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

6 Layers 80% of neurons are excitatory pyramidal 1 Million Columns 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 Population Coding Sparse Coding Brodal 1981 (after Brodmann and Vogt) Golgi stain - Nissl stain - Myelin stain

Subcortical structures thalamus brainstem midbrain, pons medulla 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

Axons – more superficial Dorsal - sensory Ventral – motor Overview receptors, spinal cord Neurons – deep Axons – more superficial Dorsal - sensory Ventral – motor 7 – Intermediate Zone interneurons 8-10 – motor neuron cells axons exit via ventral root Dorsal Root incoming sensory information Haines 1987 Iggo and Muir 1969

A) Input (motor error) = target state – current state Overview 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 B A target state motor command muscle activity force movement efference copy current state sensory feedback cortical subcortical spinal target state efference copy motor output current state somatosensory feedback

Examples of Comparison Overview neural comparison and cancellation Corinne www.thepaintedparrot.com.au Examples of Comparison Sound localization in barn owl brainstem Primary afferent depolarization in primate spinal cord A. Comparison left ear Right Mid Left right ear B. Cancellation sensory input efference copy PAD motor command motor output

in electric fish brainstem Overview neural comparison and cancellation Heiligenberg 1973 A. Spinal Cord muscle spindle tendon organ cutaneous PAD Object Localization in electric fish brainstem Primary afferent depolarization in primate A. spinal cord B. brainstem? dorsal root ganglion peripheral sensory afferents dorsal horn spinal cord B. Brain efference copy sensory input inhibition cerebral cortex motor command motor output dorsal column nuclei - medulla

Research questions about Overview neural feature extraction and extrapolation A. Extraction (*a) (*b) (*c) B. Extrapolation (*d) (*e) (*f) Time (ms) Time (ms) Research questions about neural mechanism in primate somatosensory cortex SFA STD