Motor systemsMotor systems 11

ACTIVE SENSINGACTIVE SENSING

Lecture 4: Motor systems IIILecture 4: Motor systems III

Motor systemsMotor systems 22

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

Motor systemsMotor systems 33

PID controlPID control

Present

Past

Future

Negative feedback loopNegative feedback loop

’’

’’’’

’’(t+(t+t) = -f [t) = -f [’’tt f is monotonic increasingf is monotonic increasing

’’(t+(t+t) = f [t) = f [’’tt f is monotonic increasingf is monotonic increasing

Positive feedback loopPositive feedback loop

Motor systemsMotor systems 44

The spinal loop (stretch reflex)The spinal loop (stretch reflex)

Knee joint

Motor neuron

’’spindle

Motor systemsMotor systems 55

The spinal loop (stretch reflex)The spinal loop (stretch reflex)

Knee joint

Motor neuron

’’

spindle

ss’’

Ks

KM

KKssKKMM’’

dt

Motor systemsMotor systems 66

Pain reflexPain reflex

Positive or negative? Positive or negative? What is the underlying circuitWhat is the underlying circuit??

Motor systemsMotor systems 77

Contact loop – negative or positiveContact loop – negative or positive??

What does it take to switch between negative and What does it take to switch between negative and positive FB loopspositive FB loops??

Motor systemsMotor systems 88

Basic motor control of other sensory organsBasic motor control of other sensory organs

visual

Vibrissal

Motor systemsMotor systems 99

Motor control in the visual systemMotor control in the visual system

Eye movement (oculomotor control)

Vision (perceptual control)

Motor systemsMotor systems 1010

The extra-ocular muscles (EOMs)The extra-ocular muscles (EOMs)

From Bear’s Neuroscience text book

Motor systemsMotor systems 1111

Axes of eye movement controlAxes of eye movement control

Motor systemsMotor systems 1212

Donder’s and Listing’s lawsDonder’s and Listing’s laws

Donder’s lawDonder’s law states that the states that the

orientation of the eye when looking in orientation of the eye when looking in

a specific direction is always the same. a specific direction is always the same.

Listing's lawListing's law specifies what this specifies what this

orientation is. orientation is.

It refers to the It refers to the axesaxes (the bars (the bars

protruding from the eyes) used to protruding from the eyes) used to

rotate from center to various eccentric rotate from center to various eccentric

positions. positions.

Listing found that all these axes are Listing found that all these axes are

confined to confined to a common planea common plane. .

This plane is called This plane is called Listing's planeListing's plane. .

Valid when looking with the head fixed

Motor systemsMotor systems 1313

How does the system keep Listing’s planeHow does the system keep Listing’s plane??

Ocular mechanics?Ocular mechanics?

Neuronal Neuronal

mechanisms?mechanisms?

Motor systemsMotor systems 1414

Special design of extra-ocular musclesSpecial design of extra-ocular muscles

Orbital pulleys system

Motor systemsMotor systems 1515

Demmer JL, Ann. N.Y. Acad. Sci. 956: 17-32 (2002)

Motor systemsMotor systems 1616

Demmer JL, Ann. N.Y. Acad. Sci. 956: 17-32 (2002)

Motor systemsMotor systems 1717

Demmer JL, Ann. N.Y. Acad. Sci. 956: 17-32 (2002)

Motor systemsMotor systems 1818

Demmer JL, Ann. N.Y. Acad. Sci. 956: 17-32 (2002)

Motor systemsMotor systems 1919

Special design of extra-ocular musclesSpecial design of extra-ocular muscles

proprioceptors

Motor systemsMotor systems 2020

Special design of extra-ocular musclesSpecial design of extra-ocular muscles

Proprioceptive loop

Motor systemsMotor systems 2121

Targets of proprioceptive infoTargets 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 systemsMotor systems 2222

Roles of visual proprioceptionRoles of visual proprioception

oculomotor control oculomotor control binocular visionbinocular vision spatial localisationspatial localisation

Motor systemsMotor systems 2323

Role of visual proprioception in spatial localizationRole of visual proprioception in spatial localization

P. BUISSERET, PHYSIOLOGICAL REVIEWS Vol. 75, No. 2, April 1995