Vision

A human rod can contain 10 million photopigment molecules, which consist of two parts: ______ and _____ bound together. When exposed to light, these two parts break apart.

(Rhod)Opsin and retinal

Light breaks apart ______, causing signaling processes in neurons. In the dark, neurons are constantly depolarized (less negative) and releasing neurotransmitters. When light breaks ______ apart, hyperpolarized (more negative). Reduction in release of inhibitory neurotransmitters.

(Rhod)opsin and retinal

Diverse (about 50 kinds). Control the ability of ganglion cells to respond to specific aspects of visual stimuli. Helps information be processed

Amacrine and horizontal cells

Receive information from photoreceptors and send it to the ganglion cells Takes information from one area (photoreceptors) to the other (ganglion cells)

Bipolar cells

The point where your optic nerves converge to exit the eye and into the brain is known as the optic disc. This area of the eye has no light-sensitive cells to detect light rays. This results in a break in the visual field known as your "blind spot." Where fibers pass through the retina and out of the eye.

Blind spot retina

People with extensive damage to primary visual cortex (V1) can sometimes still react to visual information that they report not seeing (may orient to a flash of light)

Blindsight

Color: Role of cones The ability to recognize color despite changes in lighting Top-down processing: our brain has expectations for what things should look like. Which can explain _______. The blue in light is definitely different than blue in the dark, but we perceive it the same (the rubix cube blue in light and yellow in dark is actually the same!)

Color constancy

Some people lack one or two of the cone types, or one of the cone types develops abnormally. Most common "color-blindness" comes from cases where the long (red) and medium (green) wavelength cones have the same photopigment instead of different ones. This is an X-chromosomal trait affect 8% of men and 1% of women. When red and green cones make the same photopigment, therefore they respond to the same wavelength of light.

Color deficiency

Seeing shape... Do not have fixed inhibitory or excitatory zones, but respond to light of a particular orientation anywhere in its large receptive field.

Complex cells

Seeing shape... Zones are not fixed Cells respond to light of a particular orientation but it can be anywhere in the cell's receptive field. - i.e. vertical bar of light on right side (A) AND vertical bar of light on left side (E) causes action potentials to fire. The excitatory zone is no longer fixed, it is only responding to a particular orientation (i.e. vertical vs horizontal), but can hit anywhere in that orientation (i.e. right vertical vs left vertical)

Complex cells

Photoreceptors... Essential for color vision (three types of ____ are sensitive to one of three different wavelengths of light), not active in faint light. Only one ganglion cell for every single ____. Different for each color. More than one kind of ____. You need lots of light to activate a _____ because they are not very sensitive to light.

Cones

A tiny area specialized for acute, detailed vision. In this area, there are no blood vessels and ganglion cell axons. Moreover, each receptor (cone) connects to a single bipolar cell, which in turn connects to a single ganglion cell (1:1:1 ration), for better acuity (sensitivity to detail). Small "receptive field" Is a pit. The ganglion cells are spread out so that there's no interference to the _____. The ____ uses photoreceptors that require more energy, but has a lot more visual information. This is where a lot of processing is happening Lots of cones and lots of high spatial visual acuity

Fovea

______ axons make up the optic nerve, which exit the eye, cross the midline at the optic chiasm and go to the lateral geniculate nucleus (LGN) in the thalamus. Information is then passed on to visual cortex. Information from the right visual field ends up in the left visual cortex

Ganglion cell

Receive information from bipolar cells. Axons make up the optic nerve. Neurons that ultimately go out of the eye to optic nerve and to thalamus.

Ganglion cells

Visual information as it goes into the brain... Information is coming to the eye (retina) and ultimately the first place it goes to is _____ to the thalamus

Lateral Geniculate nucleus (LGN)

Perception - retina... The reduction of activity in one neuron by activity in neighboring neurons. ______ sharpens contrasts to emphasize borders

Lateral inhibition

First proposed by Johannes Muller. Any activity by a particular nerve always conveys the same kind of information to the brain If you activate a particular pathway, it will be experienced by that sensory system (i.e. if you stimulate the nerves in the visual system, you perceive something visual. Such as if you press on/apply pressure to the eye, you will see light).

Law of Specific Nerve Energies

Photoreceptors... In the dark, photoreceptors are actually depolarized. When light breaks apart opsin and retinal, this causes a cascade of events that actually hyperpolarizes the cell, and causes _____ release of transmitter onto bipolar cells.

Less

brief period when other systems are activated in response. Suggesting that there are maybe relationships between the cones (i.e. red cones inhibit green cones, yellow cones (we don't have a yellow cone, but combination of blue and green) inhibit blue cones). i.e. looking at + in the center of an image of a yellow, black, and green flag. Then looking at a plain white surface and seeing colors of American flag.

Negative color afterimage

We perceive color in terms of paired opposites, red-green, black-white, yellow-blue (incomplete because of color constancy)

Opponent-Process theory

The result of the organization and integration of sensations into an awareness of objects and environmental events Subjective experience

Perception

Chemicals that release energy when struck by light.

