Chapter 6: Vision Flashcards
Sensation/Perception involves cells of the nervous system that are specialized to detect stimuli from the environment.
Sensation
Sensation/Perception is the conscious experience and interpretation of information from the sense
Perception
The _________ in the eye detect visible light.
photoreceptors
For humans, visible light is a narrow band of the spectrum of ________________ ________
electromagnetic radiation
What are the three dimensions of light?
Hue, brightness, saturation
Hue depends on the _______ of light
wavelength
Brightness depends on the _______ of light
intensity
Saturation depends on the ________ _____ of light
relative purity
The longer end of the visible light spectrum is _____.
red
The shorter end of the visible light spectrum is ______.
purple
We receive information about the environment from _______ ________.
Sensory receptors
Stimuli are detected by sensory receptors in the process known as ________ __________.
sensory transduction
The image must be focused on the _____ in order for us to see.
retina
_____ regulate the amount of light entering the eye.
Pupils
The ____ is responsible for accommodation.
lens
The ______ bends the light so that it hits the retina.
cornea
The retina contains two kinds of photoreceptors that detect light: _______ and ______
rods; cones
Three cellular layers of the retina (from deep to shallow):
Photoreceptive
Bipolar
Ganglion cell
True or false: There are more cones than rods in the retina
False, there are around 120million rods and only 6million cones
Rods/cones work under low intensity light
Rods
Rods/cones are responsible for acuity and color vision
Cones
The fovea contains only rods/cones
cones
The ______ ____ at the back of the eye has no receptors, causing a blind spot.
optic disk
Transduction
The process by which energy from the environment is converted to a change in membrane potential in a neuron.
The first step in visual perception is ______.
Transduction
___________ are responsible for transduction of light energy into changes in membrane potential
Photopigments
Molecules that make up a photopigment:
Opsin
Retinal
When photoreceptors experience darkness, they depolarize/hyperpolarize
depolarize
When photoreceptors experience light, they depolarize/hyperpolarize
hyperpolarize
The ON center bipolar cells are depolarized/hyperpolarized by glutamate
hyperpolarized
The OFF center bipolar cells are depolarized/hyperpolarized by glutamate
depolarized
The ON/OFF center bipolar cells synapse with the ________ and influence the rate of firing; they do not fire themselves.
ganglion cells
The place where a visual stimulus must be located to produce a response in a neuron is the _____________ ____.
receptive field
The location of a receptive field of a particular neuron depends on the location of the ___________ that provide it with visual information.
photoreceptors
At the fovea/periphery of the retina, many individual receptors converge on a single ganglion cell.
periphery
Why is our foveal vision very acutes while our peripheral vision is less precise?
Because the receptor-to-axon ratio is small in the fovea (1:1, e.g.) and large in the peripheral (6:1, e.g.)
Three types of eye movements:
Vergence
Saccadic
Pursuit
Describe vergence eye movements
cooperative movements that keep both eyes fixed on the same target
Describe saccadic eye movements
Shifting your gaze abruptly from one point to another
Describe pursuit eye movements
Eye moves smoothly as it focuses on a moving object
At the back of each eye, axons of the retinal ganglion cells bundle together to form the _______ ______.
optic nerve
The optic nerves convey information from the retina to the _________ of the thalamus.
Dorsal lateral geniculate nucleus (LGN)
The optic nerves join together at the base of the brain to form the X-shaped _______ ______.
Optic chiasm
Where do the axons from ganglion cells serving the nasal sides of the retina go?
They cross through the optic chiasm and ascend to the LGN on the opposite side of the brain
Where do the axons from ganglion cells serving the temporal sides of the retina go?
They remain on the same side of the brain.
True or False: Because the axons from the nasal halves of the retinas cross to the other side of the brain, each hemisphere receives information from the contralateral half of the visual scene.
True – the right hemisphere receives info from the left half of the visual field and vice versa.
The phenomenon in which cortical regions involved in conscious perception of visual stimuli are damaged, but other visual pathways that are not involved in conscious perception are intact.
Blindsight
The journey of information from light detection in the retina to the experience of complex visual scenes occurs along the ______ _______.
visual pathway
The visual pathway:
Photoreceptors of retina –> bipolar and retinal ganglion cells –> optic nerves –> LGN –> Primary visual cortex (V1) –> Visual association cortex (V2) –> may continue on to V3, V4, V5
The neurons in the LGN send their axons through ______ _______ to the V1.
optic radiations
The primary visual cortex is also called the _____ cortex.
striate
The visual association cortex (V2) is also called the ________ cortex.
extrastriate
Blindsight occurs when the cortical regions involved in ______ _________ are damaged but other pathways remain intact.
conscious perception
The LGN contains _ layers of neurons
6
Layers 1, 4, and 6 of the LGN receive input from the ipsilateral/contralateral eye
contralateral
Layers 2, 3, and 5 of the LGN receive input from the ipsilateral/contralateral eye
ipsilateral
The inner two layers of the LGN (1 and 2) are called the ________ layers.
magnocellular
The outer four layers of the LGN are called the ________ layers
parvocellular
A third set of neurons in the LGN called the __________ ________ are found below each of the magnocellular and parvocellular layers.
Koniocellular sublayers
Hubel and Wiesel discovered that neurons in the visual cortex did not simply respond to spots of light; they selectively respond to specific _______ of the visual world
features/contours