4.12 - Embodied Models of Brain Function

Question 1

Describe how coarse anatomy can explain simple behaviours.

Answer 1

Braitenberg vehicles are nice examples of how simple and even somewhat complex behaviour can be explained with the use of very coarse models. What Braitenberg did was create very simple vehicles and observe how they would behave.

One example is called “Fear”, a vehicle that has two sensors (that respond to light) and two motors. Upon getting closer to a light source, the vehicle will accelerate. But when the light gets off to one side of the vehicle, the motor of that side will drive faster, causing the vehicle to move away from the light source.

Question 2

What are muscle synergies?

Answer 2

A muscle synergy is the activation of a group of muscles to contribute to a particular movement, thus reducing the dimensionality of muscle control. A single muscle can be part of multiple muscle synergies, and a single synergy can activate various muscles.

Question 3

Explain the role of transformations in sensorimotor loops.

Answer 3

Sensory-motor coupling is the loop or integration of the sensory system and the motor system. This integration allows an animal to take in sensory information (e.g. sight) and use it to produce the correct motor behaviour. Sensory-motor integration is a flexible process because the world and we change over time, an internal model is used.

To generate a motor command, the sensory coordinates are transformed into motor coordinates.

1. Current sensory state is compared to the desired or target state.
2. The nervous system transforms the sensory coordinates into the motor system’s coordinates and the motor system generates the necessary commands to move the muscles so that the target state is reached.

Question 4

What is a linear system?

Answer 4

A system is anything with an input, a body where the input it being processed, and an output (e.g. people, brain, camera).

A linear equation has a constant rate of change and can be written in the form y = ax + b; where a,b are both constants and x a variable.

A System of Linear Equations is when we have two or more linear equations working together.

Question 5

What are two ways you can test whether a function is linear?

Answer 5

1) A quick test; multiplying the input with some number k, and checking whether the output is scaled with the same ratio.
2) The superposition princple; for all linear systems, the net response caused by two or more stimuli is the sum of the responses that would have been caused by each stimulus individually. That is, if input A produces response X and input B produces response Y then input (A + B) produces

response (X + Y).