CH 11: Learning, Memory & Amnesia Flashcards
List the 4 specific memory tests used to assess H.M.’s anterograde amnesia.
- Digital Span +1 Test
- Block-Tapping Memory-Span Test
- Mirror-Drawing Test
- Incomplete-Pictures Test
- Pavlovian Conditioning
Describe the Digital Span +1 Test - what did it test?
- Digital Span +1 Test:
- Repeat 5 digits revealed to him at 1s intervals
- -> Then add 1 new digit at end
- Tests verbal long-term memory
Describe the Block-Tapping Memory-Span Test - what did it reveal?
- Block-Tapping Memory-Span Test:
- Tap array of 9 blocks in front of him in same sequence as the tester did
- Showed that his amnesia not restricted to verbal memory
Describe the Mirror-Drawing Test - what did it reveal?
- Mirror-Drawing Test:
- Draw line w/in boundaries of target
- -> Repeat over 3 days
- -> Got better each time
- -> Indicates retention of task but didn’t remember actually doing task before
- Showed that his anterograde amnesia didn’t involve ALL long-term memories
Describe the Incomplete-Pictures Test - what did it reveal?
- Incomplete-Pictures Test:
- Showed HM form new long-term memories
Describe the Pavlovian Conditioning.
- Pavlovian Conditioning
- Hear tone just before puff of air admin to eye
- Repeat until tone alone elicited an eye blink
Describe the 1st major scientific contribution of H.M.’s case.
- Showed that the medial temporal lobes play important role in memory
- Challenged previous view that memory functions diffusely throughout brain
- ^Research to relate individual brain structures to specific mnemonic (memory-related) processes
Describe the 2nd major scientific contribution of H.M.’s case.
- Bilateral medial temporal lobectomy abolished ability to form certain kinds of long-term memories w/o disrupting performances on tests of short-term memory or remote memory
- Support theory that there’s diff models of storage for short-term, long-term & remote memory
Describe the 3rd major scientific contribution of H.M.’s case.
- Reveals that an amnesic patient may claim no recollection of a previous experience while demo memory for it via improved performance
- Ppl w/ amnesia lose ability to form explicit memories while maintaining ability to form implicit memories
Distinguish b/w EXPLICIT memories & IMPLICIT memories.
- EXPLICIT Memories = conscious long-term memories
- IMPLICIT Memories = memories that are expressed w/o conscious awareness
Describe MEDIAL TEMPORAL LOBE AMNESIA.
What are its major features?
Medial Temporal Lobe Amnesia:
= Amnesia ass. w/ bilateral damage to medial temporal lobes
- Its major features = anterograde & retrograde amnesia for explicit memories, w/ preserved intellectual functioning.
What has research on Medial Temporal Lobe Amnesia taught us about learning & memory?
- Assess implicit memory via REPETITION PRIMING TESTS = seeing list of words, then given fragments of those words & asked to fill in the blanks
- -> Amnesic complete them well despite having no explicit memory of seeing the original list
- -> Discovery of 2 memory systems = explicit & implicit
Describe the difference b/w SEMANTIC & EPISODIC memories.
Explicit long-term memories come in 2 varieties:
- SEMANTIC Memories = explicit memories for general facts/info
- EPISODIC Memories = explicit memories for particular events of one’s life
- ppl w/ Medial Temporal Lobe Amnesia have difficulty w/ episodic memories
- -> aka have trouble remembering specific life events even though memory for general info is normal
Describe GLOBAL CEREBRAL ISCHEMIA.
- The interruption of blood supply to entire brain
- Often suffers from Medial Temporal Lobe Amnesia
Describe TRANSIENT GLOBAL AMNESIA.
- Sudden onset of severe anterograde amnesia & moderate retrograde amnesia for explicit episode memory that’s transit (= only last b/w 4-6hr)
- Occurs in otherwise normal adults
Describe the case of R.B..
- Underwent cardiac bypass surgery but suffered brain damage bc pump circulating his blood to body while heart was disconnected broke down
- -> Obvious brain damage was restricted largely to the PYRAMIDAL CELL LAYER or just 1 part of the hippocampus - CA1 SUBFIELD
- -> Suggested that hippocampal damage can prod Medial Temporal Lobe Amnesia
- RB suffered Transient Global Amnesia
- -> Abnormalities to the CA1 subfield of the hippocampus
- -> Its sudden onset suggested it was stroke-induced
Describe KORSAKOFF’s SYNDROME - describe its symptoms.
Korsakoff’s Syndrome:
= Memory disorder common in ppl who have consumed ^^alcohol
Advanced stages characterized by:
- Sensory & motor problems
- Extreme confusion
- Personality changes
- Risk of death from liver, GI or heart problems
- Amnesia here is similar to Medial Temporal Lobe Amnesia
- -> ie) Early stages = anterograde amnesia for explicit episodic memories
- -> However as disorder progresses, retrograde amnesia also develops
Describe the etiology of the amnesia of Korsakoff’s syndrome.
