Pain Perception

Pain: An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. (Merskey, 1991).

Stimuli:

• Mechanical (pressure, pinch, twist, squeeze)

  • e.g.

• Thermal (hot or cold)

  • e.g.

  
  

• Electrical

  • e.g.

  
  

• Chemical

  • e.g.

  
  

• Visceral (inside the body)

  • e.g.

   

Receptors: nociceptors (free nerve endings -- some controversy narrowing down specific receptors)

• Multiple Brain areas receive signals:

  • Somatosensory cortex -
    
    
    

  • limbic system & anterior cingulate cortex -
    
    
    
    

Cognitive Aspects of Pain Perception:

• Expectation:
  

  • Hospital Study:
    
    
    
    
    

  • Placebos:
    
    
    
    

• Shifting Attention:
  
  

  • virtual reality game in hospital
    
    
    

  • giving birth --
    
    
    
    

• Content of Emotional Distraction:
  

  • deWied & Verbaten (2001) -- had men hold hand in cold water until felt pain. Men looked at pictures during the session.

     

    3 groups:

    • positive pictures (sports pictures, attractive females)

    • neutral pictures (household objects, nature, and people)

    • negative pictures (burn victims, accidents)

    Results:

    
    
    
    

• Individual Differences: different reports of the severity of pain from different people when given same level of pain stimulation.
  

  • Clark & Clark (1980) Asked both Nepalese and Westerners when they felt "faint pain" and "extreme pain".
    

    • Nepalese: faint =_____ volts ; extreme = _____ volts
      

    • Westerners: faint = _____ volts ; extreme _____ volts
      
      

  • Hall & Davies (1991) Had women emerse hands in ice water and rate level of pain on 150 point scale.
    

    • Varsity track athletes:
      

    • Nonathletes:
      
      

     

Gate Control Theory:

1) With no stimulation both large and small nerve fibers are quiet.

2) With non-painful stimulation large fibers are activated. This activates the Transmission cell AND the inhibitory interneuron, which prevents the Transmission cell from firing (gate is closed).

3) With pain stimulation, small nerve fibers become active. They activate the Transmission cell AND the excitatory interneuron. (gate is open)

Pain-Perception Disorders:

• Insensitivity to Pain: (no warning of damage)

  • Symptoms:

     

    
    

  • Very dangerous disorder
    
    

    e.g. bite off tongue or finger, keep using broken bone (higher likelihood of amputation), third degree burns, don't know having a heart attack, etc.
    

• Chronic Pain:
  

  • can result from ongoing causes
    

  • can last even after initial cause is treated
    

  • treatment includes medications, and cognitive therapies (relaxation, placebos, behavior modification, etc.)

• Phantom-Limb Pain:
  
  

  • cause not fully understood
    
    

  • Treatements can vary: