diminishes with age, especially our ability to hold on to new information and maintain optimal memory function.
Can we beat these effects of aging on the brain, especially preserving aspects of memory?
Clinical research says yes.
Studies suggest that the probiotics strains L. paracasei PS23™ and B. breve MCC1274™ in Neuralli Cognition+ can support cognitive health and improve short-term memory in aging healthy adults in clinical studies.
Healthy aging and memory
Aging does not have to mean an inevitable loss of brain function and memory. Your brain can be healthier and sharper than someone years younger. With intentional lifestyle choices and strategies centered around optimizing your brain health, memory loss and cognitive impairment do not have to be equated with getting older. Sleep, diet, stress management, a healthy social life, and exercise all have been shown in studies to benefit brain health. Certain probiotic strains have also been shown to support cognitive health and memory. This includes B. breve MCC1274, a probiotic strain in Neuralli Cognition+ found to improve short-term memory in older individuals.
MCC1274 supports memory and cognitive health in aging
Backed by four clinical trials, Bifidobacterium breve MCC1274 stands out as significantly supporting cognitive and memory function in healthy older adults. Across all four studies, people who took MCC1274 reported improvements in cognitive scores as compared to placebo.
In one randomized placebo-controlled study, researchers investigated whether the probiotic B. breve MCC1274 could support cognitive health in older adults who were experiencing problems with their memory. Participants taking MCC1274 demonstrated significant improvements in three aspects of cognition: immediate memory (a type of short-term memory), delayed memory, and visuospatial/construction ability. These results suggest that B. breve MCC1274 may help support short-term memory and cognitive function in healthy older adults.
But, what is memory exactly?
A simple definition of memory is the ability to store and retrieve previously learned information over time. On a grander scale, memory is an essential component of life that allows us to make sense of our lives. Without it, we would not be able to interact with our environment and connect life experiences that define who we are.
We know that some details, like a stranger’s name we just learned, fade from our memory in seconds. Others hang around much longer, like the name of your high school mascot or the fact that Paris is the capital of France. Then, there are the memories and skills that last a lifetime. Think of your first kiss or how you never forget how to ride a bike. These memories are not a simple reflection of a single piece of information learned a long time ago - but a rich landscape of knowledge full of emotion and a sense of self.
Cognitive research has revealed that memory is far more complex than simple short-term or long-term stores. It consists of multiple neural processes and brain regions that work together to record, organize, and recall useful information in order to accomplish tasks and goals, consciously and unconsciously. And, ultimately, memory defines who we are.
Here we take a closer look at the science of memory to help grow our understanding of how to support memory and overall brain health as we age.
Memory unraveled
Memory remains a mystery despite being the subject of philosophical and scientific inquiry since antiquity. Plato’s “wax tablet” metaphor likened memory to an imprint on a block of wax located in the soul and was a gift from Mnemosyne, Greek divinity of memory. While great advances have been made since these ancient beginnings, the fascinating nature of human memory remains a central focus of ongoing neurobiological research.
Many questions remain unanswered. Nonetheless, decades of research have revealed key principles underlying the mechanisms of how memories are formed, stored, and recalled. Understanding these mechanisms provides important context for discussions about cognitive health and memory support.
How does memory work?
Memory is not a single phenomenon, but a complex and intricate network of neurologic tasks and connections formed between distinct regions of the brain. It can be compared to an orchestra that is made up of many instruments, with each making its own distinct sound and responsible for a different part of the score. Without memory, we would not be able to connect experiences, learn, or even make sense of our lives.
Our brains have multiple processes that work together to create and maintain memories. It involves several regions of the brain, including the medial temporal lobe (especially the hippocampus) and the amygdala (i.e., basolateral complex of the amygdala). At its basis, the creation of memory involves sets of neurons that become interconnected with other sets of neurons that create organized systems that serve to represent memory. These processes enable the brain to encode, store, and retrieve information, or memories.
Neuroscientists often regard the brain as the last frontier of the human body and are continually searching for answers to how it works. This includes the process of memory.
Because memory involves so many interconnected brain systems, scientists have developed various frameworks to help explain how information is processed and retained. These theories have shaped much of what we know about memory today.
