Visual feedback Flashcards
Mastery
Exteroception:
what most important
Exteroception: Sensory information that tells us about the state of our body in relation to the world around us
Visual information is the most dominant source of exteroceptive feedback for motor control
what do mammalian eyes contain
what happens to cells membrane
RODS, CONES
Mammalian eyes contain specialized cells called photoreceptors. They absorb photons, triggering a change in the cell’s membrane potential. HYPERPOLARIZE
Rods: Human retina contains ~90-120 million rod cells. They are concentrated in peripheral portions of the retina.
Cones: Human retina contains ~4.5 million cone cells. They are concentrated in the central portion of the retina (fovea), have high spatial resolution and specialize in colour vision.
How do receptive fields change from distance from the fovea
cells in the fovea have what
what are cells in the periphery specialized in
where are rods, and what
where and cones and what
receptive fields grow
higher spatial resolution
specialized in motion detection
rods are concentrated in the periphery, low visual activity, sensitive to motion
cones are concentrated in the fovea, high visual activity, colour vision
Dorsal stream
ventro dorsal. - you can group them
Ventral stream
what are the purposes of these visual pathways
Dorsal Stream: ‘Where’ Pathway uses vision for action guidance.
Ventro-dorsal stream: visuomotor transformations for grasping. Also important for interpreting the actions of
others.
Ventral Stream: ‘What’ Pathway uses vision for perception (i.e., orientation).
Distinct visual pathways govern the use of visual feedback for perceptual judgments and online control of actions
Ventral Stream, uses
name of the issue, problem
where does it enter goal-directed processing
The ventral stream is used for object identification and recognition (perception)
form agnosia, affect the ventral
ventral stream damage can cause selective impairments in conscious object perception but intact control of objects
cant give meaning to objects, but can act thru actions
enters at stimulus ID
Dorsal stream, uses
name of the issue, problem
where does it enter goal-directed processing
Dorsal stream is used to correct ongoing actions
part of the response programming
optic ataxia
damage to structures in the dorsal stream, causes selective impairments in the inability to use vision to guide reaching movements
enters at response programming, processing of visual info
Optic flow
when the object is closer
Information provided by optic flow
time to contact
When the object is closer to the eye, the size of the image on the retina changes at a faster rate.
Information 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 through the environment
rate of expansion increases as the time to contact increases, the exponential rate of expansion
importance of visual feedback in goal directed actions
vision helps a lot more during slow movements
vision helps improve accuracy in slow deliberate movements
Dorsal and ventral stream and where it enters the goal processing
The dorsal visual stream enables fast, stimulus-dependent control of visual feedback.
The ventral visual stream enables (somewhat) slower, task-dependent control of visual feedback.
dorsal enters at response programming, fast loop, just helps change in movements, and tells us where we are in space
ventral enters and stimulus ID, slow loop, helps with goal and task-dependent control. Tells us if its a glass of water or juice or something like that
