brain mechanisms, pain modulation, & mindfulness meditation

Brain Mechanisms Supporting the Modulation of Pain by Mindfulness

Meditation

Zeidan et al. (2011), J Neuro

What is Mindfulness?

• Defined– Present-moment awareness and attention to

internal and external experiences

– Focused attention: cognitive practice of sustained attention on breath

• Psychological and physiological benefits– Increased well-being, decreased psychopathology

– Better outcomes in stressed patient populations

– Decreased subjective experience of pain

Brain Mechanisms Underlying Mindfulness

• Limbic regions

– Amygdala: functional and structural changes

• Cortical regions

– Top-down modulation of limbic regions attenuated affective response to stress

• PASL MRI measures CBF

Hypotheses

1. Meditation will reduce pain ratings

2. Meditation will modulate activity in brain regions associated with pain processing

1. PFC, ACC, anterior insula

3. Is meditation-related activation associated with pain modulation?

Methods

Stimuli & Measures• 32 5-sec heat stimuli (35-49 C)

• Experimental stimuli: 5 min 55 sec

– Heat condition: 12 sec 45C/12 sec 35C

– Neutral condition: 35 C

• Delivered to R calf by thermal stimulator

• Other measures: HR, RR, FMI, global CBF

• Visual Analog Scale

– “No pain sensation” – “Most intense imaginable”

Pain Ratings Across Sessions

• Activations and deactivations pre-training (vs rest)

• ATB

– Less DMN activation cognitively engaged

• Pain-related activity

– Consistent with previous studies

– Validates methodology

Post-Training Outcome Measures

• After 4 days of meditation training, mindfulness skills increased (FMI)

• Respiration Rate

– Decreased during meditation in presence of noxious stimuli

– Decreased in post-training

• Heart Rate

– Greater during noxious stimulation

Meditation• SI nose and throat

• Interoceptiveattention

• ACC, Insula

• Pain Modulation• OFC, ventral striatum, vlPFC

• PCC, mPFC

Pain

• Insula• ACC• SII

• Similar to pre-training and previous studies

•ACC and AI overlap pain modulation

SI and SMA: interaction between meditation and noxious stimuli

• SI activation during meditation compared to rest in the presence of noxious heat stimulation

• Right AI and bilateral ACC

– Greater meditation-induced activation greater reductions in pain intensity ratings

• OFC, thalamus

– Greatest meditation-induced activation/deactivation greater reductions in pain unpleasantness

• Meditation activates self-regulation areas

– Cognitive control: ACC

– Emotion regulation: OFC

– Interoceptive awareness: AI

Pain-related brain activity post-training

• Reduced: SI, insula, SII

• Increased: frontal pole, thalamus, mPFC, ACC

Proposed Mechanisms for Meditation-Induced Pain Reduction

1) Executive regions SII, insular cortex, PPC SI

2) ACC and right AI as pain modulatory regions affected by mindfulness

3) Increased affective regulation and reward processing by OFC

4) Limbic-thalamic gating mechanism activated by meditation

Take-Home Message

• Mindfulness is among the cognitive manipulations that can decrease pain perception

– Shares common modulatory pathway with attentionalcontrol, placebo, reducing expectations of pain

• This may occur via changes in signaling between executive regions and subcortical structures

Critique

• Small sample size

• Didn’t account for other individual trait differences that may influence pain modulation

• Long-term effects? Is sustained practice required?

• Relation to structural changes?