Pain Theories

Specificity Theory (labeled line theory)

Specific pathways transmit sensory information to the central nervous system. Pain is an independent sensation.

Rene Descartes

Created the first description of somatosensory system (1664)

History of specificity theory

Specialized spots on skin that selectively respond to pain, temperature, or touch

Charles Sherrington (1906)

Coined the term nociceptor

Ed Perl (1967, 1969)

First to record activity of individual nociceptors during application of noxious stimuli

Intensity theory (debunked)

Pain is the outcome of any type of strong sensory stimulation

Pattern theory —> population coding

Pain is signaled by the specific and particular firing of a composite population of afferent nerve fibers; time and location of firing matter

John Nafe

First to formally articulate pattern theory

Gate control theory

Pain signals are modulated in the spinal cord by non-painful peripheral inputs and descending signals from the brain

GCS theory is in starts in-

Substantia gelatinosa

Melzack and Wall articulated GCS theory

There is a gate in the spinal cord that can block or pass signals to the brain

C fibers (opens gate)

Nociceptive

S fibers

Pain input. Activation of these small fibers which inhibit interneurons, which effectively open gate

AB fibers

Non-nociceptive. Closes gate

L fibers (touch input)

Non painful input activating inhibitory interneurons which stop transmission of pain signals (gate close)

BioPsychoSocial model (George Engel 1977)

Pain emerges from a dynamic interplay between biological, psychological, social factors that vary across different individuals