Sensory Components of Motor Control PDF

BPED 54 Sensory Components of Motor Control 1st semester AY 2324 dianne.salvaleon Sensory Components of Motor Control Page 1 of 73  Topic and Learning Objectives Touch and Motor Control Describe the Motor...

BPED 54 Sensory Components of Motor Control 1st semester AY 2324 dianne.salvaleon Sensory Components of Motor Control Page 1 of 73  Topic and Learning Objectives Touch and Motor Control Describe the Motor Touch and sensory receptors in the skin that provide tactile Control sensory information to the central nervous system Discuss several movement-related characteristics influenced by feedback from the proprioceptors Vision and Motor Control Describe key anatomical components of the eye and neural pathways for vision Discuss motor control issues related to vision Of our various senses, touch, proprioception, and vision contribute to the motor control of skills in significant ways. In the study of human sensory physiology, touch and proprioception are included as senses in the somatic sensory system, whereas vision is the sense associated with the visual sensory system. In the following sections, we will look specifically at these three senses by describing their neural bases and the roles each plays in the control of human movement. Sensory Components of Motor Control Page 2 of 73  auditory sensory information important for speech production importance of auditory information in influencing athlete behavior (inner ear) control of balance possibly arm-trunk coordination (trunk-assisted reaching movement) Before beginning the discussion of these sensory systems, it is important to point out that the limiting of this chapter to these three senses should not be interpreted as suggesting that they are the only senses involved in motor control. important for speech production and anecdotal evidence from skilled athletes describes the importance of auditory information for influencing their behavior, such as determining the ball flight characteristics of a batted ball in baseball and a serve or ground stroke in tennis Important role of the vestibular system of the inner ear in the control of balance and possibly arm-trunk coordination during trunk-assisted reaching movement Sensory Components of Motor Control Page 3 of 73  touch and motor control When do we use the sense of touch when we perform motor skills? TOUCH AND MOTOR CONTROL variety of ways in which we involve our sense of touch when we perform motor skills: 1) manipulate an object 2) or a person 3) to interact with natural features in our environment this includes the detection of specific characteristics of the object, person, or environment through tactile sensory receptors in our skin that are part of our somatic sensory system Sensory Components of Motor Control Page 4 of 73  touch and motor control manipulate an object manipulate a person (body) to interact with natural features in our environment TOUCH AND MOTOR CONTROL variety of ways in which we involve our sense of touch when we perform motor skills: 1) manipulate an object 2) or a person 3) to interact with natural features in our environment this includes the detection of specific characteristics of the object, person, or environment through tactile sensory receptors in our skin that are part of our somatic sensory system the neural basis for the detection of this type of sensory information Sensory Components of Motor Control Page 5 of 73  Neural Basis of Touch Neural Basis of Touch When we touch something, mechanoreceptors in the skin activate to provide the CNS with information related to pain, temperature, and movement. These receptors, are located just below the skin surface in the dermis portion of the skin As mechanoreceptors, these sensory receptors detect skin stretch and joint movement. The greatest concentration of these receptors is in the fingertips. Sensory Components of Motor Control Page 6 of 73  Role of Tactile Sensory Information in Motor Control Five movement-related characteristics influenced by tactile sensory 1)movement accuracy decreases (i.e. skills such as typing, pointing, reaching) 2) movement consistency decreases (i.e. typing) 3) movement timing can be influenced especially in rhythmic movements that involve intermittent contact with the environment (i.e. juggling, locomotion) 4) movement force adjustments adjustments while holding and using an object are affected 5)movement distance with proprioceptive feedback estimating MD is improved The Role of Tactile Sensory Information in Motor Control Touch plays an important role in the performance of a variety of types of motor skills and motor control processes Five movement-related characteristics influenced by tactile sensory information the CNS receives from touch: 1) movement accuracy decreases when tactile information is not available, especially at the fingertips Research has demonstrated poorer accuracy when tactile feedback is removed or minimized for several skills including pointing, reaching and grasping, typing on a keyboard, maintaining a precision grip, rhythmically tapping a finger to an auditory stimulus, and playing a sequence of notes on a piano. *anesthetized the fingertips so that tactile afferent information would not be available 2) Movement consistency decreases when tactile information is not available Sensory Components of Motor Control Page 7 of 73 research demonstrated this effect for keyboard typing by comparing typing performance before and after anesthetizing a finger. They showed that without tactile sensory feedback from the finger, not only did typing accuracy decrease, as described above, but movement consistency from one trial to another also decreased. 3) movement timing can be influenced by tactile feedback, particularly in rhythmic movements that involve intermittent contact with the environment, like juggling and locomotion For example, experiments by Zelaznik and colleagues have shown that including a tactile event (e.g., a velcro strip at the top of the circle) as a timing cue improved timing accuracy for continuous circle drawing when a criterion time for completing the circle was required (e.g., Studenka, Zelaznik, & Balasubramaniam, 2012). 4) movement force adjustments while holding and using an object also depend on tactile feedback you grasp a cup and lift it from a table to drink from it, you need to regulate the amount of grip force as you move the cup to your mouth and properly position the cup to drink from it sensory feedback from the grasping fingertips intermittently updates the movement command center in the CNS to adjust grip forces as necessary. 5) estimate movement distance tactile feedback could be used to improve the use of proprioceptive feedback to estimate movement distance when the beginning and end of a pointing movement involved touching a surface Sensory Components of Motor Control Page 8 of 73  PROPRIOCEPTION AND MOTOR CONTROL Proprioception refers to our sensation and perception of limb, trunk, and head position and movement is sensory information transmitted to the CNS about such movement characteristics as direction, location in space, velocity, and muscle activation plays a significant role in closed loop models of movement control PROPRIOCEPTION AND MOTOR CONTROL Proprioception refers to our sensation and perception of limb, trunk, and head position and movement Although it is often overlooked as one of our basic senses, proprioception is sensory information transmitted to the central nervous system about such movement characteristics as direction, location in space, velocity, and muscle activation In closed loop models of movement control, proprioceptive feedback plays a significant role, whereas in open loop models, central commands control movement without involving proprioceptive feedback. Questions about whether we can control movements without proprioceptive feedback, and what role proprioceptive feedback plays in the control of coordinated movement, have intrigued movement scientists for many years Sensory Components of Motor Control Page 9 of 73  The Neural Basis of Proprioception Proprioceptors are sensory neurons located in the muscles, tendons, ligaments, and joints pick up information about body and limb position and changes in position muscle spindles, Golgi-tendon organs, joint receptors The Neural Basis of Proprioception CNS receives proprioceptive information from afferent neural pathways that begin in proprioceptors, which are sensory neurons located in the muscles, tendons, ligaments, and joints These neurons pick up information about body and limb position and changes in position. There are several types of proprioceptors, each of which detects specific characteristics of body and limb position and movement. We focus on the muscle spindles, which detect changes in muscle length, the Golgi-tendon organs, which detect changes in muscle tension, and the joint receptors, which detect changes in joint movement Sensory Components of Motor Control Page 10 of 73  Proprioceptors Muscle spindles the sensory receptor of skeletal muscle. Muscle spindles are embedded within the belly of a muscle A muscle spindle Muscle spindles play a role in detects changes in muscle proprioception via length regulating muscle contraction has both sensory and resisting muscle stretch motor components Muscle spindles. lie within the fibers of most skeletal muscles. The muscles that control the eyes, hands, and neck have the greatest number of muscle