Functional Anatomy of the Visual System (Level 5) Flashcards
How is visual stimulation encoded?
Via photoreceptors on the retina which contain light-sensitive photopigments.
What is the most intensively studied area in cognitive neuroscience?
Vision
What gives rise to an electrical signal which is transported via bipolar cells to retinal ganglion cells?
The absorption of light by light-sensitive pigments contained in photoreceptors on the retina.
What transmit visual information from the eye to the lateral geniculate nucleus (LGN)?
Retinal ganglion cells
How many types of photoreceptor are there?
Two
Which type of photoreceptor is sensitive to low levels of stimulation, and is therefore useful for night vision?
The rod photoreceptor
How are rods distributed throughout the retina?
Equally
What kind of stimulation do cones require?
Higher levels than rods
Why are cones mainly used for daytime vision?
Because they require higher levels of stimulation than rods.
How are cones distributed throughout the retina?
They are densely packed at the retinal centre (the fovea) and decrease in frequency towards the periphery of the retina.
How do cones differ?
In their sensitivity to different wavelengths.
What are essential for colour vision?
Cones
What connects the retina via the LGN to the primary visual cortex (V1) in the occipital lobe?
The major visual pathway
What happens to information transmitted via the axons from the temporal retina?
It goes to the cerebral cortex of the same side because these axons do not cross the midline.
Which cells have concentric receptive fields and an inhibitory surround?
The cells of the LGN
Which cells are maximally excited when a small spot of light excites the centre of their receptive field?
The cells of the LGN
Which cells are inhibited when a small spot of light stimulates the surround of their receptive fields?
The cells of the LGN
How many layers does the LGN consist of?
Six
How many eyes does the LGN receive input from?
Only one (monocular input)
How many layers of the LGN are termed magnocellular because of large-diameter axons?
Two
How many layers of the LGN contain small-diameter fibres and are called parvocellular?
Four
How many layers does V1 contain?
Six
Which techniques reveal areas of higher metabolic activity (blobs) surrounded by less active regions (interblobs) in V1?
Cytochrome oxidase staining techniques
What does V1 contain which are driven by monocular input?
Ocular dominance columns
Which cells within ocular dominance columns have similar orientation preferences?
Neighbouring visual cells
What varies continuously when a recording electrode is moved along the cortex?
The orientation sensitivity of neighbouring visual cells within ocular dominance columns.
How do V1 cells achieve their orientation sensitivity?
By combining the inputs of several LGN cells.
Where is the retinotopic representation of the LGN maintained?
In V1
To where is information from V1 projected?
To other cortical areas that are specialised in terms of their preferred input.
In general, what is the response profile of cells like in ‘higher’ visual areas?
It is relatively complex
What are the receptive fields of ‘higher’ visual areas like?
They are relatively large.
Where does visual processing continue after that occurring in V1?
Within specialised processing modules that are responsible for the processing of different visual features.
What is used for the ‘higher-order’ visual processing by mechanisms responsible for object identification?
The output of specialised processing modules that are responsible for the processing of different visual features.
Where does the initial analysis of colour and motion take place?
Within independent and anatomically distinct brain regions.
Which regions are connected to different parts of the geniculostriate pathway?
The independent and anatomically distinct brain regions in which the initial analysis of colour and motion takes place.
What has the magnocellular pathway been found to be very sensitive to, rather than colour?
Movement
How does the parvocellular pathway differ from the magnocellular pathway?
The parvocellular pathway is colour-sensitive but virtually motion-blind.
