Sensory input and motor programmes

Explain the difference between inherent and augmented feedback as 2 sources of sensory information

Inherent feedback is task-internal, e.g when you make a movement your proprioceptors tell you where your limbs are in space

Augmented feedback is external to the task, augmenting whatever is there internally e.g. a coach or device that enhances sensory perception

This can be separated into before, during and after (KP and KR)

Explain a closed loop control model

• have an expected state/movement

• The executive system (how you will do what you want to)

• The effector system (the body part carrying out the movement decisions)

• A comparator which compares the actual state to the expected state and calculate error (this contains proprioceptive, exteroceptive and anticipated feedback)

• The error signal feeds info back to the executive system which adapts for the next task

• (Also have online feedback which gives feedback during movement to say if you are on track or not and can execute little corrections)

Explain an open- loop control

• pre-structured commands

• No time for feedback

• Best for ballistic skills

• Best when feedback latencies (M1/M2/LL/vision are too slow

Explain when closed loop control is best

• to compare and contrast using sensory feedback

• Best for ongoing/slow actions

• >200ms these corrections are feasible

• Adds accuracy and disturbance rejection BUT it costs time

• Good for posture control and continuous tracking

What is the purpose of the ciliary muscle and optic disk in the eye?

Ciliary muscle - controls the shape of the lens

Optic disk - a blind spot where the optic nerve comes in

Explain the dorsal stream

• vision for action, gives a stream of information as you’re moving

• Has fast processing for online guidance

• Most info related to where something is happening

• Location: heads up to primal lobe (which is responsible for body sensations) so the connection between these sensations and dorsal stream vision is important for sport and action

THIS IS THE STREAM WHICH CORRECTS ERROR (BY COMPARING EXPECTED VS ACTUAL)

Explain the ventral stream

• vision for perception

• Purpose is to identify what an object is and report this to our conscious

• Slower processing and identification

• Location: Goes towards temporal lobes (where the language centre is), important as you need the understanding of language to interpret what an object is

Explain optic flow and time to contact

• focuses on the dorsal stream, it’s the ability to sense where objects are in space

• The rate of change of expansion of an object on the retina tells us how fast the object is moving towards you

• Brain can then calculate time to contact based of the rate change of expansion of the object

• If the object is getting bigger quickly relevant to current size then there is a small time to contact

Explaining time to contact coupling

When catching a ball the speed of your hands moving to catch it falls in proportion with the time to the ball to contact

So these things are manipulated to maintain the time to contact as consistently as you can, making the skill more likely to be a success

Explain the phenomenon of ‘quiet eye’

• experts excel at this as they know key visual cues and focus on them for longer, they are also better at avoiding distractions

• Phenomenon is that the final visual fixation is a critical location just before the movement onset, this is associated with more successful outcomes

What is proprioception and what are the two types ?

Proprioception is our innate sensation, it gives us kinaesthesia (the knowledge of our position and movement in space)

Muscle spindles:

• group Ia - responds more to speed

• Group II - responds more to length

• Kinematic feedback (speed and length)

Golgi Tendon Organs:

• sits in the aponeurosis and provides linear force feedback

• Kinetic feedback (force)

Explain the main type of mechanoreceptors

Cutaneous receptors

• respond to changes in grip, contact and extremes of positions

• This information goes to the spinal cord and nerve and to the brain as efferent information

  the M1 loop:

• First mode of response from the muscle to the spinal cord cord and back

• Very short reflex time

  the M2 loop:

• Second mode of response which goes to the brain

• Longer reflex time

  the long latency loop:

• Where we can introduce some voluntary control

• This has the longest reflex time but ca be trained much more than M1 or M2

How does movement duration determine motor control, feedback type and cueing strategy?

• ballistic tasks (<100ms) movement is pre-programmed and there is no time for feedback so performance depends on preparation and auditory start cues

• Moderate speed (~100-200ms) the long latency (transcortical) loop can correct movement via M1/M2 but vision is usually too slow

• Slower movements (>200ms) visual and proprioceptive feedback are available, the trajectory can be updated online “see, correct, re-aim”

Describe response programming and explain how RT complexity provides evidence for it

• Response programming is the process of preparing a GMP before movement onset, includes: muscle effector selection, sequencing order, timing and set parameters (force, speed, effector)

• RT increases as movement complexity increases as the selection costs and programming costs are separable and additive

• Shows evidence as RT increases with movement complexity even when stimulus and response choice are the same, showing how motor programming occurs prior to movement

Explain generalised motor programme theory

• Underlies a class of movements that are stored in LT memory, to form a specific version for the intended action the brain sets parameters to the existing GMP

• It has invariants which don’t change (the relative timing of components, relative force sequencing and order of muscle activations)

• The parameters are set each time (overall duration, overall force/amplitude, effector and trajectory scaling)

• Creates the prediction tha is invariants remain constant while parameters vary, performance still looks the same when time and space are normalised

What is a motor programme and its key components

It’s a pre-planned set of motor commands which are organised in advanced then released to produce movement

Key components:

• defines and issue commands (when, the force and the duration of the movement)

• Organised degrees of freedom (which joints/muscles are used - this selection can change depending on the task )

• Sets anticipatory postural adjustments (stabilises the body so we ca produce the desired movement)

• Modulates reflex pathways (adjusts reflex gain so reflexes support movement)

• Initially runs largely in open loop control until fast feedback can contribute

What does the slater-hammel experiment tell us about stopping a motor programme ?

• shows that motor programmes are released before movement begins and can only be stopped within a limited time window

• There is a finite inhibition latency (~150-300ms before movement execution) - experts are good at reacting within this

• Experiment also tells us how a go-signal is triggered a few ms before we even start the movement (~130-150ms) - once this motor command happens the movement is effectively unstoppable

• The closer you are to execution the harder it becomes to stop

• Can reach the point of no return when the stopping signal arrives to close to intended execution so stopping fails

• Stronger pre-activation makes stopping harder

What is the startle-triggered release?

• a loud auditory startling stimulus can release a fully prepared action with the same pattern, but an earlier onset

• Reaction time can be ~30-70ms faster than normal

• BUT the action must be pre-programmed and gated (delivered near the expected ‘go’ , the startle acts as a trigger

• This startle response can be trained - allowing faster response in experts