LECTURE 29 - open loop control Flashcards
what is open-loop control?
is a type of control system where the output or action is predetermined based on a set of programmed instructions or a fixed input signal, without feedback or monitoring of the actual output
who performed the early studies of open-loop control ?
Sherrington
who performed the later studies of open-loop control ?
rothwell
describe the early studies done by Sherrington :
sectioning of dorsal roots and the absence of movement
describe the later studies done by Rothwell :
individuals can program actions without sensory input
who started studying individuals with peripheral neuropathies (people who had selective damage to their dorsal roots that impeded any sort of somatosensory or proprioceptive information from their muscle spindles getting access into their CNS) ?
rothwell
it was originally thought to be compelling evidence that a closed-loop system control is the only mode of control that really supports purposeful movement …
we dont really have an open-loop system of control
what does deafferentation mean ?
refers to the loss or severing of sensory input to a particular area of the nervous system
in what study does a gentleman perform a thumb to finger movement ?
deafferentation Rothwell study
what do we see in the images in regards to deafferentation ?
successive snapshots of gentleman able to perform the movement in the absence of sensory feedback from his muscle spindles and from a somatic sensory system
where is peripheral neuropathies in their extremities ?
right hand and in both of their feet
in what case can an individual have complete vision, can plan movement but cannot make adjustments ?
open-loop control deafferentation
what is central pattern generator ?
a neural network that generates rhythmic and coordinated patterns of motor activity in the absence of sensory feedback or descending motor commands
where did we first see the central pattern generator ?
50s Soviet Union
what is “in some pint of our spinal cord, there are group of neurons or a cluster of neurons that can control these arthymeic movements” referred as ?
central patter generators
what experiment was used to demonstrate central pattern generator ?
mesencephalic (midbrain) cat supported on a treadmill
describe the mesencephalic cat supported on treadmill experiment :
- cat who’s had this midbrain procedure performed on it
- when the cat is place on a treadmill, they can walk
- treadmill is gradually increasing speed and you. can see that the cat demonstrates a fairly normal transition from walking to running
what happens as soon as you take away this input trigger (the treadmill being on) ?
the whole system will stipend the cat will cease to be able to walk (without this trigger input (that moving treadmill), the cat would not be able to walk and then as the treadmill increase speed, would not be able to elicit a transition from walk to run
why is a treadmill good in regards to these central pattern generator experiments ?
- way to promote movement
- improve cardiovascular health
- with therapy individuals can get a lot better
what type of movement is present in central pattern generator patients on a treadmill ?
rhythmic and stereotypes movement and gait
what are ballistic actions ?
rapid and explosive movements that are initiated with a high degree of force and precision and are typically executed in a single, uninterrupted motion
what are the three triphasic EMG bursts’ ?
- primary agonist burst
- antagonist burst
- secondary agonist burst
what is an example of the primary agonist burst ?
triceps : guiding limb to target
what is an example of antagonist burst ?
biceps : breaking or slowing the limb
what is an example of secondary agonist burst ?
prevents limb from oscillating
what is triphasic EMG ?
is a method of analyzing muscle activity based on the waveform of the recorded EMG signal
when are contractions all pre planned entirely in advance of movement execution ?
ballistic actions
what did Wadman et al (1976) examine ?
wanted to examine the EMG profiles by demonstrating an open-loop mode of control, because this triphasic burst of EMG activity was entirely present during these blocked trials
what were the results of the wadman et al study ?
- unblocked trials : typical triphasic EMG
- blocked trials : EMG burst similar to the unblocked trials for 110,s after the initial burst
- antagonist burst in blocked trials occurred at the same time as unblocked
