ch 7- sensorimotor control models Flashcards
Motor program theory
motor program= NOT a sequence of commands
–> if it were a sequence it would require a search through the “database” of possible sequences to match it to the task
motor command
specific info about timing and force sent from the brain to muscles
Motor program
a procedure/formula for generating motor commands that produce related movements: “class of actions”
-ex. throwing can be done underhand, overhand, sidearm etc. (all have the same goal)
A generalized motor program (GMP) controls
a CLASS of actions rather than specific movements/sequences
Components of the GMP
- Invariant features= features of the command that remain almost the same each time
- Parameters= ways that the command can be varied
Invariant features
-features remain almost the same.
-all motor skills within a class of action will have similar features
-ex. saccades: direction, amplitude may vary but kinematic profiles remain the same
Parameters
-variants
-can be added to invariant features to meet specific movement demands of a situation
Motor schema response concept
provides rules that decide the performance of a skill in a given situation/context
-selects parameters for motor program
-ex. you have an idea of what walking entails (moving your legs)
schema
a rule/set of rules that provide the basis for a decision
-identifies the class of action
-ex. you have seen many dogs, they range in appearance, you have developed a schema/set of rules for identifying a dog
Motor equivalence
varying parameters produce the same output
motor equivalence:
writing name w different body parts example
parameter= using different body parts
invariant features= aspects of the written text (the shape of letters, the general shape of words)
does the nervous system store sequences of commands to be sent out to spinal circuitry?
NO!!! there are wayyy too many sequences to store.
A motor program (rules for generating motor commands) can be stored.
motor programs are planned before the movement. can they be adjusted if the task requires it?
YES! sensory feedback can be used
-sensory feedback: stretch receptors
-visual feedback:
Limitations of sensory feedback
-Delays of sensory feedback: processing and integrating
-Noise: the info is not always accurate
-Encoding issue: needs common encoding (sensorimotor integration problem)
-Distinguishing between reafference and exafference
Delays
(sensory feedback)
the longer the path of travel, the longer the sensory info is delayed
Noise
(sensory feedback)
- Sensor noise= inaccurate/noisy sensory receptors
- Motor noise= noise in motor commands, results in variable movements
- Sensorimotor noise= noise from combining sensory feedback signals and transforming info to motor system
Potential causes of sensory noise
-Ion channel properties (random opening and closing)
-Spontaneous action potentials generated by receptors/neurons
-Muscle fatigue
Reafference
self generated motor behaviour
Exafference
external events of stimuli
How is your vision not blurry when you move your eyes to look at something (saccade)
nervous system uses predictive signalling (from efference copy signals)
Internal Models
-understand how the body works
-processes occur in the brain
-different brain regions responsible for different aspects
-argued to exist in the spinal cord
-develop over time (through experience)
3 types of internal models
- Cognitive model
- Inverse model
- Forward model
cognitive internal model
-how external objects work based on prior experience with the object/similar object (we know a ball bounces)
-you act differently depending on what the object is
-you choose a goal depending on the object or hazard in environment
inverse internal model
calculates motor commands needed from desired trajectory information