L&M Episodic and Semantic Memory PDF

Episodic and Semantic Memory (Lecture 10-12, Quiz 4) Declarative memory ○ “Knowing that ____” ○ Involves conscious recollection of events and facts ○ Typically verbalize ○ Can be acquired with a single exposure (rapid encoding) ○ Supports flexible communication...

Episodic and Semantic Memory (Lecture 10-12, Quiz 4) Declarative memory ○ “Knowing that ____” ○ Involves conscious recollection of events and facts ○ Typically verbalize ○ Can be acquired with a single exposure (rapid encoding) ○ Supports flexible communication and problem solving ○ Declarative memory is critical during early stages of skill acquisition Remembering instructions or steps involved in a skill High cognitive load when holding explicit information in mind Episodic vs semantic memory ○ Episodic memory can involve rich details about individual experiences All information is initially contextualized, experienced in a particular time and place Organized according to spatial and temporal (time-based) structure Include information about the source ○ Semantic memory can involve general knowledge that is shared across multiple experiences Organized according to meaning Episodic and semantic memory ○ Semantic memories formed by extracting the shared features of episodic memories ○ Over time, information becomes decontextualized (not associated with a specific place and time or source) Retrieving explicit memories ○ Retrieval: process of remembering information that has been stored in long term memory Can be automatic or controlled Varies in difficulty depending on many factors, including the strength of the stored memory and the availability of retrieval cues ○ Retrieval cues: information that is associated with a target memory and can aid in memory retrieval Fragments of original experience Identity Place and time Other contextual cues ○ The more often a cue has been associated with the target memory, the better it is at driving retrieval Testing memory retrieval  ○ Free recall - no retrieval cues ○ Cued recall - retrieval cues ○ Recognition - presentation of experienced material Retrieving explicit memories ○ Retrieval cues provide paths to a stored memory; multiple cues increase chance of finding the target information ○ Transfer-appropriate processing: retrieval is more likely when cues available during testing are similar to those available during encoding Cues reactivate memory for the context in which information was experiences, including external environment and internal state ○ Godden and Baddeley examined how memory performance is affected by mismatch between study and test environments ○ Divers memorized lists of words either underwater or on the beach, then were tested in either the same or different context ○ Context can include other aspects of experience, including internal state ○ Bower found that participants remembered words better when they were in same mood during encoding and retrieval Either happy or sad mood induced right before encoding and retrieval Being happy or sad didn’t change test performance overall, but participants in the same mood during encoding and retrieval recalled about 2x as many words ○ Internal state (interoceptive context) acts as a retrieval cue for events experiences in similar states in the past Forgetting ○ Exponential forgetting curve: rapid initial forgetting, but less and less forgetting over time ○ Decay: memories fade because of passage of time Passive forgetting of more remote (older) events ○ Interference: memories fade because of other, competing information held in long term memory Proactive interference: disruption of new learning by previously stored information Retroactive interference: disruption of old (previously stored) information by new learning Forgetting due to interference ○ Proactive: previously learned password associated with a website can interfere with new learning (proactive interference) ○ Retroactive: once well-learned, new password interferes with old passwords  ○ Interference is not a simple matter of over-writing previously learned information, depends on the similarity between information experienced at different times More distinctive memories (based on manner of processing, context, semantic content) are less susceptible to interference ○ McGeogh and McDonald: Participants learned list of words, then recalled them after a delay Manipulated whether participants learned a second set of material before the test The more similar the new information is to first list, the greater the amount of interference Summary ○ Declarative involves explicit knowledge about past experiences tied to specific time and place (episodic memory) and more general knowledge (semantic memory) ○ Retrieval involves reactivation (and conscious awareness) of declarative memory, and can be either automatic or controlled ○ Availability of strongly associated retrieval cues make remembering more likely ○ Forgetting occurs both due to passage of time (decay) and encoding of new, similar information (interference) Elaborative encoding ○ Processing information by connecting to prior knowledge, generating mental imagery, or otherwise embellishing to-be-learned material Elaborations provide additional retrieval cues and create more