spindles, allowing these body parts to be controlled with great precision or, in the case of the neck, allowing precise coordination between the eyes and the head and the rest of the body As mechanoreceptors, the sensory receptors of the muscle spindles respond to changes in muscle length which cause a mechanical deformation of the receptors and result in a nerve impulse. Within the muscle spindle are stretch receptors that detect the amount of stretch as well as the speed of the stretch. When a muscle stretches, the nerve impulse rate from the muscle spindle increases; when the muscle shortens, the rate reduces. Macefield (2005) the muscle-length detection capability of muscle spindles allow them to detect changes in joint angle in one axis, which provides the basis for the muscle spindles distributed throughout the muscles that act on a joint to provide feedback about complex patterns of muscle-length changes. Sensory Components of Motor Control Page 11 of 73 The nerve impulses from the muscle spindle travel along afferent nerve fibers to the dorsal root of the spinal cord. In the spinal cord, these afferent fibers divide into branches that allow the nerve impulses to do any of several things, depending on the movement situation. If the movement is a simple reflex movement, such as a knee jerk, the impulse follows a branch that synapses with an alpha motor neuron in the ventral horn of the spinal cord that activates the agonist muscle to produce the reflex movement. Another branch synapses with inhibitory interneurons that inhibit the activity of antagonistic muscles. A third branch synapses with motor neurons that activate synergistic muscles associated with the intended movement. The fourth branch continues up the spinal cord to the brainstem where it synapses with interneurons to connect with areas of the brain responsible for motor contr ol. In the control of voluntary movement the muscle spindle serves as a feedback mechanism. most important source of proprioceptive information to the CNS about the limb movement characteristics of position, direction, and velocity, as well as a sense of effort The CNS uses the limb movement feedback in the control of a discrete movement that must stop at a specific location in space and in the control of ongoing movements to ensure the spatial and temporal accuracy of the movements. some researchers (e.g., Albert et al., 2005) contend that the feedback from muscle spindles also assists the CNS in movement planning Sensory Components of Motor Control Page 12 of 73  Proprioceptors Muscle spindles Each spindle is encapsulated in connective tissue. The system consists of: extrafusal muscle fibers (alpha, α) - bulk of the muscle alpha (α) motor neurons (efferent) the most common type of muscle motor neuron synapse onto extrafusal (α) muscle fibers transmit APs from CNS to extrafusal muscle fibers intrafusal muscle fibers (gamma, γ) - fibers inside the spindle afferent sensory neurons (1a are the largest type) sensory terminals coil around noncontractile intrafusal (γ) fibers carry stretch sensory information from the spindle receptor to the CNS *in the diagram, these are are shown in blue gamma (γ) motor neurons (efferent) synapse on either side of the noncontractile center transmit APs from the CNS to muscle fiber to regulate muscle contraction *in the diagram, these are shown in red Sensory Components of Motor Control Page 13 of 73  Proprioceptors Muscle spindles In voluntary movement, the muscle spindle serves as a feedback mechanism: source of proprioceptive information to the CNS about the limb movement characteristics of position, direction, and velocity, as well as a sense of effort The CNS uses the limb movement feedback control of a discrete movement that must stop at a specific location in space control of ongoing movements to ensure the spatial and temporal accuracy of the movements. some researchers (e.g., Albert et al., 2005) contend that the feedback from muscle spindles also assists the CNS in movement planning In the control of voluntary movement the muscle spindle serves as a feedback mechanism. most important source of proprioceptive information to the CNS about the limb movement characteristics of position, direction, and velocity, as well as a sense of effort The CNS uses the limb movement feedback in the control of a discrete movement that must stop at a specific location in space and in the control of ongoing movements to ensure the spatial and temporal accuracy of the movements. some researchers (e.g., Albert et al., 2005) contend that the feedback from muscle spindles also assists the CNS in movement planning Sensory Components of Motor Control Page 14 of 73  Proprioceptors Golgi Tendon Organ consist of type Ib sensory axons that detect changes in muscle tension or force poor detectors of changes in muscle length When you lift weights, the golgi tendon organ is the sense organ that tells you how much tension the muscle is exerting. If there is too much muscle tension the golgi tendon organ will inhibit the muscle from creating more force (via a reflex arc), thus protecting you from injuring itself. Golgi-tendon organs (GTOs) are located in the skeletal muscle near the insertion of the tendons into the muscle. The GTOs consist of type Ib sensory axons that detect changes in muscle tension, or force; they are poor detectors of changes in muscle length. These sensory receptors respond to any tension created by the contracting muscle to which it is attached. The axons of the GTOs enter the dorsal horn of the spinal cord and synapse on interneurons in the ventral horn, where the interneurons synapse with alpha motor neurons that can cause inhibition of the contracting muscle and related synergistic muscles and that can stimulate the motor neurons of antagonistic muscles. Sensory Components of Motor Control Page 15 of 73  Proprioceptors Joint Receptors collective term of receptors located in the joint capsule and ligaments (such as: Ruffini endings, Pacinian corpuscles, and Golgi-like receptors) Note: not all joints contain the same types of receptors respond to changes in force and rotation applied to the joint and to changes in joint movement angle, especially at the extreme limits of angular movement or joint positions Several types of proprioceptors are located in the joint capsule and ligaments; together these are referred to as joint receptors. The specific identity of these receptors is an issue of However, there is agreement that some are the Ruffini endings, Pacinian corpuscles, and Golgi-like receptors (Macefield, 2005). Not all joints contain the same types of receptors. As a result, it is common to see researchers refer to “joint receptors” as a collective term rather than specify the individual receptors within the joint. As mechanoreceptors, the joint receptors respond to changes in force and rotation applied to the joint and to changes in joint movement angle, especially at the extreme limits of angular movement or joint positions Sensory Components of Motor Control Page 16 of 73  The Role of Proprioception in Motor Control Research indicates that people can carry out certain limb movements in the absence of proprioceptive feedback. However, there appear to be several distinct limitations to this capability. The Role of Proprioception in Motor Control Research indicates that people can carry out certain limb movements in the absence of proprioceptive feedback. Most notably, as demonstrated in the Spencer et al. (2005) experiment with the sensory neuropathy patients, the timing synchrony between limbs that characterizes the performance of bimanual coordination movements is not influenced by the lack of proprioception. However, there appear to be several distinct limitations to this capability. Because of these limitations, it is possible to identify the various roles of proprioceptive feedback in the control of human movement. We will consider three that are especially notable. Movement accuracy. Sensory Components of Motor Control Page 17 of 73  The Role of Proprioception in Motor Control Movement Accuracy Several results from the experiments demonstrate how proprioception influences movement accuracy: monkeys were clumsier while climbing, grasping, and grooming; difficulty grasping food with their hands after deafferentation (Taub and Berman) animal’s posture was altered, pointing accuracy diminished in the deafferented condition (Bizzi ) spatial position accuracy and distance movements were severely disrupted before joint capsule replacement The Role of Proprioception in Motor Control Movement accuracy. Several results from the experiments just discussed demonstrate that proprioception influences movement accuracy. In the Taub and Berman studies, the monkeys were clumsier while climbing, grasping, and grooming than they had been before deafferentation. In fact, they had difficulty grasping food with their hands in this condition. In the Bizzi experiments, the researchers noted that when the animal’s posture was altered, pointing accuracy diminished in the deafferented condition. The Kelso, Holt, and Flatt experiment showed that human participants could maintain only spatial position accuracy following joint capsule replacement; distance movements were severely disrupted. And the experiments involving sensory neuropathy patients were consistent in demonstrating that the lack of proprioception resulted in large spatial errors. In addition, the experiment by Spencer and colleagues extended