Lecture 2:
Saccades and Seeing:
Eye-movement causes havoc to the content of the retinal image.
Self-movement shifts & moves images:
Fixation- if you focus on a stationary object whilst something moves across the
retina the person appears to
be moving whereas the room
appears stationary.
During Pursuit- follow the
moving target, which remains
stationary as it is ‘glued’ to
the eye on the fovea, so
everything else appears to be
moving.
During Saccades- every time the eyes hop/move we should perceive huge
motion but we don’t see it… why?
The Bigger Problem:
The visual system continually needs information relative to spatial information.
When the circle moves and you follow the circle, the square moves
on the retina, but it appears stationary in the world, whereas the
circle is stationary (because it is stationary on the fovea), but we see
it as moving. There are different ways of looking at this, eye-centred,
world centred and ego-centred.
Circle= in the world its moving, and relative to the body it is moving,
but is stationary on the retina.
Square= stationary in the world (world-centred) and stationary relative to the
head/body (ego centred), but it moves on the retina (eye-centred).
World centred judgements= Simon’s things, like flow parsing.
Ego centred judgements= how you judge the position of motion, Tom’s stuff.
Need to know how the head and body are moving, otherwise wont know how it
is relative. This information comes from the motor system or vestibular system,
not actually thinking about moving. These are extra retinal signals- things that
didn’t originate from the retina, so information that comes from the motor
system or vestibular system.
Extra Retinal Signals:
Image information=eye-centred
Measurements= eye-centred
Interpretation= can be ego-centred.
Action interacts with the loop in different
ways, and ERS come from the action system
and allow us to interpret information about
movement on the retina.
The ERS come from the action systems and
help us to measure information on the retina.
They can be either efferent (outflow- motor
commands to the muscles of the eye, neck or legs etc.), or afferent (inflow-
proprioceptive feedback from muscles, information from vestibular system).
Saccades and Seeing:
Eye-movement causes havoc to the content of the retinal image.
Self-movement shifts & moves images:
Fixation- if you focus on a stationary object whilst something moves across the
retina the person appears to
be moving whereas the room
appears stationary.
During Pursuit- follow the
moving target, which remains
stationary as it is ‘glued’ to
the eye on the fovea, so
everything else appears to be
moving.
During Saccades- every time the eyes hop/move we should perceive huge
motion but we don’t see it… why?
The Bigger Problem:
The visual system continually needs information relative to spatial information.
When the circle moves and you follow the circle, the square moves
on the retina, but it appears stationary in the world, whereas the
circle is stationary (because it is stationary on the fovea), but we see
it as moving. There are different ways of looking at this, eye-centred,
world centred and ego-centred.
Circle= in the world its moving, and relative to the body it is moving,
but is stationary on the retina.
Square= stationary in the world (world-centred) and stationary relative to the
head/body (ego centred), but it moves on the retina (eye-centred).
World centred judgements= Simon’s things, like flow parsing.
Ego centred judgements= how you judge the position of motion, Tom’s stuff.
Need to know how the head and body are moving, otherwise wont know how it
is relative. This information comes from the motor system or vestibular system,
not actually thinking about moving. These are extra retinal signals- things that
didn’t originate from the retina, so information that comes from the motor
system or vestibular system.
Extra Retinal Signals:
Image information=eye-centred
Measurements= eye-centred
Interpretation= can be ego-centred.
Action interacts with the loop in different
ways, and ERS come from the action system
and allow us to interpret information about
movement on the retina.
The ERS come from the action systems and
help us to measure information on the retina.
They can be either efferent (outflow- motor
commands to the muscles of the eye, neck or legs etc.), or afferent (inflow-
proprioceptive feedback from muscles, information from vestibular system).