- Attributable to brain damage ass. w/ thiamine deficiency which accompanies heavy alcohol consumption
Describe the symptoms & amnesia effects of Alzheimer’s Disease (AD).
Alzheimer’s Disease (AD):
= Progressive disorder w/ mild deterioration of memory until dementia develops
–> so severe patient incapable of simple activities
–> terminal
Pre-dementia patients:
- Major anterograde & retrograde deficits in tests of explicit memory
- Deficits in short term memory & some types of implicit memory
Describe the etiology of the amnesia of AD.
- ^Reduced levels of acetylcholine
- -> Degeneration of basal forebrain = main source of acetylcholine
–> **Acetylcholine depletion = cause of Alzheimer’s dementia
- But acetylcholine is NOT only factor!
- -> Brain damage is ^^diffused
Define POST-TRAUMATIC AMNESIA.
- Amnesia produced by a non-penetrating head injury (=blow to head w/o penetrating skull)
Summarize the effects of a closed-head injury on memory (3).
- A blow to head produces coma
- When victim regains consciousness, there’s a period of confusion
- When period of confusion ends, victim has retrograde amnesia for events that occurred during the period right before the blow to head, & anterograde amnesia for events that occurred during period of confusion
Define MEMORY CONSOLIDATION.
- Storage of older memories have been strengthened
Describe the classic view of memory consolidation.
CLASSIC VIEW - Hebb:
- Memories are stored in short term by neural activity reverberating in closed circuits
- -> Circuits susceptible to disruption (ie. blow to head)
- -> Eventually induce structural changes in involved synapses
- -> Provides stable long-term storage
Describe ECS.
- ECS = Electroconvulsive Shock = controlled method of studying memory consolidation
- -> Disrupt neural activity
- -> Erase from storage only those memories that hadn’t yet been converted to structural synaptic changes
- -> Length of time of retrograde amnesia produced by ECS = estimated time needed for memory consolidation
Describe the CURRENT view of memory consolidation.
CURRENT View:
- Memory consolidation continues for a very long time
- Evidence indicates that lasting memories become more & more resistant to disruption throughout one’s life
- Each time a memory’s activated, it’s updated & linked to additional memories
- -> These additional links ^ the memory’s resistance to disruption by cerebra trauma (ie. concussion or ECS).
Describe the DELAYED NONMATCHING-TO-SAMPLE TEST.
How would normal monkeys perform vs. those w/ bilateral medial temporal lobe lesions?
What did this test provide a means for testing?
Delayed Nonmatching-to-Sample Test:
- Subject presented w/ unfamiliar sample object
- -> After delay, is presented w/ choice b/w sample object & unfamiliar object
- -> The correct choice is the unfamiliar object (bc monkey would get i.e. food reward ass. w/ unfamiliar object)
- Normal monkeys would perform correctly, whereas those w/ bilateral medial temporal lobe lesions had major object-recognition deficits
- This test provided a means of testing the assumption that amnesia resulting from medial temporal lobe damage is entirely consequence of HIPPOCAMPAL damage**
- Bc of size & location of hippocampus, all studies of hippocampal lesions in monkeys involved ASPIRATION (suction) of large portions of medial temporal cortex, in add. to hippocampus
- But in RATS: damage ass. w/ aspiration lesions of hippo limited to small area of parental neocortex
- -> also rat lesion small enough it can be lesioned electrolytically or w/ neurotoxin injections
- -> Prod less extraneous damage
Describe the neuroanatomical basis for the object-recognition deficits that result from bilateral medial temporal lobectomy.
- Hippocampus plays key role in object-recognition memory
> SUPPORT:
- Object recognition memory is ^^disrupted by medial temporal cortex lesions, but only moderately by hippocampal lesions
- Relation b/w ischemia-produced hippocampal damage & object-recognition deficits in humans, monkeys & rats
- Damage to brain structures other than hippocampus contributes to amnesia observed in patients w/ global cerebral ischemia
- -> Hippo damage following global cerebral schema = damage to CA1 subfield of hippo
Describe hippocampal PLACE CELLS.
Place Cells:
= Neurons that respond only when the subject is in specific location (i.e. in the place field of the neurons)
- ie) when rat placed in unfamiliar environment, none of its hippocampal neurons have a place field in that environment
–> Then rat familiars itself w/ environment
–> Many hippo neurons acquire a place field in it
–> aka each fires only when rat is in a particular part of the environ
-** Each place cell has a place field in a diff part of the environ
Describe the ENTORHINAL CORTEX.
- Area of medial temporal cortex that’s a major source of neural signals in hippocampus
Describe entorhinal GRID CELLS.
Grid Cells:
- Entiorhinal neurons that have an extensive array of evenly spaced place fields, producing a pattern reminiscent of graph paper
Describe the relationship b/w hippocampal Place Cells & entorhinal Grid Cells.
