Vision Flashcards
wavelength is to intensity as
colour is to brightness
depth of focus can be increased by
constricting the pupils
What is an important depth-perception cue?
binocular disparity
Where are the visual receptors?
the last layer of the retina to be reached by the light entering the eye
What can be found on the blind spot?
the axons of retinal ganglion cells
Because of optic disks we have?
a blind spot in the visual field of each eye
Colour is mediated by
photopic system
what is the Purjunkie Effect?
lights in the green-blue portion of the spectrum are brighter than equally intense lights in the yellow-red portion of the spectrum when viewed under dim illumination
What are eye movements called?
Saccades
Primary visual cortex neurons are
grouped in functional vertical columns
what is binocular disparity?
the difference in the position of the same image on the two retinas; greater for closer objects
what are stellate cells?
small star shaped interneurons
what is a blind spot?
for the bundle of retinal ganglion cells axons to leave the eye there must be a gap in the receptor layer
What is the fovea?
an indentation at the centre of the retina that is specialised for high acuity vision
what is the fovea specialised for?
high acuity vision
what is a spectral sensitivity curve?
a graph of the relative brightness of the same intensity at different wavelengths
what is a photopic spectral sensitivity curve?
judge the relative brightness of differenet wavelengths shone at the fovea
what is the scotopic spectral sensitivity curve?
judge relative brightness of different wavelengths shone on the peripheral area of the retina at an intensity too low for cones to detect
Why doesn’t the world disappear when we blink?
temporal integration
what are mach bands?
they enhance the contract at each edge and make the edge easier to see
what are simple cells?
cells that have receptor fields that can be divided into on and off regions
What is the component theory?
colour has three different kinds of receptors
what is the opponent processing theory?
two different classes of cells for encoding colour and another for brightness
What is Hemiaopsic?
having scotoma covering half of the visual field
what is a scotoma?
an area of blindness in the corresponding area of the contralateral visual field.
what is the order of the retinal geniculate striate system?
retinal ganglion cells, lateral geniculate neurons, striate neurons
What is a rhodspin?
a red pigment extracted from a rod
what happens when a rod is in the darkness?
their sodium channels partially open causing the rod to be partiall depolarized
What happens in scotopic vision?
lack of colour, dim light, low acuity. ,pore sensitive
how many rods are there on one ganglion cell?
100
Are there any rods in the fovea?
no
what does photopic vision mediate?
in good lighting, high acuity and colour
A few cones converge onto how many ganglion cells?
on ganglion cell
what are bipolar and amacrine cells specialised for?
lateral communication
Complex cells are?
binocular, rectangular and unresponsive to diffuse light.
what is the parvocellular level?
a communication channel responsive to colour
what is the magnocellular level
a communication channel responsive to movement and rods
What are on centre cells in comparison to off centre cells?
they respond to light shone at the central region of their receptive cells with on firing and off firing if light is shone at the periphery whereas off centre cells respond to light shone at the periphery of their receptive cells with on firing and on the centre with off firing.
