(The Gist of Science Reporter) The Case of the Missing…?
(The Gist of Science Reporter) The Case of the Missing…?
The Case of the Missing…?
EVERY often repeated mumbles like ‘where did I leave my keys’ or household has heard ‘where is my phone’ or ‘has anyone seen my glasses’ when they are right on your own nose.
What is happening here?
Forgetfulness – much to the amusement or ridicule for others and embarrassment for you. The question is – do we forget, or do we refuse to remember? But, take heart, Kahlil Gibran, the Lebanese poet says, “Forgetfulness is a form of freedom.” While someone else goes a step further: “Wisdom is founded on memory; happiness on forgetfulness. What is more, we live in a society that depends on public amnesia.” So much for forgetfulness which means loss of memory.
What is memory?
The modern English word “memory” comes from the Latin memoria and memoria, meaning “mindful” or “remembering”. Memory is the storehouse of things learned and retained from past activity or experience and gives us the capability to remember and recall for future needs.
Memory is appealing to us because of its struggle with forgetfulness. Memory makes us. You see, if we cannot recall the what, who, when, how and where of our everyday lives, would we be able to function?
Everything we see, hear, imagine, or think about is linked to neural responses somewhere in the brain. The brain, with all its 100 billion neurons, allows us to do incredible things like learn and speak several languages, or build superfast computers or send people to the moon and so on.
Yet, despite this amazing capacity, we routinely can’t remember where we put our keys, why we went to the other room and so on. This obvious contradiction in functionality leads us to the question of why we forget some things but remember others.
Processing of Memory:
The process of registering a memory begins at birth and occurs continuously. For us to recall events, facts or processes, we commit them to memory. For that we pick chemical and physical stimuli from the outside world, by one or more of our senses and attended to with various levels of focus and purpose.
A memory starts off on short-term basis; for example, we learn how to tie our shoes or comb our hair, and once that is done, it goes into our long-term memory and we can do it without consciously thinking about the steps involved.
Short-term memory or working memory refers to the memory you can consciously hold in your mind at any instant and recollect events that happened immediately up to a few days; it generally holds 5-9 independent items in storage that can be readily recalled.
Important memories typically move from short-term to long-term. The transfer of information for more permanent storage can happen in several steps, like through repetition — such as studying for a test and so on. Motivation can be another reason, events of keen interest like cricket score in 1985 or a song in an old Bollywood movies and so on.
The processing of memory, therefore, consists of three main stages:
Encoding: Registration, receiving, processing and combining of received information.
Consolidation or storage: Creation of a record of the encoded information in short or long-term memory.
Retrieval or recall: Calling back the stored information in response to some signal.
Memory is not a perfect processor, and is affected by many factors. The manner in which information is encoded, stored, and retrieved can all be corrupted by physical damage to areas of the brain such as the hippocampus, or decay within long-term memory and so on.
We are typically not aware of what is in our memory until we need to use that bit of information, bringing it to the forefront when we need to use it. Common tasks like combing, etc. do not need much concentration. But there are other types of memories that may need a little scratching of our head.
Types of Memory:
Implicit memory or unconscious memory uses past experiences to remember things without thinking about them; a subset of this is procedural memory – the slow and gradual learning of skills without conscious attention to learning – such as playing tennis or a musical instrument, swimming and so on. Priming is a process operating below the threshold of consciousness - indicating not all memory is consciously activated.
Explicit memory or declarative memory requires more effort to bring to the surface; involves semantic and episodic memory.
Semantic memory includes things that are common knowledge, such as the names of states, the capitals of countries and other basic facts.
Episodic memory is a unique recollection of a specific event or an episode that is encoded along an emotional, spatial and temporal plane, such as your first air travel, an enjoyable holiday or your first day at a new job and so on.
Collective memory plays an essential role in the establishment of human societies. Every social group perpetuates itself through the knowledge that has been handed down the generations, either through oral tradition or through writing.
The invention of writing made it possible for the first time for us to preserve precise records of knowledge outside of our brains. Writing, audiovisual media and computer records can be considered a kind of external memory for humans.
Sleep, Dreams & Memory:
Sleep has multiple purposes; sleep affects memory consolidation in a complex way. Sleep stages vary across the night. Early sleep is rich in NREM, but late sleep is rich in REM. These stage-changes relate to, and are caused by, neurochemical fluctuations during sleep.
Levels of Cortisol – the stress hormone – exert control over hippocampal function, they may be able to switch the brain from one memory consolidating state to the other. Cortisol levels rise over the course of a night’s sleep.
Dreams are activated memory fragments and internally constructed theme plots of perceptions, thoughts, or emotions previously experienced.
Dreams have a home, that is to say neurons firing in the primary visual cortex create the illusion of seeing things, neurons firing in the primary auditory area create the illusion of hearing things, and so forth. Variations in activity as seen in fMRI over the course of the night reveal processing, or “memory consolidation” occurring within different neural systems.
Dreams reported early in the night, largely during SWS, reflect normal episodic content; during slow wave sleep, the neocortex sends signals to the hippocampus, which responds via sharp wave ripples. Episodic memories should be better consolidated early in the night, when a modest cortisol level allows the hippocampus to function properly.
Dreams reported late at night, largely during REM sleep, reflect disrupted hippocampal → neocortical communication and hence seem fragmented and often bizarre. Procedural memories are effectively consolidated throughout the night, as high cortisol levels do not disrupt the brain systems critical to these memories.
How Individual Memories are Formed?
Memory, at its simplest, is a set of encoded neural connections in the parts of the brain – reconstructing past experiences by the synchronous firing of neurons that were involved in the original experience.
Each memory pulls a small subset of neurons in the brain, changing the way to communicate. Neurons send messages to one another across narrow gaps called synapses.
A synapse is a kind of a busy port using proteins like neurotransmitters for sending and receiving cargo of signals between neurons.
Memory is stored not like books on library shelves but as a kind of collage or jigsaw puzzle, but is constructed simultaneously from elements scattered throughout various areas of our brains while the brain is still engaged in other activities.