Download Flanders1 - Haptics Symposium

Sensorimotor Neurophysiology of Active Sensing
Overview
Dr. Martha Flanders
Department of Neuroscience
University of Minnesota
Receptors and Spinal Cord
Dr. Steve I. Perlmutter
Dept. of Physiology and Biophysics
Univ. Washington
Cerebral Cortex
Dr. Stephen I. Helms Tillery
Harrington Dept. of Bioengineering
Arizona State University
Overview cortex
Schiebel et al. 1974
6 Layers
80% of neurons are
excitatory pyramidal
1 Million Columns
0.5 mm wide
processing modules
Receptive fields
Movement fields
Brodal 1981 (after Brodmann and Vogt)
Golgi stain - Nissl stain - Myelin stain
Population Coding
Sparse Coding
Overview dorsal column nuclei, cerebellum, thalamus and cortex
thalamus
somatosensory
cortex
Cortical sheet
gray matter (neurons)
white matter (axons)
Subcortical structures
thalamus
brainstem
midbrain, pons
medulla
dorsal column nuclei
cerebellum
Spinal cord 
brainstem
(cerebellum)
Roberts and Hanaway 1970
Overview receptors, spinal cord
Neurons – deep
Axons – more superficial
Dorsal - sensory
Ventral – motor
7 – Intermediate Zone
interneurons
Haines 1987
8-10 – motor neuron cells
axons exit via ventral root
Iggo and Muir 1969
Dorsal Root
incoming sensory
information
Overview efference copy
target
state
B
A
motor
command
muscle activity
force
movement
efference
copy
current
state
sensory feedback
cortical
subcortical
efference
copy
Brain learns mapping from
A to B by comparing
efference copy to
sensory feedback
Comparison operations
occur at many levels
spinal
target
state
A) Input (motor error) =
target state – current state
motor
output
current
state
somatosensory feedback
Somatosensory feeback
(tactile and proprioceptive)
can be used to continuously
guide an ongoing
< - - - - - movement
Overview neural comparison and cancellation
Corinne
www.thepaintedparrot.com.au
Examples of Comparison
A. Comparison
left
ear
Right
Mid
Left
right
ear
Sound localization in
barn owl brainstem
B. Cancellation
sensory input
efference copy
motor command
PAD
motor output
Primary afferent
depolarization in primate
spinal cord
Overview neural comparison and cancellation
Heiligenberg 1973
A. Spinal Cord
muscle spindle
tendon organ
cutaneous
PAD
dorsal horn
spinal cord
dorsal root
ganglion
peripheral
sensory afferents
Object Localization
in electric fish brainstem
Primary afferent
depolarization in primate
B. Brain
efference copy
inhibition
sensory input
cerebral
cortex
motor output
motor command
dorsal column
nuclei - medulla
A. spinal cord
B. brainstem?
Overview neural feature extraction and extrapolation
A. Extraction
( a)
*
( b)
*
( c)
*
B. Extrapolation
( d)
*
( e)
*
Time (ms)
( f)
*
Time (ms)
SFA
STD
Research questions about
neural mechanism in
primate somatosensory
cortex