Memory Disorders Part 1

Question 1

2 types of amnesia

Answer 1

• Retrograde amnesia: loss of memories you had, but ability to form new ones
• Anterograde amnesia: previous memories intact, but loss of ability to form new ones

Question 2

Patient HM

Answer 2

• Severe epilepsy -> bilateral medial temporal lobectomy to cure it -> profound anterograde amnesia, some retrograde amnesia
• He could form some long-term memories, but was unaware of them (ex. improvements in mirror drawing test due to intact basal ganglia, Pavlovian conditioning, priming)
• showed us that anterograde amnesia can still occur despite preserved intelligence, language

Question 3

types of memory (duration)

Answer 3

• short-term

- long-term

Question 4

short-term memory

Answer 4

• aka: Working memory
• Can use digit span test, etc. to measure it
• HM could do this fairly normally

Question 5

long-term memory

Answer 5

• Consolidation of short-term memories into long-term memory
• HM was unable to consolidate, but could retrieve info from long-term memory

Question 6

types of memory (based on level of awareness)

Answer 6

• explicit memory

- implicit memory

Question 7

explicit memory

Answer 7

• your conscious memory (ie. what your first day of school was like, how many people were in your class)
• • Semantic memory: remembering facts, ie. That you started school in 2002
• • Episodic memory: remembering “episodes” of your life, ie. Your first day of school

Question 8

implicit memory

Answer 8

• your unconscious memory of how to do things (ie. Ability to ride a bike)
• used for procedural, priming, conditioning

Question 9

Korsakoff’s syndrome

Answer 9

• Brain damage that results from thiamine (vitamin B1) deficiency, which often accompanies prolonged heavy alcohol consumption
• When it’s due to alcohol, involves severe anterograde and retrograde amnesia, sensory and motor problems, extreme confusion, and personality changes
• When it’s solely due to thiamine deficiency, involves severe anterorgrade and mild retrograde amnesia
• Problem is in diancephalon (thalamus + hypothalamus) -> “medial diencephalic amnesia”

Question 10

Korsakoff’s syndrome: Why does thiamine deficiency accompany alcohol consumption?

Answer 10

Because alcohol decreases ability to absorb thiamine and because they get their energy from the sugar in alchohol, so they have less need to eat foods that could provide them with thiamine

Question 11

what is meant by “single memory, single locus”?

Answer 11

Amnesia is seen as a severe impairment of a single kind of memory (“declarative memory”) attributable to a single brain region (ex. hippocampus)

Question 12

Patient KC

Answer 12

• Suffered severe head injury at 30 when he rode his motorcycle off an exit ramp -> severe amnesia and hippocampal damage
• Loss of episodic memory
• Preserved intellectual, cognitive, language, executive function, and working memory abilities
• Some visuospatial issue (colour-matching and face recognition)

Question 13

Compare and contrast HM and KC

Answer 13

• Similar damage (hippocampal), both had severe anterograde amnesia
• Unlike HM, KC had semantic memory intact, but lacked episodic memory about his entire past (ie. the events didn’t seem like they’d happened to him)

Question 14

KC’s brain pathology

Answer 14

• Cortical atrophy; left hemisphere affected more than the right
• Posterior lesion in occipital-temporal cortex (likely due to increased cranial pressure post-trauma) -> associated with difficulties in colour perception and face matching
• Anterior lesion in frontal-parietal cortex (likely due to hematoma) -> phonemic fluency impaired
• Abnormalities and volume reductions in medial temporal lobes -> hippocampus and other structures that play a role in memory (ie. mammillary bodies, caudate nuclei, etc.) -> associated with profound memory impairment

Question 15

Results of studying KC

Answer 15

• showed complete loss of episodic memory
• showed some issues with autobiographical memory (could remember things from early years better than later years/present), mnemonic precedence (memory for location of recently-encountered objects)
• • shows that spatial memory can become independent of hippocampus over time
• showed evidence of priming and complex learning (ie. learned words and computer tasks -> semantic memory)
• • shows that these involve implicit memory and are independent from episodic memory
• helped discount impared visual imagery and deficits in retrieval as explanations for impaired autobiographical memory

Question 16

Can we learn about neuroanatomical bases of memory from KC?

Answer 16

• Yes, even though his dysfunction is widely distributed
• When he shows impaired performance, hard to conclude which specific region is responsible
• BUT when he shows preserved memory, can infer that none of his damaged regions are necessary for that task

Question 17

can spatial memory be conserved following bilateral damage to the hippocampus?

Answer 17

Yes -> at least some types of spatial memory, including representing allocentric cognitive maps, can become independent of the hippocampus over time

Question 18

what lessons does KC’s case tell us about fractionation of memory and amnesia?

Answer 18

• There are multiple forms of amnesia

- The hippocampus may not always be involved in spatial memory