midterm 2 Flashcards
Describe the role of the ventral and dorsal streams for movement control and planning
Ventral - what, dorsal - where
Be able to discern evidence supporting the separation of these two-streams.
Ebbinghaus Illusion and moving room experiment (kids overcompensate and fall backward when wall moves toward them)
Identify, describe and differentiate between sensory receptors that provide proprioceptive information to the CNS
- Vestibular apparatus: info related to head movements and body orientation, detects head orientation w respect to gravity - strongly implicated in posture and balance
- Joint receptors: info about extreme positions of joints,
- muscle spindles: info about joint position and state of muscle (stretch info).
- Golgi tendon organs: sensitive to muscle tensions, regulate levels of force created.
- Cutaneous receptors: in skin areas, detectors of pressure, temp, touch etc.
Describe the Monosynaptic Stretch Reflex
Knee jerk reaction: afferent and efferent neurons are connected by a single synapse, contraction caused by a stretch triggering muscle spindles to send a signal to the spinal cord via afferent neurons.
Differentiate between short-latency (M1) and long-latency (M2) reflexes
M1: monosynaptic reflex (autogenic or short latency)
Loop time: 30-50 ms
Structures involved: Spindles, same muscles
Modified by instructions: No
M2: Long loop reflex (or long latency)
Loop time: 50-80 ms
Structures involved: spindles, cortex or cerebellum, same muscles
Modified by instructions: Yes
closed-loop system
closeD: stable, predictable environment, object does not change during performance, self paced , object is acted upon → dart throwing.
Closed loop control systems: ex - thermometer in house going on and off when its at the right temperature or not. The loop is closed by sensory info or feedback. Closed loop = online/moment to moment control of movement - involving constant processing of feedback. They all have four distinct parts:
An executive for decision making about errors
An effector system for carrying out the decision
A reference of correctness against which the feedback is compared to define an error
An error signal, which is the information acted on by the executive
open-loop system
Open: unpredictable changing environment, object is in motion, externally paced → team games. Predictable environment: closed, unpredictable : open.
Open loop = movement is pre-programmed fully in advance and does not rely on feedback
Feedback, error detection and error correction are not needed to achieve a desired goal. This type of system is very useful in predictable environments when the movement is short.
Simple schematic: input → executive → effector → output
Examples: key press, jab in boxing, kick a punch bag
Discrete, gross, closed/predictable
Describe deafferentation (Ian Waterman) and how this provides support for concept of motor programs
Deafferentation studies: what if Ian waterman did the arm blocking study - looks the same as in a healthy control, as the action is controlled by a motor program and isnt dependent on proprioception. Feedback is not necessary to produce the movement, pattern of muscle commands is not a response to proprioceptive feedback. GL shows a triphasic pattern of muscle activity. → Same pattern of muscle commends in GL; motor program initiated under open loop control, without feedback
Define a motor program and relate it to open-loop control
a prestructured set of neural commands, organised in advance, and capable of producing movement without influence of feedback. Movement carried out open loop until enough time passed to allow closed loop processes. Representations of movements stored in memory. Sometimes, once these commands are sent, they cannot be stopped- cause there is no feedback.
Describe studies and be able to interpret results from 4 streams of evidence in support of motor programs
– RT and movement complexity: Movement complexity - # components, movement accuracy and duraton. More time required to organize more complex movements? RT should increase as movement complexity increases. gives evidence for motor programs. Whole movement is planned before initiation - movement task, number of parts, accuracy required?, duration of movement, latency to begin movement → more parts and accuracy required = more complexity, takes longer to initiate
– Anticipation and stopping: Inhibiting anticipatory actions: ex baseball batting. Anticipation timing task: stopping a preplanned response requires sufficient time before response initiation. Calculating when motor program initiated based on point of no return (PONR)/anticipation timing. AKA 50% probability of initiation = PONR. when motor program is initiated!
When motor program is released: During anticipatory period, you have selected a program and you are waiting to initiate it. After the PONR, your body executes the motor program in an open loop manner. Impossible to stop or alter - required slow, closed loop control.
– Blocking: Blocked movements and the triphasic patterns of muscle activation (agonist and antagonist)
How do we get the triphasic EMG pattern?
Agonist 1 - main impulse for movement, precedes movement onset (takes time to overcome inertia)
Antagonist - represents braking (decelerate limb)
Agonist 2 - helps to clamp limb at target, co contraction
– Deafferented movements: Deafferentation studies: what if Ian waterman did the arm blocking study - looks the same as in a healthy control, as the action is controlled by a motor program and isnt dependent on proprioception. Feedback is not necessary to produce the movement, pattern of muscle commands is not a response to proprioceptive feedback. GL shows a triphasic pattern of muscle activity.
Same pattern of muscle commends in GL; motor program initiated under open loop control, without feedback
– Start-react effect: Start-react effect = when a loud, straddling tone results in a startle response and releases whatever movement is prepared (motor program) with a much reduced RT. acoustic startle response - loud acoustic stimulus and neck clenching. Startle response in person preparing to move vs unprepared. Provides evidence for existence of motor programs.
Hypotheses: stimulus intensity effect - no, subcortical trigger - yes, movement must be prepared in advance in order to be triggered.
Identify benefits and limitations of the early notion of a motor program.
Pros: dont need to control each muscle individually - can prepackage in advance, can deal w situations where you dont have enough time to get feedback
Cons: storage problem - we store generalized programs/templates, novelty problem - how do we handle new/novel situations
Define a GMP
generalized motor program (GMP). memory for class of actions/patterns of movement, modified based on desired outcome.
List & describe the invariant features and parameters thought to characterize a GMP
Invariant features: fixed features that define the motor programs (this is the BMP) → solves storage problem
Parameters: flexible features that define how the motor program will be executed (related to schemas) → solves novelty problem
Know how to calculate relative timing to determine whether an action is from the same class of actions
Relative timing of events/actions/muscle activation is invariant (fixed pattern) and remains constant within a BMP, relative meaning % or proportion of overall duration of skill for each component of the skill.
invariant features
relative timing; internal rhythm of the skill. Relative timing of events/actions/muscle activation is invariant (fixed pattern) and remains constant within a BMP, relative meaning % or proportion of overall duration of skill for each component of the skill.
relative force; amount of force produced by muscles remains in constant proportion from movement to movement.
order of events; order of events,components (or muscles, if using the same muscles) is invariant or fixed.
