Demonstration of psychophysical methods in humans

Question 1

Microneurography in humans

Answer 1

-Originally developed by Hagbarth, Vallbo and colleagues in Sweden in 1960s
-Tungsten needle electrodes, c. 5 um tip diameter, coated with insulating material up to tip, can pick up small current due to passing action potential in nearby axon (extracellular recording)
-First studied properties of sensory axons from hand, by inserting needle electrodes into their own ulnar nerve, or median nerve

Question 2

Tactile sensations: somatosensory system

Answer 2

• Dorsal column-medial lemniscal subdivision (DCML)
• Primary afferents: Abeta fibres
• Innervate sensory endings in the skin

Question 3

Classes of tactile afferent

Answer 3

-meissner corpuscle
-pacinian corpuscle
-ruffini’s corpuscles
-merkel’s disks
-free nerve endings

FA1: MC
SA1: MD

Question 4

Psychophysical and neuronal thresholds compared

Answer 4

A: RFs in fingertips
B: RFs in palms

Psychophysical thresholds for detection correspond well to neural thresholds in fingertips, but are higher than neural thresholds in palms