L3: Long-Term Memory

Long-Term Memory

• Long-term memory involves:

  • Consolidation.

  • Encoding and retrieval processes.

  • Varieties of long-term memory.

Consolidation

• Consolidation is an ongoing process that occurs at synaptic and structural levels.

• Involves reorganization, with initial dependence on the hippocampus and medial temporal lobe.

• Over time, memory representations become more permanent in neocortical areas.

• Damage to these areas (hippocampus & medial temporal lobe) can result in amnesia.

Consolidation in Long-Term Memory

• New memory representations are initially formed by the hippocampus.

• Over time, memories become consolidated in other regions of the cortex.

• Damage in amnesia interferes with this process.

Electroconvulsive Therapy (ECT) and Memory

• Electroconvulsive therapy (ECT), used to treat severe depression, can produce both short-term and long-term memory problems (amnesia) in humans.

Retrograde Amnesia

• Retrograde amnesia involves the loss of memories prior to the onset of amnesia.

Squire, Slater & Chace (1975) Study

• Patients undergoing ECT had memory tested before and after a series of 5 ECT treatments.

• They were asked to recognize names of television shows that ran for exactly one year over a period of two decades.

• Memory deficit was observed only for the last 3 years.

Amnesia Components

• Anterograde amnesia: inability to form new memories post-trauma.

• Retrograde amnesia: loss of pre-trauma memories.

• Retrograde memory loss in amnesia shows a temporal gradient.

  • Remote memories are more intact.

  • Memory loss increases closer in time to the trauma.

Squire, Haist & Shimamura (1989) Study

• Amnesics in their 50s and matched controls were studied.

• They answered questions about public events from the 1950s-1980s and identified photos of famous people from the 1940s-1980s.

• The study revealed a temporal gradient of memory loss.

  • Memory impairment was worse closer to the trauma.

Memory Consolidation Over Time

• Newer memories are more fragile and susceptible to disruption.

Brown (2002) Meta-Analysis

• Meta-analysis examining memory recall.

  • Absolute recall = actual recall.

  • Relative recall = recall as a percentage of control group recall.

Consolidation and Memory Stability

• Transfer to cortical representations increases the stability of memories.

• Reactivation strengthens neuronal connections and creates additional copies, making memories more resistant to loss.

• This process can continue for years.

Episodic Memory

• A type of long-term, declarative (explicit) memory.

• Involves the encoding, storage & consolidation, and retrieval of specific personal experiences from a particular time and place.

Memory Systems

• Declarative Memory (Explicit):

  • Episodic Memory: Events, specific personal experiences from a particular time and place.

  • Semantic Memory: Facts, world knowledge, object knowledge, language knowledge, conceptual priming.

• Nondeclarative Memory (Implicit):

  • Procedural Memory: Skills (motor and cognitive).

  • Perceptual Representation System: Perceptual priming.

  • Classical Conditioning: Conditioned responses.

  • Nonassociative Learning: Habituation, sensitization.

Encoding

• Encoding is the process responsible for why things are either easy or hard to remember.

"Grandmother Cell"

• A neuron that is selective for one specific stimulus.

Distributed Pattern of Activation

• Theorized representation of memory where multiple neurons are activated to represent a single memory.

The Problem of Retrieval

• How to retrieve one memory among many.

Encoding: Quality of Representation

• Imagery/Richness: How vivid and detailed the memory is.

• Distinctiveness: How unique and different the memory is from others.

Shepard (1967) Study

• Recognition memory for 612 color pictures.

• Accuracy:

  • 2 hours: $99.7\%$

  • 7 days: $87.0\%$

  • 4 months: $57.7\%$

Standing (1973) Study

• Recognition memory for 1,000 & 10,000 photographs after a 2-day delay.

• Conditions:

  • Normal photos.

  • Vivid photos.

• Accuracy:

  • 1000 vivid photos: $95.2\%$

  • 1000 normal photos: $90.8\%$

  • 10000 normal photos: $72.8\%$

Picture Superiority Effect

• Pictures are better remembered than words.

• Ghering, Toglia, and Kimble (1976) found that pictures were better remembered than words over time.

Bower & Winzenz (1970) Study

• Studied word pairs using:

  • Repetition.

  • Forming a mental image.

• Imagery resulted in superior memory compared to repetition.

Autobiographical Memories

• "Mental time travel" or reliving the past.

• Highly associated with mental imagery.

• Aphantasia (poor or no mental imagery ability) associated with reduced autobiographical memories.

Encoding: Distinctiveness

• MacLeod et al. (2010) - production effect.

  • Studying a list of words by reading them aloud.

  • Leads to better recognition memory for "produced" words.

• Ozubko, Hourihan, MacLeod (2012).

  • Production effect seen with sentences & texts.

  • Memory advantages even after 1 week, similar to the memory advantage for pictures.

Distinctiveness: Properties

• Intrinsic properties.

  • Unusual.

  • Emotional.

  • Arousing.

MacLeod et al. (2010) - Production Effect

• Studying a list of words by reading them aloud.

• Leads to better recognition memory for "produced" words.

• Distinctive encoding?

Distinctiveness: Isolation Effect

• Relative distinctiveness leads to increased processing or attention.

• Von Restorff (1933) demonstrated that memory for an item depends on the context.

  • Distinctive (isolated) items are better remembered than non-isolated items.

Encoding: Depth of Processing

• Craik & Tulving (1975) examined how the depth of processing influences memory.

Craik & Tulving (1975) Study

• Participants studied a word and answered a question.

  • Structural: "Is the word in capital letters?"