distinctive memories Elaborative encoding: levels of processing effect ○ Craik and Tulving examined how the depth of processing applied to information affects memory Shallow processing: focus on surface properties that are unrelated to semantic content Deep processing: focus on meaning of material ○ Four processing conditions: Structural (capitalization): Is the word in capital letters? Phonemic (rhyming): Does it rhyme with weight? Category: Is it a type of fish? Sentence verification: He met a ___ in the street ○ After a delay, presented with list of words and tested on recognition ○ Words processed more deeply most likely to be recognized Elaborative encoding: generation effect ○ Participants studied pairs of words linked by a particular relationship  ○ Two conditions: Read: read the words Generate: given one word and the first letters of the second word, complete the second word according to the target relationship Elaborative encoding: self-referential processing ○ Information is better remembered when it is related to one’s self concept ○ Participants studied adjectives with a levels of processing manipulation Elaborative encoding: mental imagery ○ A powerful form of elaborative processing is the use of mental imagery, including rich visual and spatial mental representations Memory palace (method of loci): technique for improving memory by placing items within a mental image of a familiar context or route Semantic memory: connecting to meaning ○ Elaborative encoding typically associated with better memory performance Levels of processing effect Generation effect Self-referential processing Visuospatial imagery (memory palaces) Semantic memory: connecting to meaning ○ Can involve general knowledge that is common across multiple experiences Not tied to a specific context Memories are organized according to meaning ○ Why do we have semantic memory? Accessing prior knowledge helps us organize, interpret, and remember new experiences by connecting to meaning Improves our ability to respond to novel circumstances Semantic context ○ Semantic context: knowledge activated by details of current environment (including internal thoughts) that influence interpretation of a situation Semantic knowledge can be automatically activated or can be retrieved through effortful control ○ Phonemic restoration effect: subjects perceived different words depending on the context, couldn’t identify which phoneme was missing Semantic memory: connecting to meaning ○ Semantic memory creates meaningful organization of new experiences  Memory for an event is not just about its physical details, but your subjective interpretation ○ A meaningful context leads to events being better remembered than disconnected, independent pieces of information ○ Participants who saw the topic before reading the passage were better able to recall ideas in the text than participants who never heard the topic or saw it afterwards Elaborative encoding ○ Elaborative encoding: processing information by connecting to prior knowledge, generating mental imagery, or otherwise embellishing to be learned material Can be automatic or controlled Elaborations provide additional retrieval cues and create more distinctive memories Elaborative encoding: levels of processing effect ○ Craik and Tulving examined how the depth of processing applied to information affects memory Shallow processing: focus on surface properties (perceptual features) that are unrelated to semantic content Deep processing: focus on meaning of material ○ Four processing conditions: Structural (capitalization) Phonemic (rhyming) Category Sentence verification ○ After a delay, presented with a list of words and tested on recognition ○ Word processed more deeply are more likely to be recognized Elaborative encoding: self referential processing ○ Information is better remembered when it is related to one’s self concept ○ Participants studied adjectives with a levels of processing manipulation Elaborative encoding: generation effect ○ Participants studied pairs of words linked by a particular relationship (antonyms, belong to the same category, etc.) ○ Two conditions: Read: read the words Generate: given one word and the first letters of the second word, complete the second word according to the target relationship Elaborative encoding: mental imagery ○ A powerful form of elaborative processing is the use of mental imagery, including rich visual and spatial mental representations  Memory place (method of loci): technique for improving memory by placing items within a mental image of a familiar context or route Elaborative encoding typically associated with better memory performance ○ Levels of processing effect ○ Generation effect ○ Self referential processing ○ Visuospatial imagery (memory palaces) Semantic memory: connecting to meaning ○ Memory improves when information is connected to existing knowledge or processed in terms of meaning Semantic meaning (is this word positive or negative?) Self referential processing (does this word describe me?) Re-phrasing into own words Generating examples, related information, or explanations Memory is reconstructive ○ Declarative memory is reconstructive: interactions between episodic and semantic memory affect the interpretation, encoding, and