Learning and Memory 1 + 2

Ivan Pavlov

Russian physiologist

• pavlovian conditioning: conditioning is changing the behavior/response

pavlovian conditioning is also known as

classical conditioning

what did he do in this pavlovian conditioning. mention US, UR, CS, CR

US (unconditioned stimulus) : food

UR (unconditioned response) : salivation

CS (conditioned stimulus) : lid

CR (conditioned response) : salivation

repetitive conditioning

conditioned stimulus

• animal leanrs to associate something aversive with the tone to illicit fear response

Richard Thompson

Nictitating membrane response

• 3rd eyelid that animals have (rabbit)

• blow puff of air (unconditioned stimulus) in rabbits eye and will blink nictating membrane

• could pair this with a tone right beofre puff and that can become the conditioned stimulus and illicits the conditioned response of blinking

US: puff of air

UR: blinking nictitating membrane

CS : tone

CR : blinking at the tone

lateral interpositus nucleus

deep in middle cerebellum and its where learning is taking place

pathway for this nictiating membrane

rubrospinal tract → lateral interpositus nuclues → red nucleus → 6th CN

Evidence for lateral interpositus nucleus func

if you take this out and do this paradigm, animals will never learn to associate this tone with the puff of air that comes next

what happens if you insert a cold cyroprobe in the Lateral Interpositus nucleus

The rabbit learned the association but could not express the blink until warmed.

is there an connection with the lateral interpositus nucleus of the cerebellum and motor output like blinking

no, even if the motor output is disrupted (so the subject cannot physically blink), the learning still takes place

Purkinje cells receive input from:

1. parallel fibers → synapse on the dendrites

2. mossy fibers → synapse closer to cell body

how does purkinje cell act like a balancing system?

• if combined input reaches threshold, the cell fires

• if not, the cell doesn’t fire

output of purkinje cells goes to ……..

lateral interpositus nucleus

Thorndike’s experiment

• behavioral/operant conditioning

• put a cat in cage and pull on chain to release front door

• put food in front to get cat motivated and it finally accidentally pulled on it

• the next day cat did the same thing but took less time

• next day cat knows its the chain

Skinner - operant/skinnerian/respondant conditioning what is it

-formalized thorndike’s ideas

• operands are things in the world that results in rewards that increase the probability that increases the probability that we will act a certain way

• punished behavior → decrease prob. it will happen again

• good behavior → inc prob behavior will happen again

Pavlovian classical conditioning VS operant conditioning

Pavlovian conditioning

• learning involves forming an association between two stimuli, so animal learns that one stimulus predicts another

• ex: tone → airpuff, bell → food

operant conditioning

• learning involves an association between a behavior (response) and its outcome

• in a given siutation the animal learns the correct response to get a reward or avoid punishment

• the focus is on behavior → consequence

when rewards are given every time a behavior occurs (continuous reinforcement):

• leads to steady consistent effort

• similar to being paid per task completed (constant productivity)

When rewards depend on timing or intervals (not consistant):

• behavior becomes uneven

• periods of low activity followed by bursts of high effort

operant conditioning steups (skinner boxes) can be used to study sensory abilities in animals, not just learning.

Color? for pigeon

train pigeion to peck at a specific color, if it can, it can distinguish colors

brightness?

use same color but different light intensities

visual acuity (detail resolution)

• present patterns (stripes)

• gradually make differences smaller

• the point where it fails = limit of visual resolution

detection of stimuli, smells

• pigeons normally peck at steady rate for food

• introduce new stimulus (smell)

• if pecking changes, pigeon detexted somethhing

what is a localizationists and who is one?

