neuro 3003 exam 3

Economic decision making

Reward maximization vs. risk minimization (MIN-MAX)

Utility

strength of preference for given outcome

Min-max

• Based upon probabilities of outcome

• People tend to be more sensitive to losses than to gains

People tend to be more sensitive to losses than to gains

• Gaining $100 vs losing $1000…

How to measure decision making in lab?

• LETS GO GAMBLING!

• Also looking at timing of decisions (marshmallow experiment)

Gambling Tasks: Two or four-armed bandit tasks

Participants select different levers, each has different reward values

Medial orbital frontal cortex

positively correlated with value gained from outcome (from the gambling)

The effects of time on decisions

• Timing of expected reward influence decision

• Tend to prefer small but immediate reward instead of a larger but more delayed reward

  • no self discipline…

vmPFC

value, empathy, morality

vmPFC & striatum

encode subjective values; emotional evaluation

OFC & striatum

modulate value of decision making

Dopamine in Decision making

• Dopamine helps with learning faster

  • More dopamine = makes reward feel “better”, which strengths the association b/w the symbol and the gain

  • Less dopamine = weakens learning signal, making it harder for the brain to update the “utility” (usefulness) of a choice

Lateral PFC & parietal cortex

encodes relative desirability of choice selection, likelihood of reward for given choice (actual decision making)

Premotor cortex

motor planning

Motor cortex

executing motor movement associated with decision

Exploit

known opportunities/solutions (“if it ain't broke, don’t fix it”)

Explore

new and potentially better opportunities

Explore pros and cons

• Pros:

  • Map building

  • You can find better ways to get rewards you didn’t know existed

  • Adaptable

• Cons:

  • Failure to learn

  • Wasting time

  • High risk

Exploit pros and cons

• Pros:

  • Maximize reward with little effort

  • Low risk if its working

• Cons:

  • Never know if there’s something better

  • Ur screwed if the environment changes

Exploration

hippocampus, striatum, dlPFC, dACC

Exploitation

vmPFC, vlPFC

Males (Explore/Exploit)

Tend to explore

Females (Explore/Exploit)

Tend to exploit

Striatum

Key for procedural memory (habits)

Anterior cingulate cortex (ACC)

salience

Drift Diffusion

• Think of it like sitting back and gathering evidence before you make a choice

• How we look at this in a lab

  • Patients in an fMRI were asked to press a button when they could identify the object

  • Saw 3 patterns of BOLD response

    • Sensory: primary and secondary sensory regions

    • Accumulation: dlPFC, IPS, IT

    • Moment of decision: preSMA, ACC, thalamus

Drift Rate

average amount of evidence gained per unit of time

Central executive

planning, goal setting, attention, inhibiting inappropriate actions

• dlPFC (abstract reasoning & logic), PPC, OFC (goals)

Salience

changes in stimuli

• Dorsal anterior cingulate cortex, anterior insula, sensory & limbic regions

Default

Introspection & reflection

• Posterior cingulate cortex, medial PFC

Dorsolateral Prefrontal Cortex

• Important for executive functions

• Abstract reasoning and logic

Ventromedial Prefrontal Cortex

• Important for empathetic decision making

• Cognitive evaluation of morality

Orbitofrontal Cortex

• Important for forming associations with hedonic (good/pleasurable) experiences and other reinforcing signals

• Critical for goal-directed behavior

Damage to the OFC

• Lose ability to judge social value of their actions

• More impulsive

• Lack of focus

Salience network

regulates the other networks.

• When it detects something important, it acts as a toggle: it shuts down the Default Mode Network (daydreaming) and activates the Central Executive Network (task-focus).

• dorsal anterior cingulate cortex, anterior insula, sensory and limbic regions

Default mode or intrinsic network

Involved in internal or private considerations

• Most active during introspection and reflection

• Key brain regions: Posterior cingulate cortex, medial prefrontal cortex

Inattentional blindness

• Failure to detect an unexpected (added) stimulus when attention is too focused on something else

Change blindness

Failure to detect a change in stimulus (e.g., object moving, appearing, or disappearing)

Yerkes-Dodson Law

"arousal" (stress, excitement, or alertness) impacts our ability to perform

• Low arousal = low performance

  • too lazy to do anything

• Optimal arousal = peak performance

  • Have enough norepinephrine to be focused

• High arousal = low performance

  • Too stressed, panicked, or over-simulated

Locus Coeruleus (LC)

brain's "master switch."