the evidence for movement accuracy problems without proprioception to include Sensory Components of Motor Control Page 18 of 73 repetitive bimanual coordination movements. The influence of proprioception on movement accuracy appears to be due to the specific kinematic and kinetic feedback provided by the proprioceptors to the CNS. Feedback about limb displacement provides the basis for spatial position corrections, which enable the limb to achieve spatial accuracy by a continuous updating of limb position to the CNS, which in turn can send movement commands that will modify the position accordingly, provided that the movement occurs for a sufficient amount of time to allow movement corrections to occur. In addition, proprioceptors provide feedback about limb velocity and force, which influence movement distance accuracy. Sensory Components of Motor Control Page 19 of 73  The Role of Proprioception in Motor Control Movement Accuracy Reasons why proprioception affect movement accuracy: Prioception provide specific kinematic and kinetic feedback provided by the proprioceptors to the CNS (basis for spatial correction to achieve spatial accuracy) proprioceptors provide feedback about limb velocity and force (in turn influence movement distance accuracy) The Role of Proprioception in Motor Control Movement accuracy. The influence of proprioception on movement accuracy appears to be due to the specific kinematic and kinetic feedback provided by the proprioceptors to the CNS. Feedback about limb displacement provides the basis for spatial position corrections, which enable the limb to achieve spatial accuracy by a continuous updating of limb position to the CNS, which in turn can send movement commands that will modify the position accordingly, provided that the movement occurs for a sufficient amount of time to allow movement corrections to occur. In addition, proprioceptors provide feedback about limb velocity and force, which influence movement distance accuracy. Sensory Components of Motor Control Page 20 of 73  The Role of Proprioception in Motor Control Onset of motor command Proprioceptive feedback also influences the timing of the onset of motor commands Bard and colleagues (1992) compared movements of normal participants with a patient deafferented due to a sensory neuropathy participants were asked to simultaneously extend an index finger and raise the heel of the ipsilateral foot. When they performed this task in reaction to an auditory signal, both the normal and the deafferented participants performed similarly by initiating the finger extension first. when asked to do the task at their own pace the deafferented patients performed as they had in the reactive situation, indicating that they used a central motor command rather than proprioceptive feedback as the basis for the timing of the onset of the heel and finger movements. The Role of Proprioception in Motor Control Onset of motor commands. Proprioceptive feedback also influences the timing of the onset of motor commands. An experiment by Bard and colleagues (1992) provides a good example of evidence for this role. They compared movements of normal participants with a patient deafferented due to a sensory neuropathy. The participants were asked to simultaneously extend an index finger and raise the heel of the ipsilateral foot. When they performed this task in reaction to an auditory signal, both the normal and the deafferented participants performed similarly by initiating the finger extension first. We would expect this if a common central motor command were sent to each effector. Because of the difference in distance of efferent neural pathways to the finger and heel, finger movement would occur first. Conversely, when asked to do the task at their own pace, the normal participants raised the heel first; this suggests that they based timing of the finger movement onset on proprioceptive feedback about heel movement. In contrast, the deafferented patients performed as they had in the reactive situation, indicating that they used a central motor command rather than proprioceptive feedback as the basis for the timing of the onset of the heel and finger movements. Sensory Components of Motor Control Page 21 of 73  The Role of Proprioception in Motor Control Coordination control proprioception plays an important role in various aspects of the coordination of body and limb segments. Two coordination characteristics influenced by proprioceptive feedback: postural control note: postural control is a function of many interacting variables together with tactile information, functions to provide essential information to the CNS to enable a person to control upright stance posture in body sway situations (Jeka et al., 1998) vibration of the Achilles tendon induced a three degree backward tilt of the participants’ vertical posture. (Barbieri et al. 2008) The Role of Proprioception in Motor Control Coordination control Finally, proprioception plays an important role in various aspects of the coordination of body and limb segments. Two coordination characteristics influenced by proprioceptive feedback will serve to demonstrate this role. First, postural control requires proprioceptive feedback. Although a considerable amount of research evidence shows that postural control is a function of many interacting variables, such as vision, the musculoskeletal system, and the vestibular system, activity of the cerebellum and basal ganglia, cognitive processes, the tactile sensory system, and proprioception, problems with any of these will lead to postural dysfunction. Jeka and colleagues have demonstrated (e.g., Jeka, Ribiero, Oie, & Lackner, 1998) the importance of proprioception in postural control by showing that proprioception, together Sensory Components of Motor Control Page 22 of 73 with tactile information, functions to provide essential information to the CNS to enable a person to control upright stance posture in body sway situations. Additional evidence of the role of proprioception in postural control was provided by Barbieri et al. (2008) in an experiment in which they used the tendon vibration technique. The vibration of the Achilles tendon induced a three degree backward tilt of the participants’ vertical posture The second coordination characteristic involves the spatial-temporal coupling between limbs and limb segments. Results of the experiment by Messier et al. (2003), which we described earlier, showed that a sensory neuropathy patient demonstrated problems with coordinating the multijoint movements involved in reaching to a target in front of him. For between-limb movement coordination, the study by Verschueren et al. (1999a), which we considered earlier, showed the importance of proprioceptive feedback for the spatial and temporal coupling between the arms when we perform bimanual coordination tasks. And in another study by this same researcher and colleagues (Verschueren et al., 1999b), they demonstrated that proprioception influences the coupling between two limb segments of the same limb, such as the upper arm and forearm. Also, Spencer et al. (2005) demonstrated similar bimanual coordination problems for a sensory neuropathy patient, especially in terms of the control of spatial coordination and consistency between movements for a repetitive series of movements Sensory Components of Motor Control Page 23 of 73  The Role of Proprioception in Motor Control Coordination control proprioception plays an important role in various aspects of the coordination of body and limb segments. Two coordination characteristics influenced by proprioceptive feedback: spatial-temporal coupling between limbs and limb segments importance of proprioceptive feedback for the spatial and temporal coupling between the arms when we perform bimanual coordination tasks proprioception influences the coupling between two limb segments of the same limb, such as the upper arm and forearm The Role of Proprioception in Motor Control Coordination control The second coordination characteristic involves the spatial-temporal coupling between limbs and limb segments. Results of the experiment by Messier et al. (2003), which we described earlier, showed that a sensory neuropathy patient demonstrated problems with coordinating the multijoint movements involved in reaching to a target in front of him. For between-limb movement coordination, the study by Verschueren et al. (1999a), which we considered earlier, showed the importance of proprioceptive feedback for the spatial and temporal coupling between the arms when we perform bimanual coordination tasks. two limbs perform simultaneously as a synergy. And in another study by this same researcher and colleagues (Verschueren et al., 1999b), they demonstrated that proprioception influences the Sensory Components of Motor Control Page 24 of 73 coupling between two limb segments of the same limb, such as the upper arm and forearm. Also, Spencer et al. (2005) demonstrated similar bimanual coordination problems for a sensory neuropathy patient, especially in terms of the control of spatial coordination and consistency between movements for a repetitive series of movements Sensory Components of Motor Control Page 25 of 73  The Role of Proprioception in Motor Control Movement Accuracy The influence of proprioception on movement accuracy appears to be due to the specific kinematic and kinetic feedback provided by the proprioceptors to the CNS: Feedback about limb displacement provides