Motivation and Action: Frontal Asymmetry Flashcards
Valence hypothesis of frontal asymmetry
The left hemisphere is specialized for processing positive affect
The right hemisphere is specialized for negative affect
Robinson et al. 1988 - Mood disorders following stroke
Right hemisphere lesions - patients developed secondary mania; excessive positive emotion
Left hemisphere lesions - patients developed major depression; excessive negative emotion
Hemispheric imbalance
Two hemispheres balance and regulate each other via mutual tonic inhibition - along the corpus callosum
When one hemisphere becomes more active, it suppresses activity on the opposite hemisphere
When one hemisphere is lesioned, activity increases in the unaffected hemisphere
e.g. right hemisphere damage increases activity in the left hemisphere, which regulates positive affect and thus creates an increase in positive affect
EEG to measure asymmetric frontal cortical activity
Assess asymmetry using EEG
Measures the outcome measure - the degree of asymmetric cortical activity
Asymmetry index
Compare activity levels between comparable areas in left and right frontal cortex
EEG and Alpha Rhythm
EEG captures oscillations generated within and between populations of neurons
Neurons propagate through the skull as they’re fired, which scatter over the surface and are recorded
Different populations of neurons oscillate over time at different frequencies - can isolate them using statistical techniques
Use FFT technique to transform activity from the time domain into the frequency domain
A direct measure of neuronal activity
Less localised so low spatial resolution but high temporal resolution
Alpha band activity
An index of deactivation - has an inverse relationship with brain activity
There is a directly negative relationship between alpha activity and neuronal fibre
The greater the alpha rhythm, the higher deactivation or negative activity
Alpha band activity
An index of deactivation - has an inverse relationship with brain activity
There is a directly negative relationship between alpha activity and neuronal fibre
The greater the alpha rhythm, the higher deactivation or negative activity
Electrodes
Find equivalent electrodes (for each hemisphere), generate a voltage and compare the activity relative to the equivalent neuron on the other hemisphere
Frontal cortical alpha asymmetry index (FAI)
Difference score summarises relative activity at equivalent left and right electrodes
Positive scores = relatively greater right alpha index = greater left frontal activity
Negative scores = relatively greater left alpha index = greater right frontal activity
Resting FEA and personality
Used a self-report and measured FEA
More negative affect = increased right mid-frontal activity
More positive affect = increased left mid-frontal activity
Frontal measurements give a good estimate of natural functional organisation - ecologically valid but inferences limited to non-task related
Can compare lots of different studies using resting as there are less confounds between tasks etc.
Depression and low resting FEA - Nusslock et al. 2001
People currently suffering, previously suffered or never suffered depression
Currently and previously depressed = blunted frontal asymmetry
Indicates a stable predisposing factor to depression; present even if not current - could be a biomarker for depression
Longitudinal - Asymmetry and mood disorder
Measured at time point 1 - start of university
– lower left hemisphere asymmetry = greater right hemisphere activity = more negative thought styles
Measured again 3 years later
– strong predictive relationship between greater right activity and diagnosis of a depressive disorder 3 years later
Fox and Kalin - Anxious temperament and frontal asymmetry
Measured in early infancy and through childhood to see when biological markers arise
Brought into lab with their mother, ‘strange situation’ exposure
Measure their response to this as a measure of behaviour inhibition - a big risk factor for social anxiety disorder
– can measure this in primates to - animal models to study more invasively than in humans
Measure with EEG to separate into left/right/no difference frontal asymmetry, and measure cortisol (stress) and anxiety in response to strange situation
Greater stable right frontal activity = increased cortisol and anxiety
– share with primates
Capability model
Frontal FEA is an interaction between current state and dispositional traits.
Individual differences in FEA reflect interactions between emotional demands of specific situations and trait-related capabilities that individuals bring to them - emotion regulation
Using emotionally salient situations would better discriminate differences between people’s FEA scores/brain activity
– should see bigger differences between depressive/non-depressive when doing a demanding affective task
FEA during emotional challenges
FEA was more of a powerful predictor of depression when involving an emotional challenge
Differences are minimised in resting states
– asymmetry has a base fixed rate, but the difference becomes more apparent over different contexts/situations, e.g. why some have social anxiety and others have object phobias
Motivational direction hypothesis
Emotion motivates us to act - feelings motive
Positive/negative could actually reflect our motivational direction (approach/withdraw) rather than valence
Left frontal activity = increased approach motivation
Right frontal activity = increased withdraw motivation
Anger and approach motivation
Anger and approach motivation are correlated and functional for confrontation
High approach motivation, high negative affect - which hemisphere it is associated with should tell us which hypothesis is true
– unique way to measure this
If FEA reflects valence = anger should increase right hemisphere activity
If FEA reflects motivation = anger should increase left hemisphere
Trait anger and resting left FEA - Harmon-Jones & Allen
Measured resting FEA in adolescent boys and girls who had impulsive control problems
Measured tendency to various types of aggression and anger
Trait anger was linked to increased resting left frontal activity = which is positively valanced
– supports approach motivation
BUT, anger could feel positive to some people, especially those with anger disorders.
– to address we control for positive attitude towards anger
After controlling for positive attitude towards anger, we still see increased left frontal activity
Controlling degree of manipulation - Harmon-Jones et al.
Manipulated the degree of approach motivation during anger - more approach manipulation should increase left frontal activity if motivational hypothesis is true
Students told about the same injustice (tuition fee increase) that would happen - half could act on it by signing a petition (high approach motivation), other half told they could not act on it (low approach motivation)
Measured self-reported emotional states and FEA
Anger was increased at the same rate in both conditions
High motivation group = higher increase of left frontal asymmetry/activity, which positively correlated with signing the petition
Low motivation group = less increase of asymmetry
Embodied motivation
Emotional states are also states of the whole body as well as brain - inclining us towards certain action
Different physical states could feedback to the brain on our approach motivation, e.g. increased bodily readiness to act increasing approach motivation
Insult + embodied motivation
Ppts received neutral or insult feedback to an emotionally salient topic
Received feedback in 3 bodily conditions:
Neutral + upright
Insult + upright
Insult + reclined
Measure FEA and self-reported emotions
Self-reported emotion was not different between insult conditions
Left asymmetry increased more in the upright insult
– causal inference
Transcranial direct-current stimulation, tDCS
Non-invasive direct brain stimulation - causal inferenced
Can increase/decrease neuron excitability
Can excite one hemisphere while inhibiting another hemisphere
Anger-aggression, tDCS manipulation - Hortensius et al.
Ppts received tDCS that either stimulated the left hemisphere (inhibiting the right, responsible for withdraw motivation) or the right hemisphere (inhibiting the left, responsible for approach motivation), or placebo
Received insult feedback
Could play game where they could retaliate by blasting a noise to the insulter when they had faster RT
Left stimulation = the more anger, the more retaliation (approach motivation)
Right stimulation = no increase in retaliation even with the same levels of anger
– a clear causal role of approach motivation and anger associated with the left hemisphere
Sword and Shield Hypothesis (SSH) - Brookshire and Cassanto
Hypothesises that affective motivation and manual motor control is co-lateralised
– a functional explanation for lateralisation and approach motivation
Previous studies only looked at those with right-handedness
Dominant hand is what you approach with (sword), and non-dominant hand is what you avoid with (shield)
According to this hypothesis, right handed people should show increase in resting left hemisphere, left handed in resting right hemisphere
Measured FEA in right and left handers during resting EEG
Measured trait approach motivation
Left handers = left frontal asymmetry was correlated with trait approach motivation
Right handers = right frontal asymmetry was correlated with trait approach motivation
