Motor systems1 ACTIVE SENSING Lecture 4: Motor systems III

Motor systems2 Summary of Motor Systems I-II: Basic motor control loops

Motor systems3 PID control Present Past Future  Negative feedback loop ’’’’  ’’  ’ (t+  t) = -f [  ’  t  f is monotonic increasing  ’ (t+  t) = f [  ’  t  f is monotonic increasing Positive feedback loop

Motor systems4 The spinal loop (stretch reflex) Knee joint Motor neuron ’’’’ spindle

Motor systems5 The spinal loop (stretch reflex) Knee joint Motor neuron ’’’’ spindle  s  ’ KsKs KMKM KsKM’KsKM’KsKM’KsKM’  dt

Motor systems6 Pain reflex Positive or negative? What is the underlying circuit?

Motor systems7 Contact loop – negative or positive? What does it take to switch between negative and positive FB loops?

Motor systems8 Basic motor control of other sensory organs   visual   Vibrissal

Motor systems9 Motor control in the visual system   Eye movement (oculomotor control)   Vision (perceptual control)

Motor systems10 The extra-ocular muscles (EOMs) From Bear’s Neuroscience text book

Motor systems11 Axes of eye movement control

Motor systems12 Donder’s and Listing’s laws  Donder ’ s law states that the orientation of the eye when looking in a specific direction is always the same.  Listing's law specifies what this orientation is.  It refers to the axes (the bars protruding from the eyes) used to rotate from center to various eccentric positions.  Listing found that all these axes are confined to a common plane.  This plane is called Listing's plane. Valid when looking with the head fixed

Motor systems13 How does the system keep Listing’s plane?  Ocular mechanics?  Neuronal mechanisms?

Motor systems14 Special design of extra-ocular muscles Orbital pulleys system

Motor systems15 Demmer JL, Ann. N.Y. Acad. Sci. 956: (2002)

Motor systems16 Demmer JL, Ann. N.Y. Acad. Sci. 956: (2002)

Motor systems17 Demmer JL, Ann. N.Y. Acad. Sci. 956: (2002)

Motor systems18 Demmer JL, Ann. N.Y. Acad. Sci. 956: (2002)

Motor systems19 Special design of extra-ocular muscles proprioceptors

Motor systems20 Special design of extra-ocular muscles Proprioceptive loop

Motor systems21 Targets of proprioceptive info  EOM proprioceptors run with the motor fibers of the muscle nerves EOM -> Gasserian ganglion -> trigeminal nuclei (pars interpolaris and pars caudalis).  brain stem structures  the superior colliculus  Thalamic nuclei (LGN, LP, Pulvinar)  the cerebellum  cortical areas: 17, 18, frontal cortex. Most of these structures are involved in either vision or oculomotor control. EOM proprioceptive information ->

Motor systems22 Roles of visual proprioception  oculomotor control  binocular vision  spatial localisation

Motor systems23 Role of visual proprioception in spatial localization P. BUISSERET, PHYSIOLOGICAL REVIEWS Vol. 75, No. 2, April 1995