Psychobiology WK 4 Self-control

Top down processing

Slow, thoughtful and rational thinking

Uses cerebral cortex: lateral PFC

Leads to successful self-control

Bottom-up processing

Quick, emotional, instinctive

Uses primitive structures: Basal ganglia (ventral striatum) and limbic system

Optimal behaviour requires both top-down processing and bottom-up processing

Failure of successful top-down processing leads to bottom-up processing and therefore lack of self-control

Dieting and self-control (Kim et al 2020)

Thinner cortical thickness of PFC associated with lower dietary self-control

Higher volume of amygdala associated with dietary self-control

Balance model of self-control (Lopez et al 2017)

Hypothesis: self-control failures results from an imbalance in reward and executive control systems

Studied chronic dieters fMRI scans when viewing food cues and 1-week self-report of giving in to/resisting food

Behaviour is predicted by the balance of reward/control systems rather than one system alone

Cognitive control over temptation (Kober et al 2010)

fMRI scans of patients who were given cognitive strategies to reduce food and cigarette cravings

When asked to think about the long-term consequences, this reduced cravings

Down-regulation increased PFC activity and decreased activity in ventral striatum and limbic system

the dlPFC reduced cravings by reducing the ventral striatum (top-down wins)

Ventral Striatum

Large part of bottom-up processing

Contains Nucleus Accumbens

Associated with reward, reinforcement and addiction

Interacts with amygdala, hippocampus and Ventral Tegmental Area (dopamine-rich area of mid-brain)

Nucleus Accumbens

Lopez et al (2014)

fMRI of food images, and 1-week self-report of food desires

Higher Nucleus Accumbens activity associated with:

• Higher food desires

• Higher enactment on food desires

• Higher amount eaten

Smaller-sooner vs larger-later rewards

“Would you rather have £7 now or £10 in a month?”

Strong preferences for smaller-sooner rewards associated with higher impulsivity, poorer grades, substance use

• Higher connectivity in limbic system and Medial OrbitoFrontal Cortex (mOFC)

Stronger preferenes for larger-later rewards showed higher connectivity between cortical regions and cognitive control systems (dlPFC, Anterior Cingulate Cortex, Superior Frontal Cortex)

Lesions and impulsivity

Impulsivity = Decisions based on immediate urges without much deliberation or consideration for consequences

Combat veterans with damage to PFC showed greater impulsivity

Limitations of lesion studies

Different areas affected in different individuals - Vary in size and location

Possibility of functional re-organisation (neuroplasticity; function changes location)

Method for creating temporary lesions

rTMS: repetitive Transcranial Magnetic Stimulation

Decreases excitability in regions of brain, making neurons less likely to fire

Creates temporary lesion effect, but only decreases brain properties not structure

rTMS use and patience with rewards (Figner et al 2010)

rTMS reduced excitability of left lateral PFC

Participants were more likely to choose smaller-sooner rewards than larger-later

Although did not alter how attractive they rated the rewards

tDCS

Transcranial Direct Current Stimulation

Electrodes placed on scalp based on brain areas of interest

Modifies (increases) neurons’ excitability by changing membranes’ resting potentials

tCDS and inhibition

Using the go/no go task, they found that when activating the left dlPFC, there was:

• Improved accuracy of Go/No Go responses

• Slower reaction time

• More thoughtful, top-down processing

tDCS and risk-taking

Doing a red/blue task:

• Choosing different rewards → the red boxes were fewer, but had higher reward (risky condition)

• There were more blue boxes, but lower reward (less risky condition)

The group that had tDCS to the dlPFC chose less risky options

This effect continued on 1 and 2 month follow-ups (and even decreased)

Meditation and self-control (Tang et al 2013)

Smokers have reduced self control (i.e. reduced activity in ACC and PFC)

After taking 2 week meditation training, smoking reduced by 60%

Also increased activation in ACC and PFC

Meditation can alter self-control circuits

Praying and self-control

Studied praying and non-praying people in Alcoholics Anonymous

Those that prayed had reduced self-reported craving

Praying showed increased activation in frontal and temporal cortical areas

• Responsible for self-related cognition and reappraisal of emotion

Mashmallow test

A test of delayed gratification

Children were left in a room with a marshmallow for 15 minutes - if they waited, they got 2

Children who waited later on showed higher PFC activation, higher grades and self-esteem as adults

Children who did not wait showed higher ventral striatum activation as adults (and opposite of the above)

Adolescence and risk-taking

Adolescence is characterised by high-risk taking

Previously believed this was due to low PFC development

• However, children do not show this high level of risk-taking

Models now consider circuitry and how brain regions interact across development

Adolescence and neural connections (brain region stabilisation)

Functional conenctivity between PFC and subcortical regions do not stabilise until mid 20’s

Imbalance model of brain development

Motivational/emotional brain regions develop earlier than control regions, suggesting adolescents rely on motivational/emotional brain regions because control regions are not fully developed

Whereas in childhood and adulthood the gap between the two regions is a lot smaller

Adolescents in emotional Go/Don’t Go tasks

Adolescents performed normally (like children and adults) in non-emotional conditions

However pressed the button more on ‘Don’t Go’ tasks than children and adults when an emotional stimuli was present (usually positive social cues)

Suggests higher impulsivity and increased activity in ventral striatum (due to positive social cues being rewards?)

Adolescent small, medium and large rewards (Galvan et al 2006)

When presented with 3 different rewards (small medium or large), adolescents went for any reward but were quicker (increased nucleus accumbens activation). Possibly explained by slower development of subcortical regions

• Children were particularly slow

• Frontal activation in adolescents and children were similar

• Adults were slower but were more likely to choose the larger reward (shows reflection)

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