Movement Perception Flashcards
True or False
We don’t directly perceive movement. In reality, the only thing that we directly perceive is a sequence of fixed images. Movement is an inference that we make based on those sequences of still images.
True
Akinetopsia
A rare neuropsychological disorder in which the affected individual has no perception of motion.
This can be caused by lesions of areas MT and MST
What part of the brain perceives movement?
The part of the brain that perceives movement is the area MT.
If you injure that area you will not perceive movement but you will still perceive a sequence of still images.
Apparent Motion
The illusory impression of smooth motion resulting from the rapid alternation of objects that appear in different locations in rapid successions.
Motion Detection Circuit
- M neuron registers a change of position
- Neuron D incorporates delay
- Do this across many X comparator neurons
“What” Pathway
P ganglion cells receive information from the midget bipolar cells. P cells then project to the parvocellular layers of the LGN.
Notice that the P ganglion cells have a small receptive field. The high-resolution information coming from these P cells is at the origins of the ventral“what” pathway.
True or False
V4 is an area that specialises in motion.
False
V4 is an area that specialises in colour perception
“Where” Pathway
M ganglion cells receive inputs from diffuse bipolar cells. Then, M cells project to the magnocellular layers of the LGN.
Notice that M ganglion cells have a larger receptive field and are more sensitive to movement.
Correspondence Problem
The problem faced by the motion detection system of knowing which feature in frame 1 corresponds to which feature in frame 2
Aperture Problem
The fact that when a moving object is viewed through an aperture, the direction of motion of a local feature or part of an object may be ambiguous.
True or False
Motion information from several local apertures (or receptive fields) can be combined to determine the global motion of the object.
True
True or False
There are several directions of motion within each aperture that are compatible with the stimulation the receptor is receiving.
Whichever possible motion direction is the same in all apertures is the true global motion direction of the object.
True
Motion After Effects (MAE)
The illusion of motion of a stationary object produced after prolonged exposure to a moving object.
Existence of MAE implies an opponent process system, like that of colour vision.
Types of Eye Movement
- Smooth Pursuit
- Saccade
- Vergence
- Reflexive Eye Movement
- Microsaccade
Smooth Pursuit
Voluntary eye movement in which the eyes move smoothly in order to follow a moving object.
Saccade
A type of eye movement, voluntary or involuntary, in which the eyes rapidly change fixation from one object or location to another.
Reflexive Eye Movement
Automatic and involuntary eye movements.
For example, when the eyes move to compensate for the head and body movement while maintaining fixation on a particular target
Microsaccade
An involuntary small jerklike eye movement.
- Prevent visual fading
- Allowing us to see behind the blood vessels in our eyes
- Improve visibility of sharp objects
- Compensate for the sudden loss of acuity a few minutes outside the fovea.
How many muscles are attached to an eye and how are they organised?
Six muscles are attached to each eye and are arranged in three pairs
How are eye movements controlled?
Six muscles are attached to each eye and are arranged in three pairs. Controlled by an extensive network of structures in the brain.
Superior Colliculus
A structure in the midbrain that is important for initiating and guiding eye movements.
Different neurons in the SC (superior colliculus) produce different eye movements
Frontal Eye Field
A structure in the frontal lobe that is important for initiating and guiding eye movements.
Different neurons in the FEF (Frontal Eye Field) will move the eye to different spots in space (irrespective of the actual movement required).
Saccadic Suppression
The reduction of visual sensitivity that occurs when we do saccadic eye movements.
Saccadic suppression eliminates the smear from retinal image motion during en eye movement.
Comparator
An area of the visual system that receives one copy of the order issued by the motor system when the eyes move (the other copy goes to the eye muscles). The comparator can compensate for the image change caused by the eye movement.