Photopigments

Specialized neurons that transduce light information (rods and cones). Turns light energy into electric potentials. Releases neurotransmitters to bipolar cells. This changes activity of bipolar cells.

Photoreceptors

There is a commonality of areas of the brain across different mammals

Primary sensory cortex

The area of cortex that is the first stage of visual processing. Responsible for conscious vision. If you imagine a visual scene, activity will increase in _____. (lighting up in this area in fMRI setting). Neurons there that are responding to all cells coming from the eye. Leads to idea that if you have a visual world, the stimuli coming from the retina is now represented in the ________ because the cortex is getting information straight from the retina. You have a map of visual world in ______.

Primary visual cortex (V1)

______ has neurons that respond to activity of ganglion cells in retina. Taking visual field as it comes off of retina. The brain then breaks visual field up into features that are processed by other layer of cortex that surround _____.

Primary visual cortex (V1)

Seeing faces... Inability to recognize faces - Difficulty determining whether two clay models of faces are different (even using touch) - Can describe whether person is old or young, male or female, but cannot identify the person Can see features of face, but can't perceive experience of a face. Damage to areas such as the fusiform gyrus.

Prosopagnosia

Visual pathways... The part of the visual pathway that excites or inhibits neurons in the visual system (i.e. ganglion cells, cells in the LGN, cortical cells)

Receptive field

Local depolarization or hyperpolarization of the receptor membrane Potentials are electrically active. When energy hits them, there is depolarization or hyperpolarization

Receptor potential

Eye is organized to take light energy, lens will focus that energy onto a particular part of the _____ (in the back of the eye) - _____ processes information and turns it into signal

Retina

Rear surface of the eye, which is lined with visual receptors.

Retina

____ contains two kinds of color-sensitive ganglion cells, red-green and yellow-blue. This explains why we don't perceive greenish-red or yellowish-blue

Retina

Photoreceptors... Respond to faint light, abundant in the periphery Black and white, very sensitive to light. In periphery of the eye, you may have lots of ____ going to only one ganglion cell. Does not have high spatial acuity. Very large

Rods

Process of detecting and encoding environmental energy Neural processes involved in taking energy from environment and turning that into a neural signal

Sensation

Specialized neurons that change energy into neural signals

Sensory receptors

Seeing shape... Found in primary visual cortex and have fixed excitatory and inhibitory zones in their receptive field

Simple cells

Seeing shape... Mapping receptive field for any particular neuron they were recording from when information was presented in the visual world. _____ has a receptive field for a particular neuron. Responsive to a particular bar of light that is only in a fixed zone, then only get a small action potential vs. when bar of light is directly on/completely covering receptive field, gets many action potentials. The receptive field that is outside the excitatory zone is inhibitory due to lateral inhibition. So if a bar of light were to hit outside of excitatory zone, it will inhibit the neuron from firing.

Simple cells

There are ____ for every system (taste, hearing, touch, etc)

Specialized neurons

The process by which energy is transferred into neural signals Every sensory process is going to have a ____ system

Transduction

(Young-Helmholtz theory) The perception of color from the relative responding of three kinds of cones, each maximally sensitive to a different set of wavelengths. All colors are a combination of red, green, and/or blue. 3 cones that respond to wavelengths of red, green, and blue best. Can explain red/green colorblindness, because the two wavelengths are very similar to each other.

Trichromatic theory

The area of cortex that further processes visual information, including qualities such as shape, movement, brightness, color, etc. Takes info from primary visual cortex (V1) and breaks down into unique features about it (shape, movement, brightness, color, etc).

Visual association cortex

In (dark/light): glutamate is released, which constantly inhibits bipolar cells

dark

In the dark, photoreceptors are _____. (releasing inhibitory neuron, glutamate when they're activated in the dark)

depolarized

Photoreceptors... In the dark, photoreceptors are actually ______.

depolarized

Photoreceptors and bipolar cells (do/do not) produce action potentials

do not

Info from the retina broken to cortex down to breaking down info into particular types of light/shapes either in fixed zone (simple) or shapes that can be anywhere in the zone (complex). - This gets to a point where (complexity gets larger and larger) neurons respond to very complex features of the environment such as _____

faces

Seeing shape... Neurons in the visual cortex may be ______; that is, they respond to particular features of visual stimuli, such as shape, depth, and movement. As visual information is processed, cells may respond selectively to more and more complex shapes, so that you might have a circle detector or triangle detector.

feature detectors

For simple cells: the zones in which the receptive field is excited or inhibited is _____ (i.e. the particular cell will only respond if light hits center of ti).

fixed

The more time we spend with certain features, the more we recognize these features due to the _____

fusiform gyrus

_______ responds to very complex features (i.e. in faces)

fusiform gyrus

The ____ produces action potentials

ganglion cell

Photoreceptors release ______ as their neurotransmitter

glutamate

Photoreceptors... In the dark, photoreceptors are actually depolarized. When light breaks apart opsin and retinal, this causes a cascade of events that actually ______ the cell.