retrieval of information Fill in the gaps based on general knowledge Remember events according to our understanding of the situation or context ○ Much of the time, this is good, it helps us make sense of ambiguous, uncertain, or noisy experiences ○ Also means our memories of past events are rarely an unbiased record, instead we reconstruct past experience based on what we know now Illusory truth Distortions and false memory Memory and belief ○ Why do you hold the beliefs you do? ○ Semantic memory includes beliefs about the world, including the self, which are not tied to any particular context ○ Beliefs are strengthened through repeated exposure across many context/sources Belief through repetition ○ Jacoby: participants studied list of non-famous names and were told they were not famous people, studied either 1 or 4 times ○ Immediately afterwards, presented with a list that contained the same names, other famous names, and new non-famous names; could accurately identify non-famous names  ○ One day later, participants mistook many of the old non-famous names to be famous people ○ For statements that were initially judges neutral or false, repetition led to increase in perceived validity ○ Illusory truth effect: tendency to believe that false information is correct due to repeated exposure Repetition of false statements, whether factual or opinion based, leads to increased judgments of validity Warnings that information may be false do not prevent illusory truth effect Semantic context ○ Knowledge activated by details of current environment, including internal thoughts, that influence interpretation of a situation Semantic knowledge can be automatically activated or can be retrieved through effortful control False memory ○ Studying related words leads to retrieval of the theme word from semantic memory People report having studied the theme word ○ Unable to distinguish between words that were retrieved due to external stimulus vs internal activation of semantic context Example of source monitoring error: remembering information but being mistaken about the source of that memory False memory: misinformation effect ○ Participants shown a slideshow of a car accident Half of the participants saw a slide containing a stop sign, the other half of a yield sign ○ Then responded to series of questions, one of which was consistent or misleading ○ After 20 minute delay, asked which images had appeared in the original set of slides Consistent question condition: 75% correct Misleading question condition: 41% correct ○ Post-event information exerts a powerful influence on reconstructive memory Example of source monitoring error: incorporation of new information into their memory for past events, even is misleading or accurate ○ Eyewitness testimony, lineups, etc. ○ Investigators commonly use interrogation techniques which imply the existence of incriminating evidence (bait questions)  Rationale: innocent suspects will reject out of hand, while guilty suspects will try to explain away ○ Problem: jurors who view the interrogation confuse bait questions for actual evidence Summary ○ Semantic knowledge emerge from repeated, overlapping experiences Some beliefs, things we know about the world, are not rooted in logic or reasoning, but simple repetition (illusory truth effect) ○ Episodic memory is reconstructive: semantic knowledge has influence on how you interpret and remember past events Semantic context (false memory) Post event information (misinformation effect) Amnesia ○ Retrograde amnesia: loss of memories for events dating from before a brain injury or disruption ○ Anterograde amnesia: a severe loss of the ability to form new episodic and semantic memories ○ Amnesia can arise from many causes: Lesions (patient H.M.) Concussion, traumatic brain injury Electroconvulsive shock therapy Transient global amnesia Functional amnesia (suppression of trauma) Excessive alcohol ○ When amnesia involves loss of explicit memory, typically ties to impaired functioning of the medial temporal lobe (including hippocampus) Medial temporal lobe: constructing experience ○ Structures in the medial temporal lobe are critical for forming new explicit memories ○ Rapid encoding of events, including the relationships between stimuli, temporal order, and spatial context ○ Many brain areas contribute to your understanding of the scene Face identification Object classification Auditory/speech processing ○ MTL is necessary for binding together these elements to create a memory of the event Relationships between cues, temporal order, and spatial context Amnesia ○ Ribot gradient: a pattern of retrograde memory loss in which recently acquired memories are more prone to disruption than older memories  Temporally graded retrograde amnesia ○ We think of more recent events as being easier to retrieve from memory ○ Why are recent memories more susceptible to loss than remote memories? Consolidation ○ Consolidation period: period of time during which new episodic and semantic memories are vulnerable and easily lost or altered Consolidation is the process by which memories become stable and resilient (less susceptible to disruption) ○ Two kinds of consolidation: Synaptic (or cellular) consolidation: stabilization of new