Chapter 5 (final) Flashcards
what makes light, smell, sound or taste special
what we do with it, on its own they are not special
what are Sensations
are features of the environment, like the electromagnetic wavelengths of light or changes in air pressure, creating sound, that we use to create an understanding of the world. Think of sensations as the raw materials of perception
what is meant by sensations are transduced
These sensations are transduced, or translated, by the sensory system into the electrochemical language of the brain.
wha is perception
The brain takes a given message and combines it with previous experience to create a perception. For instance, the sensation of 675 nm of light reflecting from my water bottle is transduced by cells in my eye and my brain uses this information to perceive red - and a water bottle for that matter
ur perceptual world is created by combining two processes, what are they
botton-up and top down processing
what is bottom-up processing,
is the neural processing that starts with the physical message or sensations. This is the early level analysis that prepares the information for use
what is Top-down processing
occurs when we combine this early neural organization with our understanding of the world to interpret and organize that information into something that has value
what do The laws of Gestalt do
aka the Gestalt principles of organization outline some fundamental ways we see the world.
what are the laws of Gestalt
The principle of similarity
principle of closure
principle of good continuation
principle of common fate
what is principle of similarity
states that objects that are physically similar to one another will be grouped together
what is principle of closure
states that people tend to perceive whole objects even when part of that information is missing
what is principle of good continuation
states that if lines cross or are interrupted, people tend to still see continuously flowing lines
what is principle of common fate
states that objects that are moving together will be grouped together
how much of the cortex plays a role in the interpretation of visual information
20%
Light is a form of electromagnetic radiation. Although the spectrum spans from Gamma rays to Radio waves, we are only able to see a narrow band, ranging from around what
400-700 nanometres
From the moment a wave of light enters my eye, the eye actively adjusts its behavior in order to maximize the quality of light that hits the sensory cells in what
the retina
The first obstacle the image must go through is
the cornea
what is the cornea
This outermost, transparent, and protective layer of my eye actually contributes to my ability to focus on the image
Light refracted from the image then enters my eye through;
the pupil
what is the pupil
a hole in the front of the eye that expands and contracts depending on the environment. Because the cells in the back of the eye are sensitive to light, it is important to regulate how much light enters the eye
The size of the pupil is controlled by what
the relaxation or tension in a band of muscles attaching to the Iris
what is The Iris
gives your eyes their color, but does not play a specific functional role in vision
what is accommodation
Behind the pupil, light travels through the lens. This flexible piece of tissue is layered like an onion, and it helps refract light and bring my dog into focus against the sensory cells in my retina. This process is known as accommodation and is determined by the distance between the lens and the object being viewed.
how does accommodation change as something is near or far from you
When an object is close to you, your lens is thicker and rounder, as an object moves further away, muscles attached to the lens relax and the lens elongates
Light then must pass through how many layers of cells in the retina
5 layers
where does the light go after the 5 layers of cells
arrive at the photosensitive cells (the rods and cones) in the back of my eye
what are photosensitive cells (the rods and cones)
this is where light is transduced into cellular activity. This will be the last time the message is in the form of electromagnetic energy. From this point forward, the image will be composed of patterns of neural firing
how do rods and cons work
In the retina, specialized photosensitive cells called rods and cones transduce energy into neural language. This translation is chemically based, as each cell contains a photopigment that is sensitive to light. The chemical reaction caused by exposure to light leads the cell to send a message to the adjacent neurons, and ultimately, a neural impulse is sent to the brain.
what is the fovea
a dense cluster of cones
what do the ones do
These cells respond best when there is a lot of light in the environment. Because only a few cells connect to adjacent ganglion cells, cones also transmit information about fine detail, a process known as visual acuity
how do rods work
Rods are typically sensitive at lower levels of light and thus are the primary cells used for night vision. That is, the rods will generate a neural impulse even when there is only a small amount of light available. This is why it is sometimes much easier to see something in the dark if it falls slightly to the side of center.
what is A second difference between the rods and cones
cones are the only cells that communicate information about the wavelength, perceived as color, of an object. The rods respond only to the amount of light, but do not communicate information about the quality of that light.
After the rods and cones react to light, they send their messages where
to bipolar cells
what do Bipolar cells do
summate the firing of several photoreceptors and send a different kind of message to a ganglion cell. The number and kinds of connections that bipolar cells make are determined in large part by their location
what are diffuse bipolar cells
In the peripheral vision, cells commonly referred to as diffuse bipolar cells can receive messages from as many as 50 rods. Diffuse bipolar cells then summate the experience of the photoreceptors and send a single message to the ganglion cell
what do midget bipolar cells do
receive input from only a single cone, and this message will be sent to a single ganglion cell. This explains the difference in visual acuity across the surface of the retina. While midget bipolar cells in the center receive a large amount of information about the qualities of a single point of light, cells in the periphery receive little information from a much larger area of the retina
Each ganglion cell has a receptive field, meaning what
each ganglion responds to activity only when light falls on a specific portion of the eye and only when specific cells are active
how are The receptive fields of the ganglion cells are often organized
in a center-surround fashion. That is, when light falls on the center of the receptive field, the cell will respond more rapidly, but when the signal falls on the surround part of the receptive field, the cell reduces the firing rate. This allows for a single cell to send a variety of information about the surface of an object.
what do Small ganglion cells do
(often called P cells) receive information from the midget bipolar cells. P cells make up approximately 70% of the cells in the retina and send signals to the brain about qualities of color and detail
what do Larger ganglions do
(M cells) are found in the periphery and receive their signals from the diffuse bipolar cells. These signals send information about motion and visual stimuli in the periphery
the center-surround organization of the ganglion cells helps the brain interpret what
where edges of objects begin and end
The messages finally leave the eye and enter the brain via the optic nerve, made up of the axons of both the M and the P ganglion cells. As a result, there is a spot on the retina where there are no photoreceptors. This creates a small blind spot in each eye; why do we not notice it
it is not noticed because the brain uses information from the other eye and the assumptions about the world to “fill in” the gap
what is the optic chiasm
where the axons from each eye are reorganized for more sophisticated processing. Information from the right side of both eyes is sent to the left hemisphere, while information on the left side of the retina in both eyes is sent to the right side of the brain
the brain’s first interaction with the image itself occurs after this split in what
the Lateral Geniculate Nucleus (LGN) of the thalamus.
what is Visual Striate Cortex
The Visual Striate Cortex, or Visual Cortex (VC), is located in the occipital lobe. Here, important features of the visual world are assembled and identified. We have over 30 areas in the back of the brain dedicated to analyzing and organizing visual information. Throughout this entire pathway, every neuron maintains a spatial organization
This spatial organization is known as what
retinotopic organization
what does retinotopic organization do
is how we maintain a map of the visual world throughout processing
In the Visual Cortex, these points are assembled into lines and edges or features
what are Feature detectors
are specialized cells in the VC that respond most actively to specific stimuli
Using electron recordings of single cells in the visual cortex of their animal participants, researchers identified one type of feature detector known as what
simple cells
how do simple cells work
This cell response to small stationary bars of light oriented at specific angles
how do complex cells work
Complex cells respond most vigorously to vertical lines in motion. As the line moves further from a vertical orientation, the cell will decrease its firing rate
