TYPES OF LTM

• Atkinson & Shiffrin's model distinguishes between STM and LTM but Tulving (1972) argues it's oversimplifying matters to regard LTM as a single store.

• He proposed that there are several different types of LTM:

1. EPISODIC

2. SEMANTIC

3. PROCEDURAL

• He states that there are two broad types of LTM:

EXPLICIT and IMPLICIT.

EXPLICIT MEMORY:

• Also called declaritive memory (as it's easy to put into words).  
• Require conscious thought to recall them - such as recalling who came to dinner last night or naming animals that live in the rainforest.
• It's what most of us have in mind when we think of "memory" and whether it's good or bad.
• Explicit memory is often associative; your brain links memories together.  E.g. when you think of a word such as car, your memory brings up a whole host of associated memories from car parts to your commute to a family road trip to a thousand others things.
• Both EPISODIC and SEMANTIC memory are explicit types of memory.

• First suggested by Endel Tulving (1972).
• Refers to our LTM for past experiences e.g. our memory of a particular birthday party, or our ski holiday last year.
• It's autobiographical - any event in which we played a part, and which we remember as an "episode" (a scene of events) is episodic.
• This memory contains objects, faces, places and events.
• How well we record an episodic memory depends on several factors e.g. things that occur to us in emotionally charged conditions are often stronger memories, such as birth of a child.
• Another important factor is the strength with which your brain records the memory when you first experience it.  If you focus carefully and your brain is able to process what you see, hear, smell, taste and feel very quickly and accurately, the memory is recorded with more power, making it easier to recall later.
• The prefrontal cortex is associated with initial coding of episodic memories, with consolidation (strengthening) and storage of memories associated with the neocortex. 
• Memories of the different parts of an event are located in the different sensory areas of the brain, but are connected together by the hippocampus to create a memory of an episode, rather than a collection of seperate memories.
• It is thought that episodic memory helps individuals to distinguish the difference between real events and imaginations/delusions (see Hassibis et al (2007)).

• Herlitz et al (1997) assessed explicit LTM abilities in 1,000 Swedish participants, finding that females consistently performed better than males on tasks requiring episodic LTM, although there were no differences in semantic LTM ability.  Suggests there are gender differences in episodic memory ability, which may be explained in part by females's generally having higher verbal ability.
• The extent to which episodic and semantic memory systems are different however, is unclear.  Although different brain areas are involved, there is a lot of overlap between the two systems, with semantic memories often clearly originating in episodic memory. Whether, the gradual transofmration of episodic into a semantic LTM means a change in memory systems cannot be certain.
• Might be that episodic memory differs from semantic memory due to different types of thinking and emotion; episodic memories are associated with conscious awareness of events and emotional feelings related to them, while semantic memories are associated with objective analysis of phenomena.

SEMANTIC MEMORY:

• LTM store of general knowledge about the world e.g. how to tell the time, how to use language, the meaning of concept.
• This memory holds knoweldge that is not related to past experiences e.g. we cannot identify the particular experiences that led to us learning to tell the time or that a zebra is a striped animal.
• Scientists aren't sure where semantic memory happens in the brain.
• The strength of semantic memories, like episodic, is positively associated with the degree of processing occurring during coding.
• Unlike episodic memory, semantic memory is better sustained over time.  We are often able to retain a higly functioning semantic memory into our 60's after which it undergoes a slow decline.
• Over time there is a gradual move from episodic to semantic memory within knowledge becoming increasingly divorced from the event/experience that it was learned from.

• Kroenig (2007) created 64 imaginary, but believable drawings of animals, one of which was the prototype for "crutters" (animals that shared 3 particular features).  Alzheimer patients and participants without the condition then had to decide which of the 64 drawings were of crutters.  Participants had to either use direct comparison to make their assessments - judging which animals were crutters based on their similarity to the picture of the prototype - or they based their comparison on a stated rule that crutters matched the prototype on 3 of the 4 target features.  Alzheimer patients were as good as the non-Alzheimer participants when using direct comparison, but inferior when using the stated rule.  As using the stated rule involved higher level processing it suggests semantic memory involves different process and brain areas.
• Vicari et al (2007) reported on the case of CL, a 8 year old girl who suffered brain damage after tumour removal.  She showed deficiencies in her episodic LTM functions, especially in creating new episodic memories, but was still able to create and recall semantic memories.  Suggests episodic and semantic memories are seperate systems using different brain areas, with the hippocampus associated with episodic memory and the perirhinal cortex with semantic LTM.

• Semantic memory may involve more of a network of associated links performed in different brain areas, rather than being a single form of memory ability.  Some links may be quicker than others, or quicker to access, explaining why some semantic memories appear to be easier to recall than others.
• Fact that damage to different areas of the brain can affect semantic memory abilities differently supports the idea that semantic memory abilities are spread throughout the brain structures, whilst also supporting the idea that semantic memory may consist of several interrelated memory abilities and therefore not be a single type of memory.

• Also called nondeclaritive memory (as it's not easy to express in words).
• Refers to those memories which do not require conscious thought to be recalled.  They cannot be clearly explained or described and which lie outside our consciousness.
• Includes procedural memory, the effects of classical conditioning and priming.

• Type of implicit memory that enables us to carry out commonly learned tasks without consciously thinking about them.  Our "how to" knowledge e.g. ride a bike, drive a car, use a knife and fork, wash dishes, even walking.
• It's likely that procedural memory uses a different part of the brain than episodic memory - with brain injuries, you can lose one ability without losing the other.  
• E.g. Clive Wearing, who could play the piano still, despite having no STM ability.
• E.g. HM, was able to learn new skills but could not recall the process of learning.
• Cohen & Squire (1980) make a similar distinction between declaritive memory and procedural memory.  They define declaritive memory (explicit memory) as "knowing that" and suggest it corresponds to Tulving's episodic and semantic memories, whereas procedural memory is non-declaritive (implicit memory) as "knowing how".
• Vargha-Khardem et al (1997) investigated the effects of bilateral damage to the hippocampus in 3 different children.  They found deficits in episodic memory, so that the children could not follow conversations or stories.  They were able to read but the strands linking the words and meanings were unavailable to them.  They could learn the facts but they would not understand the earning process that they underwent to gain this information.
• Many procedural LTM's occur early in life, involving the learning of important motor skills, like walking, dressing etc.

• Also used in language, helping individuals to speak automatically, using grammar and syntax without thinking how to.
• Associated mainly with neocortex brain areas of primary motor cortex, cerebellum and prefrontal cortex.
• Unlike explicit LTM's it does not need the hippocampus to function.
• Finke et al (2012) reported the case study of PM, 68-year-old professional cellist who suffered damage to varius brain areas after contracting encephalitis, resulting in severe amnesia.  His episodic and semantic LTM's were very affected.  Could not remember musical facts such as names of ffamous composers, but his ability to read and play music was unaffected, including the learning of new and complex pieces.
• Van Gorp et al (1999) compared 37 heavy cocaine users with 27 non-abusing controls on memory ability for a 45 day period after abstaining from the drug.  Interesting finding was that the former cocaine users showed a faster increase in procedural memory ability than non-users.  As abstinence from cocaine cause dopamine production to be increased, it suggests dopamine plays a part in procedural LTM.
• Problem in deciding which brain areas are involved in procedural memory is the relative lack of research.  What is needed are case studies of people with brain damage that affects procedural memory but not explicit (episodic and semantic).  But such cases are rare.

• Procedural memories generally take longer to learn than explicit memory abilities.  This may be because procedural memory involves motor functions and spatial abilities, while explicit memory tends not to (though the learning of procedural memories can also involve higher level processing too).