Memory IV Memory Systems Amnesia

Are there multiple LTM memory systems? How do you learn a new skill? How do you learn a new fact? How about learning about an event? Is there one long-term memory (LTM) system for these types of knowledge or are there multiple LTM systems?

A Taxonomy of Memory Systems LONG TERM MEMORY EXPLICIT (declarative) IMPLICIT (non-declarative) SEMANTIC (facts) EPISODIC (events) PROCEDURAL (skills & habits) PRIMING (perceptual, conceptual) Medial Temporal Lobe ASSOCIATIVE LEARNING (classical & operant conditioning) CortexStriatumAmydala/ Cerebellum

Semantic and Episodic Memory Semantic memory –memory for facts about the world can a canary sing? who is Secretary of State of the US? Episodic memory –memory for events in our lives (temporal organization) what did you eat for breakfast? where were you for the Super Bowl game?

I remember that –I got soaked in the rain yesterday walking to class –Barack Obama is the President of the US –my first grade teacher could not pronounce my name the first day of school –California is facing severe drought conditions Semantic or Episodic Memory?

Implicit and explicit memory Implicit memory: past experiences influence perceptions, thoughts & actions without awareness that any information from past is accessed Explicit memory: conscious access to info from the past (“I remember that..” ) -> involves conscious recollection

Explicit & Implicit Memory Tests Look at the following words. I will test your memory for these words in various ways.

Memory Test Explicit test of memory: recall –Write down the words you remember from the list in the earlier slide Implicit tests of memory –On the next slide, you will see some words missing letters, some “word fragments” and some anagrams. Guess what each word might be.

Implicit Memory Tasks Word-fragment completion is an implicit memory task. Fragments are (often) completed with words previously studied in the absence of an explicit instruction to remember the word Amnesiacs often show spared implicit memory dissociation suggest different systems for implicit and explicit memory systems

Implicit vs. Explicit Memory Graf, Squire, & Mandler (1984): –Study words: cheese, house, … –Explicit memory test: cued recall. Complete fragment to a word from study list: ch _ _ _ _ –Implicit memory test: word stem completion. Complete fragment to form any word: ch _ _ _ _

Word-stem completion spared in amnesiacs Graf et al. (1984).

Implicit Memory Other forms –Procedural Memory –Perceptual learning –Classical conditioning Real-world applications –Unintentional plagiarism

Amnesia

Sources Blow to head, Concussion Korsakoff syndrome (severe vit. B1 deficiency) Alzheimer’s Damage to hippocampus, thalamic structures ECT (electroconvulsive shock therapy) Midazolam: artifically induced amnesia

Amnesia Types: –Retrograde: cannot remember old memories –Anterograde: cannot form new episodic memories

Retrograde amnesia Temporal gradient: –early memories are better remembered than memories before trauma (Ribot’s law) –Recently formed memories continue to undergo neurological change: memory consolidation

Temporal Gradient Testing memory for diary entries from retrograde amnesiac (Butters & Cermak, 1986)

Anterograde Amnesia Inability to acquire new information –Think of movie “memento” –Does not affect short-term memory –Does not affect general knowledge from the past –But, it is difficult to learn new facts –Affects memory regardless of modality (visual, auditory, tactile, etc). –Spares skilled performance

Famous Anterograde Amnesiac: HM Surgery when 27 years old (1953) to deal with severe epilepsy Removed bilaterally medial temporal lobes, including hippocampus A NPR segment on HM Henry Gustav Molaison

H.M. Could still retrieve memories acquired long before surgery –had normal vocabulary –average IQ –intact working memory Profound anterograde amnesia: could not form new explicit/declarative memories General knowledge intact but “stuck in time”: –Did not learn words introduced after 1953: “Jacuzzi”, “granola”, “flower-child”

HM able to form some new memories: mirror trace task Milner, 1965

Learning a new skill: mirror-reverse reading

Amnesics can learn to mirror-reverse read and are sensitive to repetitions

Clive Wearing Accomplished British musician Suffered from encephalitis –hippocampus destroyed in both hemispheres –frontal lobe damage as well Retrograde as well as anterograde amnesia –memory lasts between 7-30 seconds

Clive Wearing Diary entries: 8:31 AM: Now I am really, completely awake 9:06 AM: Now I am perfectly, overwhelmingly awake 9:34 AM: Now I am superlatively, actually awake

Clive Wearing: Video (~4min.) For full video segment see:

Clive Wearing Spared implicit memory –emotional memory: gradual acceptance of his condition –procedural memory: layout of his residence

Claparède study (1911) Claparède was a Swiss physician treating an amnesic woman Patient never remembered having met Claparede (doctor) before Claparade offers handshakes with pinprick Next time, no explicit memory of event Still, patient refuses to shake hands and offers explanation: “sometimes pins are hidden in people’s hands”

Amnesiacs and Trivia Questions Korsakoff patients were given feedback, then retested. No conscious memory for items but better performance. Their explanation: “I read about it somewhere” (Schacter, Tulving & Wang, 1981).

Can amnesics acquire any new knowledge? Declarative memory (memory for information/knowledge, e.g. episodic & semantic memory)  impaired Procedural memory (e.g., how to ride a bike)  yes Implicit memories (using past information possibly without being aware of it)  yes

Implications Hippocampus and surrounding structures in medial temporal love are responsible for transferring explicit memories from working memory to LTM Separate memory systems: –working memory vs. LTM –explicit vs. implicit memory

Prefrontal cortex: Short term storage of explicit memories Hippocampus: Transfers explicit memories from working memory to LTM Cerebellum: Implicit memories of skills, habits, conditioning Memory & The Brain 35