Memory Consolidation Quiz

PSYC 303 | L11 FORGETTING

• Covering various theories of forgetting
• Including introduction, classical and active decay, interference, retrieval failure, and motivated forgetting.

OVERVIEW

• Introduction
• Classical and active decay
• Interference
• Retrieval failure
• Motivated forgetting

INTRODUCTION

• The Modal Model assigns a specific forgetting form to each memory store.
• Forgetting can result from retrieval errors in long-term memory (LTM).

DURATION OF MEMORIES

• Predictions of the Modal Model
• Environmental Input leading to sensory register
• Attention leading to rehearsal, followed by decay/loss in STM
• Recall and rehearsal leading to long-term memory (LTM)
• Decay/interference can lead to loss in STM
• Retrieval error leading to loss in LTM

MEMORY DURATION ESTIMATES

• Iconic Memory: Whole Report Experiment

• Duration of iconic memory, 500ms, with assumed capacity of 4-5 items

• Later research showed location is lost within 500ms.

• Letter Memory lasts at least 1 second.

• Short-Term Memory: Brown-Peterson Task

• Technique measures STM duration by preventing rehearsal.

• Participants count backwards from a given number interrupting rehearsal of the stimulus.

• Average STM duration estimated to be 18 seconds.

• Long-Term Memory: Memory for People

• Procedure (392 participants, 17-74 years old)

• Free recall of high school class mates' names.

• Yes-no recognition of faces and names.

• Face-name matching.

• Results

• 80% (48 years retention)-90% (up to 34 years) accuracy in recognition tests.

• Free recall accuracy between 60% (15 years retention) and 30% (48 years).

• Long-Term Memory: "Permastore"

• Reading comprehension, Spanish-English recall, and recognition tests.

• 25 years retention for faces of classmates

• 48 years retention 75-80% matching name to photo.

• High-school algebra retained for 50 years.

• Long-Term Memory: First Diary Study

• Percentage of items recalled and Age of items

• Example of long-term memory persistence

• Long-Term Memory: Autobiographical Memory

• Procedure with participants ranging in age from 17-74 years old.

• Memory retention of salience, emotional involvement, and pleasantness.

• Retention periods from 1-7 years.

MEMORY DURATION ESTIMATES

• Flashbulb Memories
• Memory for the circumstances in which one learned of a public event
• Example events Include, 9/11, Death of Diana, Columbia Space Shuttle.

A DOMINANT VIEW

• The Perseveration-Consolidation hypothesis
• Current Consolidation "dogma"
• Consolidated memories are stable and persist long-term.
• Consolidation is a transient and unidirectional process that occurs after acquisition.
• Disrupting consolidation impairs memory retention.

MYSTERY OF FORGETTING

• Forgetting seen as a failure of memory processes
• 'Not memory, but forgetting is the mystery'
• Erasure/storage failure
• Memory disruption
• Retrieval failure

NO MEMORY WITHOUT FORGETTING

• What would life be without forgetting?
• Example of Funes the Memorious
• Case study of a person with exceptional autobiographical memory.

HIGHLY SUPERIOR AUTOBIOGRAPHICAL MEMORY

• Participants' exceptional autobiographical memory accuracy
• Associations with names-to-faces tasks and word recognition.
• Performance better for personal life episodes.
• Elaborate and detailed information for remote life events, similar to controls.
• No differences in verbal, prospective, semantic memory, mental imagery, creative abilities and critical thinking
• No differences in general intelligence and working memory capacity
• Similar amount of false memories.
• Demonstrated stronger obsessive-compulsive behaviors than controls.

CLASSICAL AND ACTIVE DECAY

• Decay & Interference
• Definition of Interference: New learning can overwrite existing memory
• Definition of Decay: Memory weakens over time, eventually lost
• Classic Trace Decay Hypothesis

DECAY THEORIES

• A New theory of Disuse (Trace Decay).
• Focus on retrieval failure, not storage component.
• Definitions of Storage strength (indicates how well an item was learned) and Retrieval strength (indicates how well an item can currently be accessed).
• Theory assumes that storage strength will not be reduced
• Retrieval strength changes over time and as a function of retrieval.
• Increased Adaptability: Over time, old memories can become less accessible.
• Use can strengthen memories.

USE CAN STRENGTHEN MEMORIES

• Reminiscence: When subjects repeatedly retrieve a specific memory (e.g., a word list).
• Hypermnesia: An overall increase in the number of remembered items; recall of items not recalled in earlier tests.
• Testing Effect: An overall increase in the number of remembered items.

