PSYC 301 - Emotion, Stress, Executive Function

emotions

short-lasting, intense feelings that shape how we act and make decisions

evolutionary benefits of emotions

• critical for decision-making, eg: value assessment

• impairment of emotional areas also impairs rational decision-making

  • cannot assign value or make cost-benefit decisions otherwise

• emotions were selected FOR during natural selection

right hemisphere model

brain is split in half, where right hemisphere is dominant for emotions and left hemisphere is dominant for logic

valence model

• right hemisphere feels negative emotions

• left hemisphere feels positive emotions

  • evidence: right hemisphere damage leads to higher baseline mood, left hemisphere leads to lower baseline mood

6 universal emotions

• anger, fear, surprise, sadness, disgust, happiness

• evidence against: when asked to categorize pictures based on emotions, the only universally understoond and agreed upon emotion was happiness

our current understanding of emotion lateralization

• more complicated than just left and right

• emotions involve bilateral networks, across many brain regions

LeDoux - rat study

• classical conditioning of fear, using a sound combined with shock

• rats with amygdala lesions could not be classically conditioned into it

• discovered “low” and “high” road to fear

high roads of fear

• sensory info goes from sensory organs → thalamus → cortex → amygdala

• rats with lesions did not know when to be afraid and could not learn

• this ability to learn fear is complicated, nuanced - uses highest level of cortical functioning

low roads of fear

• sensory info goes from sensory organs → thalmus → amygdala

• bypasses cortex

• does not require conscious processing as info does not reach consciousness

  • eg: flashing an image for 20 ms

Kluver-Bucy syndrome

• occurs as a result of amygdala damage in primates

• symptoms:

  • lack of fear, actively seeking out predators like snakes and humans

  • hyperorality and repeated investigation of familar objects

    • this points toward issues perceptual issues

  • hypersexuality

amygdala role in emotion

• fires equally for appetitive (positive) and aversive (negative) stimuli

  • some cells respond to both, looking at how much arousal instead of valence

• stimulation devaluation occurs when the amygdala constantly updates

  • eg: primates will constnatly eat chocolate if amygdala damage

appetitive values

learnt slowly by the amygdala, because they do not pose immediate threat to our health

aversive values

learnt quickly by the amygdal, because they are immediately needed for survival purposes

ultimatum game and anger (fairness)

• rejecting unfair offers correlates with anterior insula activation

• therefore, anger motivates fair, prosocial behaviour

slot machine task and frustration (motivation)

• near misses on a slot machine: triggers anterior cingulate activation

• increases motivation to keep playing due to frustation - you feel like you are very close to succeeding

anger/fairness activates the…

anterior insula

frustration/motivation activates the…

anterior cingulate cortex

bilateral vmPFC damage

• intellectual abilities usually preserved

• severe executive function, eg:

  • inability to priorize tasks

  • emotion dysregulation

  • acknowledge they are doing something wrong but still continues

  • difficulty starting tasks

  • cognitive inflexibility

  • attention/concentration issues

unilateral vmPFC damage

• right vmPFC causes more severe disruptions in executive functions

• left vmPFC damage causes less severe, relatively normal/typical life

Phineas Gage

• survived a metal rod piercing his skull and damaging left PFC

• behavioural changes: impulsive, socially inappropriate, irresponsible

• some recovery occurred: worked, damage not noticeable to outsiders

• died of epilepsy 12 years after injury

symptoms of prefrontal damage

• impaired emotion regulation

• poor decision-making, judgement

• socially inappropriate behaviour

• trouble with long-term planning and prioritization

active stress

stress triggered by external factors

passive stress

stress triggered by removing something that is otherwise beneficial to you

benefits of acute stress

enhances performance on:

• implicit memory

• simple, well-practiced, habitual tasks

• short-term immune function

fast stress response mechanism

uses NE, E, in the adrenal medulla and travels via the sympathetic nervous system

HPA axis

• slow pathway that releases cortisol over minutes/hours

• normal fluctuations in cortisol is part of the healthy stress regulation

harms of chronic stress

• leads to physical and cognitive impairments

• depletes energy

• chronic HPA activation raises cortisol levels, impairing memory and immune function

stress immunization

exposure to controllable stressor builds future resilience

• eg: studying for exams helps handle future stressors, even if the future ones are uncontrollable

learned helplessness

exposure to uncontrollable stressor reduces future resilience

• eg: common in ACEs, which lead to stronger stress responses even in manageable situations

costs of acute stress

impairs prefrontal cortex functioning, eg:

• working memory

• cognitive flexibility

• executive function

Yerkes-Dodson curve

• low stress = underarousal, poor performance

• optimal stress = focused ,strong PFC tuning

• high stress = PFC inhibited, neurons disconnect, performance drops

adaptive nature of stress

• during danger, the brain silences PFC and long-term decision-making

• instead, shifts control to subcortical structures like the basal ganglia

• this promotes, fast, instinctual, survival responses

reversibility of chronic stress

effects on PFC and hippocampus can reverse when the stressor is removed

catecholamines and chronic stress

• chronic stress elevates baseline DA and NE

• shifts function away from optimal arousal to overarousal

effect of chronic stress on cognition

• impairs performance on memory and executive tasks

• brain must work harder to perform at the same level of someone not chronically stressed

effect of chronic stress on brain structure

• reduced hippocampal volume

• thinning PFC

• neurons don’t die, but lose dendrites and spines

cognitive/behavioural effects of poverty

• chronic, uncontrollable stress

• affects performance on unrelated cognitive tasks

  • study: people were told to pay off a car bill, then unrelated tasks - poorer performance for low SES individuals

• constant financial stress occupies cognitive resources

decision-making effects of poverty

• irregular reward schedules (eg: unreliable transit) increases impulsivity, even in people with high self-control

• poverty shifts brain function from PFC and goal-directed thinking to basal ganglia/amygdala, habitual/reactive behaviour

developmental effects of poverty

• disproportionately affects children within the first 3 years of life

• being fostered into a higher SES family leads to more chance of recovery

key symptoms of ADHD

• hyperactivity, impulsivity, inattention

• affecting daily functioning, academic and social success

• influenced by developmental maturity and social norms

  • eg: girls often underdiagnosed due to inattentive type being less noticeable

brain mechanisms of ADHD

• hypoactive DA system, especially in PFC and basal ganglia

  • PET scans show reduced DA activity, no change in NE activity (only subcortical, ligand does not bind in cortex)

• PFC underactivity leads to executive function deficits

pharmacological treatments of ADHD

psychostimulants like amphetamines and ritalin

how do psychostimulants work for ADHD?

• they block DA and NE transporters, increasing the availability of DA and NE

  • this boosts DA/NE levels, improving PFC function

• moves the individual from the underaroused zone, where neurons fire for everything, to optimal arousal where neurons fire for specific tasks

ADHD relation to stress/burnout

• symptoms overlap with the effects of chronic stress

  • poor focus, impulsivity, executive dysfunction

• burnout can worsen ADHD symptoms

• ADHD may increase vulnerability to burnout

patient SM

• bilateral amygdala calcification due to Urbach-Wiethe disease

• cannot expeirence fear

behavioural consequences of patient SM

• does not avoid dangerous situations, eg: physical assault, snakes, walking home late at night

• no sense of personal space, trusts strangers too easily

• quality of life is impaired by her inability to assess risk

role of amygdala - SM cannot…

• fear learning/response

  • low road: fast, unconscious processing

  • high road: conscious, contextual processing

• encodes both positive and negative stimuli

functional utility of fear

• helps make quick, survival decisions

• without fear, judgement is impaired leading to unsafe behaviour

• adaptive and essential for survival