the remembering brain Flashcards
SHORT TERM / WORKING MEMORY
▫ Information currently “in mind” ▫ NOT memory for what happened a few minutes or hours ago ▫ Different kinds of working memory • Information currently held in mind • Different kinds: ▫ Verbal (e.g. hold a phone number in mind) ▫ Visual • Limited capacity • Capacity often tested by measuring span • Try to remember the numbers: ▫ 8, 4, 2
STM SPAN/ CAPACITY
Short-term memory • Limited capacity • Capacity often tested by measuring span • Try to remember the numbers: ▫ 7, 3, 8, 1, 4, 8, 7, 9 3, 8, 8,3 • Typical span is 7 plus or minus 2
Influences on capacity STM
• Chunking: capacity is 7 plus or minus 2 chunks, not items XIBMSATMTVPHDX • But the number of chunks isn’t the only influence on capacity… • Word length ▫ Span is lower for longer words (e.g. skeleton, binoculars) • Opportunity to rehearse ▫ Articulatory suppression
\Working Memory
• Concept of working memory expands on that of short-term memory ▫ Working memory plays a wider, more active role in cognition (e.g. reasoning), vs. STM implies a passive role in retention • Working memory = a limited-capacity store for retaining information over the short term (maintenance) and for performing mental operations on this store (manipulation)–
Example: doing mental arithmetic
25 – 7 + 2
= 20
What did you have to do?
Had to keep the three numbers in mind (maintenance)
and perform subtraction and addition on them (manipulation)
Long-term memory
• Stored information: what happened seconds, minutes, or years ago • Need not be presently active or consciously accessible • Unlimited capacity • Different kinds…
LTM - DECLARATIVE VS. NON DECLARATIVE
• Declarative (explicit) vs. non-declarative (implicit) memory • Declarative memory: consciously accessible ▫ Includes episodic + semantic; impaired in HM ▫ This suggests MTL is critical for declarative memory • Non-declarative: not consciously accessible ▫ Skills, priming, habits ▫ Are these impaired in HM?
EPISODIC
(LTM)Episodic memory:
Memory for events of own life
Anterograde: strongly impaired ▫ Retrograde: gradient of impairment
SEMANTIC MEMORY
(LTM) Semantic memory ▫ Memory for facts about the world ▫ Anterograde: strongly impaired ▫ Retrograde: seemingly not impaired? ▫ But: most semantic knowledge acquired early in life, and is frequently re-encountered (rehearsed) ▫ When this is taken into account, there is also a gradient of retrograde impairment for semantic • Take-home: episodic and semantic memory are different, but both depend on the MTL
NONDECLARATIVE
(LTM)Non-declarative: not consciously accessible ▫ Skills, priming, habits ▫ Are these impaired in HM? ▫ Inference: Non-declarative does not depend on the MTL
(Skills can still play piano, knows how to use a knife and Recognizes wife. Knows who his sister is, Knows facts about the world, can still talk
Not shown: would be able to keep a phone number in mind so long as he can rehearse it)
PRIMING
NONDECLARATIVE
PRIMING -
- Definition: Exposure to a stimulus that influences later responses to that stimulus
- Word stem completion: Try it!
- Ele____
- Did you put elephant or element?
- Earlier exposure to “elephant” made you more likely to complete the stem as “elephant”
*
•Priming NOT impaired in amnesia even though recognition (episodic memory) is impaired
MEDIAL TEMPORAL LOBE
STRUCTURES?
MTL CONSISTS OF :
HIPPOCAMPUS
PARAHIPPOCAMPAL CORTEX
PERIRHINAL CORTEX
ENTORHINAL CORTEX
retrograde vs. anterograde amnesia
•Anterograde amnesia
▫Difficulty with memory for events AFTER brain damage
Forming new memories
•Retrograde amnesia:
▫difficulty with memories from BEFORE brain damage
Retrieval of old memories
REMOVAL OF MTL including hippocampus (PATIENT HM)
Whats spared // impaired?
