Memory is the mother of all wisdom.
Memory is the most commonly recognized cognitive function. It is the cornerstone of all learning and knowledge. What we store in our memory helps us processes situations. In fact it’s our memory that makes our life; that we remember our family members, that we remember what we like what we don’t like, what a particular food tastes like, what actions to take when we face particular situation. Even bad memories are useful, it helps us avoid awkward situations, helps us in decision making.
Let’s understand how things work; as we are reading this article couple of things are happening; we are digesting new information at the same time we are using information already stored in our memory. The new information will evoke some new beliefs, ideas, values that are unique to us and help us interpret the information we are trying to gather, we will try to make sense of it, we will see how it fits in our coordinates of belief, understanding, interest, and then decide if we really want to keep the information by either making a new memory(finding new place to store the information) or altering (adding or changing) an existing memory or we might decide to discard or forgot the new information altogether. Thus memory is a learning process, constantly making new links to existing information or adding new ones. Recent studies have shown that memory is not a file cabinet system, as we would normally think it to be. It is dynamic. Memory is not concentrated or generated in one particular location of the brain. It is a collaboration of virtually every part of the brain.
Ask yourself — what’s your favorite food? Instantly a picture of your favorite food appears in your mind. How did you get this picture instantly? This was the outcome of a process scattered throughout the brain that involved multiple neural networks. Research shows that construction of memory is not single system phenomenon, it is comprised of a network of system each playing a unique role in creating, storing and recalling the snapshot. All these systems work together synchronously to make it happen. What’s interesting is to note that when you thought about your favorite food and the picture of you food appeared in your mind, was it just the picture of the food that came up to your mind? You also remembered if the food is hot, spicy, sweet; where you had it the last time; the name of the food and similar associated details. Each of these are stored in different part of the brain and all comes together to form a complete image, feeling. It’s like assembling a jigsaw puzzle.
Where are things stored?
Memories aren’t stored in just one part of the brain. Different types of memory are stored in different brain regions. Like, for
- Explicit memories : Episodic memories are autobiographical memories from specific events in our lives, like the beautiful evening you had with you partner, the last soccer match you watched etc. Stored in the hippocampus, the neocortex and the amygdala.
- Implicit memories :stored in the basal ganglia and cerebellum.
- Short-term working memories : stored in prefrontal cortex.
The neocortex is the largest part of the cerebral cortex. It is the sheet of neural tissue that makes up the outside wrinkly surface of the brain. Neocortex(in humans) is involved in functions like sensory perception, generation of motor commands, spatial reasoning and language. Over time, information from certain memories that are temporarily stored in the hippocampus are transferred to the neocortex as general knowledge. Researchers suggests the transfer from hippocampus to neocortex happens during our sleep.
The amygdala attaches emotional significance to memories like joy, fear etc. So for such memories to be permanent there is a strong interactions between the amygdala, hippocampus and neocortex. The amygdala doesn’t just modify the strength and emotional content of memories; it also plays a key role in forming new memories specifically related to fear. Fearful memories are formed only after few repetitions. Anxiety like fear in learning is also associated with amygdala.
The basal ganglia are structures lying deep within the brain and are involved in a wide range of processes such as emotion, reward processing, habit formation, movement and learning. They are particularly involved in coordinating sequences of motor activity, as would be needed when playing a musical instrument, dancing or playing basketball.
The cerebellum, located at the rear base of the brain, is to do with all about fine motor control, those delicate ballet steps or those violin moves. It is also involved with vestibulo-ocular reflex, which helps us maintain our gaze our location as we rotate our heads.
The prefrontal cortex (PFC) sitting at the front of our brain is all about complex cognitive functions. Research reveals PFC becomes active when we involved with activity requiring short term or working memory. While the left PFC is more involved in verbal working memory the right is more active in spatial working memory.
Till this point we looked into where are memory “stored”. Now lets look into How are they stored?
