Vision Flashcards
What is the objectivist, the subjectivist and the synthetic view of vision and perception ?
- Objectivist - the senses create an accurate representation of the world
- Subjectivist - The senses create a world due to them organising their input
- Synthetic - The senses evolved to reflect some of the world very accurately
what is perception and sensation ?
Sensation is a stimulation of a sensory organ
Perception is the way the senses organise and interpret their input of stimulus in the brain
What is transduction ?
the convergence of the physical signals from the environment to the neurone signals of the central nervous system.
What are the properties of light ?
Light travels in waves. Objects are seen because of the way the light reflects off them.
-Amplitude - the ‘height’ of the wave - the amplitude determines the brightness the image is seen in.
-Length - the length of the wave determines the colour - short wave length = violet light , long wave length = red light in human eyes
-Purity - the purity is the length of the whole wave
this determines the saturation of the colour
where are photoreceptors found ?
The retina at the back of the eye
Why is the first representation of the object upside down ?
The lens transducts the light as it enters the eye - this means that the first representation of the image will be recieved upside down.
how does light enter the eye ?
- light enters through the pupil
- the lens and the cornea focus the light
- light is reflected onto the retina where there are many photoreceptors
- the photoreceptors are excited by the light
What cells make up the optic nerve ?
The basal ganglia , the bipolar cells - they join at the back of the retina to form the optic nerve - this grouping of axons is the point of the blind spot in the eye.
what is the difference between the cornea and the lens of the eye ?
the cornea is not adjustable where as the len is adjustable by the muscles in the eye
What is the fovea ?
the fovea is the central part of the retina, it is here that the vision is more detailed, in this part each receptor connects to one bipolar cell and in turn connects to one ganglion cell.
What is the receptive field ?
the receptive field is the region of the sensory surface that a be stimulated and can cause a change in the firing rate of the cells
What are the types of photoreceptors in human eyes ?
Rods and cones - there are always more rods than cones. the cones are for perceiving colours . there are different cones to respond to different lengths of light
the rods are situated more abundantly in the periphery of the eye.
What happens in the primary visual cortex?
the primary visual cortex is the link from the eyes, to the brain.
the axons will cross over so half of the axons from each eye swap sides at the point of the optic chasm
information is sent from the optic chasm to the the thalamus and the visual cortex.
What is the hypercomplex cells ?
hypercomplex cells can detect moving lights - they will have a strong inhibitory area on one side of the cell, so will respond to light that doesn’t enter the inhibitory area
how does the colour cortex work ?
the colours are usually perceived by using the wavelength. when an image has another colour light shining on it , it can alter the way some colours look, the colour cortex uses the colour the brain reports seeing the image, regardless of the wavelength of the light
it responds to the objective experience of the colour.
