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