CH 11: Learning, Memory & Amnesia

Question 1

List the 4 specific memory tests used to assess H.M.’s anterograde amnesia.

Answer 1

1. Digital Span +1 Test
2. Block-Tapping Memory-Span Test
3. Mirror-Drawing Test
4. Incomplete-Pictures Test
5. Pavlovian Conditioning

Question 2

Describe the Digital Span +1 Test - what did it test?

Answer 2

1. 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

Question 3

Describe the Block-Tapping Memory-Span Test - what did it reveal?

Answer 3

2. 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

Question 4

Describe the Mirror-Drawing Test - what did it reveal?

Answer 4

3. 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

Question 5

Describe the Incomplete-Pictures Test - what did it reveal?

Answer 5

4. Incomplete-Pictures Test:

- Showed HM form new long-term memories

Question 6

Describe the Pavlovian Conditioning.

Answer 6

5. Pavlovian Conditioning
   - Hear tone just before puff of air admin to eye
   - Repeat until tone alone elicited an eye blink

Question 7

Describe the 1st major scientific contribution of H.M.’s case.

Answer 7

1. 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

Question 8

Describe the 2nd major scientific contribution of H.M.’s case.

Answer 8

2. 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

Question 9

Describe the 3rd major scientific contribution of H.M.’s case.

Answer 9

3. 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

Question 10

Distinguish b/w EXPLICIT memories & IMPLICIT memories.

Answer 10

• EXPLICIT Memories = conscious long-term memories

- IMPLICIT Memories = memories that are expressed w/o conscious awareness

Question 11

Describe MEDIAL TEMPORAL LOBE AMNESIA.

What are its major features?

Answer 11

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.

Question 12

What has research on Medial Temporal Lobe Amnesia taught us about learning & memory?

Answer 12

• 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

Question 13

Describe the difference b/w SEMANTIC & EPISODIC memories.

Answer 13

Explicit long-term memories come in 2 varieties:

1. SEMANTIC Memories = explicit memories for general facts/info
2. 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

Question 14

Describe GLOBAL CEREBRAL ISCHEMIA.

Answer 14

• The interruption of blood supply to entire brain

- Often suffers from Medial Temporal Lobe Amnesia

Question 15

Describe TRANSIENT GLOBAL AMNESIA.

Answer 15

• 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

Question 16

Describe the case of R.B..

Answer 16

• 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

Question 17

Describe KORSAKOFF’s SYNDROME - describe its symptoms.

Answer 17

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

Question 18

Describe the etiology of the amnesia of Korsakoff’s syndrome.

Answer 18

• Attributable to brain damage ass. w/ thiamine deficiency which accompanies heavy alcohol consumption

Question 19

Describe the symptoms & amnesia effects of Alzheimer’s Disease (AD).

Answer 19

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

Question 20

Describe the etiology of the amnesia of AD.

Answer 20

• ^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

Question 21

Define POST-TRAUMATIC AMNESIA.

Answer 21

• Amnesia produced by a non-penetrating head injury (=blow to head w/o penetrating skull)

Question 22

Summarize the effects of a closed-head injury on memory (3).

Answer 22

1. A blow to head produces coma
2. When victim regains consciousness, there’s a period of confusion
3. 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

Question 23

Define MEMORY CONSOLIDATION.

Answer 23

• Storage of older memories have been strengthened

Question 24

Describe the classic view of memory consolidation.

Answer 24

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

Question 25

Describe ECS.

Answer 25

- 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

Question 26

Describe the CURRENT view of memory consolidation.

Answer 26

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).

Question 27

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?

Answer 27

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

Question 28

Describe the neuroanatomical basis for the object-recognition deficits that result from bilateral medial temporal lobectomy.

Answer 28

- 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

Question 29

Describe hippocampal PLACE CELLS.

Answer 29

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

Question 30

Describe the ENTORHINAL CORTEX.

Answer 30

- Area of medial temporal cortex that's a major source of neural signals in hippocampus

Question 31

Describe entorhinal GRID CELLS.

Answer 31

Grid Cells: - Entiorhinal neurons that have an extensive array of evenly spaced place fields, producing a pattern reminiscent of graph paper

Question 32

Describe the relationship b/w hippocampal Place Cells & entorhinal Grid Cells.

Answer 32

- 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

Question 33

Describe the role of the hippocampus in spatial memory & other types of memory it supports.

Answer 33

1. Certain cells in hippo shown to code for TEMPORAL aspects of an experience 2. Hippo plays role in learning about social organization in humans 3. Cells in hippo & its surrounding structures shown to play role in coding of concepts

Question 34

List 3 amor structures of the Medial Temporal Lobes.

Answer 34

1. Hippocamps 2. Amygdala 3. Medial Temporal Cortex = entorhinal, peripheral & parahippocampal cortices

Question 35

Define a CONCEPT CELL.

Answer 35

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

Question 36

Explain what an ENGRAM CELL is.

Answer 36

Engram Cells: = Neurons that maintain an engram - Engram = hypothetical permanent change in brain, accounting for the existence of memory

Question 37

Describe what OPTOGENETICS is.

Answer 37

- Neuroscientists insert an opsin gene into a particular neuron - -> Use light to hyperpolarize/depolarize those neurons

Question 38

Describe how Engram Cells were identified using Optogenetics.

Answer 38

(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**

Question 39

List the types of memories that are stored in: INFEROTEMPORAL CORTEX.

Answer 39

Inferotemporal Cortex: = Cortex of the inferior temporal cortex - Important role in storing memories of VISUAL input

Question 40

List the types of memories that are stored in: AMYGDALA.

Answer 40

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

Question 41

List the types of memories that are stored in: PREFRONTAL CORTEX.

Answer 41

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

Question 42

List the types of memories that are stored in: CEREBELLUM.

Answer 42

Cerebellum: - Storage of memories of learned sensorimotor skills. - Plays role in certain types of memory w/ no obvious motor component

Question 43

List the types of memories that are stored in: STRIATUM.

Answer 43

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

Question 44

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?

Answer 44

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

Question 45

Provide evidence that LTP is related to neural mechanism of learning & memory (8).

Answer 45

1. LTP can be elicited by low levels of stimulation that mimic normal neural activity 2. LTP effects are most prominent in structures implicated in learning & memory (i.e. hippocampus) 3. Learning can produce LTP-like changes in hippocampus 4. Many drugs that influence learning & memory have parallel effects on LTP 5. Induction of maximal LTP blocks the learning of a Morris water maze until the LTP has subsided 6. Mutant mice displaying little hippocampal LTP have difficulty learning Morris water maze 7. Behavioural changes that appear to be memories can be induced in mice via LTP 8. LTP occurs at specific synapses shown to participate in learning & memory in simple invertebrate NS's **see pg 294-295**

Question 46

***FINISH LO 11.18 - 11.22***

Answer 46

do it...