Biological Bases and Memory

A Unitary Model of Memory

  • Input: Information enters the memory system.

  • Encoding: Information is converted into a usable format.

  • Storage: Encoded information is retained over time.

  • Output: Information is retrieved when needed.

  • Retrieval: The process of accessing stored information.

  • Forgetting: Memory loss occurs.

  • Retention for Decades: Long-term memory holds information potentially for a lifetime.

  • Massive Capacity: Long-term memory has a vast storage capability.

Hermann Ebbinghaus (1850-1909)

  • First person to investigate memory scientifically and systematically.

  • Ebbinghaus's Forgetting Curve: Shows how memory of information decreases over time if there is no attempt to retain it.

Peterson and Peterson's (1959) Experiment

  • Demonstrates the rapid decay of short-term memory.

  • Procedure:

    • A warning signal (green light) indicates the start of a trial.

    • Participants are presented with a stimulus consisting of three letters and a three-digit number (e.g., "CJL 547").

    • Participants count backward by threes from the number for a retention interval of 3 to 18 seconds (e.g., 547, 544, 541).

    • A recall signal (red light) prompts participants to recall the letters.

  • Results: Memory decays rapidly over short retention intervals.

Memory Span

  • Miller (1956): The Magic Number 7 \pm 2

  • Short-term memory has a limited capacity of about 5-9 items.

Types of Memory

  • Semantic Memory: Recollection of ideas, concepts, and facts.

  • Autobiographical Memory: Memory for one's personal history, a combination of episodic and semantic memory.

  • Emotional Memory: Emotion-memory interactions, often important in episodic memory.

What is Memory?

  • Recording of the past for later use in the present.

  • Changes in our brains that encode experience.

  • Information stored in our genes.

  • Agonistic displays in humans and mandrills.

  • The stories we tell.

  • Our cultural practices.

Levels of Explanation

  • Biological:

    • Brain systems: Neuroanatomy, animal research, brain imaging.

    • Neurochemistry: Neurotransmitters and hormones, animal studies, drug studies.

    • Genetics: Gene mechanisms, heritability, twin and adoption studies.

  • Individual:

    • Individual differences: Personality, gender, developmental age groups, self-concept.

    • Perception and cognition: Thinking, decision making, language, memory, seeing, hearing.

    • Behavior: Observable actions, responses, physical movements.

  • Social:

    • Interpersonal behavior: Groups, relationships, persuasion, influence, workplace.

    • Social cognition: Attitudes, stereotypes, perceptions.

  • Cultural:

    • Thoughts, actions, behaviors in different societies and cultural groups.

    • Norms, beliefs, values, symbols, ethnicity.

Key Concepts and Terms (Memory 2)

  • Sensory Memory

  • Short-Term and Long-Term Memory

  • Patient H.M. (Henry Molaison)

  • Patient K.F.

  • Atkinson and Shiffrin's Multi-Store Model of Memory

  • Serial Position Effect

  • Primacy and Recency Effects

  • Bias in Encoding - Phonetic vs. Semantic

  • Baddeley and Hitch Working Memory

  • Chunking

  • Maintenance Rehearsal - Craik and Watkins

Patient H.M. (Henry Molaison)

  • Underwent a medial temporal lobectomy to control seizures.

  • Surgery: Removed portions of the medial temporal lobes, including the hippocampus and perirhinal cortex.

  • Developed dense anterograde amnesia (inability to form new long-term memories) with intact short-term memory.

  • Provided significant evidence for separate memory systems.

Patient K.F.

  • Suffered a motorcycle accident resulting in removal of a left parietal subdural hematoma.

  • Impact: Impaired short-term memory but intact long-term memory.

  • Testing: LTM tested with incomplete words and pictures test.

  • Significance: Provided evidence for the existence of separate memory systems in the opposite direction to Patient H.M.

Memory Systems

  • Short-Term Memory (STM):

    • Lasts for approximately 15-20 seconds.

