KINE 4500 Neural Control of Movement Lecture #1:Introduction to the Neural Control of Movement Neural control of movement Kinesiology: study of movement Here we re looking at the control system, and what can happen when it breaks down KINE 3020: introduction to basics of motor neuroscience: what and where the parts are This course: Apply those basics to behavioural systems e.g. walking, reaching, looking, eyehand coordination Emphasis on the neural basis of motor behaviour Basic issues that comprise motor control research Degree of freedom problem Do-it-yourself Bernstein demo... Degree of freedom problem - redundancy in the motor system CORTICAL STRUCTURES How do we generate a movement in the face of all this redundancy? subcortical structures / spinal circuitry MUSCLE ACTIVATION target acquisition ( goal ) CONSTRAINTS! Minimization principles Synergies KINETICS joint torques forces force vel. force accel. Mechanical properties 1
Basic issues that comprise motor control research Serial order problem: how do we generate a sequence of movements? Spoonerisms Co-articulation patient deficits Serial order issue Question: where do we generate a sequence of movements? Brain imaging data: sequence task Sequence - specific areas activate regardless of effector performing the sequence Third issue: perceptual-motor integration Feedforward - feedback integration subcortical structures / spinal circuitry MUSCLE ACTIVATION CORTICAL STRUCTURES target acquisition ( goal ) KINETICS joint torques forces force vel. force accel. Perceptual-motor integration problem Frame of reference: sensory information integrated into motor plan Perceptual-motor integration problem Frame of reference: motor system can affect perception as well The exciting world of the spinal frog and it s wipe reflex 2
These three basic issues all assume that the movements have been learned! Fourth Issue: Skill acquisition Innate versus learned Motor development and learning Retention of motor skills Skill acquisition retention of motor skills Procedural versus declarative memory Example from 3020: Motor Consolidation Learning a new motor skill with or without interference Can learning a second, similar task at or about the same time interfere with learning the first task? Summary: Issues in motor control Motor control: The study of how the nervous system and the periphery function together to plan and coordinate movement 4 basic issues: degree of freedom serial order perceptual-motor integration skill acquisition To study these issues: Many ways to study motor control In this course, we will be surveying different motor behaviours and their control using Behavioural research Physiological research Clinical research These 4 issues are not independent!! 3
Sensory receptors The study of motor behaviour: Psychophysics The measurement of regularities in how movements are performed or learned Allows one to indirectly understand the underlying control system: the central nervous system (A lot of the psychophysical findings and behavioural phenomena have been covered in 3020) Emphasis: biological basis of motor behaviour Survey the basic structures in the brain and periphery that are involved in the coordination and control of movement Three types of movement Reflex movements Rhythmic movements Voluntary movements An example of the problems involved in generating movements: a simple reaching movement The central nervous system must: Contract and relax muscles in a coordinated way about joints Send timed commands to multiple muscles Account for physics, e.g. postural adjustment Account for the motor plant : mechanical properties of muscles, joints, etc subcortical structures / spinal circuitry MUSCLE ACTIVATION CORTICAL STRUCTURES KINETICS joint torques forces force vel. force accel. target acquisition ( goal ) To do this, nervous system has 3 basic levels of control: motor cortical areas brainstem and sub-cortical areas spinal cord 1 2 Cerebral cortex motor areas Basal ganglia 3 thalamus Brain stem Spinal cord Muscle contraction and movement Other sensory input Key concept: coexistence of serial and parallel processing in the brain Allows lower centres to deal with reflex movements while higher structures can just give more general commands (If not, would have basic lives ) Meanwhile, parallel organization adds efficiency Review of the basic features of these three levels of motor control (3020 recap) source: http://www9.biostr.washington.edu/cgi-bin/da/imageform 4
Spinal cord Contains neuronal circuits for stereotyped and automatic movements Consists of gray matter and white matter Kandel et al. Essentials of neural science and behaviour, 1995, Fig. 26-3 Gray matter: Cell bodies of interneurons and motor neurons ventral horns: cell bodies of motor neurons located in the ventral gray matter White matter: axons of other neurons coursing up and down the cord All motor commands eventually converge on motor neurons final common pathway Dorsal - towards back Ventral - towards front Kandel et al. Principles of Neural Science, 2000, Fig.33-13 Spinal motor neurons execute movement Motor nuclei:clusters of motor neurons that innervate individual muscles Motor nuclei follow 2 important rules proximal distal rule flexor extensor rule Kandel et al. Essentials of neural science and behaviour, 1995, Fig. 26-3 The brain stem modulates the action of spinal motor circuits Brainstem-spinal cord projections fall into two categories: contains motor nuclei to facial muscles and many groups of neurons that project to the spinal gray matter source: http://www9.biostr.washington.edu/cgi-bin/da/imageform Medial brainstem pathways concerned with control of posture three major tracts vestibulospinal reticulospinal tectospinal Kandel et al. Essentials of neural science and behaviour, 1995, Fig. 26-4 5
Second category: lateral brainstem pathways Concerned with goaldirected limb movements projections terminate on dorsolateral part of spinal gray matter major tract: rubrospinal tract Kandel et al. Essentials of neural science and behaviour, 1995, Fig. 26-4 Cerebral cortex modulates the action of motor neurons in the brain stem and spinal cord Control signals from cortical motor areas control complex and precision movements Kandel et al. Principles of Neural Science, 2000, Fig.38-1 Cortical motor commands descend on spinal motor neurons directly and indirectly lateral ventral Indirect influence via action on brainstem pathways 2 direct descending tracts corticobulbar corticospinal largest descending tract from the brain 75% of fibres cross midline to form lateral corticospinal tract 25% uncrossed fibres form ventral corticospinal tract Kandel et al. Essentials of neural science and behaviour, 1995, Fig. 26-5 Motor cortex and brainstem also influenced by subcortical structures Summary: Neural control of movement Behaviour involves movement, which in turn depends on timed contraction of muscles, controlled by central motor systems These systems are hierarchically organized, but function in parallel as well for efficiency Different components of the motor system carry out distinct but interrelated functions basal ganglia 6