Over 130 years ago Santiago Ramón y Cajal first suggested that the brain stores information by rearranging the connections, or synapses, between neurons. Memories are stored as microscopic chemical changes at the connecting points between neurons in the brain. The brain stores memories by changing how neurons talk to each other. When one neuron fires an action potential, another neuron activates. Over time, this connection gets stronger.
Three types of neurons are responsible for information transfer in the nervous system.
- Sensory Neurons: These are neurons associated with the sensory nervous system, like skin etc. Once they detect any stimulus from each of the senses and communicate the information to the interconnecting neurons.
- Interconnecting Neurons: These neurons enact as the bridge between the sensory neurons and pass the information to motor neurons.
- Motor Neurons: These are neurons connect to the muscle tissue and activate them.
While researches are still on, by now we have a decent understanding that memory building is a 3 step process
- Encoding
- Storage
- Retrieval
Creating a memory starts with Encoding. It is a biological phenomenon that starts with perception of an experience using our senses. Consider, for example, the memory of the time when you met a your partner. Our eyes gathered physical information about the person. Our auditory system picked up the sound of that person’s voice. Our olfactory component would have gathered personal scent. These sensory cues are largely responsible in forming our perceptions. Each of these separate sensations travelled to the part of your brain called the hippocampus, which integrated these perceptions as though they were a part of a single experience. Subsequently the hippocampus, along the frontal cortex analyses these sensory inputs and decides if it’s worth remembering the information. If so they may become part of your long-term memory.(note the word “may”, it will be explained as we go along). Although memory starts with perception, it is encoded and stored with the help of neurons. Neurons are the information carrier communicating with other neurons via an electrochemical process. The synapse carries electrical pulses, via which information is transferred. Nerve cells are connected with other cells via a point known as a synapse. These synapses transfer the electrical pulses containing information and trigger the release of chemical messengers called neurotransmitters. Each brain cell can form thousands of links like this, giving the typical brain about 100 trillion synapses. This linkage is also constantly altered. As new memories are formed, new synapses are added, thus increasing the number of connections within the brain. Once memories are ‘encoded’, they are transferred to either the long-term memory or the short-term memory. This transfer is a part of memory storage, which is the second step in the formation of memory.
Memory Storage : There is no need for us to remember every perceived detail of life in our brain. The different stages of human memory functions as a filter that helps us to manage the flood of information we’re confronted with on a daily basis. As soon as we intercept certain data or note an event, the information is encoded into the short-term memory. Short-term memory has a fairly limited capacity; it can hold about seven items for no more than 20 or 30 seconds at a time. Once this information is processed, two different things can happen; the information can be lost or it can be transferred into long-term memory which has unlimited capacity to retain information for a long time. There are two different types of memory included in LTM.
- Unconscious memory: This includes the formation of memory without us being aware of it. These memories are slow to acquire, but resistant to change or loss. Examples are our procedural memories like eating with spoon, writing on a piece of paper.
2. Conscious memory: These pertains mainly to facts, names and dates and similar. It’s swiftly acquired, and quickly lost. However constant repetition can transform conscious memory into unconscious memory. Practice makes perfect.
Now that we have formed the memory, its time to retrieve the stored memory or Memory Retrieval. When you want to retrieve a particular memory, you have to reach out to the unconscious level of memory storage. This data is transferred to the conscious level at your will.
So that was in a nutshell how memories are formed , stored and retrieved when necessary.
As we part, just wanted to mention; we often hear terms like good memory /poor memory. It’s often spoken loosely. A person might be a fairly good at remembering some types of things and not so good at remembering others. So good and poor memory might be very relative. When there are repeated failure to remember something there can be a problem or physical disease. Simply put such cases are when our brain fails to put the jigsaw puzzle pieces together. However in general failure to remember something can be due to anything from faulty encoding of data, the information simply failed to make it to the long-term memory or distractions that occur while you’re trying to remember something and gets in the way of encoding memories, like trying to read a book in a crowded public setting, the information is not effectively saved it in our memory and hence we fail to retrieve. Most cases when we fail to remember something it’s our short-term memory at fault!
