Chapter 4 Sensory Contributions to Skilled Performance

1. Chapter 4 Sensory Contributions to Skilled Performance C H A P T E R 4 Sensory Contributions to Skilled Performance

2. Objectives • This chapter will help you to understand the following: • The types of sensory information available for motor control • Motor control as a closed-loop processing system • How feedback and feedforward information work in the conceptual model • The roles of vision in motor control

3. Exteroception • Provides information to the processing system about the state of the environment in which one’s body exists • Inherent feedback • Information sources such as vision and audition

4. Proprioception • Provides information about the state of the body itself • Inherent Feedback • Information sources such as vestibular apparatus, joint receptors, muscle spindles, Golgi tendon organs, and cutaneous receptors (continued)

5. Proprioception (continued) • The central nervous system is thought to use a complex combination of the inputs from these various receptors as a basis for body awareness • Perception of a movement’s trajectory can be affected by how the movement is produced (actively or passively)

6. Closed-Loop Control Systems • All closed-loop control systems have four distinct parts: 1. An executive for decision making about errors 2. An effector system for carrying out the decisions 3. A comparator against which the anticipated feedback is compared to actual feedback to define an error 4. An error signal, which is the information acted on by the executive

7. Figure 4.1

8. Figure 4.2

9. Limitations of Closed-Loop Control • The inclusion of the stages of information processing in the system illustrates the following: • The flexibility in movement control • A big disadvantage at the same time—they are slow, especially when there is high demand for processing time, resources, or both, as in many complex actions

10. Tracking Tasks • The system can produce corrections at a maximum rate of about 3 per second. • Each correction is based on a collection of information about the errors that have occurred over the past few hundred milliseconds and goes through the stages of information processing. • Tracking with more than 3 changes in direction per second is performed poorly.

11. Rapid, Discrete Tasks • A feedback-based view of movement control fails to account adequately for movement production in very quick skills. • Feedback arising from the rapid movement would not have enough time to be processed before the movement was completed, which led scientists to believe that most rapid movements must be programmed in advance.

12. Proprioceptive Closed-Loop Control • Several reflex-like processes account for corrections leading toward goal achievement in a closed-loop manner without involving the information processing stages • In moving from the M1, M2, triggered reactions, and M3 (or voluntary reaction time), these responses show systematically increased flexibility but decreased latency.

13. Figure 4.3

14. Two Visual Systems • Two essentially separate visual systems underlie human functioning. • Visual information is delivered from the retina of the eye along two separate processing streams to different places in the brain. • There is good evidence that these two different pathways of information are used differently in the control of behavior.

15. Dorsal Stream Movement Control • The dorsal stream is believed to be specialized for online movement control. • Dorsal vision involves the entire visual field and operates nonconsciously. • Optical flow provides numerous kinds of information about movement through the environment, such as time to contact, direction of movement of objects, and balance. (continued)

16. Dorsal Stream Movement Control (continued) • Optical array is the collection of rays of light that are reflected from objects in the visual environment. • Optical flow is the change in patterns of light rays from the environment as they flow over the retina during continuous movement of the eye through the environment, allowing perception of motion, position, and timing.

17. Ventral Stream Processing • The ventral stream provides information about the what in motor control. • It is sensitive only to events in central vision. • Ventral vision has access to consciousness, so it is processed through the information processing stages leading to action in much the same way as any other information source.

18. Figure 4.10

19. Audition and Motor Control • A delay in hearing auditory feedback can result in slowed speech and errors in timing and movements such as playing an instrument. • Vision (even if incorrect) can override correct auditory information.