Models of memory
German psychologist Hermann Ebbinghaus is accredited with pioneering the experimental study of memory. In 1885, Ebbinghaus published his “forgetting curve” research which uncovered the nature of the learning curve, or the idea that rehearsing and repeating information enhances the retention of said knowledge. Ebbinghaus was followed by psychologist William James, who proposed a dual-store model of memory in 1890 that consisted of a primary and secondary memory - the early equivalents of short-term/working memory and long-term memory.
Scientists have since come up with several theoretical frameworks, or models of memory, in order to explain how memory works. Here are three of the most significant models that are still in wide use in the literature.
Multi-store memory model
One common theory about memory assumes that there are three stores of memory through which information flows (sensory, short-term and long-term). This is known as the multi-store memory model, or the Atkinson-Shiffrin model (1968), and it is one the most well-known theories in the field (Figure 1).
The model categorizes memory into three structural components: the sensory register, the short-term store, and the long-term store. Raw sensory data or information first enters the sensory register where it is held very briefly and soon decays or is lost if a person doesn’t pay attention to it. The short-term store is defined by this model as the “working memory”, where information from both the sensory register and long-term store is manipulated to accomplish tasks. The long-term store holds the information transferred from the short-term store.
Whether information moves into the long-term store or is forgotten is determined by how that information is processed. To explain this, Atkinson and Shiffrin likened the brain to a computer that uses different control processes to govern information:
Attention
The act of attending or selectively focusing on incoming information or raw data briefly held in the sensory register while filtering out “noise” or irrelevant information in the background. Example: Your ears pick up the sound of a person announcing a delay and gate change for your flight in a crowded and noisy airport terminal.
Rehearsal
The conscious repeating or rehearsing of recently attended information that holds information in short-term stores so it is not forgotten. Example: You rehearse the gate letter and number in your head a few times as you walk to the new gate.
Encoding
The process by which the brain transforms raw sensory input into a construct or format that can be stored and retrieved as a memory from long-term memory stores. Example: You notice your new gate number is your lucky number and the first letter of your name. This association is encoded and moved into your long-term memory store.
Retrieval
The process of bringing back or retrieving information from long-term stores into short-term so it can be actively used. Example: On the way to the new gate, you stop for lunch for 30 minutes. As you pay the bill, you quickly remember the letter and number stored in your long-term memory and head to your gate.
The Atkinson-Shiffrin multi-store model is often called the “modal model” because the researchers elegantly described several prevailing ideas of their time into one information processing theory of human memory. Their ground-breaking theoretical framework of memory is regarded as one of the most influential developments in memory research.
Working memory model
While the multi-store model provided great insight into the structure of memory, it was seen by some researchers as an oversimplified description of short-term or working memory.
In 1974, British psychologists Alan Baddeley and Graham Hitch proposed a working memory model which elaborated on the concept of working memory described by Atkinson and Shiffrin. They argued that working memory is not simply a component of a short-term store, but a dynamic, multi-component system consisting of multiple subsystems that support storage and manipulation of information (Figure 2).
Components of the working memory model include the following:
- Phonological loop - the “inner ear” and “inner voice” of your working memory. The phonological loop is similar to the idea of rehearsal described in the Atkinson-Shiffrin model. You use this when you say things to yourself or recall what someone else said over and over again (in a loop) to help recall necessary information, like a phone number or address.
- Visuospatial sketch pad - enables you to picture things in your mind and work on them, like a mental map. You are drawing from your visuospatial sketchpad when you visualize the way back to your house during a long walk.
- Episodic buffer - acts as a go-between that temporarily stores and integrates information from all the components of working memory and long-term memory. When you give someone directions, your episodic buffer helps you to integrate the visual picture of the map, repeat verbal cues, and access your long-term memory to guide someone to a location.
- Central executive - the “command center” that oversees manipulation, recall, and processing information for meaningful functions like decision-making or problem-solving. It is like the boss of your working memory, acting to direct your attention, switch between tasks, and coordinate other mental systems.