synaptic connections over relatively short time frame (hours) Systems consolidation: transition from hippocampal-dependent to cortex-dependent memory over longer time frame ○ Experiment gave patients with depression a TV show test before and after ECT treatment ○ Memory for recent TV shows was disrupted by ECT; memory for older TV shows left intact Reconsolidation ○ Evidence for consolidation process suggest that, once consolidated, a memory is stable and will not change ○ But even after a long period of time, when consolidation should be complete, reactivating a memory can make it newly susceptible to disruption or change Reconsolidation: the process where each time an old memory is recalled or reactivated, it may become vulnerable to modification ○ Participants were told two stories accompanied by slide shows A week later, memory of story B was reactivated through recall test: shown slide of story B and asked to recall hidden details No reactivation of story A Immediately after reactivation, one group underwent ECT Final memory test a day later In control (no ECT) group, reactivation of story B improved final memory relative to story A (testing effect) In ECT group, reactivation of story B prior to ECT treatment led to poorer memory Medial temporal lobe: constructing experience ○ MTL damage leads to loss of ability to encode new episodic memories (anterograde amnesia)  ○ MTL damage also impairs ability to retrieve recent episodic memories (temporally-graded retrograde amnesia) Indicates that episodic memory retrieval initially depends on MTL, but after consolidation can be retrieved without it Two competing theories of the role of hippocampus/MTL in consolidation: Standard consolidation theory Multiple trace theory Standard consolidation theory ○ According to this, the main function of the hippocampus is to index (bind together) different components of an event (represented in the cortex) Cortex: modality specific representations (sounds, smells, objects) Hippocampus: relational binding, providing an index for elements that make up events ○ During consolidation, hippocampal replay of past experience facilitates formation of new associations in cortex Doesn’t depend on conscious awareness (can occur during sleep) Transferral of memory from hippocampus to cortex; after consolidation is complete, hippocampus is no longer necessary for retrieval ○ Standard consolidation theory accounts for the temporally graded nature of amnesia Once consolidation is complete, hippocampus is no longer necessary for retrieval If consolidation is not complete, disruption of hippocampus interferes with retrieval ○ Same problems with the standard theory Can’t account for other evidence that the hippocampus is still involved in retrieval of remote, highly detailed episodic memories Doesn’t explain how memories can be disrupted through reconsolidation (including continued involvement of the hippocampus) Effects of misinformation on childhood memory Multiple trace theory ○ A given event can be associated with multiple memory traces (encoded in hippocampal-cortical connections) In addition to initial encoding, memory reactivation leads to creation of new traces  Remembering something from the past is itself an event that is encoded in memory ○ More traces (due to frequent retrieval) leads to more resilient memory ○ Both the initial coding and any subsequent retrieval involve the coordination of the hippocampus and cortex ○ Loss of hippocampus means that people lose ability to form new memories and for mental time travel to past events ○ Cortical memories represent semantic knowledge that is created out of episodic memory Explains how you can know things about your past without retrieving detailed episodic memories Summary ○ Memory changes with use: when a memory is reactivated, returns to an unstable state and is susceptible to change Enhancement (testing effect) Disruption (interference) Distortion (misinformation effect) Quiz review ○ Patient H.M. have impairment of declarative memory but intact nondeclarative memory, this case is evidence that forming new declarative memories depends on the medial temporal lobe ○ Interference refers to forgetting that’s the result of two memories involving overlapping or similar content ○ The scuba divers who remembered the most information were those who learned and were tested in the same environment ○ With elaborative encoding, you’re more likely to remember the face of someone you just met judging whether the person reminds you of a close friend ○ With damage to bilateral medial temporal lobes, they are most likely to remember events from many years prior to the stroke (draw the ribot gradient from memory) ○ Directed forgetting is a procedure in which participants are first asked to learn information and later asked to remember or forget specific items, typically memory is worse for items that a participant was directed to forget ○ In slow wave sleep, replay occurs where the brain replays events experienced throughout the day, replaying the events teaches other part of the brain to associate certain information and events ○ Functional amnesia is a sudden retrograde memory loss that seems to result from psychological causes rather than physical causes such as brain injury