  • Phonemic: "Does the word rhyme with X?"

  • Semantic: "Would the word fit in the sentence 'He met a ___ in the street'?"

• Conditions varied from low to high depth of processing.

Self-Reference Effect

• An especially effective (deep) type of processing.

• Deeper = more personally meaningful.

• Encoding instructions:

  • Visual features - Shallow.

  • Word meaning - Deep.

  • Does the word apply to you? - Deepest.

• Self-reference: most distinctive, elaborative.

Nairne, Thompson, Pandeirada (2007) Study

• Learned word lists.

• Rated relevance for:

  • Survival.

  • Moving.

  • Pleasantness.

Nairne, Thompson, Pandeirada (2007) Survival Condition

• Imagine that you are stranded in the grasslands of a foreign land, without any basic survival materials.

• Over the next few months, you’ll need to find steady supplies of food and water and protect yourself from predators.

• Participants rated how relevant each word would be for them in this survival situation.

Nairne, Thompson, Pandeirada (2007) Moving Condition

• Imagine that you are planning to move to a new home in a foreign land.

• Over the next few months, you’ll need to locate and purchase a new home and transport your belongings.

• Participants rated how relevant each of these words would be for them in accomplishing this task.

Nairne, Thompson, Pandeirada (2007) Pleasantness Condition

• Participants rated the pleasantness of each word.

Nairne, Thompson, Pandeirada (2007) Results

• Free recall was highest for words rated for survival relevance.

• Survival processing a special adaptation?

Retrieval

• Key factors:

  • Distinctiveness.

  • Encoding specificity.

The Problem of Retrieval

• How to retrieve one memory among many.

Retrieval: Distinctiveness

• Memory interference.

  • Need to search through many similar memories.

  • Makes remembering difficult.

• Isolation effect.

  • Relative distinctiveness == easier retrieval?

Retrieval: Encoding Specificity

• To get information in memory, you must reinstate the conditions at encoding.

• Memory is better if the retrieval context matches the encoding context.

Tulving & Thompson (1970) Study

• Studied cue-target pairs.

  • HOT – COLD (strong associate).

  • SNOW – COLD (weak associate).

• Later, the cue was given to remember the target.

• Expected: Strong associate = better retrieval cue.

• Results showed encoding specificity.

Specific Forms of Encoding Specificity

• Transfer-appropriate processing.

• State-dependent learning.

Transfer-Appropriate Processing

• Memory is best when using the same processing at encoding and retrieval.

• Morris, Bransford, and Franks (1977) study.

  • Encoding conditions:

    • Semantic (does target word fit sentence?).

    • Rhyme (does the target word rhyme?).

Test Conditions + Results

• Test conditions:

  • Standard recognition (did you see word in the list?).

  • Rhyme memory (does look rhyme with a word from the list?).

• Advantage of semantic processing during study only with a standard test.

• No advantage with a rhyming test.

State-Dependent Learning

• Memory is best when the environmental or mental context is the same at encoding and retrieval.

• Godden & Baddeley (1975):

  • Memory is best when the study environment (wet or dry) matched the test environment (wet or dry).

• Smith (1985):

  • Memory is best when the study environment (jazz or Mozart music) matched the test environment (jazz or Mozart music).

• Schab (1990):

  • Memory is best when the study environment (odour or no odour) matched the test environment (odour or no odour).

State-Dependent Learning (cont.)

• Eich et al. (1975):

  • Memory is best when the study environment (drug or no drug) matched the test environment (drug or no drug).

Episodic Memory: Familiarity and Recollection

• Familiarity:

  • Feeling of recognition without specific details.

• Recollection:

  • Recall of specific episodic details or associations.

Familiarity vs. Recollection

• Familiarity = fast, automatic, (unconscious?).

• Recollection = slow, deliberate, conscious.

• Converging data from the study of:

  • Subjective experience.

  • Effect of attention.

  • Time course of retrieval.

Subjective Experience: Remember vs. Know

• Gardiner, Ramponi & Richardson-Klavehn (2000).

• People studied a word list and later described subjective feelings during a recognition test.

• They labeled feelings: “Remember”, “Know”, “Guess”.

Subjective Experience: Objectively

• Remembering is associated with accurate memory for source, context, and associations.

• Declines rapidly over time.

• Large impact of reduced attention.

Attention: Jacoby, Woloshyn & Kelley (1989)

• People saw a list of famous & non-famous names under full or divided attention (detect digits in the auditory stream).

• Later, they made fame or recognition memory judgments.

• Divided attention had no effect on fame judgments.

• Divided attention had a large effect on recognition memory judgments.

• Fame judgments = familiarity.

• Recognition memory = recollection + familiarity.

• Recollection requires conscious attention, while familiarity is automatic and unconscious.

Time Course of Retrieval: Jacoby, Jones & Dolan (1998)

• Study two word lists: List 1 (Saw) & List 2 (Heard).

• Memory test (source discrimination): say “yes” only to Heard words.

• Good source discrimination with no deadline.

• Poor source discrimination when quick responses were required.

• Source judgments = recollection (familiarity is not useful).

• In recognition memory, the contribution of recollection and familiarity changes over time.

• Initial reliance on familiarity until recollection becomes available later in time.

Summary of Lecture 3 Topics

• Memory Consolidation: Temporal gradient in retrograde amnesia.

• Memory Encoding: Imagery/Richness & Distinctiveness.

• Memory Retrieval: Encoding Specificity (Transfer-Appropriate Processing & State-Dependent Learning).

• Episodic Memory: Familiarity & Recollection Subjective Experience, Attention, Time Course