Lecture 8: Sensorimotor System PDF

Lecture 8: Sensorimotor System How you move Required readings: Chapter 8 Goal: Sip from a cup What are the steps required? 1. Formulate a goal (prefrontal cortex) 2. Calculations in other (pre-motor) areas take place to accomplish goal 3. Primary motor cortex sends commands to the spi...

Lecture 8: Sensorimotor System How you move Required readings: Chapter 8 Goal: Sip from a cup What are the steps required? 1. Formulate a goal (prefrontal cortex) 2. Calculations in other (pre-motor) areas take place to accomplish goal 3. Primary motor cortex sends commands to the spinal cord 4. Spinal cord communicates with muscles to move body parts 5. Body parts move to grab cup 6. Feedback for adjustments Learning Objectives What are the three principles of sensorimotor function? Explain what hierarchically organized means. Explain the important role of sensory input for motor output. Describe how learning changes the nature and locus of sensorimotor control. Describe and/or draw the general model of sensorimotor function.  Three principles of sensorimotor function 1. The Sensorimotor System Is Hierarchically Organized Organized like a large company President (association cortex) gives direction to lower levels Lower levels (motor neurons and muscles) take care of details This organization is beneficial because it allows higher levels to focus on complex functions key words operates as a large company the head is the ( association cortex) lower level is the ( motor neurons and muscle) this is beneficial because the higher levels focus on their functions Three principles of sensorimotor function 2. Motor output is guided by sensory input Sensorimotor system carefully monitors the external world Able to adjust its own actions (sensory feedback) Only ballistic movements are not guided by sensory feedback Sensory inputs help with: Picking things up Adjusting to unanticipated external forces Maintaining constant force Motor output guided by sensory input means that your body’s movements are constantly adjusted based on the sensory feedback it gets. you started working out, perfecting your form later your form is bad the sensorimotor corrects the form Three principles of sensorimotor function 3. Learning Changes the Nature and Locus of Sensorimotor Control Initially, actions are under conscious control With practice, they become integrated sequences of action They are automatically adjusted without conscious regulation So, in simple terms, as you practice a skill, it moves from being something you have to think about, to something that your body just "does" without you having to consciously manage every little detail. smooth movement after initial learning General Model of Sensorimotor System Hierarchical Functionally segregated Parallel pathways Information flows down Feedback circuit Figure 8.1  Learning Objectives Sensorimotor association cortex Explain the role of the posterior parietal cortex in sensorimotor function and describe what happens when it is damaged or stimulated. Explain the role of the dorsolateral prefrontal association cortex in sensorimotor function. Secondary motor cortex Explain the general role of areas of the secondary motor cortex. Describe the major features of mirror neurons and explain why they have received so much attention from neuroscientists.  Learning Objectives Primary motor cortex Describe the conventional and current views of primary motor cortex function and the evidence upon which it is based. General Model of Sensorimotor System Figure 8.1 Sensorimotor Association Cortex Two main areas: 1. Posterior parietal cortex 2. Dorsolateral prefrontal cortex 1. Posterior Parietal Association Cortex Provides information on where body parts are in relation to the external world VAS Receives input from visual, auditory, and somatosensory systems Output goes to secondary motor cortex and frontal eye field Electrical stimulation of this area makes subjects experience an intention to perform an action important role in directing behaviour by providing spatial information and in directing attention eye movement and shift in attention Damage to the Posterior Parietal Association Cortex Variety of deficits Damage to the Posterior Parietal Association Cortex Variety of deficits Apraxia = inability to perform movements on command Occurs when posterior parietal association cortex is lesioned Associated with left hemisphere damage but symptoms are bilateral Damage to the Posterior Parietal Association Cortex Variety of deficits Apraxia = inability to perform movements on command Occurs when posterior parietal association cortex is lesioned Associated with left hemisphere damage but symptoms are bilateral Contralateral neglect Usually produced by very large right parietal lesions Individuals only attend to right side of body or items in environment Individuals are capable of unconsciously perceiving objects on the left  2. Dorsolateral Prefrontal Association Cortex Involved in assessments of external stimuli Projects to secondary motor cortex, primary motor cortex, and frontal eye field May work with posterior parietal cortex in decisions to initiate movement You see the ball (this is sensory input). Your brain processes the information (like "the ball is coming toward me"). Your brain then decides how to move: Your primary motor cortex sends the command to your muscles to catch the ball. Your secondary motor cortex helps plan how to position your body and hands. Your frontal eye field helps you focus on the ball with your eyes. The posterior parietal cortex helps you understand where the ball is in space, so you know where to reach to catc it. General Model of Sensorimotor System Figure 8.1  Areas of Secondary Motor Cortex Receives input from association cortex Project to primary motor cortex, other areas of secondary motor cortex, and brainstem There are at least eight areas of secondary motor cortex Your association cortex helps you recognize the ball and decide to catch it. The secondary motor cortex plans the movements needed, like reaching out your hand and positioning your body. The primary motor cortex sends the command to your muscles to actually carry out those movements. Your brainstem helps coordinate some basic functions like making sure your body stays balanced as you reach for the ball Areas of Secondary Motor Cortex Receives input from association cortex Project to primary motor cortex, other areas of secondary motor cortex, and brainstem There are at least eight areas of secondary motor cortex Stimulation produces complex movements (activated before and during voluntary movements) Areas encode spatial relations and program movements Mirror Neurons Fire when an individual makes goal-directed movements Fire when an individual observes someone else performing goal- directed movements May be a mechanism for social cognition Motor cortex in humans may contain mirror neurons (indirectly measured using fMRI) Mirror Neuron Firing Figure 8.5 Responses of a mirror neuron of a monkey.