Learning and Memory

What is learning?

Defined as relatively permanent changes in behavior caused by experience

Learning is NEVER isolated. It involves what systems?

Perceptual, motor, and memory systems simultaneously

Which type of learning involves changes to sensory association cortex?

Perceptual Learning

What is perceptual learning?

Learning to recognize stimuli (faces, objects, sounds)

What is an example of perceptual learning?

Recognizing your friend's voice faster over time

What is short-term memory?

Temporary storage for brief retention

What is an example of short-term memory?

Remembering a phone number for a few seconds

What is delayed matching-to-sample (DMTS) task?

Subject sees a sample stimulus and after a delay, they must choose which stimulus matches what they saw

What is DMTS used to study?

Working memory and temporal lobe function

What is motor learning?

Learning to perform new actions (playing piano, riding a bike)

What does motor learning depend on?

Motor cortex, basal ganglia, cerebellum

More practice on motor learning leads to what?

Stronger, more efficient motor circuits

What is Stimulus-response learning?

Learning to make a specific automatic response when a specific stimulus appears

Stimulus-response learning includes what two types of conditioning?

Classical conditioning and operant (instrumental) conditioning

What is classical conditioning?

A neutral stimulus (CS) is repeatedly paired with an unconditioned stimulus (US) → the CS begins to trigger a conditioned response (CR)

What is an examples of classical conditioning?

Tone (CS) + shock (US) → fear response (UR)

Eventually tone alone → fear (CR)

Hebb Rule

Cells that fire together wire together. When a presynaptic neuron repeatedly fires while the postsynaptic neuron is activated, the synapse strengthens.

Tone activates auditory pathways leads to what?

Lateral amygdala

Shock activates pain pathways leads to what?

Lateral amygdala

Pairing them strengthens synapses in the amygdala leads to what?

Emotional learning

CR decreases or increases when CS is presented without US

Decreases

1 multiple choice option

Extinction

NOT "unlearning". The original association still exists but is suppressed

What is Instrumental (Operant) Conditioning?

Behavior is shaped by consequences

Reinforcing stimulus decreases or increases behavior frequency (food, water, reward)?

Increases

1 multiple choice option

Punishing stimulus decreases or increases behavior frequency (shock, timeout)?

Decreases

1 multiple choice option

What is the source of the Ventral Tegmental Area (VTA)?

Dopamine

Nucleus accumbens (NAc) involves what?

Reinforcement and motivation

Medial forebrain bundle (MFB)

Strong "reward pathway"

Dopamine release strengthens connections between

Sensory circuits that detect cues and motor circuits that produce rewarding behaviors

When animals receive reinforcing stimulation, dopamine levels _____.

Spike

Low dopamine = _______ → poor learning

Low motivation

What is Anterograde Amnesia?

Cannot form new long-term memories

Anterograde amnesia is usually due to _____ or _______.

Hippocampal; medial temporal lobe damage

What is retrograde amnesia?

Cannot recall events before trauma

Why does gradient matter?

Longer gradients suggest consolidation takes a long time and involves gradual transfer from hippocampus to cortex

What type of gradient is often shown in retrograde amnesia (older memories intact; recent ones lost)?

Temporal

Hippocampus is crucial for what?

Explicit (declarative) memory formation

Hippocampus is NOT crucial for?

Procedural learning and implicit memory

(H.M. Case) After the removal of the medial temporal lobes, it caused what?

Severe anterograde amnesia

What was still intact from the H.M. case?

Short-term memory, long-term memories from before surgery, and implicit learning

What were the implicit learning procedures from the H.M. Case?

Mirror tracing, rotary pursuit, incomplete pictures test, and eye-blink conditioning

Explicit (Declarative) memory depends on what?

Hippocampus and medial temporal lobe

Explicit (declarative) memory is conscious, verbalizable memory that includes what two types?

Episodic and semantic

Episodic is events or facts?

Events

1 multiple choice option

Semantic is events or facts?

Facts

1 multiple choice option

What is Implicit (non-declarative) memory?

Skills, habits, priming, conditioning

What does implicit (non-declarative) memory depend on?

Striatum, cerebellum, amygdala

Encoding

Attending + processing new information

Consolidation

Stabilizing memories over time

Storage

Long-term retention in cortex

Retrieval

Accessing stored information

What is Korsakoff's Syndrome?

Caused by thiamine (vitamin B1) deficiency → seen in chronic alcoholics.

Standard Consolidation Theory

Hippocampus temporarily stores memories. With time, memories transfer to neocortex.

Multiple-Trace Theory

Each retrieval creates a new "trace." Older memories survive damage better because they have more traces.

Reconsolidation

When memories are retrieved, they become labile again and must be reconsolidated. Disruption (ECS, protein synthesis blockers) → memory impairment.

Post-traumatic amnesia

After concussion: brief anterograde + retrograde amnesia. Older memories remain but recent ones fail → supports gradual consolidation.

ECS Studies

Shocking brain immediately after learning erases memory, shocking after delay does not, and reconsolidation studies show memory becomes vulnerable again each time it is retrieved.

Hippocampal damage from Anoxia

CA1 neurons highly sensitive to oxygen deprivation; Damage → anterograde amnesia (similar to H.M. but milder).

What is a classic test for declarative memory?

Monkey sees an object → delay → must choose new object to get reward. Monkeys with medial temporal lobe lesions show impairments proportional to delay length.

Morris Water Maze

Rats learn location of hidden platform; requires hippocampus.

Radial Arm Maze

Test of spatial working memory; hippocampal lesions → repeated errors.

What are the characteristics of place cells (CA1, CA3)?

Fire when animal is in a specific location, stable when environment is stable, change when environment changes, fire even in darkness → rely on internal cues.

Head Direction Cells (Postsubicular neurons)

Fire when the animal's head points in a specific direction and part of the brain's "internal compass."

Grid Cells (Entorhinal Cortex)

Fire in a hexagonal grid pattern across environment, provide metric for navigation → path integration, and feed into place cells.

What is Long-term potentiation (LTP)?

Persistent strengthening of synapses after high-frequency stimulation

Long-term potentiation is studied in?

Perforant pathway → dentate gyrus

Schaffer collateral → CA1

What are the requirements of long-term potentiation (LTP)?

High-frequency stimulation → temporal summation

Postsynaptic depolarization

Glutamate release → AMPA + NMDA activation

Mg²⁺ block removed → Ca²⁺ enters

Calcium-dependent cascades → synapse strengthening

What are the synaptic changes of LTP?

More AMPA receptors, structural changes (perforated synapses), and nitric oxide → increases presynaptic glutamate

LTD

Low-frequency stimulation → weakened synapse and important for forgetting, adapting, and motor learning

Mossy Fiber LTP

Does not require NMDA receptors and depends on presynaptic Ca²⁺ and cAMP/PKA signaling

Early LTP

Lasts 1-3 hours, no new protein synthesis, and increased probability of neurotransmitter release

Late (Persistent) LTP

Lasts 24+ hours and requires new RNA and protein synthesis

Late (Persistent) LTP involves what?

cAMP → PKA → MAPK → CREB

Growth of new synapses

What is the symptoms of Korsakoff's Syndrome?

Severe anterograde amnesia

Confabulation — unintentionally inventing memories