10.1 Describe how specialized receptors in the eye can represent light as a neural activity: How do our brains obtain sensory information?
Our brains don’t directly obtain sensory info, but we have special receptors in our sensory systems that encode specific sensory info as changes in our membrane potentials
each system processes different info, but they have overlap
10.1 Describe how specialized receptors in the eye can represent light as a neural activity: What are specialized receptors?
Neurons with modifications to their structure so it best responds to a specific external stimuli
mostly unique for each system, each process a diff. form of info
10.1 Describe how specialized receptors in the eye can represent light as a neural activity: What is the specialized receptor for the visual system?
Photoreceptor: light sensors, encodes light (photons) as changes in membrane potential, or electrochemical signals
*photons: # of photons = brightness, photon wavelength = color
10.1 Describe how specialized receptors in the eye can represent light as a neural activity: How do photoreceptors work?
filled with disks that have rhodopsin proteins: specialized G-proteins activated when struck by photon
when activated G-proteins interact with ion channels. the membrane potential is changed (how light is encoded)
10.1 Describe how specialized receptors in the eye can represent light as a neural activity: What are the different types of photoreceptors for different stimuli?
different photoreceptors for different stimuli: amount and color of light
Rods: low-light environments, low resolution/non-color
Cones: high resolution, color vision
10.1 Describe how specialized receptors in the eye can represent light as a neural activity: What is the structure of rods?
more disks than cones (to capture as many photons as possible)
since there’s lower number of photons, compromises in resolution and non-colored vision
10.1 Describe how specialized receptors in the eye can represent light as a neural activity: What is the structure of cones?
fewer disks than rods, cone type is named after relative wavelength, 3 cone types:
short = blue
medium: green
long 10.1 = red
uses **population coding: summates relative activity to represent more complex things with increased accuracy, which allows us to see the entire color spectrum
10.1 Describe how specialized receptors in the eye can represent light as a neural activity: What are the different types of color blindness?
red-green color blindness: malfunctioning of medium or long cones
10.2 Be able to illustrate how an image from the outside world can be encoded by the retina with many photoreceptors to form a retinotopic map: What is the retina?
a collection of over 100 million photoreceptors on the eye
10.2 Be able to illustrate how an image from the outside world can be encoded by the retina with many photoreceptors to form a retinotopic map: What is the flow of info on the retina?
photons travel through cell layers to reach photoreceptors on the back of the retina
photoreceptors encode # and wavelength of photons as membrane potential changes
photoreceptors communicate with bipolar cells, which the stimulate RGC (retinal ganglia cells)
axons in RGCs send APs to the brain
10.2 Be able to illustrate how an image from the outside world can be encoded by the retina with many photoreceptors to form a retinotopic map: What is the retinotopic map?
each spot of the retina is like a point on a grid: each point has rods and cones to encode visual info > retinas encoded intensity and color of the photons when they hit the “point”
summary: the location where the photons land on the retina correspond to where visual info comes from: forming retinotopic map
10.3- Be able to draw the neural connections that visual
information follows from the eye to the primary visual cortex. Be sure to include where visual information from either retina is
represented in the brain: What is the entire visual pathway?
since photoreceptors don’t have axons that go directly to brain, encoded info passes through bipolar cells to RGCs, which travel along RGC axons to brain
10.3- Be able to draw the neural connections that visual
information follows from the eye to the primary visual cortex. Be sure to include where visual information from either retina is
represented in the brain: What is the pathway of APs from the eye to the brain?
travel pathway of APs to brain: Retina → Optic nerve → Optic chiasm → Optic tract → Thalamus → Optic Radiations → V1
10.3- Be able to draw the neural connections that visual
information follows from the eye to the primary visual cortex. Be sure to include where visual information from either retina is
represented in the brain: What is the optic nerve?
contains all visual info from an eye: a cut nerve results in full vision loss of the specific eye
RGC axons condense to form the optic nerve
10.3- Be able to draw the neural connections that visual
information follows from the eye to the primary visual cortex. Be sure to include where visual information from either retina is
represented in the brain: What is the optic chiasm?
the RGC axons combine to form optic nerves, and optic nerves combine to form the optic chiasm
splits info from each eye in half and combines it with info from the other eye
10.3- Be able to draw the neural connections that visual
information follows from the eye to the primary visual cortex. Be sure to include where visual information from either retina is
represented in the brain: What are the optic tract and optic radiations?
optic tract: axons that leave from the optic chiasm
optic radiation: axons that leave from the thalamus
10.3- Be able to draw the neural connections that visual
information follows from the eye to the primary visual cortex. Be sure to include where visual information from either retina is
represented in the brain: How are the visual fields divided?
left eye: temporal (right visual field), nasal (left visual field)
right eye: temporal (left visual field), nasal (right visual field)
10.4 Explain how visual info is organized in the primary visual cortex: What is the primary visual cortex?
(V1) the cortex region that initially processes visual info, receives info from the thalamus and relays it to other brain areas after initial processing
- is present on both hemisphere, **each V1 hemisphere process info from the OPPOSITE visual field: ex. right visual field is processed by left hemisphere V1, vice versa
10.4 Explain how visual info is organized in the primary visual cortex: How is the visual cortex structured?
many interconnected columns, each one corresponding with a place on retina
the columns then receive connections from rods/cones on a given spot in visual retina
10.4 Explain how visual info is organized in the primary visual cortex: What does the visual cortex process?
processes all info from a given area of a retina: light intensity, color, simple movement, bars of different angles
10.4 Explain how visual info is organized in the primary visual cortex: Why are bars at different angles a good way to encode visual info?
it is very sensitive to edges: a biologically informative visual cue, allows multiple columns to work together to represent something complicated
effective and dynamic
