Neural Mechanisms: Contributions And Control

1. Neural Mechanisms: Contributions And Control Chapter 4

2. Nervous System • Movement prep, execution, and control occur here • CNS vs. PNS • CNS - Brain and spinal cord • PNS - nerves that extend off of the brain and spinal cord; ;link body and CNS • Afferent vs. Efferent (PNS) • Afferent - conducts nerve impulses from sensory receptors to the CNS • Efferent - transmits impulses from CNS to limbs, muscles, etc.

3. Sensory Receptors: Stimuli Detection • Exteroceptors: located at or near surface of body • Detect stimuli outside the body • Provide information about the environment: What’s happening? Do I feel pain? • Interoceptors: hunger • Detect stimuli from the internal viscera • Provide information about the internal environment • Proprioceptors • Provide information regarding body position and movement: muscle tension, joint position

4. Vision • Dominant sensory system • 70% of sensory receptors are in the eyes • Information from other sensory receptors may be ignored in favor of visual information

5. Two Visual Systems in Motor Control • Visual information is delivered from the retina along two separate pathways to two different places • Focal vision, specialized for object identification • Ambient vision, specialized for movement control • Although separate, these systems function in parallel

6. Focal Vision • Functions to identify objects primarily located in the central region of the visual field • Answers the question “What is it?” • Voluntary; strongly linked to consciousness • Function hampered in low light conditions

7. Ambient Vision • Involves both the central and peripheral visual fields • Not affected by changes in light strength • Provides information about our own movements in relation to other objects • Answers questions “Where is it”; “Where am I in relation to it?” • Often functions at subconscious level • Fine motor control may occur without us knowing it

8. Parallel Processing • Ambient vision processes the broader environment • Focal vision processes the environment immediately in front

9. Comparison of the two systems

10. Focal Vision and Movement Control • Since focal vision is at the conscious level, visual information is processed through the information processing stages • Vision is a source of exteroceptive information about the environment • Movement control only occurs as information is processed through the stages • Focal vision helps one accurately ID a pencil from a pen • Is it as easy to make the ID in low light situations?

11. Ambient Vision and Movement Control • The flow of light and changes in that flow across the retina provide a person with the following information about their movement • Stability and balance • Velocity of the movement through the environment • Direction of movement relative to the position of fixed objects in the environment • Movement of environmental objects relative to the person • Time until contact between the person and an object in the environment

12. Time to Contact • As an object approaches the size of the object will increase in the retinal image • Faster the enlargement, the faster the object is approaching • Used to determine when an action should be initiated • Ambient vision is used to detect last moment changes

13. Ambient Vision and Movement Control • Because ambient information functions at the subconscious level, it is relatively fast • However this information is sent to lower levels of the CNS • Not at the same level as where the CNS selects and initiates movement • Therefore, ambient vision operates to make minor adjustments to already programmed actions • Ie. Compensate for a head movement when getting ready to swing a golf club or a change in posture when walking with crutches

14. Vision and Performance • The performer must be able to make quick and accurate decisions with focal vision • The performer must also be able to anticipate someone else’s movement or their own in relation to an object or a person through ambient vision • Anticipation helps to decrease the information processing time • Visual search strategies will assist in the development of this ability

15. Visual Search Strategies • Directs learner to information rich areas where critical cues occur • Provide extensive practice opportunities in situations that contain common task relevant cues • Later in development/experience: Design situations with high variability while still requiring the learner to search for same cues each attempt • Helps prepare learner to generalize visual search strategies for performance or game situations

16. Visual Dominance • Vision exerts a strong influence on motor control, but it may not always be positive • One may need to use other modes on control • For example, monitor the sound of the engine rather than rely only on gauges in the car • Over-reliance on vision may create ineffective performance • The firefighter who only notices the flames in front and fails to listen to the cracking of timber to the right or left may be injured

17. Practical Application • Visual Dominance • Trace between the lines looking through the mirror. • Describe how you performed. What difficulties did you experience? What conflicts existed between your visual information and your proprioceptor information? • Describe the link between visual and proprioceptive feedback in the execution of visuomotor tasks. • Based on your findings, summarize different ways you might help learners in your content field learn to link visual and proprioceptive feedback. • Turn in your results at our next class.