    • Has limited capacity - Miller (1956) The magic number 7 \,\pm 2 items.

  • Long-Term Memory (LTM):

    • Retention for decades.

    • Massive capacity.

  • Sensory Memory:

    • Storage of information prior to STM.

George Sperling's Experiment

  • Procedure:

    • 12 letters are flashed on a screen for 50 milliseconds.

    • The screen goes blank.

    • A tone indicates which row to recall (upper, middle, or lower).

  • Results: Participants are able to recall 3 out of 4 letters from the cued row.

  • Conclusion: Sensory memory lasts for 0.3 to 3 seconds.

Atkinson and Shiffrin's (1968-71) Multi-Store Model of Memory

  • Sensory Memory:

    • Duration: 300-3000 ms

  • Short-Term Memory:

    • Duration: Approximately 20 seconds.

    • Capacity: Limited (7 \pm 2 items).

    • Forgetting: Rapid.

  • Long-Term Memory:

    • Duration: Decades.

    • Capacity: Massive.

    • Forgetting: Very slow (or no) forgetting.

  • Processes:

    • Rehearsal: Maintains information in STM.

    • Retrieval: Transfers information from LTM to STM.

Serial Position Effect

  • Immediate recall of a list of words results in better memory for items at the beginning (primacy effect) and end (recency effect) of the list.

  • Primacy Effect: Attributed to LTM.

  • Recency Effect: Attributed to STM.

  • Manipulation: Delaying recall after the list is presented diminishes the recency effect.

Bias in Encoding

  • Phonetic (STM) vs. Semantic (LTM):

    • Poor recall from STM for words that sound the same (e.g., man, can, map, ran, rap).

    • Poor recall from LTM for words that mean the same (e.g., huge, large, wide, tall).

Baddeley and Hitch (1974) Working Memory Model

  • Central Executive: Controls attention and manipulation of information.

  • Visuospatial Sketchpad (VSS): Handles visual and spatial information (inner eye).

  • Phonological Loop (AL): Processes auditory information (inner ear and inner voice).

  • Episodic Buffer (EB): Temporary storage that integrates information from different sources and links to LTM (chunking, LTM integration).

  • Working Memory as a Mental Workbench: Focuses on the active manipulation of information rather than passive maintenance.

  • Capacity Limitation: Due to processing rather than storage limitations.

Chunking

  • Grouping individual items into larger, more meaningful units to bypass the limited capacity of working memory.

  • Rehearsal: Crucial for the transfer of information into LTM.

Craik and Watkins (1973) Maintenance Rehearsal

  • Holding words starting with a specific letter in memory until the next one occurs.

  • Result: Maintenance rehearsal alone is not sufficient for effective transfer to LTM.

Elaborative Rehearsal/Encoding

  • Depth of Processing:

    • Shallow: Sound, shape.

    • Deep: Meaning (semantic structure).

Bransford and Johnson (1972) - Elaborative Encoding

  • Experiment:
    * One group was given information prior to reading a paragraph, while the other group was not.

  • Results:

    • The informed group had higher comprehensibility ratings and remembered more information.

    • Uninformed group rating: 2.8 and remembered 13%.

    • Informed group rating: 4.5 and remembered 32%.

  • Conclusion: Elaborative encoding improves comprehension and memory.

Schema

  • A mental framework or organized pattern of thought about some aspect of the world.

  • Elaborative processing allows prior knowledge to shape encoding.

Semantic Networks

  • Information is stored in a semantic network in LTM, where related concepts are linked.

Anterograde Amnesia

  • Inability to form new long-term memories after the onset of amnesia.

Retrograde Amnesia

  • Loss of memory for events that occurred before the onset of amnesia.
    *for HM, retrograde amnesia is approx. 2 years.

Memory Consolidation

  • The process by which memories become stable and durable.

  • Information in long-term memory is initially in a labile form and is then consolidated over time into a more damage-resistant form.

  • Consolidation may occur over periods of years, such that remote memories are more damage-resistant.

