PSYCH 15 Lecture Notes - Lecture 9: Rhinal Cortex, Anisomycin, Cerebellum
Ch 11: Learning, Memory, and Amnesia
Amnesic Effects of Bilateral Medial Temporal Lobectomy
- After a bicycle accident at 7yo, HM suffered from intractable epilepsy
o Suffered from partial seizures (100s a day) for many years
o Epilepsy was localized to the medial temporal lobes (MTL) bilaterally
o 27yo; HM underwent resection of his MTL on both sides
o Hippocampus was removed bilaterally, in addition to adjacent areas
o Seizures were dramatically reduced but so was his long-term memory
o Mild retrograde amnesia and severe anterograde amnesia
o Henry Gustav Molaison – passed away in 2008
- Retrograde v Anterograde Amnesia
o Retrograde
▪ Backward-acting
▪ Unable to remember the past
o Anterograde
▪ Forward-acting
▪ Unable to form NEW memories
o HM unable to form most types of new long-term memories (LTM), but his short-term memories
(STM) are intact
Foral Assesset of HM’s Aterograde Aesia: Disoery of Uosious Meories
- Digit Span
o Repeat digits back to someone – at each step, increase the amount of number you have to
recite back by one
o HM can repeat digits, but only could do 8 digits
▪ Only provided the time between learning and recall is within the duration of STM
- Block-tapping memory-span test
o Tap block back and increase the # of blocks you have to tap back each time
▪ Like the digit span but not verbal
o This deostrated that HM’s aesia as global (not limited to one sensory modality)
o HM only had a block-tappig spa of loks; ould’t do or ore
- HM improves w practice on sensorimotor tasks (mirror-drawing, rotary pursuit) and on non-
sensorimotor tasks (incomplete-pictures)
o Without recalling previous practice sessions
- HM readily lears resposes thorough lassial Paloia oditioig, ut has o eory of
conditioning trials
3 Major “ietifi Cotriutios of HM’s case
- Medial temporal lobes are involved in memory
- STM, remote memory, and LTM are distinctly separate
o HM is unable to move memories from STM to LTM, a problem w memory consolidation
- Memory may exist but not be recalled – as when HM exhibits a skill he did not know he had learned
(explicit v implicit)
Explicit Memories: conscious memories, declarative memories
- Ex: what you had for dinner last night, what your name is
Implicit Memories: unconscious memories, non-declarative memories
- When HM shows the benefits of prior experience, riding a bike
find more resources at oneclass.com
find more resources at oneclass.com
Medial Temporal Lobe Amnesia
- Not all patients w this form of amnesia are unable to form new explicit long-term memories
- Semantic memory (general info) may function normally while episodic memory (events that one has
experienced) does not
- Medial temporal lobe amnesiacs may have trouble imagining future events
Effects of Cerebral Ischemia on the Hippocampus and Memory
- RB suffered damage to just one part of the hippocampus bilaterally and developed amnesia (cerebrela
ischemia)
- RB’s ase suggests that hippoapal daage aloe a produe aesia
- HM’s daage ad aesia ere ore seere tha RB’s
Aesia of Korsakoff’s “ydroe
- Most commonly seen in severe alcoholics (or others w thiamine deficiency)
- Characterized by amnesia, confusion, personality changes, and physical problems
- Damage in the medial diencephalon: medial thalamus and/or mammillary bodies
- Amnesia comparable to medial temporal lobe amnesia in the early stages
- Differs in later stages (it becomes progressive, complicating its study)
Aesia of Alzheier’s
- Begins w slight loss of memory and progresses to dementia
- General deficits in predementia AD:
o Major anterograde and retrograde amnesia in explicit memory tests
o Deficits in STM and some types of implicit memory – verbal and perceptual
- Implicit sensorimotor memory is intact
Amnesia after Concussion: Evidence for Consolidation
- Posttraumatic amnesia: concussions may cause retrograde amnesia for the period before the blow and
some anterograde amnesia after
- The same is seen w comas
o The severity of the amnesia correlates to the duration of the coma
- Period of anterograde amnesia suggests a temporary failure of memory consolidation
Gradients of Retrograde Amnesia and Memory Consolidation
- Concussion disrupt consolidation (storage) of recent memories
- He’s theory: eories are stored i the short ter y eural atiity
- Interference w this activity prevents memory consolidation
o Ex: blows to the head (concussion), ECS (electroconvulsive shock)
▪ Causing a seizure
▪ Short term memory loss is a big side effect
- Long gradients of retrograde amnesia are inconsistent with consolidation theory
The Hippocampus and Consolidation
- HM has some retrograde amnesia (forgot 2 years of his life)
- Perhaps the hippocampus stores memories temporarily (standard consolidation theory)
o Consistent w the temporally graded retrograde amnesia seen in experimental animals w
temporal lobe lesions
- Or, perhaps, the hippoapus stores eories peraetly, ut they eoe stroger oer tie
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Retrograde v anterograde amnesia: retrograde, backward-acting, unable to remember the past, anterograde, forward-acting, unable to form new memories, hm unable to form most types of new long-term memories (ltm), but his short-term memories (stm) are intact. For(cid:373)al assess(cid:373)e(cid:374)t of hm"s a(cid:374)terograde a(cid:373)(cid:374)esia: dis(cid:272)o(cid:448)ery of u(cid:374)(cid:272)o(cid:374)s(cid:272)ious me(cid:373)ories. Hm improves w practice on sensorimotor tasks (mirror-drawing, rotary pursuit) and on non- sensorimotor tasks (incomplete-pictures: without recalling previous practice sessions. Hm readily (cid:862)lear(cid:374)s(cid:863) respo(cid:374)ses thorough (cid:272)lassi(cid:272)al (cid:894)pa(cid:448)lo(cid:448)ia(cid:374)(cid:895) (cid:272)o(cid:374)ditio(cid:374)i(cid:374)g, (cid:271)ut has (cid:374)o (cid:373)e(cid:373)ory of conditioning trials. Medial temporal lobes are involved in memory. Stm, remote memory, and ltm are distinctly separate: hm is unable to move memories from stm to ltm, a problem w memory consolidation. Memory may exist but not be recalled as when hm exhibits a skill he did not know he had learned (explicit v implicit) Ex: what you had for dinner last night, what your name is. When hm shows the benefits of prior experience, riding a bike.
