Higher Visual Processing Flashcards
From where are the visual information streams segregated?
From retina to visual cortex
Is information from each eye mixed in the thalamus?
No
What type of information do M ganglion cells carry?
Motion
What type of information do P ganglion cells carry?
Colour
What is the input layer from the thalamus into sensory cortices?
Layer IV
In which layer of V1 do M cells terminate?
Layer IVC alpha (superior)
In which layer of V1 do P cells terminate?
Layer IVC beta (inferior)
Which layer of V1 is important for motion detection?
Layer IVB
From layer IVC, where does information go?
Other layers of V1
To what area do layers II, III, and IVB send their information?
Other cortical areas like
- V2, 3, 4, 5
- MT
To what area does layer V send its information?
Superior colliculus
Pons
To what area does layer VI send its information?
Lateral geniculate nucleus
What is the diameter of M ganglion cells?
Large
Are M ganglion cells wavelength sensitive?
No
To what part of the brain do M ganglion cells project?
Magnocellular layer of LGN
Where do M cells from the thalamus project to?
Layer IVC alpha of V1
Where do cells from layer IVC alpha project to?
Layer IVB of V1
Where does mixing of information from the two eyes occur?
In layer IVB of V1
What kind of selectivity do some cells have in layer IVB?
Orientation selectivity
Directional selectivity
How much of the cortex is involved in vision?
40%
What is the Brodmann’s area of the secondary visual cortex (V2)?
Area 18
What are the two streams of visual processing?
Dorsal
Ventral
What does the dorsal pathway process?
Where; eg: movement
What does the ventral pathway process?
What; eg: object recognition
What is area MT?
In middle temporal lobe
Specialised for processing object motion
Where does MT receive information from?
Range of cortical areas including V2 and V3
Direct input also from layer IVB of V1
What is the size of the receptive fields in area MT?
Large
What do the receptive fields of area MT respond to?
Movement
What kind of selectivity do cells in area MT have?
Directional selectivity
What kind of columns does area MT have?
Direction of motion columns
What produces the perception of white light?
Equal activation of red, green, and blue cones
What allows the first response in the perception of colour?
Combined response of all 3 cones
What kind of receptor field do some P ganglion cells have?
Colour opponent centre-surround
Describe red ON-centre P ganglion cells
Centre responds to red
Surround responds to green
Describe blue ON-centre P ganglion cells
Centre responds to blue
Surround responds to yellow
Describe the receptive fields of neurons in V4
Large
Orientation selective
Colour selective
What is V4 important for?
Perception of shape and colour
Where is area IT?
In inferior temporal lobe
What do neurons in area IT respond to?
Wide variety of abstract shapes and colours
What is area IT important for?
Visual memory
Perception, especially of faces
Are colour deficiencies acquired or inherited?
Both
What proportion of males and females have colour blindness?
8% of males
0.5% of females
What is monochromacy?
Have only one type of cone - usually blue
What is dichromacy?
Have only two types of cones
What is anomalous trichromacy?
Have all three types of cones, but one expresses abnormal pigment and doesn’t work the same as normal cones
What is protanope?
No red cone
What is protanomal?
Abnormal red cone
What is deutanope?
No green cone
What is deutanomal?
Abnormal green cone
What is tritanope?
No blue cone
What is tritanomal?
Abnormal blue cone
What does it mean to be colour blind?
Trouble dealing with colour in everyday life
How can you test for colour blindness?
Using pseudoisochromatic plates
