How Fragile is Your Memory? Susie Wang XSAC Lecture 17/5/12
Outline How memory works: • What is Memory? • Types of Memory & Amnesia • Memory Formation When memory breaks: • False Memories • Memory Erasure Conclusion
What is memory? “The retention of learned information” – p726, Bear, Connors & Paradiso. “The internal repository of stored information” – p193, Smith & Kosslyn.
What is memory? • Memory is not a videorecording • Different aspects of memory are stored and processed in different regions • We remember the gist of things
Types of Memory • Amnesia: partial or total loss of memory due to brain damage • There are two main types: • Retrograde amnesia • Anterograde amnesia
Retrograde Amnesia Memory loss of events before brain damage [Clip: Bourne Identity] • Things you forget: • Your name, your age, family, events from your childhood. • Things you may not forget: • Skills, such as how to punch people • Facts, such as that French is spoken in France
Anterograde Amnesia The inability to form new memories • [Clip: Clive Wearing] • Things you forget: • Events that just happened to you • New facts learned after acquiring amnesia • Things you may not forget • How to punch people, drive, etc. • Your name, your family members, childhood
Anterograde Amnesia [Clip: Memento 1] • Short term memory • Long term memory • Brain damage in: temporal lobe and hippocampus
Patient H. M. • Surgical operation removed medial temporal lobe and hippocampus • To some extent, H.M. has retrograde and anterograde amnesia. “Right now I’m wondering, have I done or said anything amiss? You see at this moment everything looks clear to me, but what happened just before? That’s what worries me. It’s like waking up from a dream. I just don’t remember”. (Smith & Kosslyn, 2009)
Long Term Memory “The kind of knowledge that persists so that it can be retrieved long after the experience is past” – p193, Smith & Kosslyn2009. Used to make judgements regarding the future
Long Term Memory [Clip: Sammy Jankis] Types: • Non-declarative • Priming • Skills • Habituation and conditioning • Declarative • Semantic: facts • Episodic: first-person memory
Memory Formation Encoding Consolidation Storage Retrieval
Encoding • The process in which information is transformed into memory • Regions of importance: Medial temporal lobe and hippocampus • The temporal lobe • The temples • Tempus: Latin for time • Memory of past events
Consolidation • When memories become more stable over time, and are stored in long-term memory • In structures other than the medial temporal region
Storage • Long term memory for events is widely represented. Multiple areas are involved. • May exist in synapses (electrical communication between cells in the brain) • Regions of the brain?
Retrieval • Cues! • Encoding specificity • Returning to the scene of the crime • Remembering whilst underwater • Remembering whilst drunk • Cue-dependent forgetting • Childhood amnesia: cues to retrieving early memories are inaccessible because they were stored differently (without language)
Retrieval “Each item [in memory] cannot be retrieved in precisely the same form as it was initially stored; it is better to think of a representation as being recreated or evoked than as being searched for. ” • Smith 1996 When you retrieve a memory, you are actually recreating it.
False Memories • Repeated prompting for information • Incorrectly remembering having seen objects that look similar or are conceptually related • “Lost in the shopping mall” • Imagination inflation
Imagination Inflation • Check the Pepsi machine for change OR get down on one knee and propose marriage to the machine • Wave from the top of the steps OR recite the balcony scene lines from Romeo and Juliet • Look up a word in the dictionary OR pat the dictionary and ask how it’s doing • Lie down on the couch and relax OR lie down on the couch and talk to Freud
Limitations • Most psychology studies rely on statistical analyses • Significance refers to when we can rule out that the result happened by chance or accident • Ethical limitations on the strength of manipulations • Most people did not believe false memories • Plausibility, relevance and memorability are important factors in whether false memories are adopted
Extreme False Memories • There are extreme cases that people have called “false memory syndrome”, where events described are not plausible and are highly memorable. • Sexual abuse, Alien abductions, Satanic rituals • Therapy for recovering repressed memories
Memory Erasure [Clip: Eternal Sunshine of the Spotless Mind] • Selective removal • Neural map of memories • Cues again!
Memory Erasure “Rapid erasure of long-term memory associations in the cortex by an inhibitor of PKMz” Shema, Sactor & Dudai 2007 • PKMz: Protein kinase M zeta, a type of biological molecule that increases the rate of chemical reactions (called an enzyme) • Involved in maintaining long-term memories in many areas of the brain • The inhibitor is called ZIP. • ZIP blocks or decreases the activity of PKMz.
Memory Erasure • Taste aversion in rats Findings: 1) Memories can be altered long after they are formed and consolidated in the cortex 2) Rats given ZIP had weaker memories for the bad taste • Removal of the memory of the event, or just memory of the bad taste?
Memory Erasure • PKMzalters the structure of synapses • But synapses are not the end of the story! • Constant enzymatic activity
Memory Erasure “On par with a heavy night of drinking…” • Eternal Sunshine of the Spotless Mind The state of intoxication mimics the brain activity found in people who have lesions in the temporal lobe • Decrease in amount of information remembered • Information encoded in a qualitatively different way • Korsakoff’s Syndrome
War of the Ghosts • If we have time, story-time! • Listen to the story • Try and write down what happens, step by step.
Conclusion • Memories are fragile • Complicated brain system, still a lot unknown • Memory and the self