While this model helped to describe the dynamics underlying the storage and manipulation of information to accomplish tasks, it did not fully explain why some pieces of information are permanently retained while others are forgotten. To address this limitation, researchers began looking beyond structural components to focus instead on the nature of cognitive analysis itself, leading to the development of the Levels of Processing model.
Levels of Processing model
Instead of separating memory into rigid storage boxes of sensory, short-term, and long-term systems like the X model, this model posits that the level of cognitive processing applied to incoming information determines how deeply it is encoded into memory. Its creators, Craik and Lockhart, theorized that how long someone holds onto a memory is determined by shallow to deep levels of processing (Figure 3).
To prove this, researchers Craik and Tulving (1975) conducted several experiments that involved questioning undergraduates about a series of long words. They theorized that when the students were asked to process the actual meaning of the words, their brains would build much stronger, longer-lasting memory traces. To test this, they would flash words on a screen and ask participants three types of questions:
- Structural: "Is the word in capital letters?" (Shallow)
- Phonetic: "Does the word rhyme with weight?" (Medium)
- Semantic: "Does the word fit into this sentence?" (Deep)
When tested later, participants overwhelmingly remembered the words that required semantic thinking. Craig and Tulving concluded that when the participants looked at the structure of a word (structural) or recognized rhyming patterns (phonetic processing), they were using shallow to medium processing because the information would quickly fade. And when the participants thought about what the word actually meant (semantic processing), they were using deep processing. Thus, how deeply a person thinks about and understands incoming information influences the length of time the memory remains.
These three memory models, among others that followed that built upon their theoretical frameworks, significantly advanced scientist's understanding of memory and how information is stored and processed by the brain. Despite these findings, no single model of memory has been able to truly capture the intricate complexity of human memory and this exploration continues to inspire ongoing research.
Modern memory models: Stages, types, and processes
While memory models were designed to explain how memory works, researchers also have worked to classify memory in ways that make it easier to study and describe. After more than a century of scientific inquiry in memory, the fields of neuroscience, psychology, and biology have yet to reach a consensus on a unified definition of memory.
And, perhaps there is no need. Each of these fields contributes complementary ideas about the categorization of memory. Now that scientists have access to technology that can literally see inside the brain and record the physical changes that occur with memory formation, newer memory models are focused on what is going on at the neurological level, as opposed to simply theoretical models.
These newer models of memory map directly to the physical structures of the brain, like the hippocampus and cortex, to explain how memory and learning changes structures in the brain. The most current research reveals that glial cells like astrocytes that were previously thought to be only support cells play a pivotal role in the processes of memory. These star-shaped cells form intricate and vast networks that significantly expand the brain’s storage capacity far beyond what neuronal synapses can manage all alone.
Some models emphasize the flow of information through memory systems using mathematical models, while others focus on the mental operations involved in learning and recall as seen in physical models. Together, these approaches have led scientists to categorize memory in three broad ways: by its stages (how long information is retained), by its types (what kind of information is stored), and by its processes (how information is encoded, stored, and retrieved).
|
As stages: How long do we retain information? |
Sensory memory Short-term memory (includes working memory) Long-term memory |
|
As types: What kind of information is stored? |
Explicit memory Implicit memory |
|
As processes: How is the information processed in the brain? |
Encoding Storage Retrieval |
Table 1: Conceptualization of memory in terms of stages, types, and processes.
Memory as stages: How long is information stored?
Earlier, we were introduced to the multi-store (Atkinson-Shiffrin) model of memory that describes memory as being processed in three stages. This view of memory helps us to answer the question: “How long do we retain information?”
Sensory memory
Also called the sensory register, this stage of memory is very brief and is often thought of as the first stage of memory. Sensory memory gives the brain time to process incoming information from our senses and perceptions. There are three types of sensory memory: iconic memory, echoic memory, and haptic memory.
Visual sensory memory, or iconic memory, is incredibly brief, lasting for 1/4th of a second - meaning you can hold visual information in your brain for about this long. Echoic memory is your auditory sensory memory and is held in your brain for quite a bit longer, up to four seconds. Echoic memory is why you are able to write down notes as you listen to a lecture, even after the speaker has stopped speaking. Haptic memory holds on to information acquired through touch. This memory explains why you may still feel the pressure and warmth of a person’s hand on yours briefly after the handshake ends.
