Motivation and Action: Frontal Asymmetry

Question 1

Valence hypothesis of frontal asymmetry

Answer 1

The left hemisphere is specialized for processing positive affect
The right hemisphere is specialized for negative affect

Question 2

Robinson et al. 1988 - Mood disorders following stroke

Answer 2

Right hemisphere lesions - patients developed secondary mania; excessive positive emotion
Left hemisphere lesions - patients developed major depression; excessive negative emotion

Question 3

Hemispheric imbalance

Answer 3

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

Question 4

EEG to measure asymmetric frontal cortical activity

Answer 4

Assess asymmetry using EEG
Measures the outcome measure - the degree of asymmetric cortical activity

Question 5

Asymmetry index

Answer 5

Compare activity levels between comparable areas in left and right frontal cortex

Question 6

EEG and Alpha Rhythm

Answer 6

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

Question 7

Alpha band activity

Answer 7

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

Question 8

Alpha band activity

Answer 8

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

Question 9

Electrodes

Answer 9

Find equivalent electrodes (for each hemisphere), generate a voltage and compare the activity relative to the equivalent neuron on the other hemisphere

Question 10

Frontal cortical alpha asymmetry index (FAI)

Answer 10

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

Question 11

Resting FEA and personality

Answer 11

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.

Question 12

Depression and low resting FEA - Nusslock et al. 2001

Answer 12

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

Question 13

Longitudinal - Asymmetry and mood disorder

Answer 13

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

Question 14

Fox and Kalin - Anxious temperament and frontal asymmetry

Answer 14

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

Question 15

Capability model

Answer 15

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

Question 16

FEA during emotional challenges

Answer 16

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

Question 17

Motivational direction hypothesis

Answer 17

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

Question 18

Anger and approach motivation

Answer 18

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

Question 19

Trait anger and resting left FEA - Harmon-Jones & Allen

Answer 19

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

Question 20

Controlling degree of manipulation - Harmon-Jones et al.

Answer 20

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

Question 21

Embodied motivation

Answer 21

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

Question 22

Insult + embodied motivation

Answer 22

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

Question 23

Transcranial direct-current stimulation, tDCS

Answer 23

Non-invasive direct brain stimulation - causal inferenced
Can increase/decrease neuron excitability
Can excite one hemisphere while inhibiting another hemisphere

Question 24

Anger-aggression, tDCS manipulation - Hortensius et al.

Answer 24

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

Question 25

Sword and Shield Hypothesis (SSH) - Brookshire and Cassanto

Answer 25

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