the basis for spatial position corrections proprioceptors provide feedback about limb velocity and force, which influence movement distance accuracy. The Role of Proprioception in Motor Control Movement accuracy. The influence of proprioception on movement accuracy appears to be due to the specific kinematic and kinetic feedback provided by the proprioceptors to the CNS. Feedback about limb displacement provides the basis for spatial position corrections, which enable the limb to achieve spatial accuracy by a continuous updating of limb position to the CNS, which in turn can send movement commands that will modify the position accordingly, provided that the movement occurs for a sufficient amount of time to allow movement corrections to occur. In addition, proprioceptors provide feedback about limb velocity and force, which influence movement distance accuracy. Sensory Components of Motor Control Page 26 of 73  VISION AND MOTOR CONTROL When you’re learning a new motor skill, when do you use vision? Sensory Components of Motor Control Page 27 of 73  VISION AND MOTOR CONTROL We have a tendency to give vision a predominant role when we perform motor skills VISION AND MOTOR CONTROL Our own personal experiences as well as research evidence tells us that of all our sensory systems, we tend to use and trust vision the most. anecdotal experiences: 1) For example, when you first learned to type or play the piano, you undoubtedly felt that if you could not see your fingers hit each key, you could not perform accurately. 2) Beginning dancers and stroke patients learning to walk have a similar problem. They often act as if they cannot perform the activity if they cannot watch their feet. shows our tendency to give vision a predominant role when we perform motor skills. Research: Lee and Aronson (1974) “moving room” experiment Sensory Components of Motor Control Page 28 of 73 Infants stood in a room in which the walls could move forward and backward. However, the floor was stationary and did not move. In this sensory conflict situation, the infants’ vision indicated they were moving, but their proprioceptors indicated they were not. The researchers observed the infants’ postural responses to the movement of the walls. When the walls moved, the children made posture correction adjustments that were in keeping with trying to maintain their standing balance as if the floor were moving. But because the floor did not move, their proprioceptors were not signaling that their bodies were losing stability. Only their visual systems detected any loss of balance. It is important to note that similar “moving room” effects on postural control have been reported more recently (see Barela, Barela, Rinaldi, & de Toledo, 2009; Chung & Stoffregen, 2011; Stoffregen, Hove, Schmit, & Bardy, 2006). moving room experiments demonstrate the special priority we assign to vision in our daily activities. In those experiments, when the proprioceptors and vision provided conflicting information to the central nervous system, people gave attention to vision while ignoring the proprioceptors. The result was that they initiated unnecessary postural adjustments PRIORITY is given to vision For today's meeting: we will discuss the role of vision in motor control in several ways 1) neurophysiology of vision as it relates to motor control Sensory Components of Motor Control Page 29 of 73 2)methods researchers use to investigate the role of vision in motor control 3)look into several motor control issues that provide us with a general understanding of the many roles vision plays in the control of coordinated movement Sensory Components of Motor Control Page 30 of 73  VISION AND MOTOR CONTROL Research: “Moving Room” Experiment by Lee and Aronson (1974) Infants in standing in a room: conditions: moving wall, stable floor infants made postural corrections that were in keeping ith trying to maintain their standing balance as if the floor was moving demonstrate the special priority we assign to vision in our daily activities; ignoring proprioceptrors VISION AND MOTOR CONTROL Our own personal experiences as well as research evidence tells us that of all our sensory systems, we tend to use and trust vision the most. anecdotal experiences: 1) For example, when you first learned to type or play the piano, you undoubtedly felt that if you could not see your fingers hit each key, you could not perform accurately. 2) Beginning dancers and stroke patients learning to walk have a similar problem. They often act as if they cannot perform the activity if they cannot watch their feet. shows our tendency to give vision a predominant role when we perform motor skills. Research: Lee and Aronson (1974) “moving room” experiment Sensory Components of Motor Control Page 31 of 73 Infants stood in a room in which the walls could move forward and backward. However, the floor was stationary and did not move. In this sensory conflict situation, the infants’ vision indicated they were moving, but their proprioceptors indicated they were not. The researchers observed the infants’ postural responses to the movement of the walls. When the walls moved, the children made posture correction adjustments that were in keeping with trying to maintain their standing balance as if the floor were moving. But because the floor did not move, their proprioceptors were not signaling that their bodies were losing stability. Only their visual systems detected any loss of balance. It is important to note that similar “moving room” effects on postural control have been reported more recently (see Barela, Barela, Rinaldi, & de Toledo, 2009; Chung & Stoffregen, 2011; Stoffregen, Hove, Schmit, & Bardy, 2006). moving room experiments demonstrate the special priority we assign to vision in our daily activities. In those experiments, when the proprioceptors and vision provided conflicting information to the central nervous system, people gave attention to vision while ignoring the proprioceptors. The result was that they initiated unnecessary postural adjustments PRIORITY is given to vision For today's meeting: we will discuss the role of vision in motor control in several ways 1) neurophysiology of vision as it relates to motor control Sensory Components of Motor Control Page 32 of 73 2)methods researchers use to investigate the role of vision in motor control 3)look into several motor control issues that provide us with a general understanding of the many roles vision plays in the control of coordinated movement Sensory Components of Motor Control Page 33 of 73  VISION AND MOTOR CONTROL We have a tendency to give vision a predominant role when we perform motor skills PRIORITY is given to vision VISION AND MOTOR CONTROL Our own personal experiences as well as research evidence tells us that of all our sensory systems, we tend to use and trust vision the most. anecdotal experiences: 1) For example, when you first learned to type or play the piano, you undoubtedly felt that if you could not see your fingers hit each key, you could not perform accurately. 2) Beginning dancers and stroke patients learning to walk have a similar problem. They often act as if they cannot perform the activity if they cannot watch their feet. shows our tendency to give vision a predominant role when we perform motor skills. Research: Lee and Aronson (1974) “moving room” experiment Sensory Components of Motor Control Page 34 of 73 Infants stood in a room in which the walls could move forward and backward. However, the floor was stationary and did not move. In this sensory conflict situation, the infants’ vision indicated they were moving, but their proprioceptors indicated they were not. The researchers observed the infants’ postural responses to the movement of the walls. When the walls moved, the children made posture correction adjustments that were in keeping with trying to maintain their standing balance as if the floor were moving. But because the floor did not move, their proprioceptors were not signaling that their bodies were losing stability. Only their visual systems detected any loss of balance. It is important to note that similar “moving room” effects on postural control have been reported more recently (see Barela, Barela, Rinaldi, & de Toledo, 2009; Chung & Stoffregen, 2011; Stoffregen, Hove, Schmit, & Bardy, 2006). moving room experiments demonstrate the special priority we assign to vision in our daily activities. In those experiments, when the proprioceptors and vision provided conflicting information to the central nervous system, people gave attention to vision while ignoring the proprioceptors. The result was that they initiated unnecessary postural adjustments PRIORITY is given to vision For today's meeting: we will discuss the role of vision in motor control in several ways 1) neurophysiology of vision as it relates to motor control 2)methods researchers use to investigate the role of vision in motor control Sensory Components of Motor Control Page 35 of 73 3)look into several motor control issues that provide us with a general understanding of the many roles vision plays in the control of coordinated movement Sensory Components of Motor Control Page 36 of 73  VISION AND MOTOR CONTROL OUTLINE: 1. Neurophysiology of vision; 2. Role vision plays in the control of coordinated movement For today's meeting: we will discuss the role of vision in motor control in several ways 1) neurophysiology of vision as it relates to motor control 2)methods researchers use