- Hippo place cells depend on input from entorhinal grid cells:
(1) There’s a major pathway from entorhinal cortex to hippo
(2) Entorhinal grid cells respond relatively reflexively to location, whereas hippo place cells respond to place in combo w/ other features of environ - Hippocampal place cells obtain their spatial info via grid cells in entorhinal cortex
- -> This even spacing of the place fields in the grid cells could enable spatial computations in hippocampal place cells
- Place cells can still function after entorhinal grid cells have been eliminated
Describe the role of the hippocampus in spatial memory & other types of memory it supports.
- Certain cells in hippo shown to code for TEMPORAL aspects of an experience
- Hippo plays role in learning about social organization in humans
- Cells in hippo & its surrounding structures shown to play role in coding of concepts
List 3 amor structures of the Medial Temporal Lobes.
- Hippocamps
- Amygdala
- Medial Temporal Cortex = entorhinal, peripheral & parahippocampal cortices
Define a CONCEPT CELL.
Concept Cells:
= neurons, such as those found in medial temporal lobe, that respond to ideas/concepts rather than to particulars
- Highly selective
- -> Each neutron responded to only a small # of test objects/indiv
- -> Each neutron responds to >1 concept, but there’s usually an obvious relation b/w them
- aka Jennifer Aniston Neurons
Explain what an ENGRAM CELL is.
Engram Cells:
= Neurons that maintain an engram
- Engram = hypothetical permanent change in brain, accounting for the existence of memory
Describe what OPTOGENETICS is.
- Neuroscientists insert an opsin gene into a particular neuron
- -> Use light to hyperpolarize/depolarize those neurons
Describe how Engram Cells were identified using Optogenetics.
(1) Tagging Stage:
- Neurons active during learning task are induced to express opsin while animal engages in particular learning task
(2) Manipulate Stage:
- Previously active neurons are now inhibited or excited by using light to influence the actively opsin-tagged neurons
–> Now able to observe, suppress, or activate engram cells in different parts of NS
see pg 291-292
List the types of memories that are stored in: INFEROTEMPORAL CORTEX.
Inferotemporal Cortex:
= Cortex of the inferior temporal cortex
- Important role in storing memories of VISUAL input
List the types of memories that are stored in: AMYGDALA.
Amygdala:
- Plays special role in memory for the emotional significance of experiences
- Little evidence that it STORES memories
- -> Involved in strengthening the emotional significant memories stored in other structures
- -> May be why emotionally-provoking events are remembered better than neutral events
List the types of memories that are stored in: PREFRONTAL CORTEX.
Prefrontal Cortex:
= Area of frontal cortex anterior to motor cortex
- Patients w/ damage to prefrontal cortex display no deficits on conventional memories tests
- -> BUT 2 episodic memory abilities are often lost by patients w/ large prefrontal lesions:
(1) Anterograde & retrograde deficits in memory for temporal order of events, even when they can remember the events themselves
(2) Deficits in working memory - -> Thus patients have difficulty performing tasks that involve series of responses
- Specific complex patterns of prefrontal activity ass. w/ various memory functions
List the types of memories that are stored in: CEREBELLUM.
Cerebellum:
- Storage of memories of learned sensorimotor skills.
- Plays role in certain types of memory w/ no obvious motor component
List the types of memories that are stored in: STRIATUM.
Striatum:
- Storage of memories for consistent relationships b/w stimuli & responses
- -> The type of memories that develop incrementally over many trials
- Plays role in certain types of memory w/ no obvious motor component
Describe the phenomenon known as LONG-TERM POTENTIATION (LTP).
What are LTP’s 2 key properties proposed as characteristics of physiological mechanism of learning & memory?
Long-Term Potentiation (LTP):
= The enduring facilitation of synaptic transmission that occurs following activation of synapses by high-intensity, high-frequency stimulation of presynaptic neurons
- Most frequently studied in the rodent hippocampus
Key Properties:
(1) LTP can last for a long time
- Several months after multiple high-frequency stimulation
(2) LTP develops only if firing of the presynaptic neuron is followed by firing of postsynaptic neuron
Provide evidence that LTP is related to neural mechanism of learning & memory (8).
- LTP can be elicited by low levels of stimulation that mimic normal neural activity
- LTP effects are most prominent in structures implicated in learning & memory (i.e. hippocampus)
- Learning can produce LTP-like changes in hippocampus
- Many drugs that influence learning & memory have parallel effects on LTP
- Induction of maximal LTP blocks the learning of a Morris water maze until the LTP has subsided
- Mutant mice displaying little hippocampal LTP have difficulty learning Morris water maze
- Behavioural changes that appear to be memories can be induced in mice via LTP
- LTP occurs at specific synapses shown to participate in learning & memory in simple invertebrate NS’s
see pg 294-295
FINISH LO 11.18 - 11.22
do it…