TOWARDS A MODERN DECAY THEORY

• Memories are made by changing the structure of synapses.
• Learning involves sending signals to change synapse.
• Formation of memory involves increasing the number of connectors at the synapse.
• Loss of memory during decay involves removal of connectors (AMPARs).
• Blocking the removal of AMPA receptors stops forgetting.
• Blocking AMPARs in the hippocampus preserve allocentric memory.
• GluN2B/NMDAR expression correlates with imprinting period.
• Enhancing plasticity accelerates forgetting.

ACTIVE DECAY

• Long-term memory not lost due to decay
• Built-in mechanisms governing forgetting
• Active forgetting automatically eliminates modifications to synapses formed during learning.
• A promiscuous encoding strategy is possibly the reason for built-in passive decay.
• Active decay an example of memory curation to keep only important memories.

POSSIBLE FUNCTIONS OF ACTIVE DECAY

• Preventing active decay in the hippocampus may have preserved spatial knowledge normally forgotten
• Preserving spatial information permits animals to discriminate a novel context
• Active decay memory preserved memory in a similar state that memories are shortly after training.

POSSIBLE FUNCTIONS OF ACTIVE FORGETTING

• Generalization Allows the recognition of instances of a category.
• Development of Categories
• Stronger forgetting in representing perceptual details.
• Instances within the same category share feature conjunctions.

POSSIBLE FUNCTIONS OF ACTIVE DECAY

• Cognitive Flexibility Requires Active Decay
• Trained mice to find a platform at location A, then the platform was moved to another location.
• Mice who had a genetic blockade to active decay found it harder to forget the prior location.
• This is important for learning, as it demonstrates learning and forgetting is important for cognitive flexibility.

LINKING AUTISM, COGNITIVE FLEXIBILITY AND ACTIVE DECAY

• Slower forgetting in fMR1-KO
• Impaired reversal learning in fMR1-KO
• Humans with autism show behavioral inflexibility.
• KO flies had less forgetting, impaired reversal learning, less forgetting of outdated memories.

INTERFERENCE

• Interference as a Retrieval Problem
• Retrieval cue competition - Over time, the same cue becomes associated with more possible targets.
• Cue competition - Items compete for retrieval
• Cue overload - More competitors lead to a pronounced interference effect.

FORMS OF INTERFERENCE IN LEARNING

• Proactive interference: Older memories interfere with new memories.
• Retroactive interference: Newer memories interfere with older memories.

AN EARLY DEMONSTRATION

• Retroactive Interference in Cockroaches
• A demonstration using cockroaches in a treadmill to show how activity after learning can interfere with the old learning.
• Measure of the loss in cockroach memory after a certain interval.

RETROACTIVE INTERFERENCE

• The stronger the new learning, the stronger the retroactive interference
• Example of retroactive interference task using paired associates.

PROACTIVE INTERFERENCE

• The more previous learning, the stronger the proactive interference
• Example of proactive interference task using paired associates.

PART-SET CUING

• Part-set cuing impairment: the recall of non-cued items is worse when some items are already presented as cues.
• May explain collaborative inhibition

RETRIEVAL-INDUCED FORGETTING

• Retrieval-induced forgetting is when non-retrieved items are recalled worse than retrieved items or items in categories that were not retrieved earlier during retrieval practice.
• Practical Implications of Retrieval-Induced Forgetting
• Interrogation, therapeutic use, and observer effects.

DIFFERENCES BETWEEN PARADIGMS

• Part-set cuing versus Retrieval Practice
• Subtle differences in the paradigms used to study interference.

POSSIBLE INTERFERENCE MECHANISMS

• Associative Blocking (or response competition).
• Associative Unlearning.
• Inhibition.

INHIBITION MAY EXPLAIN RETRIEVAL-INDUCED FORGETTING

• Divided Attention - reduced attentional resources
• Effect of Stress on Retrieval-Induced Forgetting - Stress can abolish retrieval-induced forgetting.

RETRIEVAL FAILURE

• Two possible positions on forgetting
• Nothing is ever really lost
• Real memory loss exists

AVAILABLE, BUT NOT ACCESSIBLE

• Demonstration that proper cues can overcome forgetting.
• Context-Dependent Memory.