to investigate the role of vision in motor control 3)look into several motor control issues that provide us with a general understanding of the many roles vision plays in the control of coordinated movement Sensory Components of Motor Control Page 37 of 73  NEUROPHYSIOLOGY OF VISEION VISION: EYE: “eye acts like a camera, is the result of the sensory forming crisp, clear images of the receptors of the eyes world.... Like a quality 35-mm receiving and transmitting camera, the eye automatically wavelengths of light to the adjusts to differences in illumination visual cortex of the brain by and automatically focuses itself on way of sensory neurons objects of interest... “ (p.281) Bear, Connors, and Paradiso (2001) known as the optic nerve special features: tracking objects, sensor cleaning The Neurophysiology of Vision Vision is the result of the sensory receptors of the eyes receiving and transmitting wavelengths of light to the visual cortex of the brain by way of sensory neurons known as the optic nerve. Bear, Connors, and Paradiso (2001) state, “the eye acts like a camera, forming crisp, clear images of the world.... Like a quality 35-mm camera, the eye automatically adjusts to differences in illumination and automatically focuses itself on objects of interest. The eye has some additional features not yet available on cameras, such as the ability to track moving objects (by eye movement) and the ability to keep its transparent surfaces clean (by tears and blinking)” (p. 281). Sensory Components of Motor Control Page 38 of 73  Basic Anatomy of the Eye Cornea : a clear surface that allows light to enter the eye does not have blood vessels behind the cornea: pupil, iris, lens Pupil: opening that lets light into the eye diameter increases and decreases according to the amount of light detected by the eye diameter change is controlled by smooth muscle fibers within the iris Iris: surrounds the pupil and provides the eye its color human eye is a fluid-filled ball with distinct components Cornea is the most anterior component. It is a clear surface that allows light to enter the eye and serves as an important part of the eye’s optical system. Because it does not have blood vessels, it can be surgically removed with relative ease and, if necessary, a donated cornea can be transplanted. Behind the cornea are the pupil, iris, and lens. pupil is the opening that lets light into the eye diameter increases and decreases according to the amount of light detected by the eye This diameter change is controlled by smooth muscle fibers within the iris iris surrounds the pupil and provides the eye its color. Sensory Components of Motor Control Page 39 of 73 Sensory Components of Motor Control Page 40 of 73  Basic Anatomy of the Eye Lens : transparent structure located behind the iris responsible for allowing the eye to focus at various distances held in place by the zonular fibers and its shape is controlled by the ciliary muscles Sclera : surrounds cornea, lens, pupil and iris; anterior portion of firm white capsule “white” of the eye help maintain the shape of the eye and protect the eye’s inner structure attachment site for the extrinsic eye muscles responsible for eye movement lens, which sits just behind the iris, is a transparent structure that is responsible for allowing the eye to focus at various distances. The lens is held in place by the zonular fibers and its shape is controlled by the ciliary muscles shown in figure 6.5. The sclera, which makes up 80 percent of the eye, surrounds these structures. The anterior portion of this firm white capsule forms what we commonly call the “white” of the eye. The sclera functions to help maintain the shape of the eye and protect the eye’s inner structure. It also is an attachment site for the extrinsic eye muscles responsible for eye movement. Sensory Components of Motor Control Page 41 of 73  Basic Anatomy of the Eye aqueous humor & vitreous humor: chambers of fluid AH a clear fluid that fills the chamber between the cornea and lens VH viscous substance that fills the chamber between the lens and the back wall of the eye The eye contains two chambers of fluid: aqueous humor is a clear fluid that fills the chamber between the cornea and lens, and vitreous humor is a viscous substance that fills the chamber between the lens and the back wall of the eye. Sensory Components of Motor Control Page 42 of 73  Basic Anatomy of the Eye PAUSE The eye contains two chambers of fluid: aqueous humor is a clear fluid that fills the chamber between the cornea and lens, and vitreous humor is a viscous substance that fills the chamber between the lens and the back wall of the eye. Sensory Components of Motor Control Page 43 of 73  NEURAL COMPONENT OF THE EYE and VISION Retina: structure that lines the back wall of the eye part of the eye & extension of the brain (Widmaier, Raff, & Strang, 2006) contains various types of neurons and photoreceptor cells COMPONENTS: fovea centralis: where objects seen in central vision are focused; visual acuity optic disk: where axons of the retina’s neurons converge to transmit information to the optic nerve PHOTORECEPTORS (rods and cones) Roles in vision relevant to motor skills: responsibility for light detection shifts rods: low light levels; cones: bright lights temporary blindness NEURAL COMPONENT OF THE EYE and VISION The neural aspects of vision begin with the retina retina the structure that lines the back wall of the eye part of the eye but is actually an extension of the brain (Widmaier, Raff, & Strang, 2006). contains various types of neurons and photoreceptor cells primary components: 1) fovea centralis: where objects seen in central vision are focused (hence the term foveal vision) and is therefore responsible for visual acuity 2) optic disk: where the axons of the retina’s neurons converge to transmit information to the optic nerve contains photo receptor cells (rods and cones) that play important roles in vision three roles relevant to motor skills of photo receptor cells: Sensory Components of Motor Control Page 44 of 73 1)rods respond to low levels of light (which makes them responsible for night vision); cones respond only to bright light. Because of the specific levels of light to which they respond, these photoreceptors are the cause of the “temporary blindness” experience you have when the lighting in a room changes from very bright to dark. In such a situation the responsibility for light detection shifts from the cones to the rods, a process that requires a brief amount of time. Sensory Components of Motor Control Page 45 of 73  NEURAL COMPONENT OF THE EYE and VISION Retina PHOTORECEPTORS (rods and cones) ct’d role in vision cones: located centrally, impt. in central vision and visual acuity; Color vision three types of cones: blue, green, and red rods: located peripherally, impt. in peripheral vision 2) (relates to their location on the retina) Cones are concentrated at the center, which gives them a critical role in central vision and visual acuity. Rods are located more on the retina periphery and, therefore, are important for peripheral vision. 3) cones play a critical role in color vision: By combining these cells' signals, the brain can distinguish thousands of different colors. Light moves through the lens of the eye to the back of the eye, which is the retina. Here, there are millions of rods and cones. 2. When light hits the discs in the outer segment of the rods and cones, the little bits of light (photons) activate the cells. Rods can be activated in low light, but cones require much brighter light (many more photons). Most of the light not absorbed by the rods or cones is absorbed by the epithelial cells behind them. The discs of rods hold rhodopsin and the discs of cones hold photopsin. Both of these photoreceptor proteins are special molecules that change shape when activated by light. This shape change allows the proteins to activate a second special protein molecule that then starts Sensory Components of Motor Control Page 46 of 73 causing other changes involved in sending a visual signal. For the signal to be sent through the cell, charged molecules called ions are let in and out of the cell in an action potential. 3. When the signal reaches the inner end (left side) of the rods and cones, the signal is passed to sets of neural cells. 4. The signal moves through neural cells in the optic nerve. 