• Pavlov

• believe that there is a part of the brain responsible for learning

karl lashley and his experiment

• disagreed w pavlov

• used mazes and placed rat in start location and the. goal was to get to the end where there would be a reward

• rat kept getting faster and faster to get to the end

operant conditioning

• series of cuts in cerebral cortex → animals could still learn

karl lashley’s two ideas

1. mass action

• the more brain taken out, the worse they did on the maze, but they’re still able to learn the maze

1. equipotentiality

• all the brain is equal and can code for information

what did those who disagreed with lashley think

• assumed memory was stored in cerebral cortex

• maze learning is too complex to isolate memory

• involves visual, smell, touch → multiple active brain processes

Eric Kendall

looked at aplysia’s learning and memory at molecular level

why use aplysia? 3 reasons

1. small nervous system - 10000 cells

2. neurons are big so its easy to stick an electrode in

3. identifiable neurons

habituation

decrease in responding to repeated stimulus → every animal does this

example of habituation

someone playing a tone for the first time will give you a startle response

but if they keeping doing this you won’t be startled

habituation vs sensory adaptation

habituation happens on a psychological level

how do they do this aplysia?

• light tap on its face where siphon is thats attached to their gills (respiratory organ)

• causes the siphon to contract, gills withdraw

• over time, they won’t respond to it anymore

explains how this occurs in cells

1. action potential arrives at the presynaptic terminal → depolarization

2. depolarization opens voltage gated Ca2+ channels

3. calcium influx as it enters the cell

4. synaptic vesicles move and dock at the presynaptic membrane

5. vesicles fuse with membrane and release neurotransmitters into the synapse (Exocytosis)

6. neurotransmitters cross synaptic cleft and bind to receptors on postsynaptic cell

repeated stimulation causes a _______ in amount of neurotransmitters and quanta thats released from presynaptic sensory neuron

decrease

learning memory

the change in the amount of neurotransmitter thats released from 1 cell to the other cell in the synapse

sensitization experiment

same as habituation but add a shock

• person is startled even after habituated → more aroused, viligant

how doe sensitization happen on a cell level

• A tail shock activates interneurons

• These interneurons form axo-axonic synapses onto the presynaptic terminal of the sensory neuron (the one from the siphon/touch pathway—not the tail itself)

• The interneuron releases serotonin (5-HT)

From there:

• Serotonin triggers a second messenger cascade in the sensory neuron terminal

• This increases neurotransmitter release onto the motor neuron

• Result: enhanced withdrawal reflex (stronger response)

sensitization makes ______ channels open more slowly, but ______ conductance increases.

postassium K+

calcium

what is the effect on the action potential?

• action potential is broader/larger → longer depolarization

• slower k+ channel opening delays depolarization

at the synapse what happens

• more time for calcium to enter the pre synaptic terminal

• more vesicle docking and neurotransmitter release

• increase neurotransmitters in synaptic cleft

Donald Hebb

• convergent activity strengthens synapses

• when things don’t happen at the same time, then you don’t strengthen the association

Carla Schatz said …. which is also known as …..

cells that fire together, wire together. Cells that are out of sync, dont link

long term potentiation (2TP)

2TP idea

• If a presynaptic neuron repeatedly helps fire a postsynaptic neuron → connection strengthens

• strengthens synaptic connections

• If they’re not synchronized → connection weakens or doesn’t form

2TP experiment

• Baseline: one stimulus every ~30 sec → small, consistent response

• High-frequency stimulation (train): many stimuli in rapid succession → responses summate → big depolarization

• Afterward: go back to a single stimulus → response is now bigger than before

That lasting increase = Long-Term Potentiation (LTP)

👉 Key idea: the synapse has been strengthened by prior activity (a form of cellular memory)

3 types of long term potentiation

specificity, cooperativity, associativity

2 types of glutamate receptors that are on the post synaptic

AMPA and NMDA

AMPA is a _______ receptor that is ______ activated, that will allow ______ to rush into the cell

ionotropic

glutamate

sodium

NMDA is a coincidence detector, it only responds to glutamte if these 2 conditions are met

1. post synaptic cell depolarized (Activated)

2. glutamate must be present (can only bind to NMDA)

NMDA receptor is blocked by _______ at resting potential.

_________ (Via AMPA) removes this blockage

magnesium

depolarization

if NMDA receptor opens causes ________ and ________ influx

Na+

Ca 2+

glutamate comes down and binds to AMPA receptors to let Na+ come through

once depolarized, it allows Mg to pop out of NMDA receptor so NA+ and Ca2+ can come in.