18. Proprioceptor Information • Golgi tendon organs; protects tendons & muscles from excessive tension • Muscle spindles;tells CNS how much and how fast a muscle is changing length • Joint kinesthetic receptors; info about movements being too slow, fast or in the wrong direction • Vestibular apparatus; info about posture and balance

19. Proprioception & motor control • Proprioceptors send info on initial conditions & limb position to the generalized motor program (recall schema) • Proprioceptors evaluate for correctness to the intended goal (recognition schema) • How does this information supplement the focal and ambient vision information?

20. Implications for learning how to interpret proprioceptive information • Help beginners develop their frame of reference about a movement (How does it feel?; How should it feel?) • Explore various possibilities to begin to develop their reference • Gain information through proprioceptors as well as vision • Manual assistance with cues

21. What do you think? • A middle-aged man wants to learn to rope jump for fitness. Unfortunately, he is visually impaired having lost most sight in a work-related accident. Explain how the man would control the movement. Then describe how you would assist the man in achieving the goal. Discuss some things you might do to encourage the use of other sensory information. Provide supporting rationale for your suggestions.

22. CNS and Memory • Processes required to plan movement in some way are stored in the CNS • Use of perception, making decisions on movement response and production often come from some type of information that is stored from previous experiences • Storage of information from previous attempts is in memory

23. Memory • Ability to store and recall information

24. WORKING MEMORY • Refers to short-term • Working memory serves as interactive workspace • Duration • Use information or lose it • Hold information for only 20-30 seconds • Capacity • Seven +/- 2 items • Increased size of item depends on chunking

25. WORKING MEMORY Processing Activities • Use information to solve a specific movement problem • Use information to perform the goal of movement • Use information in preparing the information for storage

26. LONG-TERM MEMORY • Permanent storage of information • Duration of information storage is permanent • Forgetting occurs when we cannot find a memory, or it is a retrieval problem • Capacity of information storage is unlimited

27. Subsystems of Long-term Memory • Episodic memory • Contains information about personal experiences and events that are associated with a specific time and context • Semantic memory • Represents general knowledge that is developed by our experiences but is not associated with time • Procedural memory • Retains information regarding how to do something • The memory of skills, operations and actions

28. Relating LTM to motor control • Episodic memory retrieves information • Used as a guidance for what to do from past experiences • Semantic memory relays what you have learned to do previously (concepts) • Procedural memory puts the plan into motion (blueprint)

29. GMP provides the ‘blueprint’ • Motor program and schema are in procedural memory • In a specific situation, episodic & semantic systems help to determine ‘what to do’ • Information interacts with info in procedural memory • Motor program is selected with parameters • Skill is executed

30. Forgetting • Decay theory • Interference theory • Proactive interference • Retroactive interference

31. CAUSES OF FORGETTING • Trace decay—time is a factor in working memory • Proactive interference—activities that occur prior to the presentation of information that is to be remembered • Retroactive interference—interfering activity occurs during retention • Forgetting—this is greatest when there is similarity between what is remembered and the interfering activity

32. Proactive Interference in working memory New Info Recall Info not to be recalled Time

33. Why does proactive interference impact forgetting? • Confusion • Similarity of movements mixes up the encoding of information • Ways to decrease impact • Active rehearsal (talk to yourself, visualization)

34. Retroactive interference and working memory Information to be remembered Recall Time Info not to be remembered

35. Why does retroactive interference impact forgetting? • Too much similarity between the goal movement and other interfering activity • Perhaps the number of movements to be made or observed during retention interval exceeds attention capacity • Ways to decrease impact • When giving info, avoid showing improper techniques after proper technique until practice has occurred

36. FORGETTING AND LONG-TERM MEMORY • Working memory ‘forgets’ more than long-term memory • Certain types of motor skills are remembered more • Continuous versus serial discrete skills (more cognitive processing or procedural knowledge) • Procedural skills deteriorate over time (use it or lose it) • Long-term memory forgetting may be due to misplacing information or a retrieval problem

37. STRATEGIES THAT ENHANCE MEMORY PERFORMANCE • Increase the movement’s meaningfulness • Imagery (powerful rehearsal strategy) • Verbal labeling; critical element cue, ‘elbows in’ • Inform one about information to be tested (intention to remember) • Group or organize information into ways that are meaningful (subjective organization) • Skilled person seems to organize information as result of practice; “chunks remembered”

38. STRATEGIES THAT ENHANCE MEMORY PERFORMANCE • If the context of practice and test are similar, memory is enhanced • This relationship between practice and test context is called the encoding specificity principle • Important that practice conditions are similar to how skills will be used in game or real life

39. Practical Application • Generate a list of tips that practitioners could use to help a learner to ‘remember’.