Neuroscience of Memory • Research question: are there independent memory

systems? • Use amnesia case studies – search for double dissociations

• What do the case studies tell us about the functions of the damaged brain areas?

• “The Last Hippie” by Oliver Sacks

• “A few more questions convinced me that Greg F had virtually no memory of events much past 1970, certainly no coherent chronological memory of them. He seemed to have been left, marooned, in the sixties – his memory, his development, his inner life had since then come to a stop.”

Amnesia

• Anterograde amnesia

• Memory loss after point of damage

• E.g. H.M.; Korsakoff’s syndrome; encephalitis

• Retrograde amnesia

• Can’t remember events prior to point of injury

• “Soap opera amnesia”

• E.g. K.C.

Movies and memory (amnesia!) http://socrates.berkeley.edu/~kihlstrm/movies.htm

• Bourne Identity (Matt Damon)

• Who Am I? (Jackie Chan)

• The Long Kiss Goodnight (Geena Davis)

• Memento (Guy Pierce)

• The Eternal Sunshine of the Spotless Mind

• 50 First Dates (Drew Barrymore)

Case studies: Amnesia http://www.liveleak.com/view?i=fd0_1261475829

• H.M. (1926 – 2008) • “Every day is alone.”

• Background • Brain surgery (1953) due to

epileptic seizures • Temporal lobotomy (removal

of both hippocampal areas) • Anterograde amnesia

• Cognitive findings • STM intact; LTM deficit • Implicit memory intact;

explicit memory deficit • Intact repetition priming

• Procedural memory intact • Intact problem solving

Clive Wearing • Dense retrograde and anterograde amnesia patient

• Born in 1938, contracted viral encephalitis in 1985

• Prior to illness a very successful musician

• Husband to 2nd wife; has children from 1st marriage

• What is he (in terms of cognition) able and not able to do?

• BBC 2005 – “Man with the 7s memory”

• 20 yrs post injury – 67 yrs old • http://www.youtube.com/watch?v=wDNDRDJy-vo&feature=related

• 1998 documentary

• 13 yrs post injury – 60 years old • http://www.youtube.com/watch?v=Lu9UY8Zqg-Q&feature=related

• http://www.youtube.com/watch?v=xCyvzI2aVUo&fea

• http://www.youtube.com/watch?v=9BrCBq2FY_U&feature=related

Underside of brain Main structures of medial temporal lobe (MTL)

Brain areas associated with memory

• Explicit memory • Medial temporal lobe

• Hippocampus

• Perirhinal cortex

• Implicit memory • Striatum for procedural skills

• Neocortex for priming tasks

• Semantic memory • Left inferior prefrontal cortex

• Neocortex - widely distributed

• Episodic memory • Right anterior and dorsolateral prefrontal cortex

• Medial temporal lobes

Case studies & brain areas • H.M.: anterograde amnesia (retrograde 2yr) • STM intact; LTM deficit; intact implicit memory

• Bilateral medial temporal lobes

• Posterior region of hippocampus intact

• R.B.: anterograde (retrograde 1yr) • Memory deficits less severe than H.M.

• Lesion to CA1 pyramidal cells (bilateral) of hippocampus

• K.C.: retrograde and anterograde amnesia • STM and semantic intact; no episodic memory

• Medial temporal lobe, frontal parietal, occipital

• Greater damage on left side

• M.S.: Intact explicit; impaired implicit • Right occipital lobe – areas 18 and 19

• Korsakoff’s syndrome • Dorsomedial nucleus of thalamus & mamillary bodies

Medial temporal lobe

• Medial temporal lobe NOT responsible for… • Implicit memory or procedural memory

• Not where LTM are stored

• STM or WM

• Medial temporal lobe IS responsible for… • Conscious LTM formation

• Consolidation: Strengthening association

• Transfer of info from STM to LTM

• Problems and other theories • Based on case studies

• MTL for encoding or retrieval?

• Subtraction technique with imaging

Synapse level • Memory is represented by changes at the synapse (Hebb) • Structural changes • Neurotransmitter changes • Neural firing changes

• Long-term potentiation (LTP)

Imaging studies: Memory and the brain

• Research question: • What areas of the brain are responsible for :

• Each type of memory • Each stage of memory process (e.g. encoding)

• What is the pathway of activation and time course of processing information?

• Methodology: • fMRI: baseline vs memory conditions ; subtraction technique • ERP: examine general locations, provide time course

• Conclusions: • Specific areas may have specific memory functions, but areas

interact (e.g. consolidation) • Each feature of an experience (e.g. visual) may be stored in

distinct areas of the cortex (responsible for that type of process) • MTL (especially hippocampus) involved in explicit, episodic

memory; involved in consolidation of memory (stm to ltm)

Davachi et al (2003)

• Method • Viewed 200 words; create image of place to go with word; DV: brain imaging

using fMRI during encoding phase

• Delay 20hrs; recognition test for old and new words (only behavioral results)

• Results • 54% acc for ‘old’ words

• Words that generated more activity at study in perirhinal cortex were more likely to be remembered

• Conclusions • Can predict recall based

on encoding activity

Wagner, et al. (1998)

Study: decide if word is abstract or concrete vs. upper or lower case

Test: fMRI of “semantic areas”

“greater recruitment of the left prefrontal and (parahippocampal/fusiform gyri) will tend to produce more memorable verbal experiences.”

Talmi, Grady, Goshen-Gottstein, & Moscovitch (2005). Neuroimaging the serial position curve.

Early vs late

probes

Hippocampus

Early vs late

probes

Perirhinal

cortex

Early vs

control

Left medial

temporal lobe

Early vs

control

Entorhinal

cortex

Early vs late probe = item presented at beginning of list vs end of list

Rajah & McIntosh (2005)

Found similar pattern of neural interactions within each model so “episodic and semantic retrieval may reflect variation along a continuum of processing during task performance within the context of a single memory system.”