Types of Long Term Memory - Episodic LTM
Explicit (declarative) LTM's are ones recalled only if consciously thought about , while implicit (non declarative) LTM's don't require conscious thought to be recalled
Explicit memories are also often formed from several combined memories
Episodic LTM was first suggested by Endel Tulving (1972)
The memory that gives individuals an autobiographical record of personal experience eg the circumstances of their children being born
The strength of episodic memories is influenced by the emotions present at the time a memory is coded eg traumatic events are often well remembered due to the high level of emotion associated with it
Strength of episodic memories is also affected by the degree of processing of information at coding , with highly processed episodic events recalled more easily
Episodic memory helps individuals to distinguish the difference between real events and imagination/delusions
The prefrontal cortex brain area is associated with initial coding of episodic memories , with consolidation and storage of the memories associated with the neocortex
Memories of the different parts of an event are located in the different visual , auditory , olfactory , etc areas of the brain , but are connected together in the hippocampus to create a memory of an episode rather than remaining a collection of separate memories
Memory : performance , knowledge and experience - Endel Tulving (1989)
Aim
To investigate possible differences in the processing of episodic and semantic memory tasks
To assess the effectiveness of neuro imaging as a means of investigating mental processes
Procedure
6 volunteers were injected with a small amount of radioactive gold which was scanned to detect its location with a gamma ray detector
Tulving was one of the participants , along with his wife and his colleagues
Each participant performed 8 successive trials , each lasting 80 seconds , involving 4 semantic and 4 episodic topics in a randomised order
Individual trials were separated by 2 minutes of rest each . A participant would lie , face up , on a couch with their eyes closed and indulge in either episodic or semantic retrieval. The retrievals involved silent mental thought rather than physical stimulation or recording of behaviour
Participants selected what topics they would think about
At a signal from a researcher a participant would begin thinking about a topic , the gold being injected in after 60 seconds and the scanning occurring about 8 seconds later , after the gold tracer had arrived in the brain . The scanning process took about another 2.4 seconds
Findings
3 participants produced inconclusive data for reasons that were not apparent
Data from the other 3 participants showed consistent differences in cortical blood flow patterns between semantic and episodic thinking
There was greater activation in the frontal lobes of the cortex during thinking about episodic memories and greater activation in the posterior region of the cortex when retrieving semantic information
Conclusions
Episodic and semantic LTM's appear to involve different brain areas and therefore are separate forms of LTM
The fact that episodic and semantic LTMs involve different brain areas suggests a biological basis to differences in LTM
Evaluation :
The identification of the involvement of frontal lobes during episodic recall is supported by observations of the memory abilities of brain damages amnesiacs . Those with impaired episodic LTM tend to have damage to the frontal lobes
The study provided , through successful use of neuro-imaging, an effective means of objectively studying and measuring cognitive processes within live participants
As only 3 out of 6 participants showed differences between processing of episodic and semantic LTM's , the findings cannot be seen as conclusive or generalisable to the population as a whole
As Tulving himself was one of the participants , plus his wife and another colleague , it may have been difficult to conduct the study and analyse the findings in an unbiased , objective manner
Evaluation
The extent to which episodic and semantic memory systems are different is unclear , as although different brain areas are involved , there is also a lot of overlap between the 2 systems , with semantic memories often clearly originating in episodic memory. Whether , therefore , the gradual transformation of an episodic into a semantic LTM means a change in memory systems cannot be certain
It may be that episodic memory differs from that of semantic memory in terms of different types of thinking and emotion : episodic memories are associated with conscious awareness of events and emotional feelings related related to them , while semantic memories are associated with objective anlysis of phenomena
