Lectuer 1 Flashcards
Why do we move they eyes
To improve input from the outside world by bringing an image onto the fovea and keeping it there
What is the role of the occipital lobe in the visual system
It is the receiving station from the eye
What’s is the role of the Parietal lobe in the visual system
It is responsible for object location
What is the role of the anterior lobe in the visual system?
To recognise objects
What is the role of the frontal lobe inn the visual system?
To control eye movement
What are the diffrent types of eye movements?
Saccades
Fixations
Smooth pursuit
Otokineatic nystsagmus
Vestibular ocular reflex
Vengeance movements
How does the eye scan a visual scene
Fast eye moments (saccades) and steady fixations
What is the purpose of VOR?
To stabilise the image when the body or head is moving
What is the purpose of smooth pursuit?
It track a moving object
What is the purpose of optokinetic nystagmus?
To track a whole moving visual field
A saccade is
Very fast (900 degrees per second)
Voluntary
Conjugate
What comprises a fixation
Microscaadees drift and tremor
What are the features of smooth pursuit?
It’s voluntary(althiuyghn needs to see a moving target)
Requires the brain to estimate how fast a target is moving
It’s conjugate
What are the features of OKN
Has a slow and fast phase slow inn the direction of the target and fast to reset the eyes.
It is involuntary and driven by a moving visual field
And conjugate
What are the features of VOR
Keeps gaze steady
Extremely rapid
Involuntary (driven by vestibular system)
Conjugate
What part of the vestibular system measures head rotation?
The semicircular canals (which lie in three orthogonal planes)
What part of the vestibular system measures changes in horizontal movement?
The utricle
What part of the vestibule system measures vertical acceration?
The saccule
What are the the features of vergance eye movements?
Disconjugate
Voluntary
What parts of the brain control diffrent parts of the saccade?
The cortex selects and analyses targets.
The basal ganglia suppresses the initiation of a saccade
The superior colliculus determines the size of the saccade
The brain steam generates the saccades velocity and time
How does the brain steam initiate and maintain a saccade?
There is a pulse step machism, tho overcome the intial and viscoses forces if the eye and then a step to maintain the eye against eleastic forces.
How will saccades be effected by damage to the brain steam?
They may be
Absents as the brain steam is responsible to generate saccades
Slow and limited movement as it is responsible for velocity
What do we mean when we say the superior colliculus is retinotopic?
It refers to the fact that the visual input is mapped to neurones
What does the superior colliculus control in saccades?
Direcets saccades towasers relevant targets due to it retinotopic and neural activity patterns.
Role in the initiation of saccades
Contributes to the speed of the saccade
What will we see if there is damage to the superior colliculus?
There will be less spontaneous scaages towards a particular direction
Overall fewer scaccdes away from a fixation target
Reduced litany express saccades
How does the basal ganglia affect saccades?
Acts as a gate, and when controlled by the cortex disinhibits the target selected allowing for a saccade to be made, also prevents unwanted reflexive saccades to disruptive stimuli
What will damage to the basal ganglia lead to in terms of saccades?
May be problems in
Suppression of saccades
Initiation of saccades in tasks that require learned or predictive behaviour
And reduced dis inhibition leading to reduced movement- ie in Parkinson’s
How are terternally generated movements move the eyes ?
The frontal eye fields are the main area involved in issuing commands to move the eye, it receives input form the prefrontal cortex and parietal cortex and outputs to the basal ganglia, basal gangia to superior collie curls and then brain steam to move eyes.
In externally gene treated movements the parietal cortex feeds the FEF and this lead to eye mpbvemnt
How are internally generated moments reach the eye
Prefrontal cortex, to FEF then to basal ganglia to superior collicus to break steam to eye