Most of the information in your sensory memory is forgotten. You process things you pay attention to in your short-term memory.
Short-term memory
Short-term memory can be thought of as our brain’s version of a scratchpad used to temporarily recall a limited amount of information taken in via our senses. The chunks of information stored on this temporary scratchpad are held for a very short time, typically up to 30 seconds.
Short-term memory is used to recall images, numbers, or words in the immediate sense. If not processed into long-term memory, these bits of info are forgotten as short-term memory is a very limited and temporary storage space that cannot be manipulated.
The terms short-term memory and working memory are often used interchangeably. However, albeit related, they are distinct from each other. As opposed to a type of memory, working memory is more a theoretical framework that is made up of brain structures and processes used to store and temporarily manipulate information as seen in Baddeley and Hitch’s working memory model (Figure 2).
Long-term memory
Short-term memory and long-term memory can be distinguished from each other simply by storage capacity and duration. If short-term memory is a very temporary scratchpad, long-term memory can be considered your forever diary, offering endless pages to hold information. Its seemingly unlimited capacity allows us to hold and retrieve information from minutes to years, or even a lifetime, serving as a permanent storage house for experiences, knowledge, and skills.
And, like many of our diaries, it’s not simply a file folder, full of dry descriptions of past events or stores of knowledge. Instead, our long-term memories are often rich, multi-sensory experiences - where the smell of rain or a mother’s hug can instantly draw up a childhood memory in intricate detail. These complex experiences are stored as neural networks across different brain regions, including the amygdala, the brain’s emotional center.
Fundamentally, long-term memory is divided into two broad classes: explicit and implicit memory. It is in this classification that we see how theoretical and biological models work together to explain how memory works. We will explore both classes, along with their unique subtypes, in the next section.
Memory in terms of types: What information is stored?
In the 1960s, scientists discovered the molecular basis for memory formation - long-term potentiation. They found that when two neurons repetitively and simultaneously became activated, then the connection between them became strengthened. The newly discovered “cells that fire together, wire together” phenomenon formed the basis of synaptic plasticity as well as explained how our neurons store and manage memories in long-term memory.
This synaptic strengthening ultimately supports two fundamentally different ways we recall or retrieve information, categorized by our level of conscious awareness: explicit memory and implicit memory (Table 2).
|
Explicit (Declarative) Conscious recollection |
Implicit (Non-declarative) Unconscious awareness |
|
Includes episodic and semantic memory Personally-experienced events, facts; conceptual meaning and relationships. |
Includes procedural and priming memory Skills, actions, emotional conditioning |
|
Brain regions: Hippocampus, temporal lobe |
Brain regions: Cerebellum, amygdala, striatum, neocortex |
Table 2: Types of long-term memory.
Explicit memory
Declarative memory, or explicit memory, includes information like places, things, and events and can be recollected by a conscious effort. This information is stored in the temporal lobe of the cerebrum and hippocampus. Explicit memory has been subdivided into episodic memory and semantic memory,
Episodic memory
We use episodic memory to form, store, and recall conscious memories of everyday events (along with contextual details associated with these events). Episodic memory gives us a sense of self-continuity over time and can be likened to a neurological time machine our brains use to go back in time to remember events or experiences from the past.
Examples include how you felt during an argument a week ago, details of a heated conversation with your supervisor yesterday, or remembering the day your parents brought home your baby sister. Episodic memory is highly sensitive to aging, but studies show that a healthy lifestyle can play a protective role in its preservation.
Semantic memory
This memory type is made up of pieces of information like what concepts mean and how they are related to each other. It is your long-term storehouse for general knowledge, concepts, and facts about the world around you.
Examples of semantic memory include knowing the capitals of states, who the president is (or was), what a slang term means, and understanding that gravity is what pulls objects to the ground. Semantic memory is typically well preserved in aging. In fact, research has shown that semantic accuracy and vocabulary may improve in healthy aging due to crystalized intelligence, or the accumulation of knowledge and life experience. The retrieval of that knowledge, however, may be a little slower as compared to younger individuals.
