Lecture 23 - Visual Feedback to Control Voluntary Motor-Actions Flashcards
What is the dorsal visual stream important for?
Controlling actions
What is the ventral visual stream important for?
perceptual judgements
What is exteroception?
Sensory information that tells us about the state of our body in relation to the world around us
What is the most dominant source of exteroceptive feedback for motor control?
visual information
What are the 2 photoreceptors in human eyes?
Rod and cones
Are there more rods or cones?
rods (90-120 million)
cones have about 4.5 million
Where are rods concentrated?
peripheral portions of the retina
Where are cones concentrated?
central portion of retina (fovea)
Which photoreceptors have high spatial resolution (visual acuity) and specialize in colour vision?
cones
Where does the specialization of visual pathways for perceptial judgments and online control of actions begin?
The retina
What happens to rods and cones when they interact with light?
They hyperpolarize
What are rods senstive to?
Motion
Do rods or cones have multiple cells attached to one ganglion?
Rods
What is the dorsal stream know as?
the ‘where’ pathway
What is the ventral stream know has?
The ‘what’ pathway
What does the dorsal stream use vision for?
Action guidance
What does the ventral stream use vision for?
perception (ie. orientation)
What is the ventral-dorsal stream for?
Group with dorsal stream
visuomotor transformations for grasping and important for interpreting the actions of others
Which stream is used for object identification and recognition (perception)?
ventral stream
What is form agnosia?
Ventral stream damage
can cause selective impairments in conscious object perception but intact control of actions
Is the ventral or dorsal stream unconscious visual processing?
dorsal
Is dorsal or ventral stream slow processing of visual information?
ventral
Which stream does visual feedback processing occur, and is used to correct ongoing actions?
Dorsal
What is damage to the dorsal stream called? What does it cause?
Optic ataxia
selective impairments in the inabiklity to use vision to guide reaching movements (cannot orient hand properly to fit in a slot
What could cause optic ataxia?
Stroke or physical trauma
What is optic flow?
Light moving across the retina
optic flow
What occurs when the object is closer to the eye?
Size of the image on the retina changes at a faster rate
What informnation is provided by optic flow?
- time to contact
- direction of movement relative to objects in environment
- movement of objects in the environment
- stability and balance
- velocity of movement rhough the environment
Optic flow
Rate of expansions increases as time to contact _____?
decreases
Does vision help improve the accuracy of slow, deliberate movements or fast movments?
Slow deliberate movements (light less useful for faster movements)