hyperpolarizes

Seeing faces... In ________, neurons have large receptive fields, which always include information from the fovea. They often respond to complex shapes. Face recognition seems to be processed in the fusiform gyrus, which is part of the ________.

inferior temporal cortex

In the presence of light: photoreceptors are ______

inhibited (hyperpolarized)

Photoreceptors... Light hyperpolarizes the photoreceptor. Because the photoreceptor normally _____ the bipolar cell, light causes a depolarization in the bipolar cell, which excites the ganglion cell to produce action potentials.

inhibits

Perception - retina (optical illusion produced by _______) - Produced by rods - In between squares should look the same color, but the edges of the squares makes middle look darker.

lateral inhibition

Information in the right visual field will end up in the ____ lateral geniculate nucleus (LGN)

left

Visual information as it goes into the brain... Information from the ____ visual field hit the right part of the retina for both eyes. In the right eye, that visual information is going to the optic chiasm, while staying on the same side. Information is staying right and going to right thalamus. Information from the right side of the retina of the left eye is crossing the optic chiasm to go to the right side of the thalamus. Everything from the ____ visual field will end up in the right lateral geniculate nucleus (LGN)

left

In (dark/light): depolarization of photoreceptor, glutamate no longer released, activating bipolar cell. Photoreceptors are inhibited in ____.

light

The ______ of the lateral geniculate nucleus (LGN) pathway carries information about large, fast things (low spatial frequency, high temporal frequency) and is colorblind.

magnocellular

Cortex looks for ______ in patterns that you see. (i.e. looking for faces when looking at rock formations)

meaningfulness

The _____ pathway of the lateral geniculate nucleus (LGN) carries information about small, slow, colorful things (high spatial frequency, low temporal frequency). allows the perception of fine details, colors, and large changes in brightness.

parvocellular

In the ______ part of your retina, several receptors (rod) converge onto bipolar and ganglion cells (several photoreceptors can activate a ganglion cell), hence the ______ of your eye is more sensitive in dim light. Has lots of rods and is sensitive, but not good accuracy.

peripheral

All visual information goes to the ______ (first part of visual cortex that receives information from the thalamus)

primary visual cortex

Color: Role of cones The cortex compares information from various parts of the retina to determine the brightness and color of each area. This is also true for brightness. The perception of color also depends on higher-level processing in visual cortex (called ______). When cortex starts to get involved. Not just retina involved (after perceptions), the cortex is involved in processing. Processing in the retina and in the brain. A square looks darker than B square because of perceived shadow even though they're the same color. Orange dot looks brighter than the other due to background/surrounding providing context.

retinex theory

Information in the left visual field will end up in the _____ lateral geniculate nucleus (LGN)

right

Visual information as it goes into the brain... Information from the _____ visual field hit the left part of the retina for both eyes. In left eye, that visual information is going to the optic chiasm while staying on the same side. Information is staying left and going to the left thalamus. Information from the left side of the retina of the right eye is crossing the optic chiasm to go to the left side of the thalamus. Everything from the ____ visual field will end up in the left lateral geniculate nucleus (LGN)

right

Seeing shape... Neurons respond to very specific features in environment. Some neurons may be fatigued if you constantly give them this information - ________: we have neurons in our brain that respond to specific features (i.e. movement), the neurons will eventually get fatigued so that _______ occurs in which they are adapting (not firing as much in presence of stimuli). When you get this fatigue, you'll get rebound (i.e. looking at a spinning spiral for a long time. Then look away and you see everything moving (just like the spiral was)). - Firing rate is less upon immediate re-presentation of another stimulus: rebound experience. This all means that there are neurons that respond to specific features (i.e. responding to that specific movement). Primary visual cortex gets map of visual world, but then we start to have neurons that are responding to very specific components of that visual field.

selective adaptation

Seeing shape... Support for the idea that some neurons respond best to a specific type of stimulus comes from the concept of _______. - When we view a stimulus with a specific property (i.e. movement) for a long time, neurons that respond to that property adapt: 1) firing rate decreases 2) firing rate is less upon immediate re-presentation of stimulus

selective adaptation

People can end up with damage in the pathway from lateral geniculate nucleus (LGN) to primary visual cortex (this pathway leads to the experience of vision). So, damage may cause blindness. But because there may still be axons that go to the _______, you could have people who are blind but still react to flashes of light (reflexive orientation). This is something called blindsight (visual response but no experience of vision)

superior colliculus

Visual pathways... Some of the axons in this process (coming from the retina in ganglion cells) may also go to the _____. The _____ is important for reflexive orientations towards stimuli. So going there rather than only primary visual cortex, because if it was something dangerous, processing isn't important, reflex is.

superior colliculus

All concepts in visual system are relevant to all of _____

the sensory systems

Seeing faces... Damage to the inferior temporal cortex can produce _____

visual agnosia