REMINDER

• Encoding-Specificity Principle
• Transfer-Appropriate Processing

OPTOGENETIC DEMONSTRATION

• Method to label cells in dentate gyrus expressing c-Fos
• Neuronal activity leads to c-Fos expression.
• Only when animals not given Dox, the light-sensitive ion channel expresses in dentate gyrus.
• Activating the channel causes neurons to fire.

ANIMALS EXPRESS FEAR BEHAVIOUR

• Animals express fear behavior when "learning" neurons are activated.
• Context A (24 hours) and B (24 hours)
• Test 1 and 2 contexts.

REVISITING THE OPPOSING POSITIONS

• Retrieval failure.
• Storage failure.

EPISTEMOLOGICAL PROBLEM

• Retrieval failure.
• Storage failure.
• Standard experimental approach cannot decide the issue.

AN APPROACH TO FAIRLY TEST THE POSITIONS

• Two orthogonal predictions.

SECOND CONTEXTUAL FEAR CONDITIONING

• Amnesia induced with a standard intervention.
• Second learning of contextual fear requires NMDA receptors in the amnesic animals.

SECOND LEARNING AFTER EXTINCTION

• Extinction reflects inhibition not loss of memory.
• Animals can acquire second contextual fear conditioning without the processing.

HOW TO RECONCILE THESE FINDINGS

• All consolidation theories argue that the hippocampus is necessary for event-like memories.
• This requires a storage index representation in the hippocampus (which needs NMDARs).
• Loss of this index therefore prevents retrieval of the context memory.

MOTIVATED FORGETTING

• Methods: participants see images.
• Free Recall and Yes/No Recognition
• Results: Older people recall fewer details and images are less recognized.

POSSIBLE REASONS FOR THE POSITIVITY BIAS

• Sense of well-being.
• Emotion regulation
• Emotional responses regulated cognitively.

POSSIBLE REASONS FOR THE POSITIVITY BIAS

• Freud's three psychic elements and their interactions.
• Consciousness and unconscious states
• Ego's function

DIRECTED FORGETTING

• Forgetting on command
• Item-method
• List-method

DIRECTED FORGETTING

• Item-method directed forgetting requires greater effort than encoding.

DIRECTED FORGETTING

• List method paradigm
• Results: List 1 memory less than List 2 in Forget group
• Proactive interference found in remember group, not in the forget group

DIRECTED FORGETTING

• Item method and list method differences
• List-based forgetting participants may not know until after List 1 until they have to forget it.
• Item-based directed forgetting inhibits encoding of the item.

DIRECTED FORGETTING

• Retrieval Inhibition Hypothesis - Forget instructions inhibit unwanted List 1 items.
• Context Shift Hypothesis - Forget instruction results in separate lists.

RETRIEVAL SUPPRESSION

• Think/No-Think Paradigm
• Retrieval suppression tasks
• Positive & Negative Control Effects
• Brain areas associated with retrieval suppression

PSYCHOGENIC AMNESIA

• Dissociative memory disorder, psychological trauma or stress.
• Retrograde memory loss, specific to autobiographical memory, reversible.
• Global amnesia affects complete life history
• Situation-specific amnesia affects specific traumatic events

DIFFERENCE BETWEEN PSYCHOGENIC AND TRANSIENT GLOBAL AMNESIA

• Retrograde memory performance
• Transient global amnesia, older memories less affected than newer, more recent memories

PSYCHOGENIC FUGUES: CASE STUDY

• Detailed case study of a 40-year-old woman who experienced psychogenic fugue.

RECOVERY OF FORGOTTEN MEMORIES

• Spontaneous Recovery
• Requires active decay in prefrontal cortex.

RECOVERY OF FORGOTTEN MEMORIES

• Spontaneous Recovery of Episodic Memories
• Task: Study list, intervening, recall. - results, retroactive interference.

RECOVERY OF FORGOTTEN MEMORIES

• Hypermnesia
• Reminiscence
• Schematization
• Cue reinstatement helps retrieving forgotten memories.

RECOVERY OF FORGOTTEN MEMORIES

• The recovery of false memories
• Procedure
• Results - A third of participants believed the false memory.

RECOVERY OF FORGOTTEN MEMORIES

• How to determine whether a recovered traumatic memory happened
• Challenges to determining if a recovered memory is true or false.
• Methods of assessing corroboratory evidence
• Possible misattribution errors

RECOVERING OF FORGOTTEN MEMORIES

• Memory recovered through suggestive therapy
• more likely to reflect the therapist suggests
• memories may lack corroborative evidence