What does perception depend on? What type of sensory receptors are stimulated
(e.g., law of specific nerve energies: certain receptor/brain area you will have a
certain perception experience.)
How many / how much they are stimulated ex: a lot= bright light, not a
lot = dim light
In what pattern they are stimulated
What neurons those sensory neurons project to
Describe the general path that stimulus energy takes through our brain, leading
to conscious perception.
Receptors on sensory neurons: retinal photoreceptors
Nerve to the CNS: optic nerve
Thalamus: lateral geniculate nucleus
Primary cortex: primary visual cortex 1 (V1), also called striate cortex
Association cortex: V1-V8
How does light enter the eye? Describe the path it takes through the cell layers
of the retina and the path of signal transduction.
Enters through the pupil. Focused by cornea and lens to the retina at the back of
the eye. (Patrick cries like ryan)
Describe the path it takes through the cell layers of the retina and the path of
Photoreceptors > Horizontal cells > Bipolar cells > Amacrice cells > Ganglion
Dark: Inhibitory neurotransmitter released – postsynaptic cell not able to fire
Light: Inhibitory neurotransmitter NOT released – postsynaptic cell CAN fire
How are rods and cones similar and different?
– Respond well to faint light; overstimulated by bright light
– Abundant in periphery (outer areas of eye)
– Necessary for black and white vision
Cones – Need bright light to respond but provide more detailed info
– Abundant in center, especially fovea (center of the eye), which is a
depression in the retina where light hits unimpeded by other cells
– Essential for color vision – contain specialized photopigments tuned
to diff wave lengths of light.
On what point of the retina are cones most densely packed?fovea
With which types of cells do photoreceptors synapse? Bipolar cells Do they
excite or inhibit those cells (review slide 17 of the notes)? Inhibit.
On what is our perception of color based?
Our perception based on the wavelength with which photons hit photoreceptors.
Describe the path of the optic nerve – what and where do fibers cross, and to
what two areas do they project?
The optic nerve meets at the optic chiasm.
The axons of what type of cells make up the optic nerve, and what is the result
of the optic nerve passing through the retina? The ganglion cells make of the
optic nerve, and the result is a blindspot.
What type of ganglion cells that project to the lateral geniculate thalamus are
important for distinguishing detail and which are more important for perceiving
motion? How else do these cell types differ?
Parvocellular: small receptive fields, good at discerning detail, color,
and answering “what”
Magnocellular: large receptive fields, good at discerning motion, depth,
and answering “where”
Koniocellular: diverse group with multiple functions
What is V1 necessary for? Visual Imagery
What is it not necessary for? Blindsight
Lecture 20 Describe the path that sound takes through the ear – at which point(s) does the
sound travel as waves of air and where is it converted to waves through fluid?
Receptors on sensory neurons: hair cells on the basilar membrane of the cochlea
Nerve to the CNS: auditory nerve
Thalamus: medial geniculate nucleus
Primary cortex: primary auditory cortex 1 (A1)
Association cortex: additional auditory areas
Changes from air to fluid in the middle ear in the ossicles
At what points would damage cause conductive versus nerve deafness?
Conductive deafness: Middle-ear abnormalities such that the sound isn’t
conducted properly to the receptor cells
Nerve deafness: Inner-ear abnormalities that damages the cochlea, including
some or all of the receptors, and/or auditory nerve
What properties of sound do we perceive as pitch and loudness?
– Wave amplitude relates to loudness (e.g., larger wave height =
– Wave frequency relates to pitch (e.g., tighter waves / higher
frequency = higher pitch)
How are these attributes coded by activity of the auditory receptors?
How frequency is coded depends on its size:
– Low frequencies: hair cells on the apex of the basilar membrane
fire in time to sound waves (e.g., 200 Hz = 200 action potentials per
– High frequencies: groups of hair cells on the base of the basilar
membrane fire across different phases in response to sounds
waves, and their combined activity codes for a tone
Loudness is coded by how many