    *   **Encoding:** The conversion of information into a form that can be stored in memory.
*   **Storage:** The creation of a trace of this information within the nervous system.
*   **Consolidation:** The strengthening of this trace over time.
*   **Retrieval:** An attempt to recover a memory trace.

Memory Improvement

  • Visual Imagery: Using mental images to enhance memory.

  • Method of Loci: A mnemonic technique that involves associating items to be remembered with specific locations.

  • Encoding-Retrieval Context: Memory is best when the context at encoding matches the context at retrieval (Godden and Baddeley, 1975).
    * context-dependent memory is enhanced when learning and recall happen in the same places or environments.

Context-Dependent Memory

  • Demonstrated by Godden and Baddeley (1975) using divers who learned and recalled information either underwater or on land.
    *for learn above water:
    *Recall above water (13)
    *Recall under water (11)
    *for learn under water:
    *Recall above water (10)
    *Recall under water (14)

Memory and Forgetting

  • Key Concepts and Terms:

    • Episodic Memory

    • Semantic Memory

    • Skill Learning, Priming, Habit, Conditioning

    • Implicit and Explicit (Procedural and Declarative) Memory: Memory

    • Forgetting

    • Trace Decay

    • Retroactive and Proactive Interference

    • Feeling of Knowing

    • Memory Persistence and Trauma

    • Post-Traumatic Stress Disorder (PTSD)

    • Memory Distortion

    • Reconsolidation

Temporal Lobe Amnesia

  • Impaired formation of long-term episodic memory.

  • Intact short-term memory.

  • Semantic memory encoded prior to trauma is relatively intact.

  • Impaired ability to gain new semantic knowledge following amnesia onset.

Impact Memory

  • Skill learning, habits, priming, and conditioning are intact post-trauma.

Implicit vs Explicit Memory

  • Implicit (Procedural): Skills, priming, habits.

  • Explicit (Declarative): Episodic, semantic.

Memory Errors Contributing to Forgetting

  • Transience/Memory Decay:Reduced memory over time.

  • Blocking/Retrieval Failure: Inability to remember needed information.

  • Absentmindedness/Encoding Failure: Reduced memory due to failing to pay attention.

  • Persistence: The resurgence of unwanted or disturbing memories.

Transience/Memory Decay

  • Trace Decay: A change in the biology of the memory trace.

  • Interference: Weakening connections between neurons?

Retroactive Interference

  • New learning interferes with old learning (e.g., learning Italian interferes with recalling Spanish).

Proactive Interference

  • Old learning interferes with new learning (e.g., habitually parking in the same spot interferes with remembering a new parking location).

Absentmindedness/Encoding Failure

  • Results from shallow encoding due to a failure to pay attention.

  • Attention is the gateway to memory.

Memory Persistence

  • Memory for Traumatic Events:

    • In most cases, memory of a traumatic event is enhanced due to arousal and attention.

    • Poor memory is less common and may result from context effects or disruption of biological processes.

Post-Traumatic Stress Disorder (PTSD)

  • Symptoms:

    • Avoidance symptoms.

    • Psychophysiological reactivity.

    • Re-experiencing the traumatic event.
      ERROR
      TYPE DEFINITION EXAMPLE
      Transience/memory decay Forgetting Reduced memory over time Forgetting the plot of a movie
      Blocking/retrieval failure Forgetting Inability to remember needed information Failing to recall the name of a person you meet on the street
      Absentmindedness/encoding failure Forgetting Reduced memory due to failing to pay attention Losing your keys or forgetting a lunch date
      Persistence Remembering The resurgence of unwanted or disturbing memories one Remembering an embarrassing faux pas
      would like to forget

Errors Contributing to Memory Distortion

  • Misattribution: Assigning a memory to the wrong source.

  • Bias: Influence of current knowledge on memory for past events.

  • Suggestibility: Altering a memory because of misleading information.