• The Signal: The LC releases Norepinephrine (NE), the chemical responsible for alertness and the "fight or flight" response.

• The Reach: Notice how the blue lines spread from the LC to almost everywhere:

  • Neocortex: To sharpen focus and executive planning.

  • Amygdala: To heighten emotional awareness (fear/anxiety).

  • Thalamus: To open the "gates" for sensory information.

• The Result: This widespread release shifts the entire brain into a state of high readiness

(Selective) attention

ability to focus awareness on one stimulus, thought, or action while ignoring other irrelevant stimuli, thoughts, and/or actions.

Informational Bottleneck

Selective attention is limited; perceptual processing has a small capacity

Context SWITCHING

Time and attentional cost to task or context switching; our attention becomes fragmented

NO context switching

Deep work or flow; when we do our best work

Overt attention

adjusting gaze to directly look at a target stimulus

Covert Attention

ability to perceive stimuli outside of fovea (peripheral vision)

Posner cueing tasks

covert attention is directed while your eyes stay at one point

• Invalid: arrow pointing at opposite place

• Neutral: double headed arrow

• Valid: Arrow pointing at right place

Brain activity higher when directly focusing on something

Attention as a Cause

attention is a physical "signal" that actively filters what you see

• Ex: you choose to listen to something

• Limited number of sensory signals reach the later stages of the processing:

  • LGN → V1 → higher order visual areas

  • Feedback from frontal & parietal cortex and superior colliculus in midbrain

Attention as an Effect

Attention is the result of your brain making a decision

• The Mechanism: Your brain is always running a "competition" between different possibilities based on:

  • Value: What is most rewarding?

  • Needs: Am I hungry?

  • External World: Is that a loud noise?

  • Prior knowledge

• The Winning Signal: Whichever goal or stimulus "wins" the competition in your motor and value circuits becomes what you are "attending" to.

First Order (FO) Thalamus

Relays raw sensory data from the outside world (Ex: a bright flash "grabs" your focus)

Higher Order (HO) Thalamus

Receives input from the cortex and sends it back to other cortical areas; your goals and expectations use the thalamus to filter out noise and highlight relevant data.

Superior Colliculus

• Priority mapping

• Damage = makes you spatially unaware

  • leads to decreased performance in an

    attention task

Goal-directed attention

• Curiosity, motivation, focus

• Endogenous (top-down)

• Voluntary

Stimulus-driven attention

• Reaction, fear. pop-up ads

• Exogenous (bottom-up)

• Reflexive

Visual attention pathway

• Processing at the sensory level (subcortical and cortical levels)

• Association areas

• Executive function areas (planning and decision making)

Cortical salience network

• Critical for monitoring and noting important changes and internal/external stimuli

• Automatic grasp of attention based upon salient stimuli

• Key regions: dorsal Anterior Cingulate Cortex, Anterior Insula, sensory and limbic regions

Dorsal frontoparietal network

Voluntary or endogenous control of attention aka Central Executive Network or dorsal network

Right temporoparietal network

Reflexive or exogenous capture of attention aka Salience Network or ventral network

Hemispatial Neglect

• parietal lobe damage where people lose perception of one side

• patients are not blind, but they lack the "mental searchlight" to acknowledge or process the left half of the world

  • Can’t copy left side of pictures, or eat the left side of their plate because they forget the left exists

Balint’s Syndrome

• can’t switch attention easily due to Bilateral lesions of parietal lobe

  • Oculomotor apraxia: difficulty steering visual gaze (can’t pinpoint stuff)

  • Optic ataxia: unable to reach for objects using visual guidance

  • Simultagnosia: extreme restriction of attention; only seeing one object at a time

Learning

the process of acquiring new information

Memory

the ability to store & retrieve that information

Engram

memory trace, persistent change in the brain that reflects the storage of memory

Meadow vole males

• Polygynous

• Large home ranges

  • Good spatial abilities; larger hippocampus

Place cells

encode the position of the animal in space (hippocampus)

