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LECTURE 15: VOLUNTARY MOVEMENT REQUIRED READING: Kandel text, Chapters 33 & 38 oluntary movement differs from reflexes in several important ways: 1) Voluntary movement is governed by conscious planning 2) It is organized around performance of a specific task 3) Sensory stimuli do not dictate the resulting movement, although they guide the specified task 4) Task performance becomes more efficient with experience 5) Voluntary movement can be initiated internally without a sensory stimulus trigger VOLUNTARY MOVEMENT OFTEN REPRESENTS COMPLEX MOTOR TASKS THAT ARE ACCOMPLISHED IN SEEMINGLY EFFORTLESS FASHION, WITH NO THOUGHT GIVEN TO THE MUSCLE GROUPS AND JOINTS THAT PARTICIPATE
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LECTURE 15: VOLUNTARY MOVEMENT

Feb 09, 2016

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LECTURE 15: VOLUNTARY MOVEMENT. REQUIRED READING: Kandel text, Chapters 33 & 38. Voluntary movement differs from reflexes in several important ways: Voluntary movement is governed by conscious planning It is organized around performance of a specific task - PowerPoint PPT Presentation
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Page 1: LECTURE 15:  VOLUNTARY MOVEMENT

LECTURE 15: VOLUNTARY MOVEMENTREQUIRED READING: Kandel text, Chapters 33 & 38

Voluntary movement differs from reflexes in several important ways:1) Voluntary movement is governed by conscious planning

2) It is organized around performance of a specific task

3) Sensory stimuli do not dictate the resulting movement,although they guide the specified task

4) Task performance becomes more efficient with experience

5) Voluntary movement can be initiated internally withouta sensory stimulus trigger

VOLUNTARY MOVEMENT OFTEN REPRESENTS COMPLEX MOTOR TASKS THAT AREACCOMPLISHED IN SEEMINGLY EFFORTLESS FASHION, WITH NO THOUGHT

GIVEN TO THE MUSCLE GROUPS AND JOINTS THAT PARTICIPATE

Page 2: LECTURE 15:  VOLUNTARY MOVEMENT

SENSORY INPUTS GUIDE VOLUNTARY MOVEMENT THROUGHFEED-BACK AND FEED-FORWARD MECHANISMS

Page 3: LECTURE 15:  VOLUNTARY MOVEMENT

EXAMPLE OF FEEDBACK AND FEEDFORWARD MOVEMENT CONTROL:CATCHING A FALLING BALL

Visual input provides feed-forwardcontrol of the task enabling us to:

1) Position hand under where ball isanticipated to fall

2) Partially stiffen joints in anticipationof ball’s impact on hand

Somatosensory and proprioceptive inputsprovide feed-back control used

to grasp ball.

Some aspects of feedback controlinvolve task-specified programming

of spinal reflexes

Page 4: LECTURE 15:  VOLUNTARY MOVEMENT

PROCESSING OF A MOTOR TASK BEGINS WITH AN INTERNAL REPRESENTATIONOF THE DESIRED RESULT OF MOVEMENT

EXAMPLE 1: HANDWRITING IS SIMILAR STYLE REGARDLESS OF LIMB USED TO WRITEWe write text to conform to an internally preimaged style template

Page 5: LECTURE 15:  VOLUNTARY MOVEMENT

PROCESSING OF A MOTOR TASK BEGINS WITH AN INTERNAL REPRESENTATIONOF THE DESIRED RESULT OF MOVEMENT

EXAMPLE 2: REACHING IS A STRAIGHT-LINE TASK, REGARDLESS OF DIRECTION AND MUSCLES/JOINTS REQUIREDWe program the direction and endpoint of task, and use sensory input during task for guidance correction

Page 6: LECTURE 15:  VOLUNTARY MOVEMENT

PROCESSING OF A MOTOR TASK BEGINS WITH AN INTERNAL REPRESENTATIONOF THE DESIRED RESULT OF MOVEMENT

EXAMPLE 3: SPEED OF REACHING IS PRE-SCALED TO THE DISTANCE OF TARGETThe endpoint is built into the premotor program

Page 7: LECTURE 15:  VOLUNTARY MOVEMENT

EFFICIENCY OF EXECUTING MOTOR TASK IMPROVES WITH PRACTICE (LEARNING)