Neurons and Neurotransmitters

  • Neurons communicate with each other across special junctions called synapses. When an action potential arrives at an axon terminal a special chemical called a neurotransmitter is released at the synaptic cleft. Receptors at the postsynaptic neuron respond to the neurotransmitter and generate a graded potential. This signal can only be sent one way at the synapse.

Neurons, Neurotransmitters, Drugs, and Mental Function

Key Concepts and Terms

  • Synapse

  • Neurotransmitter

  • Synaptic cleft

  • Vesicles

  • Synthesis, Storage, Release, Binding, Reuptake

  • Agonist and Antagonist Drug Action

  • Acetylcholine

  • Dopamine

  • Parkinson's Disease

  • Schizophrenia

  • Deep Brain Stimulation

Agonist

  • Drugs that bind to a receptor of a cell and trigger a response by the cell are agonists. An agonist often mimics the action of a naturally occurring substance. An indirect agonist enhances the release or action of an endogenous neurotransmitter.

Antagonists

  • Drugs that block or suppress agonist-mediated responses are known as antagonists.

Parkinson's Disease

  • Affects approximately 1% of the population.

  • Symptoms characteristics: tremor, muscular rigidity, slowness of movement (bradykinesia), postural instability, involuntary shifts of posture (dystonia and dyskinesia drug side effect), shuffling, wide-based gait with forward leaning posture leading to festination.

Schizophrenia

  • Affects approximately 1% of the population.

    • Positive Symptoms: Delusions, hallucinations, disorganized thinking.

    • Negative Symptoms: Blunted affect, poverty of speech and thought, apathy.

    • Cognitive Symptoms: Poor working memory, disruption in executive function and attention.

Coffee

  • Adenosine antagonist.

Marijuana

CB1 receptor antagonist.

Prozac

  • Serotonin reuptake inhibitor (SSRI).

Ecstasy (MDMA)

  • Serotonin agonist (+na. +dop.).

Cocaine

  • Dopamine agonist.

Methamphetamine

  • Indirect agonist of dopamine, noradrenaline and serotonin.

Ketamine

  • Blocks NMDA receptors.

Reflex

  • A simple automatic response to a stimulus.

    • Stereotyped

    • Subconscious

    • Unlearned

  • Eyeblink, swallowing, pupil dilation/constriction, piloerection, photic sneeze (10% population).

Alpha Motor Neurons

  • There are serveal million neurons concerned with the generation of the movement but all of the commands to muscles are community through approximately 400,000 alpha motor neurons.

Polysynaptic Reflex

  • Sensory neurons Cell body of sensory neuron in dorsal root ganglion. Sensory (stretch) receptors

Vestibulo-Ocular Reflex (VOR) - Modifiable

Memories of Experience Could Be Stored as Patterns of Activity in Networks of Neurons

  • This could be instantiated in the brain as changes in synaptic connections.

  • An increase in neurotransmitter release.

  • An increase in postsynaptic response.

  • An increase in synaptic connections between neurons

Does Learning Produce a Change in Synaptic Connectivity?

  • IC: Impoverished condition

  • SC: Social condition

  • EC: Enriched condition

  • Experience which is likely to lead to memory formation changes the structure of the brain. This change in structure includes a change in synaptic connectivity. Changes in synapses are, in turn, associate with better memory and learning capabilities.

Circadian Rhythms

  • Are the physical, mental, and behavioral changes an organism experiences over a 24-hour cycle.

Examples of Circadian Rhythms

  • Core temperature

  • Sleep propensity

  • Melatonin
    Body Time | Clock
    Noon | 12 pm
    Sleep |
    Wake up |
    Elapsed |

  • Michel Siffre: French explorer and Adventurer

  • Sleep-wake cycle becomes detached from external time

  • Synchronized
    * Active on blocks

  • Free running
    * Active in blocks that aren't entrained to actual time

Suprachiasmatic Nucleus of the Hypothalamus (SCN)

  • Pineal gland releases hormone melatonin at night

  • Effect of SCN removal on sleep patterns in lab rats

  • Normal
    * Activity

  • Without SCN
    *Days