Memory and Disorders Flashcards
Introduction to memory
Memory - process of storing and retrieving information.Important process to human life.
The importance of memory means that damage to the brain can have a detrimental effect, producing memory disorders. Study of memory disorders has contributed to understanding of memory.
One of the most influential models of memory is the multi-store model proposed by Atkinson and Shiffrin (1968).
3 stores are proposed,
- sensory stores
- short-term stores
- long-term store.
Model proposes that information is lost because it decays and that long-term memories are lost through the process of retrieval.
Describe the case of HM
Epileptic who had temporal lobes removed which reduced LTM. Suffered from mild retrograde amnesia - inability to remember the past. Could still recall from childhood, why it is mild. Also, severe anterograde amnesia - no longer form new memories. Most STM intact.
Tests of measurment
- Block-tapping memory test - STM good for spatial info
- Digit-span test - Recall digits provided the time between learning and recall was within the duriation of STM.
- Incomplete Pictures & Mirror Tracing - Ev of new memory. He improved performance over time, but could not refer back to the first time when he performed the task.
Findings
- Led to distinction between STM and LTM. Separate.
- He had problems with memory consolidation. Could not move memories from STM to LTM.
- 2 categories of LTM, explicit and implicit memory.
- Shown that medial temporal lobe important within memory. Challenging view at the time that memory functions were diffused throughout the brain.
What is the difference between retrograde and anterograde amnesia?
Retrograde: Inability to recall past memories
Anterograde: Inability to create new memories
Describe the case of Clive Wearing
Herpes simplex encephalistis, inflammation in left temporal lobe, severe damage to hippocampus. Extremely short memory span.
- Able to remember he was married = spared semantic memory
- Could not remember wedding = impaired episodic memory
- Could not remember divorce = Impaired semantic memory
- Asked if remembered PM John Major, but earlier on seen car with plate ‘JMV’ and instantly said ‘John Major vehicle’ showing he had implicit memory for his name.
Describe the case of K.C.
Damage to brain, both hippocampi. Suffered from anterograde amnesia and gradual retrograde amnesia. Could not store new memories and recall past just before accident, but could recall far back memories. Intact semantic memory, but lacked episodic memory of past.
It was suggested that hippocampus important for episodic memory, however damage left semantic intact, leading to the suggestion that episodic and semantic memory could be formed and stored separtely, processed by different brain regions.
Visual imagery, emotion centres in the brain and fontal areas invovled in self-referential processing important for autobiographical memories.
Describe the case of Jon and his memory problems
Examined by Baddeley, Vargha-Khadem and Mishikin (2001).
Had developmental amnesia due to premature birth and anoxia, resulted in severe hippocampal damage. From age of 5, memory problems apparent. However, had good intelligence and semantic memory, impaired recall, but intact recognition. Led to suggestion that episodic memory not necessary for recognition or acquisition of semantic knowledge.
Describe the case of Patient R.B. (Memory)
Suffered damage to one part of hippocampus (CA1 pyramidal cell layer) and developed amnesia. Suggests that hippocampal damage alone can produce amnesia.
Transient global amnesia the strongest evidence that selective hippocampal damage can cauase medial temporal lobe amnesia. Shorter, lasts 4-6 hours, happens suddenly in normal adults.
This also related to abnormalities in the CA1 subfield of the hippocampus.
What is memory consolidation and is there any evidence for it happening?
Evidence for consolidation is post-traumatic amnesia - usually due to concussion. May cause retrograde amnesia for time before injury and anterograde for time after.
Period of anterograde amnesia suggests a temporary failure of memory consolidation. Concussions disrupt recent memories, suggesting that older ones have been stregthened = evidence of memory consolidation.
Describe Hebb’s (1949) theory of memory consolidation
Argued that memories of experiences are stored in the short-term by neural activity. These memories at risk of disription, but eventually structural changes in synapses provide them with stable long-term storage. Suggests that it is a brief process.
Usually studied by using electroconvulsive shock (ECS) - intense, seizure-inducing current to the brain through electrodes on scalp.
Squire, Slater and Chace (1975) in response to Hebb (1949)
Found a long-gradient of ECS-produced retrograde amensia when measuring memory for TV shows prior to ECS therapy.
Found that lasting memories become more reistant to disruption throughout life. It is not a brief process like Hebb suggests.
What does standard consolidation theory propose about the hippocampus?
Proposes that the hippocampus stores memories temporarily.
Also suggested that the hippocampus involved in establishing memories, but that they become stronger and less dependent on the hippocampus over time. Building of connections.
What is global cerebral ischemai?
Interuption of blood supply to the brain.
Often suffer from medial temporal lobe amnesia e.g. patient R.B.
Describe the nonmatching-to-sample model of explicit memory in Monkeys
- How perceive explicit memory with an animal?
- Experiment showed that monkeys with bilateral medial temporal lobectomies have problems forming long-term memories for objects in delayed non-matching-to-sample test.
- Monkey shown distint object under which it finds food
- After a delay, monkey presented with 2 object, sample and unfamilar.
- Must remember the sample object so it can select the unfamilar object and find food under it.
- Well trained monkeys performed well
- Those with bilateral medial temporal lobe lesions performed poorly.
- Similar to those of HM.
- Shows that amnesia from medial temporal lobe damage is due to hippocampal damage
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Describe the nonmatching-to-sample model of explicit memory in rats
- Better at lesioning hippocampus than monkeys as little damage to other areas. Using aspiration in monkeys.
- Tested using Mumby box.
- Hippocampus large role in object-recognition memory
What evidence is there to suggest that damage to the medial temporal cortex is responsible for object-recognition deficits after medial temporal lobectomy?
3 major structures of medial temporal lobe are the
- Rhinal cortex
- Amydala
- Hippocampus
Removal of rhinal cortex produces severe and permnanent deficits. Removal of the hippocampus produces only moderate deficits. Amydala has no effect.
