4.12 - Embodied Models of Brain Function Flashcards
How can coarse anatomy explain simple behavior?
Coarse anatomy can explain simple orientational behaviors, called ‘taxes’, such as phototaxis (orienting towards light), phonotaxis (orienting towards sound), chemotaxis (orienting towards chemical concentration)…
Braitenberg vehicles are examples of how simple anatomy can lead to interesting behaviors when embedded in the sensorimotor loop.
One example is called “Fear”, a vehicle that has two sensors that excite two motors, ipsilaterally. Upon getting closer to a light source, the vehicle will accelerate and move away from the source.
If the two sensors inhibit motors contralaterally, we can talk about being attracted by light.
What are muscle synergies?
A muscle synergy is a group of muscles and their skeletal constraints that contribute to a particular (stereotypical) movement.
(“Their action is more than the sum of their parts”).
Muscle synergies reduce the dimensionality of muscle control. Single synergies activate multiple muscles.
Explain the role of transformations in sensorimotor loops.
Sensorimotor coupling is the loop between the sensory system and the motor system that is closed via the environment.
This integration allows an animal to transform sensory information (e.g. sight) into motor behavior.
What is a linear system?
A linear system is a system that obeys the additivity and the homogeneity properties.
additivity:
f(x+y) = f(x) + f(y)
homogeneity
f(a.x) = a . f(x)
What are two ways you can test whether a function is linear?
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).
What are decussations?
Decussations are fiber crossings that connect non-homologous areas of the brain. Such as sensors and actuators.
What is a ‘system’?
def 1. A system is something that converts input to output (animals, cameras, computers).
def 2. (etymology) A system is a ‘whole’ made of ‘parts’
(Figure: a black box converting stimulus to a response)
What concept is depicted in this figure?
a “system”
What are sensorimotor loops?
The idea that motor actions create specific feedbacks to the sensory systems.
Another way to say this is that the embodiment of the brain necessitates certain aspects of the feedback.
What is the importance of embodiment?
To explain brain function one often needs to include the body as part of the explanation.
Examples include the curvature of eyeballs related to visual processing. Distance between eyes is related to parallax and estimation of distances. The inertia (mass) of the arm is required to explain grasping.
What is non-linearity?
It is any deviation from a linear relationship between input and output of a system.
Common non-linearities in neural systems include ‘saturations’ and ‘thresholds’.
What is a sensorimotor contingency?
It is a quantifiable and predictable relationship between motor action and its sensory consequence.
What are degrees of freedom of a joint?
the number of independent types of motion that the join can produce (e.g., rotation, translation…)
Why do we say that the neural motor control system is redundant?
because there are more muscles than ‘degrees of freedom’
What is the projection scheme from motor neurons and muscle fibers?
One motor neuron projects to different muscle fibers, but a single muscle fiber receives from a single motor neuron
https://nba.uth.tmc.edu/neuroscience/s3/chapter01.html
