Sensorimotor Neurophysiology of Active Sensing

Overview

Dr. Martha Flanders Department of NeuroscienceUniversity of Minnesota

Receptors and Spinal Cord

Dr. Steve I. PerlmutterDept. of Physiology and Biophysics Univ. Washington

Cerebral Cortex

Dr. Stephen I. Helms TilleryHarrington Dept. of Bioengineering Arizona State University

Overview cortex

Brodal 1981 (after Brodmann and Vogt) Golgi stain - Nissl stain - Myelin stain

Schiebel et al. 1974

6 Layers 80% of neurons are excitatory pyramidal

1 Million Columns 0.5 mm wide processing modules

Receptive fieldsMovement fields

Population CodingSparse Coding

Overview dorsal column nuclei, cerebellum, thalamus and cortex

thalamussomatosensory cortex

Roberts and Hanaway 1970

brainstem(cerebellum)

Cortical sheet gray matter (neurons) white matter (axons)

Subcortical structures thalamus brainstem midbrain, pons medulla dorsal column nuclei cerebellum

Spinal cord

Overview receptors, spinal cord

Haines 1987

Iggo and Muir 1969

Neurons – deepAxons – more superficial

Dorsal - sensoryVentral – motor

7 – Intermediate Zone interneurons

8-10 – motor neuron cells axons exit via ventral root

Dorsal Root incoming sensory information

Overview efference copy

cortical subcortical spinal

efference copy

somatosensory feedback

motor output

targetstate

current state

sensory feedback

motor command

targetstate

currentstate

muscle activityforcemovement

efference copy

A) Input (motor error) = target state – current state

Brain learns mapping from A to B by comparing efference copy to sensory feedback

Comparison operations occur at many levels

Somatosensory feeback (tactile and proprioceptive) can be used to continuously guide an ongoing < - - - - - movement

AB

Overview neural comparison and cancellation

A. Comparison

B. Cancellation

Mid LeftRight

motor command

efference copy sensory input

motor output

leftear

right ear

PAD

Corinnewww.thepaintedparrot.com.au

Examples of Comparison

Sound localization in barn owl brainstem

Primary afferent depolarization in primate spinal cord

Overview neural comparison and cancellation

A. Spinal Cord

B. Brain

motor command

efference copy sensory input

motor output

inhibition

dorsal horn spinal cord

dorsal root ganglion

peripheralsensory afferents

PAD

muscle spindle tendon organ cutaneous

cerebral cortex

dorsal columnnuclei - medulla

Heiligenberg 1973

Object Localization in electric fish brainstem

Primary afferent depolarization in primate A. spinal cord

B. brainstem?

A. Extraction

B. Extrapolation

Time (ms) Time (ms)SFA

(*b)

(*f)

(*c)

(*e)

(*d)

(*a)

STD

Research questions aboutneural mechanism in primate somatosensory cortex

Overview neural feature extraction and extrapolation