5. The optic nerve will send this information to the brain, where separate signals can be processed so you see them as a complete image. Sensory Components of Motor Control Page 47 of 73  NEURAL COMPONENT OF THE EYE and VISION Retina receives light waves from the cornea and lens waves are refracted (bent) in such a way that an observed image is turned upside down and reversed right to left on the retina Image size and distance from the eye are determined by the size of the angle the light waves from the image form when they pass through the cornea: more bending for bigger and closer images: larger image on retina less bending for smaller and more distant images: smaller image on retina when is it important in control situations? when a person must make contact with or intercept a moving object The retina receives light waves from the cornea and lens, where the waves are refracted—that is, bent—in such a way that an observed image is turned upside down and reversed right to left on the retina. Image size and distance from the eye are determined by the size of the angle the light waves from the image form when they pass through the cornea; there is more bending for bigger and closer images to create larger images on the retina, and less bending for smaller and more distant images to create smaller images on the retina. This distinction is important for motor control in situations in which a person must make contact with or intercept a moving object Sensory Components of Motor Control Page 48 of 73  NEURAL COMPONENT OF THE EYE and VISION optic nerve (cranial nerve II) serves as the means of information transmission from the eye to the brain composed of axons of neurons in the retina optic chiasm where optic nerves from the two eyes meet nerve fibers either continue to the same side of the brain or cross over to the opposite side of the brain then continue to the visual cortex at the back of the brain’s cortex changing to opposite side depends on the visual field on the retina from which the fibers originate optic nerve Axons of neurons in the retina called ganglion cells form cranial nerve II and serves as the means of information transmission from the eye to the brain optic chiasm, the optic nerves from the two eyes meet near the base of the brain where the nerve fibers either continue to the same side of the brain or cross over to the opposite side of the brain and continue to the visual cortex at the back of the brain’s cortex. Whether optic nerve fibers cross at the optic chiasm or change to the opposite side of the brain depends on the visual field on the retina from which the fibers originate. The optic nerve fibers project to several brain structures, with the largest number passing through the lateral geniculate nucleus of the thalamus. visual field: Sensory Components of Motor Control Page 49 of 73 refers to the image or scene being viewed One portion, referred to as the nasal part of the visual field, is detected by the inner halves of each eye, while the temporal part of the visual field is detected by the outer halves of each eye. The optic nerve fibers associated with the nasal part, which is projected through the lens and cornea to the interior side of the retinas, cross over at the optic chiasm to the opposite hemisphere of the cortex while the optic nerve fibers associated with the temporal part pass through the optic chiasm to remain in the same cortex hemisphere. The visual cortex of the brain unites these images in a way that allows us to see three dimensional images. As we will discuss later in this chapter, this binocular vision—that is, seeing with both eyes—is the basis for our depth perception as we observe the world around us. Sensory Components of Motor Control Page 50 of 73  NEURAL COMPONENT OF THE EYE and VISION visual field the image or scene being viewed; 200 deg horizontally, 160 degrees vertically each eye sees a portion of the image or scene nasal part of the visual field detected by inner halves of each eye optic nerve fibers cross over at the optic chiasm to the opposite hemisphere of the cortex temporal part of the visual field detected by outer halves of each eye optic nerve fibers pass over at the optic chiasm remaining in the same cortex hemisphere NOTE: visual cortex unites these images in a way that allow us to see 3D images visual field: refers to the image or scene being viewed One portion, referred to as the nasal part of the visual field, is detected by the inner halves of each eye, while the temporal part of the visual field is detected by the outer halves of each eye. The optic nerve fibers associated with the nasal part, which is projected through the lens and cornea to the interior side of the retinas, cross over at the optic chiasm to the opposite hemisphere of the cortex while the optic nerve fibers associated with the temporal part pass through the optic chiasm to rem ain in the same cortex hemisphere. The visual cortex of the brain unites these images in a way that allows us to see three dimensional images. As we will discuss later in this chapter, this binocular vision—that is, Sensory Components of Motor Control Page 51 of 73 seeing with both eyes—is the basis for our depth perception as we observe the world around us. Sensory Components of Motor Control Page 52 of 73  THE ROLE OF VISION IN MOTOR CONTROL Monocular versus binocular vision to the use of monocular (i.e., one eye) compared to binocular (i.e., two eyes) vision to perform motor skills motor control system operates more effectively and efficiently when it receives visual information from both eyes (binocular vision) with monocular vision movement accuracy decreases and movement efficiency as the distance of the object increases problem appears during movement preparation; and with monocular vision people consistently underestimate the distance to objects and the size of the objects move their head to obtain more accurate information about size and distance of an object Vision plays many roles in the control of coordinated movement. Monocular versus Binocular Vision to the use of monocular (i.e., one eye) compared to binocular (i.e., two eyes) vision to perform motor skills Research evidence (e.g., Coull et al., 2000; Goodale & Servos, 1996; Servos, 2000; Zago, McIntyre, Senot, & Lacquanti, 2009) has shown that the motor control system operates more effectively and efficiently when it receives visual information from both eyes Although people can reach and pick up objects when the use of only one eye is available, the accuracy and efficiency of the movement decrease as the distance to the object increases. Experiments (e.g., Coull et al., 2000; Grant, 2015) that have shown this influence of distance provide support for the view that Sensory Components of Motor Control Page 53 of 73 binocular vision is important for depth perception The monocular vision problem appears to be due to movement preparation and execution problems Without binocular vision during movement preparation, people consistently underestimate the dist ance to objects and the size of the objects. These underestimates are not corrected during the movement itself, which indicates the need for binocular vision to provide important limb movement error-correction information. errors in movement kinematics during the movement and movement endpoint accuracy Interestingly, when people are not permitted to use binocular vision and must reach for and grasp an object using monocular vision, they will move their heads in a manner that enables them to obtain more accurate information about the size of an object and the distance to it (see Marotta, Kruyer, & Goodale, 1998). Binocular vision also provides better movement control than monocular vision for other motor skills, such as locomotion and intercepting moving objects. For example, research evidence shows that when a person is walking along a pathway and must step over an obstacle, binocular vision is important for the detection of the three dimensional characteristics of the environment needed to initiate and step over the obstacle (Patla, Niechwiej, Racco, & Goodale, 2002). This information enables the person to move the stepping leg accurately to clear the obstacle while stepping over it. Here again we see evidence for the importance of binocular vision for visual depth perception. Sensory Components of Motor Control Page 54 of 73 Finally, binocular vision also provides important information to help us intercept moving objects research evidence supporting this role for binocular vision was reported in an experiment in which participants used monocular or binocular vision to hit a moving object (Scott, van der Kamp, Savelsbergh, Oudejans, & Davids, 2004). Results showed that the participants using monocular vision missed the object more frequently, indicating that binocular vision provides important information to guide interceptive actions in skills such as hitting a moving ball. Sensory Components of Motor Control Page 55 of 73  THE ROLE OF VISION IN MOTOR CONTROL Monocular versus binocular vision execution problems binocular vision is important for depth perception provide important limb movement error-correction information errors in movement kinematics during the movement and movement endpoint accuracy binocular vision provides better movement control than monocular vision for other motor skills (i.e., locomotion, intercepting moving objects) binocular vision is important for the 3D characteristics of the environment binocular vision provides information to help us intercept moving objects Research (Scott, van der Kamp, Savelsbergh, Oudejans, & Davids, 2004) showed that the participants using monocular vision missed the object more frequently Interestingly, when people are not permitted to use binocular vision and must reach for and grasp an object using monocular vision, they will move their heads in a manner that enables them to obtain more accurate information about the size of an object and the distance to it (see Marotta, Kruyer, & Goodale, 1998). Binocular vision also provides better movement control than monocular vision for other motor skills, such as locomotion and intercepting moving objects. For example, research evidence shows that when a person is walking along a pathway and must step over an obstacle, binocular vision is important for the detection of the three dimensional characteristics of the environment needed to initiate and step over the obstacle (Patla, Niechwiej, Racco, & Goodale, 2002). This information enables the person to move the stepping leg accurately to clear