reading 4

Question 1

Name the four major historical theories of pain

Answer 1

1) Specificity (Labeled Line) Theory
2) Intensity (Summation) Theory
3) Pattern Theory
4) Gate Control Theory

Question 2

What is the main idea of the Specificity Theory of pain?

Answer 2

Each somatosensory modality (e.g., touch, pain) has a dedicated receptor, primary afferent, and pathway to the brain. Pain is carried by nociceptors along a dedicated pathway.

Question 3

Which historical figure first proposed a detailed somatosensory pathway for pain?

Answer 3

René Descartes
- He distinguished between nociception (neural signals) and pain perception (experience in the brain)

Question 4

What was Descartes’ metaphor for pain signaling?

Answer 4

Fibers as hollow tubes; a tug on a fiber opens a “gate” and lets “animal spirits” flow to muscles, causing movement and perception of pain.

Question 5

how did Charles Bell contribute to specificity theory?

Answer 5

nerves are heterogenous bundles; differnet fibres for different stimuli

Question 6

how did Bell-Magendie Law contribute to specificity theory?

Answer 6

dorsal roots sensory, ventral roots motor

Question 7

how did Sherrinton contribute to specificity theory?

Answer 7

coined “nociceptor”, emphasized specific fibres for noxious stimuli

Question 8

how did Von Frey contribute to specificity theory?

Answer 8

identified skin spots for touch, temp, and pain
- developed von Frey hairs

Question 9

What is the Intensity (Summation) Theory of pain?

Answer 9

Pain is not a distinct modality; it occurs when a stimulus exceeds a threshold or is repeated enough to summate in the nervous system.

Question 10

What is the Pattern Theory of pain?

Answer 10

Sensory modality and pain arise from the pattern of neural firing—the spatial and temporal activity of nerves encodes stimulus type and intensity, rather than dedicated fibers.

Question 11

What is the Gate Control Theory of pain?

Answer 11

Pain signals are modulated in the dorsal horn by:
- Small fibers (C fibers): open the gate → increase pain transmission
- Large fibers (Aβ fibers): close the gate → inhibit pain
- Descending pathways: from brainstem/supraspinal regions also modulate the gate.

Question 12

What are the three dimensions of pain according to Melzack & Casey (1968)?

Answer 12

1) Sensory-discriminative: intensity, location, quality, duration
2) Affective-motivational: unpleasantness, avoidance
3) Cognitive-evaluative: appraisal, context, culture, attention

Question 13

How does cognitive state influence pain?

Answer 13

Cognitive modulation can change the affective-motivational component without altering intensity (e.g., hypnosis, placebo effects).

Question 14

What are some shortcomings of the older pain theories?

Answer 14

• Specificity Theory: doesn’t account for wide-dynamic range neurons, deep tissue/visceral pain, or chronic pain plasticity.
• Intensity Theory: fails to explain specific nociceptor activation.
• Pattern Theory: ignores dedicated receptors.
• Gate Control Theory: oversimplified spinal circuitry, some details incorrect, but inspired research.

Question 15

What is the modern view of pain?

Answer 15

Pain is multidimensional, processed by networks in the CNS, influenced by sensory, affective, and cognitive factors, and subject to plasticity in chronic conditions.

Question 16

What is the “labeled line vs pattern” debate in contemporary pain research?

Answer 16

Peripheral nociceptors encode stimuli in a labeled-line fashion, but how CNS neurons process this into conscious pain perception remains unclear

Question 17

Q: Who are the authors of this paper? year?

Answer 17

A: Massieh Moayedi and Karen D. Davis (2013)

Question 18

Q: What type of article is this?

Answer 18

A: A review of pain theories and their evolution

Question 19

Q: Does the paper conclude that one theory fully explains pain?

Answer 19

A: No — it argues that no single theory completely accounts for all aspects of pain perception