Long Term Memory

Atkinson’s and Shiffrin’s (1968) multi-store model.

Introduction

          According to Stage model of memory Long term memory is the third stage of memory. The information that enters LTM remains their for lifetime or permanently. It has limitless storage capacity. The longer an item stays in short-term memory, the stronger its association becomes in long-term memory (Atkinson and Shiffrin, 1968). Items or information are transferred from short-term to long-term memory through Synaptic consolidation. The information is encoded into semantic, visual and acoustic forms for storage into the long term store. The information is encoded in the synapses in the form of engram (memory trace) becoming resistant to external interference but remains prone to manipulation. The information travels from the STM to LTM via temporary transit hub popularly known as hippocampus area. This area doesn’t store information by itself.

Characteristics

1.       Long Term Memory is the last stage of memory system.

2.       LTM has unlimited capacity.

3.       LTM is the outcome of permanent physical changes in the brain.

4.       In LTM information remains intact but all of it may not be accessible.

5.       Maintenance rehearsal is one of important tools of LTM.

6.      Most of the information is encoded as images, sounds, smells and tastes (Cowan, 1988).

7.     In LTM, information is stored in meaningful (Meaningfulness is subjective) & organized form (Ciccareli & Meyer, 2016).

8.       Information is prone to manipulation in LTM.

9.       Information stored in the LTM tends to fading leading to forgetting.

Types of Long Term Memory   

          The LTM is broadly divided into two types i.e. Explicit (Declarative) and Implicit (Non-Declarative or Procedural) memory.

(i)       Explicit or Declarative – All information pertaining to facts, names, dates etc. comes under explicit memory. In other words memories that are consciously recalled to brought to mind and “declared”. Such Memories are encoded by the hippocampus but consolidated and stored in other parts of the brain. It can be of either Episodic or Semantic type (Tulving, 1972).

        (a)      Episodic – The biographical details of our lives such as personal life   experiences these experiences are generally emotional in nature. Emotions provoking experiences are hard to forget. Episodic memory involves conscious thought and declarative in nature.

        (b)      Semantic – The memory of general knowledge, concepts, ideas and rules of logic are found in semantic memory. For example 2+1 = 3 or name of our college etc. This kind of memory is not dated. Since the contents of semantic memory relate to facts and ideas of general awareness and knowledge, it is affect-neutral and not susceptible to forgetting (NCERT).

(ii)      Implicit or Non-declarative or Procedural – The memories relating to procedures for accomplishing various tasks and skills such as how to ride a bicycle or memory of motor skills. In other words it is the memory of ‘How to do things’? It involves unconscious thought process. 

Other classifications of LTM

(i)       Autobiographical Memory – These are personal memories and unique to each individual. They are not distributed evenly throughout our lives. Some periods in our lives produce more memories than others. For instance, no memories are reported pertaining to early childhood particularly during the first 4 to 5 years. This is called childhood amnesia. There is a dramatic increase in the frequency of memories just after early adulthood, i.e. in the twenties. Perhaps emotionality, novelty, and importance of events contribute to it.

(ii)      Flashbulb Memories – The detailed memories of arousing or surprising events. They are like a camera images frozen in memory and tied to particular places, dates, and times. If asked, individual can explain the details of the event meticulously. As if some photograph of the event is lying inside our brain.

Factors affecting LTM

1.       Maintenance rehearsal – Repeating of information over and over again.

2.       Elaborate rehearsal – Giving meaning to the information

3.       Sleep – A state of altered consciousness where memory consolidation occurs.

4.       Attention – Ability to focus on one or more stimuli simultaneously.

5.       Neural structure – A structural change in the neural system (engram) leads to LTM.

6.       Forgetting – An inability to recall stored information.

7.       Intervals – Time gap between the materials learned.

8.       Amnesia – An inability to create new long-term memories

9.       Ageing – With increasing age people face retrieval related problems which occurs due to changes in the frontal lobe and hippocampus region.

References:

1.       NCERT, XI Psychology Text book.

2.       Atkinson, R. C. & Shiffrin, R. M. (1968). Human memory: A proposed system          and its control processes. Psychology of Learning and Motivation. 2. pp. 89–         195. doi:10.1016/s0079-7421(08)60422-3. ISBN 9780125433020.

3.       Dudai, Yadin (2003). "The neurobiology of consolidations, or, how stable is           the engram?". Annual Review of Psychology. 55: 51–86.           doi:10.1146/annurev.psych.55.090902.142050. PMID 14744210.

4.       Ciccarelli, S. K. & Meyer, G. E. (2016). Psychology. New Delhi: Pearson.

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