the obstacle while stepping over it. Here again we Sensory Components of Motor Control Page 56 of 73 see evidence for the importance of binocular vision for visual depth perception. Finally, binocular vision also provides important information to help us intercept moving objects research evidence supporting this role for binocular vision was reported in an experiment in which participants used monocular or binocular vision to hit a moving object (Scott, van der Kamp, Savelsbergh, Oudejans, & Davids, 2004). Results showed that the participants using monocular vision missed the object more frequently, indicating that binocular vision provides important information to guide interceptive actions in skills such as hitting a moving ball. Sensory Components of Motor Control Page 57 of 73  THE ROLE OF VISION IN MOTOR CONTROL Central and Peripheral Vision Central vision foveal vision detects information only in the middle 2 to 5 degrees of the visual field Peripheral vision detects information in the visual field outside these limits visual field extends approximately 200 degrees horizontally and 160 degrees vertically the roles of central and peripheral vision in the control of movement. Central vision, which is sometimes called foveal vision, detects information only in the middle 2 to 5 degrees of the visual field Peripheral vision, on the other hand, detects information in the visual field outside these limits. For most people, the visual field extends approximately 200 degrees horizontally and 160 degrees vertically. to demonstrate how central and peripheral vision each provide distinct information for motor control: two types of motor skills related to everyday living: reaching and grasping an object, and locomotion grasping an object: First, imagine yourself sitting at a table with the intent to pick up a cup sitting on the table. In this situation, as you prepare to move, central vision Sensory Components of Motor Control Page 58 of 73 fixates on the cup to obtain information on its size, shape, and distance from your present position. As you begin to reach for the cup your moving hand is seen by peripheral vision, which will provide online feedback to guide the reaching and grasping of the cup. As your hand nears the cup, central vision becomes critical again for providing information needed to actually grasp the cup. research supporting role of central and peripheral vision on prehension task situation: Sivak and MacKenzie (1990) showed that when participants could use only central vision to reach and grasp an object, the organization and control of the movement to the object was affected, but not the grasping of the object. When the researchers blocked the participants’ use of central vision, which meant they could use only peripheral vision for reaching and grasping an object, problems occurred with both the transport and grasp phases. peripheral vision in the control of limb movements, especially those involved in manual aiming and prehension (see Gaveau et al., 2014 and Jeannerod & Marteniuk, 1992) locomotion: when we walk along a pathway, central vision provides information that guides us so that we can stay on the pathway, whereas peripheral vision is important to provide and update our knowledge about the spatial features of the walking environment, such as pathway dropoffs or bumps (Turano, Yu, Hao, & Hicks, 2005). The information received through peripheral Sensory Components of Motor Control Page 59 of 73 vision during locomotion is particularly important to help people maintain their action goal without being affected by pathway problems, such as obstacles, other people, or irregular steps on a stairway. combined prehension and locomotion: locomotion, Graci (2011) had participants pick up a full glass of water on a table located at the end of their walking path and move the glass to a new location on the table. They performed this task with either full vision of their lower body, the table and glass, and with occluded vision, which prevented them from using peripheral vision to see the table and their lower body when they reached the table. They could always see the glass of water. One of the effects of not having peripheral vision available was the time to contact the glass, which was calculated from the end of their last step until their hand reached the glass, Without the availability of peripheral vision, they increased their time to contact the glass by approximately 40 percent. Sensory Components of Motor Control Page 60 of 73  THE ROLE OF VISION IN MOTOR CONTROL information the central and peripheral vision provide: (reaching and grasping an object; locomotion) Reaching and Grasping central vision fixates on on cup to obtain information on its size, shape, and distance from your present position provide information needed to actually grasp the cup peripheral vision will provide online feedback to guide the reaching and grasping of the cup Locomotion: (walking on pathway) central vision provides information that guides us so that we can stay on the pathway peripheral vision is important to provide and update our knowledge about the spatial features of the walking environment, such as pathway dropoffs or bumps (Turano, Yu, Hao, & Hicks, 2005) particularly important to help people maintain their action goal without being affected by pathway problems to demonstrate how central and peripheral vision each provide distinct information for motor control: two types of motor skills related to everyday living: reaching and grasping an object, and locomotion grasping an object: First, imagine yourself sitting at a table with the intent to pick up a cup sitting on the table. In this situation, as you prepare to move, central vision fixates on the cup to obtain information on its size, shape, and distance from your present position. As you begin to reach for the cup your moving hand is seen by peripheral vision, which will provide online feedback to guide the reaching and grasping of the cup. As your hand nears the cup, central vision becomes critical again for providing information needed to actually grasp the cup. research supporting role of central and peripheral vision on prehension task situation: Sensory Components of Motor Control Page 61 of 73 Sivak and MacKenzie (1990) showed that when participants could use only central vision to reach and grasp an object, the organization and control of the movement to the object was affected, but not the grasping of the object. When the researchers blocked the participants’ use of central vision, which meant they could use only peripheral vision for reaching and grasping an object, problems occurred with both the transport and grasp phases. peripheral vision in the control of limb movements, especially those involved in manual aiming and prehension (see Gaveau et al., 2014 and Jeannerod & Marteniuk, 1992) locomotion: when we walk along a pathway, central vision provides information that guides us so that we can stay on the pathway, whereas peripheral vision is important to provide and update our knowledge about the spatial features of the walking environment, such as pathway dropoffs or bumps (Turano, Yu, Hao, & Hicks, 2005). The information received through peripheral vision during locomotion is particularly important to help people maintain their action goal without being affected by pathway problems, such as obstacles, other people, or irregular steps on a stairway. combined prehension and locomotion: locomotion, Graci (2011) had participants pick up a full glass of water on a table located at the end of their walking path and move the glass to a new location on the Sensory Components of Motor Control Page 62 of 73 table. They performed this task with either full vision of their lower body, the table and glass, and with occluded vision, which prevented them from using peripheral vision to see the table and their lower body when they reached the table. They could always see the glass of water. One of the effects of not having peripheral vision available was the time to contact the glass, which was calculated from the end of their last step until their hand reached the glass, Without the availability of peripheral vision, they increased their time to contact the glass by approximately 40 percent. Sensory Components of Motor Control Page 63 of 73  THE ROLE OF VISION IN MOTOR CONTROL Central and Peripheral Vision OPTICAL FLOW refers to the moving pattern of rays of light that strikes the retina of the eye from all parts of the environment source of information available to peripheral vision for controlling actions “flow” indicates the dynamic nature of this visually detected information visual system detects and uses patterns of optical flow that covary precisely with the speed and direction of our head motion (head turning, postural sway or locomotion) movement of an object, a person, or a surface provides the visual system with a different pattern of optical flow that specifies the direction and speed with which that particular feature of the environment is moving Differentiating the various patterns of optical flow allows us to effectively control posture, locomotion, and object manipulation and to coordinate our actions with the regulatory conditions in the environment optical flow: One of the most important sources of information available to peripheral vision for controlling actions refers to the moving pattern of rays of light that strikes the retina of the eye from all parts of the environment. The