Transcript Flanders2 - Haptics Symposium

Sensorimotor Neurophysiology of Active Sensing
Part 2: Dr. Steve I. Perlmutter
Somatosensory System
Receptor Function
Spinal Cord Circuitry
Proprioception
Touch
Temperature & Pain
Signaling in the Nervous System: Action Potential Generation
Ionic gradients generate a voltage across the membranes of neurons;
membrane voltage is regulated by ionic channels and pumps
The action potential is a brief, all-or-none electrical depolarization
of the neuron membrane
The rate and timing of action potentials convey information from
one neuron to another.
In primary sensory neurons, action potentials are elicited
by transduction of a sensory stimulus into a receptor potential
Receptor
potential
Spike
generation
Spike
conduction
In mechanoreceptors, mechanical energy causes ionic channels in the cell’s
membrane to open, leading to a change in membrane voltage, the receptor potential
Touch receptors endings in the skin
Hair follicle
Receptor
(RA, SA)
Touch acuity: receptive field size of receptors
Meissner
corpuscle
Merkel receptors
Ruffini corpuscle
Pacinian
corpuscle
Touch acuity: receptor density
Meissner corpuscles
Merkel disk receptors
Johansson & Valbo
Touch acuity: 2-point discrimination
Temporal resolution of touch: slowly vs. rapidly adapting receptors
Meissner corpuscle
Merkel disk receptor
Ruffini ending
Torebjork & Ochoa
Touch sensitivity: response to stimulus intensity
Activation Threshold
Touch sensitivity: frequency response of receptors
Touch sensitivity: receptor firing vs. perception
Monkey hand
Human psychophysics
Primary sensory afferents enter the spinal cord and project to 3
main targets
Axon branches to
other CNS regions
Information is transmitted from the primary sensory afferent to
other neurons in the CNS at synapses.
First main target for somatosensory information is other neurons in the spinal cord