•Dissociation #1:
•Short-term memory: Spared
•Long-term memory: Impaired
- Forgot the events of daily life as quickly as they occurred
- Inference: LTM but not STM depends on the MTL
- But: Childhood memories relatively intact…
HM: Dissociation #2
•Severe anterograde amnesia
•Gradient of retrograde amnesia
•Inference: MTL is critical for forming new memories and retrieving recently formed old memories
▫Less critical for retrieving distant memories
HM: Dissociation #3???????
•Episodic vs. semantic memory
•Episodic memory:
▫Memory for events of own life
▫Anterograde: strongly impaired
▫Retrograde: gradient of impairment
- ▫*
- So HM has a problem with long term memory, especially with forming new memories*
- Is that true for all kinds of long term memory?*
•Semantic memory
▫Memory for facts about the world
▫Anterograde: strongly impaired
▫Retrograde: seemingly not impaired?
▫But: most semantic knowledge acquired early in life, and is frequently re-encountered (rehearsed)
▫When this is taken into account, there is also a gradient of retrograde impairment for semantic
•Take-home: episodic and semantic memory are different, but both depend on the MTL
▫
•Together, episodic and semantic memory are called declarative memory
Third dissociation: episodic vs. semantic (notice question mark here)
•Consolidation hypothesis
▫Consolidation is the process by which moment-to-moment changes in brain activity are translated into permanent structural changes in the brain
•
•How does the ‘consolodation hypothesis’ explain:
▫Anterograde amnesia?
▫Gradient in retrograde amnesia?
*hint - consolodation takes years
Anterograde amnesia: events can’t be turned into permanent changes in the brain
Retrograde amnesia: memories that aren’t fully consolidated will be damaged
The MTL and consolidation
•Why are other forms of memory not affected by impaired consolidation? What is special about declarative memory?
▫Declarative memories may involve binding together different types of information
▫MTL may be an indexing system that links together different aspects of an event
**
- What kinds of information might be involved in your memory for an episode from your life?*
- Think about your last birthday party…*
- Information from different senses, emotion, semantics (understanding of what happened – what did this event mean), what were you thinking at the time, what did you learn from the episode*
Where are long-term memories stored?
▫Can the MTL be the place where memories are stored?
•HM’s oldest episodic and semantic memories were intact
▫Can the MTL be the place where memories are stored?
▫No. Otherwise those older memories would have been also eliminated.
•Memories appear to be stored where the information was initially processed…
Breaking down episodic memory
(not just one thing - there are multiple types)
•Recollection: vivid re-experiencing of a memory and details of the context in which it was encoded ****NOT VAGUE
▫“I met Steve at Sarah’s party last Thursday and we talked about Breaking Bad”
•Familiarity: feeling of knowing that an item was encountered, but without any contextual details
▫“I know that guy from somewhere…”
•Aggleton & Brown (1999) propose that recollection and familiarity are supported by different MTL structures
▫
Recollection, familiarity and the brain
•How to study the formation of different kinds of memories: Subsequent memory paradigm
▫Scan (fmri/ pet) subjects as they study various items *** Which brain areas were active??
▫Later, outside the scanner, give a memory test
▫What brain areas were active when a subject successfully formed a memory?
•What areas of the brain were active for items that were later recollected vs. familiar?
RECOLLECTION: HIPPOCAMPUS, PARAHIPPOCAMOAL CORTEX
^was the context remembered along with the item?
E.g., where I met Steve (context) in addition to Steve’s face (item)
FAMILIARITY: OTHER MTL STRUCTURES - ESP PERIRHINAL CORTEX
•There are different types/systems of memory
•The medial temporal lobes are critical for certain types
▫Episodic + semantic ( = declarative)
▫Less so for older memories
▫Amnesia is a deficit in declarative memory
•Some types of memory do not depend on the medial temporal lobes
▫STM/Working Memory
▫Non-declarative memory
e.g. skill learning, priming
•What areas of the brain were active for items that were later recollected vs. familiar?
RECOLLECTION: HIPPOCAMPUS, PARAHIPPOCAMOAL CORTEX
^was the context remembered along with the item?
E.g., where I met Steve (context) in addition to Steve’s face (item)
FAMILIARITY: OTHER MTL STRUCTURES - ESP PERIRHINAL CORTEX