Grid cells

encode coordinates (location, distance, directionality) (entorhinal cortex)

London taxi drivers

• Extensive mental map of streets

• Repeated spatial learning

• Bigger hippocampus

stages of memory

Encode —> Store —> Retrieve

Working memory

• Active maintenance of info in the limited, short-term memory

• Depends upon a quick-learning memory store

Process of converting STM or WM to LTM

• Left frontal lobe active when try to retrieve info

• Hippocampus active when retrieval successful

Working memory changes with age

• Working memory stabilizes between 15 and 22

• Stable WM until ~50

• Linear decline thereafter

  • Younger adults show increased dlPFC activity with increased WM demands

  • older adults show increased dlPFC activity during WM maintenance - suggests lower efficiency

Sleep and memory consolidation

need sleep for memory formation (slow oscillation and fast spindle coupling)

The Fast-Learning Store: The Hippocampus

• captures new information rapidly

• fast and volatile" synaptic changes; It is highly plastic but has limited capacity

The Slow-Learning Store: The Neocortex

• a long-term storage vault for stable, structured knowledge

• Uses Hebbian plasticity (LTP/LTD) that develops over time. It requires many repetitions or sleep to "solidify" connections

Systems Consolidation

Over time, the memory is "transferred" or "replayed" from the hippocampus to the cortex.

• Hippocampal Independence: Eventually (last panel), the cortical modules are so well-integrated with each other that they no longer need the hippocampus to retrieve the memory

Stress

disturbance of homeostasis

Stressor

condition, agent, or other stimulus that causes stress (e.g., heat, cold, hunger, threat, anticipation)

Stress response

a suite of physiological and behavioral responses that help to re-establish homeostasis

Allostasis

The adaptive processes that maintain homeostasis through the production of mediators; achieving stability through change

Allostatic load

Refers to the wear and tear that results from either too much stress or inefficient management of allostasis

GAS - Stage 1: Alarm Reaction

• many stressors involve only this stage

• Mobilize resources – inhibit digestion, increase HR/BP/breathing

• Heightened sensory acuity and memory

  • Activation of SNS and NE and E

  • Activation of HPA axis and release of cortisol

Stage 1: Alarm Reaction (SNS)

Earliest stage of Alarm Reaction mediated by the activation of SNS (Epinephrine and Norepinephrine)

Stage 1: Alarm Reaction (HPA)

Next stage of Alarm Reaction mediated by the activation of HPA axis

• ANS (fight or flight, more immediate, peaks first)

• HPA: cortisol: slow wave, peaks at 10 minutes, “the brake”

  • ensures the body does not overreact and return systems to a stable state

  • Negative feedback loop

GAS - Stage 2: Resistance

• Surge capacity: mental and physical resources to cope for a longer period of time

  • Increased cortisol synthesis, liver makes glucose for energy, increased lipid mobilization, muscle decreases protein synthesis

• Increased Cortisol, energy usage - Just trying to cope for a hot minute

GAS - Stage 3: Exhaustion

• After the mental and physical reserves are depleted

• Fatigue rapidly, heart disease, reproductive disorders, stomach ulcers, hippocampal neuron death, immune suppression

• Depleted/defeated - This is where the issues arise (heart disease, ulcers, neuron death

General Adaptation Syndrome

• Not all stressors put us through all stages

• Some stages can last longer for different stressors or for different people

• Period of chronic, unabated stress (global pandemic, civil unrest, politics, war, global climate change, loss of job, grief, etc.)

Cortisol as a necessity

• Increased attention to task

• Increased glucose for brain function

• Need to react quickly to dangerous stimuli

• Some anxiety, increased alertness improves performance

• Increased energy to combat stress

• Anti-inflammatory action

A little bit of stress as a good thing

Allostasis & General Adaptation Syndrome

Different types of allostatic adaptations

Repeated "Hits (Allostaic load)

• occurs when a person faces multiple, closely-spaced stressors

• The body never has enough time to fully recover between events, leading to a constant state of high physiological arousal

Lack of Adaptation (Allostaic load)

• Normally, the body "gets used" to a repeated, non-threatening stressor (like public speaking)

• In this case, the body fails to habituate, treating every single instance as a brand-new, high-level emergency