Both explicit and implicit memory are components of motor learningImproved efficiency in reaching task is form of implicit learning

Page 8: LECTURE 15:  VOLUNTARY MOVEMENT

CENTRAL PATHWAYS FOR VOLUNTARY MOTOR CONTROL

Motor areas of cerebral cortex project directly and indirectly to spinal cord motor neurons and interneurons

Motor areas also project to basal ganglia and cerebellum, which project back to cortex via thalamus

Cerebellum critical for integrating desired task and sensory inputs into motor planning and executionCerebellum is a major site for learning within motor circuits

Basal ganglia control muscle tone (readiness) and execution of rapid motor tasks

Page 9: LECTURE 15:  VOLUNTARY MOVEMENT

MOTOR CORTEX AND PREMOTOR CORTICES PROJECT TO MOTOR UNITSAND CONSTITUTE SOMATOTOPIC MAPS OF THE BODY

Motor cortex axons project to motor neurons both monosynaptically and through brain stem nucleiFOCAL STIMULATION IN MOTOR AREAS INDUCES CONTRACTION OF SPECIFIC MUSCLE OR MUSCLE SET

FOCAL LESIONS IN MOTOR AREAS CAUSE LOSS OF SPECIFIC MUSCLE SETS

Page 10: LECTURE 15:  VOLUNTARY MOVEMENT

SOMATOTOPIC MAP IN MOTOR CORTEX CHANGES FOLLOWING FOCAL LESION

Remapping of motor cortex following lesion is influenced by experience in the weeks after injury

Profound neurological implications for role of physical therapy following brain injury

EXPERIMENT-INDUCED FOCAL STROKE AFFECTING MUCH OFEXPERIMENT-INDUCED FOCAL STROKE AFFECTING MUCH OF HAND/DIGIT REGION OF MOTOR CORTEXHAND/DIGIT REGION OF MOTOR CORTEX

PHYSICAL THERAPY FOR HANDNO PHYSICAL THERAPY FOR HAND

REMAINING HAND REPRESENTATION INMOTOR CORTEX LOST

(converted to arm/shoulder representation)

LOSS OF GRASPING CAPACITY

REMAINING HAND REPRESENTATION SPAREDAND MORE CORTEX RECRUITED

(converted from arm/shoulder representation)

GRASPING CAPACITY RESTORED

~ 1 MONTH

Page 11: LECTURE 15:  VOLUNTARY MOVEMENT

MOTOR CORTEX IS ESSENTIAL FOR FINE CONTROL OF THE DIGITS

Severing corticospinal tract causes permanent loss of fine digit control

Coordinated use of more proximal muscles improves over time, making use of indirect projectionsfrom motor cortex through brain stem

Page 12: LECTURE 15:  VOLUNTARY MOVEMENT

FIRING OF MOTOR CORTEX NEURONS DURING VOLUNTARY MOVEMENTDIRECTLY ACTIVATES MOTOR NEURONS IN SPINAL CORD

Technique of POST-SPIKE FACILITATION OF MUSCLE ACTIVITY

Page 13: LECTURE 15:  VOLUNTARY MOVEMENT

EACH MOTOR CORTEX NEURON ACTIVATES MUTLIPLE MUSCLES TO DIFFERENT DEGREESDIRECTION OF LIMB MOVEMENT IS SUM OF CORTICAL NEURON VECTORS

Page 14: LECTURE 15:  VOLUNTARY MOVEMENT

PREMOTOR AREAS CONTRIBUTE TO MOTOR PLANNING

EEG recordings show that medial premotor area is active to performanceor mental rehearsal of complex tasks

Page 15: LECTURE 15:  VOLUNTARY MOVEMENT

THE MOTOR CORTEX IS DRIVEN BY DIFFERENT PREMOTOR AREASIN RESPONSE TO VISUAL CUES VERSUS PERFORMING REHEARSED TASKS

Page 16: LECTURE 15:  VOLUNTARY MOVEMENT

HOW DO WE KNOW THAT MOTOR CORTEX ACTIVITY DETERMINESVOLUNTARY MOTOR FUNCTION?

http://ondemand.duke.edu/video/22553/monkeys-thoughts-make-robot-wa