internal models Flashcards
what is an internal model
relationship between actions and the properties of the body and environment
(forward or inverse)
what is an inverse model
calculating the motor commands that are required to move the arm to accomplish a specific goal based on the difference between goal and current position
what are the different ideas of how inverse models are completed
- select motor commands that minimse energetic cost of mvmt
- select motor commands that minimise variance of mvmt endpoints
(all models assumes the NS has an accurate representation of the physical properties of the body and environment)
what does the brain need to know in the inverse model
- length of segments
- centre of mass
- inertia of the arm segments
- initial and final joint configurations
what are the inverse kinematics involved in the inverse model
takes hand trajectory as input and determines the joint angle required to produce it
what does inverse kinematics require
length of segments
initial and final joints configurations
what are the inverse dynamics involved in the inverse model
takes joint motion profiles as the input and calculates the torques required to produce them
what does inverse dynamics require
length of the segments
inertia and centre of mass
interactions between segments
what is a forward model
models the sensory consequences of action (motor command underway)
estimates the sensory consequences of action using efference copies of descending motor commands and representations of properties of the body and environment
what does the forward model need to know
length of segment
centre of mass
segment inertia
what is the pathway for the forward model
- efference copies of descending motor commands are combined with a rep of the body to estimate the resulting body motion
- estimated motion is used to predict the associated sensory feedback
- estimated and actual sensory feedback are compared
what is a comparator
subtracts predicted sensory feedback from actual sensory feedback
difference = discrepancy between expectations and reality
what does a comparator create
creates error signal that can be used to update the motor command
sensory based correction
what info does the anterior lobe of cerebellum receive
somatosensory feedback from the upper limb
what info does the posterior lobe of cerebellum receive
visual feedback