Implicit memory
Implicit, or non-declarative, memory is a type of skilled-based knowledge that is learned gradually yet without the ability to report what is being learned. When we ride a bike or when a smell draws up in emotion, we are using implicit memory. Implicit memory is unconscious and is stored in different areas of the brain, like the neocortex, striatum, amygdala, and cerebellum.
Procedural memory
“Autopilot mode” - When you ride a bike even though you haven’t ridden one in years, you are using procedural memory. This type of long-term memory is used when you are doing something, physical or mental, that you have learned as a process. These skills, like driving, seem basic, but are a result of practicing until you learn, or get it right. It is related to kinesthetic memory, which is specific to physical behaviors (i.e., skipping).
Priming
When you use information from a prior experience that influences your behavior without you realizing it, you are using a type of memory called priming. This act of unconscious memory causes you to think or act in a way after being exposed to a certain word or experience.
Priming occurs when your brain generates a response without any conscious effort on your part, making it easier for you to recognize things in context. You are using priming when you grab your umbrella rushing out the door the moment you notice it’s dark and overcast outside. Your brain instantly recognized the dark shapes as rainclouds, which prompted you to grab your umbrella before you even thought about the weather.
All memory involves changes occurring as a result of experience, or learning, so individuals can alter future behaviors based on past experience. Memory can be conscious or unconscious in nature. We use explicit memory to consciously recall facts or details. At the same time, we use implicit memory (specifically procedural memory) to utilize ingrained knowledge without awareness in order to accomplish tasks and reach desired goals. For example, a person moving away and training their replacement at work might suddenly realize how unconscious many of the steps in their daily procedures actually are, as these deeply learned professional habits occur naturally without a second thought.
Whether these memories are conscious or unconscious, they all rely on the same underlying mechanics to function. Understanding how the brain actually handles this information requires looking at memory in terms of biological processes.
Memory in terms of processes: How is information handled?
While we may not know exactly how memory works at the cellular level, modern neuroscience understands that it involves distinct firing patterns of individual neurons. Our brains store memories in these neural firing patterns that can be replayed over and over again. The process of memory formation and retrieval in such patterns is thought to involve three steps: encoding, consolidation/storage, and retrieval.
When we receive sensory information from the environment, our brains encode or convert this information into a “brain-friendly” format, or a neural representation that can be easily stored. The moment we pay attention to (or focus on) something we see, hear, smell, or touch, our brains begin the process of encoding. This selective or directed attention plays a critical role in determining if information gets processed for storage, or forgotten.
Once this attention is directed, our brains convert this encoded information into a memory trace, or engram, to begin the process of consolidation. A memory trace is a physical or biological change in the brain that occurs when a memory is formed. During this stage, the hippocampus forms connections with different areas of the brain, weaving the new memory into neural networks that represent long-term memory stores.
The consolidation stage is not instantaneous, but occurs over time, with newer memories susceptible to interference and forgetting. Sleep is crucial during this consolidation stage, because it is when our memories are stabilized and moved from the hippocampus into the cortex as long-term memory.
Once consolidated, memories are stored in different regions of the brain as complex neural networks. The retrieval process occurs when our brains access stored information to be used in the present. This step involves reactivating neural pathways built during encoding and consolidation.
Keep memory sharp as you age
Brain cells and networks age in many of the same ways that our other organs do. And just as with “physical health”, cognitive health is not necessarily related to chronological aging. Current research shows that certain interventions that help to keep our bodies healthy, like lifestyle (i.e., diet, sleep, and exercise) and probiotics, can also play a big role in promoting cognitive health and resilience as we age.
How might probiotics for your brain support your memory as you age?
Through a bidirectional conduit known as the gut-brain axis (GBA), the gut exerts a direct influence on the brain via several pathways, including the vagus nerve, the circulatory system, and the immune system. Specialized probiotics may act via one or more of these pathways to regulate cognitive functions, including memory.
Neuralli Cognition+ contains a clinically studied probiotic strains that has demonstrated benefits for supporting immediate and delayed memory and cognitive health in healthy aging adults.
Taken together, these findings reinforce a simple idea: supporting memory requires a multifaceted approach that addresses the many factors that influence brain health over time.
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