Types of long term memory

Question 1

Same or different?

Answer 1

There is some debate over whether episodic and semantic memory are different forms of LTM or part of the same LTM store.
More recently Tulving (2002) has taken the view that episodic memory is a ‘specialised subcategory’ of semantic memory (so essentially the same store). In his research into amnesia, he showed it is possible to have a fully functioning semantic memory with a damaged episodic memory. Some people with amnesia know that past events have happened (semantic), but cannot re-experience them (episodic). However, Tulving concluded it is not possible to have a fully functioning episodic memory alongside a damaged semantic memory.
On the other hand, John Hodges and Karalyn Patterson (2007) found that some people with Alzheimer’s disease (a type of dementia) could form new episodic memories but not semantic memories (the researchers called this semantic dementia). This suggests that episodic memory does not require a functioning semantic memory and therefore must be separate. Though evidence from abnormal conditions (such as Alzheimer’s) may not apply to everyone because the condition itself may have other confounding effects.
Therefore, on balance, this evidence shows that episodic and semantic memories are closely related but ultimately different forms of LTM

Question 2

Clinical evidence

Answer 2

One strength is evidence from the famous case studies of HM (Henry Molaison) and Clive Wearing.
Episodic memory in both men was severely impaired due to brain damage (caused by an operation and infection respectively). But their semantic memories were relatively unaffected. They still understood the meaning of words. For example, HM could not recall stroking a dog half an hour earlier but he did not need to have the concept of ‘dog’ explained to him. Their procedural memories were also intact.
They both still knew how to walk and speak, and Clive Wearing (a professional musician) knew how to read music, sing and play the piano.
This evidence supports Tulving’s view that there are different memory stores in
LTM - one store can be damaged but other stores are unaffected.

Question 3

Counterpoint

Answer 3

Studying people with brain injuries can help researchers to understand how memory is supposed to work normally. But clinical studies are not perfect. A major limitation is that they lack control of variables. The brain injures experienced by participants were usually unexpected. The researcher had no way of controlling what happened to the participant before or during the injury.
The researcher has no knowledge of the individual’s memory before the damage.
Without this, it is difficult to judge exactly how much worse it is afterwards.
This lack of control limits what clinical studies can tell us about different types of LIM.

Question 4

Conflicting neuroimaging evidence

Answer 4

One limitation is that there are conflicting research findings linking types of LTM to areas of the brain.
For example, Randy Buckner and Steven Petersen (1996) reviewed evidence regarding the location of semantic and episodic memory. They concluded that semantic memory is located in the left side of the prefrontal cortex and episodic memory on the right. Howaver, other research links the left prefrontal cortex with encodina of edisodic ramories and the right prefrontal cortex with edisodic retrieval (Tulving et al. 1994).
This challenges any neurophysiological evidence to support types of memory as there is poor agreement on where each type might be located.

Question 5

Real-world application

Answer 5

Another strength is that understanding types of LTM allows psychologists to help people with memory problems.
For example, as people age, they experience memory loss. But research has shown this seems to be specific to episodic memory - it becomes harder to recall memories of personal events/experiences that occurred relatively recently though past episodic memories remain intact. Sylvie Belleville et al. (2006) devised an intervention to improve episodic memories in older people. The trained participants performed better on a test of episodic memory after training than a control group.
This shows that distinguishing between types of LTM enables specific treatments to be developed