Behavorial Neuroscience Unit 3

Plasticity

• ability of the nervous system to change with experience

• foundation of all learning

  • not just mental, but also physical: involves acual changes in how neurons communicate

• changes mainly occur at synapes: connection between neurons

plasticity occurs in

sensory, motor, dedicated learning areas

sesnory areas

process incoming information

motor areas

control actions

dedicated learning areas

• amgydala for emotional learning

• Hippocampus - memory

• Association cortex - integrating information

Pavlovian (Classical) Conditioning

• learn that assocation between stimuli, not actions

  • one stimulus predicts another

Unconditioned Stimulus (US)

naturally produces a response

Unconditioned Response (UR)

automatic response to US

Conditioned Stimulus (CS)

previously neutral stimulus that becomes meaningful

Conditioned Response (CR)

learned response to CS

Pavlovian Fear Conditioning Process

1. Animal is placed in a box with an electrified floor

2. Shock (US) produces fear (UR)

3. Tone (CS) is paired with shock

4. Eventually, tone alone produces freezing (CR)

Associative Learning

• involves linking sensory inputs across modalities

  • Ex: tone w/ auditory system & shock w/ somatosensory system

plasticity in auditory cortex

After conditioning:

• The auditory cortex changes its activity

• It becomes more responsive to the conditioned tone

Amgydala critical for

• forming fear associations

Inputs for amygdala

• Cortex - detailed sensory processing

• Thalamus - rapid sensory input

Outputs for Amygdala

• Hypothalamus → triggers:

  • Hormonal responses

  • Freezing behavior

  • Changes in blood pressure

Key function for amygdala

• binds sensory information together

• tone alone can activate shock-related neurons

• how brain encode assocation

Hebbian learning

• “fire together, wire together”

• when two neurons are active at the same time, the connection between them strengthens

• makes future activation more likely to occur

  • neural basis of associative learning

memory

• process of encoding, storing, and retrieving information

  • not perfect recording of events, more like a reconstruction

    • when you recall something, brain rebuilds the memory (explanation for why memories can be influenced by bias, prior knowledge, and context)

Declarative Memory

• memories that can be consciously recalled and described

  • includes both episodic and semantic memory

Episodic Memory

• events from personal life: time, place, and experience

  • allows to mentally relive past events

Semantic Memory

• facts and general knowledge that isn’t tied to a specific experience

Procedural memeory

• NON-DECLARATIVE MEMORY

• develops through practice and repetition & does not require conscious awareness

• Can perform actions w/o being able to fully explain how

  • ex: how do you swing a golf club?

Hippocampus

• Structure located in temporal lobe

• essential for forming new declarative memories

• organized and process info before it is stored long-term

Case of H.M

• had parts of hippocampus removed to treat epilepsy

• developed anterograde amnesia (couldn’t form new episodic memories)

• recall older ones before surgery

• still able to learn new skills (showed procedural memory was intact)

Subsequent Memory Effect

 observed using brain imaging during learning.

• fMRI study where subjects must memorize a list of 100 words. 

• While memorizing, brain is scanned for activity. 

• After the scan, subjects wait half an hour before being asked to recall words.

• Imaging data (during learning) can predict what words they will remember later (due to higher hippocampus activity when learning those words)

  • shows that you can predict subsequent memory based on how active the hippocampus is.

Episodic memory in animals

• studied through behavior than verbal report

• Radial arm maze: central platform with 8 arms coming off of it. Some arms have food, some do not. 

• In the maze, animals must remember which arms they have already visited

• They avoid revisiting the same arms, showing memory of past actions

If the hippocampus is damaged:

• Animals repeatedly enter the same arms

• This shows the hippocampus is required for this type of memory

Place cells

• neurons located in the hippocampous

• fire when animal is in a specific location

• create a cognitive map of environment

Memory Processing

3 main stages:

encoding: aquiring new info

storage: stabilizing and storing

retrieval: accessing stored information

Amnesia

• memory loss

Anterograde Amnesia

• inability to form new memories

retrograde amnesia

• inability to recall past memories

temporally graded retrograde Amnesia

• recent memories are more affected, while older ones are less affected

• occurs b/c older ones already stored in the cortex, while recent ones still depend on the hippocampus

Electroconvulsive Therapy (ECT)

• cause temporary memory loss

• memory loss strongest for recent events

• older ones less affected

  • ex: people remember the drive to appointment, but nothing after.

  • Memory worse after and less severe the further back you go

role of hippocampus

• temporary storage of new memories

• required for encoding and consolidation

• long term memories are eventually stored in the cortex

Temporary leison

• turning off hippocampus at certain stages of memory processing

Consolidation

• process of stabilizing memory after learning

  • involves transfer of memory from hippocampus to cortex

  • occurs after event/episode

  • stengthens neural connections over time

Sleep and Memory

• while asleep, hippocampus replays events from the day

  • strengthens memory and improves retention

  • consolidation acts as filter: strengthens important info more than less important info

Procedural Memory

• involves skills and habits that are learned through practice.

  • It relies on brain systems that support movement and action learning rather than conscious recall.

Motor Cortex

• responsible for executing learned movements

Basal Ganglia

• responsible for learning action sequences and habits

  • subcortical structure

  • plasticity here necessary for non-declarative memory

Procedural Learning Cycle

• Perform an action

• Evaluate the outcome

• Adjust future behavior

  • linking actions w/ consequences: makes procedural memory a form of reinforcement learning

Reinforcement Learning

• learning based on the consequences of actions

  • behavior shaped by whether outcomes are rewarding or punishing

Law of Effect

• Behaviors followed by positive outcomes are more likely to be repeated, while behaviors followed by negative outcomes are less likely to occur again.

