Neuroscience Of Perception Flashcards
Outline the pathway of visual processing in simple terms?
Retina to LGN to V1 to multiple areas
What is the first initial stage of visual processing?
The light projects an image to the back of the retina which is then inverted.
-The photoreceptors sit at the back which respond to electromagnetic waves and photons which then turns the physical input into action potentials.
The electrical signal then goes through intermediate layers horizontal and amacrine cells. The Bipolar cells is responsible for this transmission.
The ganglion cell then generates another electrical signal that will leave the retina towards the brain.
What is the density or distribution of photoreceptors in the retina?
The cones are in the very centre of the fovea where they are very dense which gives them high acuity. Not many in the periphery out of the fovea.
The rods are not in the middle of the fovea but very dense at the periphery but more dense the closer to the fovea.
What is the fovea and where is it?
The back of the centre of the retina and it is where the image of the light is projected.
What are cones responsible for?
Capturing colour and they need a well lit environment in order to work properly
What three cones Do we have ?
S-cones which are sensitive to short wavelengths such as blue
M-cones which are sensitive to medium wavelengths such as green
L-cones which are sensitive to longer wavelengths such as red
Describe the process of colour detection of cones?
They do not respond to one single wavelength but a range of wavelengths. The photoreceptors are still active when the radiation is outside the wavelength of maximum responsiveness.
Since they are sensitive to a specific window of frequencies, they filter part of the information from the environment.
Describe the function of rods?
They are concerned with light intensity and work best in dimly lit conditions.
They provide information about different shades of grey.
Why is there a blind spot beside the fovea on the right?
It is where the Nerve Fibres of the ganglion cell that leave the eye. (Optic nerve)
There are no photoreceptors on the blind spot so no vision is possible.
How do you study the property of the ganglion cell?
Stick an electrode in the axon of the ganglion cell to measure the speed or rate of the electrical signal.
What are ganglion cells also known as?
Output units.
describe the structure of a ganglion cell?
It is made of many dendrites and are receiving input from photoreceptors.
What two types of ganglion cells do we have?
M cells aka Mango : low resolution, transient (brief response to resolution)
P cells aka Parvo: high resolution, sustained, colour
What pathways does the ganglion cell feed into?
Dorsal and ventral pathway which feeds into the Lateral geniculate nucleus.
What do the axons of the ganglion cells (m and P cells) form?
The optic nerve which leaves the blind spot.
Describe the function of ganglion cells
Integrate information received by the photoreceptors so that they respond to stimulations of small regions of the retina.
How is the flow of information modulated from ganglion cells?
They are modulated by cells transversally (amacrine cells)
What is the P cell responsible for?
they show slow and sustained responses
They convey information about colour and fine details and have high spatial resolution
What are M cells responsible for?
They have low spatial resolution, show transient responses (they reach a peak and fall of rapidly).
They are very sensitive to timing of stimulation and so ideal for detecting motion.
What pathway does The P cell feed into?
Parvocellular pathway
