What is memory ?
Memory is a mechanism through which retain information acquired during our lifetime. This may be our day to day learning or the sensory inputs we receive from outside environments.
Memory does not comprise a single unitary system, but rather an array of interacting systems, each capable of encoding or registering information, storing it, and making it available by retrieval. Without this capability for information storage, we could not perceive adequately, learn from our past, understand the present, or plan for the future.
What are the various types of memory from functional point of view ?
Memory has many sub divisions or types depending on the kind of function that is done by the brain. Some of them are given below ..
Sensory memory : In order to see a continuously moving image it is necessary for the brain's visual system to store the information from rom one frame until the arrival of the next. The visual store responsible for this is one of a whole series of sensory memory systems that are intimately involved in our perception of the world.
An analogous series of sensory memories occurs in hearing. If a nine digit telephone number is read in front of someone. And then he is asked to repeat it, he likely to repeat it right. But if he is asked to write it he is likely to make errors. The greater number of such telephone number will likely to increase the number of errors he makes. However here the objective is to explain that when we remember the sound patter it is easier to repeat but converting the representation of sound pattern to visual pattern increases the likelyhood of errors.
Our system has a system of storage and retrival for other senses in the same way.
Short term memory : Short-term memory (or "primary" or "active memory") is the capacity for holding a small amount of information in mind in an active, readily available state for a short period of time.
Working memory : In both language comprehension and arithmetic, therefore, there is a need for the temporary storage of information in order to perform various functions subsidiary to understanding or calculating. Once the task has been achieved, the subsidiary information is no longer required. We call it working memory.
Working memory is the executive and attentional aspect of short-term memory involved in the interim integration, processing, disposal, and retrieval of information. This forms a small intermediate storage like one we use in computers.
Long term memory : Long term memory can store information for few days to decades or even for the lifetime. Short-term memory is a temporary potentiation of neural connections which can become long-term memory through the process of rehearsal and meaningful association. This represents information that is stored for considerable periods of time. Indeed, some theorists claim that information in memory never disappears, but simply becomes less and less accessible.
Remembering your own name, how to speak, where you lived as a child, or where you were last year or indeed five minutes ago are all assumed to depend on long-term memory. Such memory is primarily concerned with storing information, unlike sensory memory and short-term memory where the storage is an incidental feature of other aspects of the system.
Implicit memory : People rely on implicit memory every day in the form of procedural memory, the type of memory that allows people to remember how to tie their shoes or ride a bicycle without consciously thinking about these activities.
Implicit memory is a type of memory in which previous experiences aid in the performance of a task without conscious awareness of these previous experiences (Schacter, 1987). Evidence for implicit memory arises in priming, a process whereby subjects show improved performance on tasks for which they have been subconsciously prepared (Graf and Mandler, 1984).
Explicit memory : Explicit memory is the conscious, intentional recollection of previous experiences and information. We use explicit memory throughout the day, such as remembering the time of an appointment or recollecting an event from years ago. Whatever we can remember when we try to recollect is explicit memory.
Decliarative memory : Declarative memory is the aspect of human memory that stores facts. It is so called because it refers to memories that can be consciously discussed, or ''declared.'' It applies to standard textbook learning and knowledge, as well as memories that can be 'travelled back to' in one's 'mind's eye'. It is contrasted with procedural memory, which applies to skills. Declarative memory is subject to forgetting, but frequently-accessed memories can last indefinitely.
Semantic memory : Semantic memory refers to the memory of meanings, understandings, and other concept-based knowledge unrelated to specific experiences. The conscious recollection of factual information and general knowledge about the world is generally thought to be independent of context and personal relevance.
Episodic memory : Episodic memory refers to the memory of events, times, places, associated emotions, and other conception-based knowledge in relation to an experience. Semantic and episodic memory together make up the category of declarative memory, which is one of the two major divisions in memory.
Procedural memory : Refers to the use of objects or movements of the body, such as how exactly to use a pencil or ride a bicycle. While speaking what muscle movements are t be done in what sequence.
Spatial memory : spatial memory is the part of memory responsible for recording information about one's environment and its spatial (pertaining to space and location with respecto external environment) orientation. For example, a person's spatial memory is required in order to navigate around a familiar city.
Other important functions associated with memory ..
Memory plays a big role in our learning process. We will never be able to think if we are stuck in the present. Even for doing the next immediate task we have to associate with our previously done tasks. There are few very important functions which are assoiated with memory are listed below…
Language learning .. The way we learn and process language very much depends on certain basic abilities we have. Any language has its own set of sounds, vocabularies, grammar and the way we reproduce the language.
Vocabulary and Grammar : This is where the ability remember and select of words comes into play.
Language perception : When we listen to others .. we need to understand what they mean. We remember the experiences of our life, compare with beliefs and values and the make sense of what is being spoken about.
On the other side if we have to say something then we need to first make ourselves ready for that action by preparing to make sense whatever we going to communicate on.
Speech motor movements : When we try to express ourselves we have to make sounds and these sounds come after you re-execute the learned movements. It is purely a function of memory and brain. Our brain control the movements that we make for producing the sound,
Association : Every piece of information in our memory is connected to other pieces in some way or another. For example, if you are given the word "apple", what do you think of? Perhaps something like this: APPLE: red, round, sweet, teacher, tree, fruit. This property of memory is known as memory association.
Recognition : Our brain is capable of associate past experiences, learnings and sensory signals to the received inputs from our sensory organs and create perceptions which helps us in recognition of objects, faces, pictures etc.
Brain mapping for memory functions : Scientists and neurologists have come to know lot about our brain functions by making a functional map of brain. It was observed by them that certain specific functions are impaired when some lesions (abnormality/damage) have formed in specific part of brain. Thus most of our present knowledge of brain functions have been contributed by study of brain damaged persons.
Scientists have tried to map all of the memory functions discussed above one or more areas of the brain. We have been able to study brain functions and mappings with the help of medical equipments producing various kind of images during execution of specific tasks. In this process we try to access which of the brain ares are activated during a specific type of activity is performed.
Brain mapping may be dealt as a seperate topic in more detailed way in another article.
References
http://en.wikipedia.org/
Biological Psychology, 10e by James W. Kalat
Essentials of Human Memory, Alan D. Baddeley
Medical Encyclopedia from MobileReference
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