word “flow” is significant because it indicates the dynamic nature of this visually detected information. When our head moves through the environment, whether through head turning, postural sway, or locomotion, our visual system detects and uses patterns of optical flow that covary precisely with the speed and direction of our head motion. Similarly, movement of an object, a person, or a surface provides the visual system with a different pattern of optical flow that specifies the direction and speed with which that particular feature of the environment is moving. Differentiating the various patterns of optical flow allows us to effectively control posture, locomotion, and object manipulation and to coordinate our actions with the regulatory conditions in the environment. (For an excellent review of research concerning optical Sensory Components of Motor Control Page 64 of 73 flow and an experiment involving the use of optical flow, see Konczak, 1994, and for a review of the development of responsiveness to optical flow, see Anderson, Campos, & Barbu-Roth, 2004.) Sensory Components of Motor Control Page 65 of 73  THE ROLE OF VISION IN MOTOR CONTROL Two visual systems for motor control the visual system is actually two anatomical systems that operate in parallel PAILLARD (1980) proposes two channels: KINETIC VISUAL CHANNEL responsible for processing visual information in peripheral vision process high-speed movement information and control limb movement direction STATIC VISUAL CHANNEL process visual information in central vision and for slow-speed movements The distinctive behavioral roles for central and peripheral vision, along with supporting neurophysiological evidence, have led some researchers to propose that the visual system is actually two anatomical systems that operate in parallel Paillard (1980), for example, proposed that a kinetic visual channel was responsible for processing visual information in peripheral vision. This channel would process high-speed movement information and control limb movement direction. To process visual information in central vision and for slow-speed movements, Paillard proposed a static visual channel. 2 Other researchers have proposed similar two-channel visual systems but have given them different names. Some examples include the focal vision system, which is responsible for the detection of static objects by central vision, and the ambient vision system, which detects objects and movement around us, involving Sensory Components of Motor Control Page 66 of 73 peripheral vision (Trevarthen, 1968); another is vision-for-perception system, which would be responsible for recognizing and describing what a person is seeing, and the vision-for-action system which would be responsible for perceptually gui ded movements ( Brown, Halpert, & Goodale, 2005; Goodale & Milner, 1992). When described in anatomical terms, the two visual systems identified by Goodale and Milner (1992) have been referred to as the ventral stream, which is used for fine analysis of the visual scene into form, color, and features—in other words, what a person is seeing—and the dorsal stream, which is responsible for the spatial characteristics of what is seen as well as for guiding movement (e.g., Cameron, Franks, Enns, & Chua, 2007; Reed, Klatzky, & Halgren, 2005). As this designation of the two systems suggests, the neural pathways of the two systems are anatomically distinct. To use the Goodale and Milner terms for the two systems, the vision-forperception system processes visual information via a cortical pathway leading from the primary visual cortex to the temporal lobe, whereas the vision-foraction system routes information from the primary visual cortex to the posterior parietal cortex (Brown, Halpert, & Goodale, 2005; Reed et al., 2005). One important characteristic of the two systems relates to our conscious awareness of the information detected by each system. We are generally consciously aware of information detected by the ventral stream, but not of that detected by the dorsal stream. This disassociation leads to some interesting behaviors in patients with damage to the ventral or dorsal stream. For example, a patient with damage to the ventral stream could have no conscious perception of the size or orientation of an object, but could pick up and manipulate the object without any Sensory Components of Motor Control Page 67 of 73 problems (Goodale & Milner, 1992). Sensory Components of Motor Control Page 68 of 73  THE ROLE OF VISION IN MOTOR CONTROL Two visual systems for motor control the visual system is actually two anatomical systems that operate in parallel GOODALE and MILNER(1992) proposes two channels (in terms of anatomical visual systems/neural pathway of two systems are anatomically distinct): VENTRAL STREAM is used for fine analysis of the visual scene Into form, color, and features what a person is seeing system processes visual information via a cortical pathway leading from the primary visual cortex to the temporal lobe consciously aware of information detected by this system DORSAL STREAM which is responsible spatial characteristics of what is seen guiding movement system routes information from the primary visual cortex to the posterior parietal cortex When described in anatomical terms, the two visual systems identified by Goodale and Milner (1992) have been referred to as the ventral stream, which is used for fine analysis of the visual scene into form, color, and features—in other words, what a person is seeing—and the dorsal stream, which is responsible for the spatial characteristics of what is seen as well as for guiding movement (e.g., Cameron, Franks, Enns, & Chua, 2007; Reed, Klatzky, & Halgren, 2005). As this designation of the two systems suggests, the neural pathways of the two systems are anatomically distinct. To use the Goodale and Milner terms for the two systems, the vision-forperception system processes visual information via a cortical pathway leading from the primary visual cortex to the temporal lobe, whereas the vision-foraction system routes information from the primary visual cortex to the posterior parietal cortex (Brown, Halpert, & Goodale, 2005; Reed et al., 2005). One important characteristic of the two systems Sensory Components of Motor Control Page 69 of 73 relates to our conscious awareness of the information detected by each system. We are generally consciously aware of information detected by the ventral stream, but not of that detected by the dorsal stream. This disassociation leads to some interesting behaviors in patients with damage to the ventral or dorsal stream. For example, a patient with damage to the ventral stream could have no conscious perception of the size or orientation of an object, but could pick up and manipulate the object without any problems (Goodale & Milner, 1992). Sensory Components of Motor Control Page 70 of 73  THE ROLE OF VISION IN MOTOR CONTROL PERCEPTION-ACTION COUPLING “when you want to kick a moving ball or stop it with your foot, your eyes and feet coordinate so that you can successfully carry out the intended action” The spatial and temporal coordination of vision and the hands or feet in these types of skill performance situations is an example of PERCEPTION-ACTION COUPLING. Perception-action coupling is not confined to the hands and feet or to the visual system but can be seen in any situation where an action, such as posture or locomotion, is coordinated with features of the environment When you play a video game on your computer and you must move the mouse or joystick quickly and precisely so that the object you control on the screen hits a target, or when you want to quickly unlock the door to your residence, your eyes and hand work together in a coordinated way to allow you to carry out these actions. The spatial and temporal coordination of vision and the hands or feet in these types of skill performance situations is an example of what is known as perception-action coupling. this means that the visual perception of the object and the limb movement required to achieve the action goal are “coupled,” or coordinated, in a way that enables people to perform eye-hand and eye-foot coordination skills. Perception-action coupling Sensory Components of Motor Control Page 71 of 73 is not confined to the hands and feet or to the visual system, but can be seen in any situation where an action, such as posture or locomotion, is coordinated with features of the environment. Sensory Components of Motor Control Page 72 of 73  Review Touch and Motor Control Describe Touch andtheMotor sensory receptors in the skin that provide Control tactile sensory information to the central nervous system Discuss several movement-related characteristics influenced by feedback from the proprioceptors Vision and Motor Control Describe key anatomical components of the eye and neural pathways for vision Discuss motor control issues related to vision Of our various senses, touch, proprioception, and vision contribute to the motor control of skills in significant ways. In the study of human sensory physiology, touch and proprioception are included as senses in the somatic sensory system, whereas vision is the sense associated with the visual sensory system. In the following sections, we will look specifically at these three senses by describing their neural bases and the roles each plays in the control of human movement. Sensory Components of Motor Control Page 73 of 73