What is Memory?  Memory is quite complex. It involves the participation of multiple systems through out the brain.  It is a mental process of storing and retrieving information and experience.


ENCODING. This is the process of getting information into memory. In order for our brains to remember the information it must be coded which is a record of the information. It requires, in general, selective attention, the focusing of awareness on a particular set of stimuli or events. The four primary types of encoding are visual encoding (the process of encoding images and visual sensory information), acoustic encoding (the use of auditory stimuli or hearing to implant memories), and semantic encoding is the process of encoding sensory input that has particular meaning or can be applied to a particular context, rather than deriving from a particular sense Tactile encoding is the encoding of how something feels, normally through the sense of touch.

Memory Storage is the more or less passive process of retaining information in the brain whether in the sensory memory, the short-term memory or the more permanent long-term memory. Each of these different stages of human memory function as a sort of filter that helps to protect us from the flood of information that confront us on a daily basis.  Consolidation is the process of stabilizing memories after acquisition.

Retrieval accessing or recalling stored memories when needed; in plain language this is remembering.



Evidence has accumulated to suggest the existence of at least three distinct memory systems : sensory, short term and long term. Though the mechanisms of these three systems differ, they do flow naturally from one into the other and can be regarded as three necessary steps in forming a lasting memory

1. SENSORY MEMORY is an ultra-short-term memory and decays or degrades very quickly.  It retains sensory information received through our five senses : seeing, hearing, smell taste and touch. Such information can either be ignored or recognized. If recognized then the sensory stimulus passes into our sensory memory. Echoic memory is involved in processing auditory information and lasts for several seconds. For instance this type of memory allows you to remember a conversation you just had. Iconic memory is involved in processing visual information. Iconic memories last for only a fraction of second and allow you to keep visual images in your brain.  Information is passed from the sensory memory into short term memory via the process of attention (the cognitive process of selectively concentrating on one aspect of the environment while ignoring other things), which effectively filters the stimuli to only those which are of interest at any given time

2. SHORT TERM MEMORY Sensory information is transferred to short-term memory where it is available for about 30 seconds. Short-term memory can be thought of as a “scratch pad” to be used for temporary recall of information which is being processed. During short-term memory one is remembering and processing information at the same time.

Attention is a key factor in maximizing short term memory. An average person can retain 5-9 digits a few seconds after hearing or reading them. To retain more information in short-term memory, and to keep it intact for a longer period, psychologists advise the following strategies for improving short-term memory: chunking and rehearsal.  Chunking is the organization of material into shorter meaningful groups to make them more manageable. For example, a hyphenated phone number, split into groups of 3 or 4 digits, tends to be easier to remember than a single long number. Chunking and rehearsal are helpful in keeping short-term memory intact, but information stored in short-term memory fades in time and is soon forgotten. These methods are therefore not applicable for storing information in long-term memory

The term working memory is often used interchangeably with short-term memory, although technically working memory refers more to the whole theoretical framework of structures and processes used for the temporary storage and manipulation of information, of which short-term memory is just one component.

The central executive part of the prefrontal cortex (part of the frontal lobe) appears to play a fundamental role in short-term and working memory. It both serves as a temporary store for short-term memory, where information is kept available while it is needed for current reasoning processes, but it also “calls up” information from elsewhere in the brain.

The central executive controls two neural loops, one for visual data (which activates areas near the visual cortex of the brain and acts as a visual scratch pad), and one for language (the “phonological loop”, which uses Broca’s area* as a kind of “inner voice” that repeats word sounds to keep them in mind). These two scratch pads temporarily hold data until it is erased by the next job.

* Broca’s area is in the frontal lobe and contains motor neurons responsible for speech production and articulation

3. Long term memory not only stores all the significant events that mark our lives, it lets us retain the meanings of words and the physical skills that we have learned. Its capacity seems unlimited, and it can last days, months, years, or even an entire lifetime! But it is far from infallible. It sometimes distorts the facts, and it tends to become less reliable as we age.  Long-term memories are distributed throughout the cortex rather than being stored in one   particular brain region.

Two main types of long-term memory have been identified

a. Declarative memory also referred to as explicit memory  is everything that you remember that can be described in words such as facts, data, and events . Declarative memory is further subdivided:

i. Semantic memory is your memory about general factual information, knowledge, and concepts about the world. Semantic memory refers to general knowledge about the world that you share with others and is not dependent upon context or personal experiences. Semantic memory is what allows us to recall that 2 plus 2 equals four or that the capital of Trinidad is Port of Spain. Other examples of semantic memory include

  • The knowledge that an elephant is a gray animal
  • The understanding of the concept of time
  • The knowledge that Trinidad is a country
  • How to spell your name

ii. Episodic Memory is the memory of personal experiences (sometimes referred to as autobiographical memory) and specific events that occurred at a specific place and at a particular time. This also includes the context surrounding the event and the associated emotions. We are able to recall this information at a later date. Unlike semantic memory, episodic memory is dependent upon context and your personal experiences. Examples of episodic memory would be the ability to recount what you did today and where you were when you heard shocking news. Another example would be remembering where you parked your car

  • The memory of your first date
  • The memory of your high school graduation
  • The memory of your first college course

b. Non declarative memory It is also known as implicit memory, because you express it by means other than words. For example, when you ride a bike, juggle some balls or simply tie your shoelaces, you are expressing memories of motor skills that do not require the use of language. There are subdivisions  of non declarative memory

 i.   Procedural Memory:

The procedural system stores information on how to do something. Procedural memory holds our knowledge about our skills and habits. This knowledge base represents our life’s work. It is the information that was acquired slowly through continued practice. Procedural memory is unconscious, because it is composed of automatic sensorimotor behaviors that are so deeply embedded that we are no longer aware of them

ii    Primed memory is memory activated through priming, or the process of subconsciously introducing information beforehand to aid in remembering

iii.  Simple classical conditioning involves the pairing of two stimuli, an unconditioned stimulus and a conditioned stimulus. When paired together repeatedly, the response associated with the conditioned stimulus can be elicited by the unconditioned stimulus alone

Sources http://www.human-memory.net/types_short.html