Operant Conditioning (Skinner)

• Behavior is controlled by its consequences, and actions are strengthened or weakened over time depending on outcomes.

Reinforcement and Punishment

Consequences can either increase or decrease behavior.

Reinforcement

done to increase behavior

Punishment

done to decrease behavior

Negative

taking something away

Positive

adding something

Positive reinforcement:

•  adding something pleasant to increase behavior

Negative reinforcement

• removing something unpleasant to increase behavior

Positive punishment:

adding something unpleasant to decrease behavior

Negative punishment:

removing something pleasant to decrease behavior

Dopamine

• Neurotransmitter involved in learning from rewards

Where is dopamine released in

• nucleus accumbens (NAc), part of the basal ganglia

When is dopamine especially active in

 especially active during unexpected rewards

What does dopamine signal

prediction error, which reflects the difference between expected and actual outcomes

Positive prediction error

•  reward is better than expected or unexpected → dopamine increases

Negative Prediction Error

reward is worse than expected or missing → dopamine decreases

Learning over time

• dopamine activity changes as expectation changes when learning progresses

• shows that the brain learns to anticipate outcomes rather than simply respond to them.

early learning

dopamine is released at the reward

later learning

• dopamine shifts to the cue that predicts the reward

basal ganglia

• critical for reinforcement learning

• link actions w/ outcomes

• damage or loss of dopamine disrupts this learning process

working memory

• system used to hold and manipulate information

• closely linked to attention and necessary for tasks that require active thinking

Phonological loop

• Actively rehearses verbal information (words, numbers)

• Involves inner speech and repetition

• Activity in the temporal lobe

Episodic buffer

• Integrates information from different sources

• Links working memory with long-term memory

• Combines information into a single representation (e.g., scenes)

• Activity in the temporal lobe

Visuospatial sketchpad

• Processes visual and spatial information

• Example: mentally rotating objects

• Example: visualizing locations or layouts

• Activity in the parietal cortex

Central executive

• Directs attention

• Controls and coordinates the other components

• Activity in the frontal lobe

Working Memory and Attention

• Attention determines what information enters working memory

• Without attention, information is less likely to be maintained

Hemispatial Neglect

• disorder caused by damage to the right parietal cortex

• Individuals ignore the left side of space

• They may only draw half of an object or fail to attend to one side of their body

Modularity

Memory systems are specialized but interconnected.

• Declarative memory, procedural memory, and working memory interact

• They do not function as completely separate systems

Emotions

• consists of multiple components that work together

  • physiological arousal, conscious feelings, communicative expressions, memory component

James-Lange Theory

• Stimulus → physiological response → emotion

• The body reacts first, and the brain interprets that reaction as an emotion

What does the James-Lange Theory propose?

that emotions result from the interpretation of physiological responses

Fear pathway

fear response that preps body for threat

• Amygdala detects threat

• Hypothalamus activates the HPA axis

• This leads to stress responses and autonomic arousal

amgydala

 critical for processing emotionally significant stimuli.

• It detects threats and other important signals

• It plays a central role in emotional learning

what can damage to the amygdala result in

Kluver-Bucy syndrome, which is characterized by reduced fear and abnormal emotional responses.

Placid

• reduced physiological and emotional response to stimuli

Conscious emotion

 experience depends on awareness of internal bodily states.

Interoceptive awareness:

• awareness of internal physiological signals

Insular cortex:

• gets sensory input from the organs and makes the internal state conscious. The internal state is not conscious until it reaches the cortex.

• damage can lead to apathy: no longer experience addiction

PTSD

abnormal processing of fear and threat.

1. Detecting threats

• Something may trigger fear response when it would not have beforehand. There is an increase in threat detection.

2. Fear memory

• They remember the emotional response

• Memories are strong and vivid, and produce all the emotional responses

Emotional Expression

 amygdala responds to emotionally significant stimuli, not just fear.

• It responds to salient emotional stimuli, threatening or not.

Positive Emotions

• Joy, happiness, love, etc.

• These cause pleasure

Valence

• refers to whether an emotion is positive or negative

Orofacial reactions:

• Responses to something sweet or bitter (facial)

• Used as a measure of pleasure in animals

Pleasure vs Reward

Pleasure and reward involve different systems.

Dopamine

is related to reward and learning

Opioids

• are responsible for the experience of pleasure (regardless of if it is expected or unexpected).

Opioid agonists

• (e.g., endorphins, morphine, heroin) increase pleasure by promoting Opioid release.

Opioid antagonists

reduce pleasure by blocking Opioid release.

• Episodic memory

• Glucocorticoids (stress hormone, a type of cortisol) 

• Modulate activity in the hippocampus (helps encode the info/more likely to retain it).

• Enhance synaptic plasticity

Working memory

• Noradrenergic pathway

• Locus coeruleus: sends axons into cortex. Neurons release noradrenaline (similar to adrenaline, but it is a neurotransmitter)

• Enhances attention and working memory

Non-declarative learning

• Emotion strengthens:

• Pavlovian fear conditioning

• Law of effect

Synaptic Plasticity

Synaptic plasticity refers to changes in the strength of synapses.
This is the biological basis of learning.

Learning happens through physical changes in neural connections.

Excitatory Synapse

Uses glutamate

Ionotropic glutamate receptors:

• Cause ions to flow into postsynaptic dendrite when activated, causing a change in voltage.

AMPA receptors (a type of ionotropic glutamate receptor)

Allow Na⁺ influx (passes through the channel)

Cause EPSP (positive voltage change)

EPSP (Excitatory Postsynaptic Potential)

• Positive change in voltage in the postsynaptic neuron

• Caused by influx of Na⁺