Behavioral Neuroscience Exam 2 (Lecture 2 The Visual System)

Lecture 2

What is Sensation?

the process of detecting the presence of stimuli

What is Perception?

the higher-order process of integrating, recognizing, and interpreting patterns of sensations

What is the Iris?

gives our eye color

What is the function of the Pupil?

the whole in the iris that open and closes in response to changes in light

What is Sensitivity?

the ability to detect movement and edges in low light

What is Acuity?

the ability to detect fine details

What is the function of the Cornea?

shields the delicate inner structures of the eye from injury, infection, and debris. 

What is the function of the Lens?

refracts or focuses incoming light onto the retina by bending.

What is the Sclera?

The white of the eye

What is Accommodation?

The process of adjusting the configuration of the lenses to bring images into focus on the retina

When the pupils are constricted, the image falling on each retina is ______ and there is a _______depth of focus. 

sharper, greater

When the level of illumination is too low to adequately activate the receptors, the pupils _______ to let in more light, thereby _______acuity and depth of focus.

dilate, sacrificing

When the level of illumination is _____ and sensitivity is thus not important, the visual system takes advantage of the situation by ________the pupils

high, constricting

What is the Retina?

converts light to neural signals, conducts them toward the CNS, and participates in the processing of the signals

True/False: Light enters the eye through the iris, the hole in the retina

False

What are the two problems associated with the five different layers of the Retina? 

1. Incoming light is distorted by the retinal tissue through which it must pass before reaching the receptors

2. for the bundle of retinal ganglion cell axons to leave the

   eye, there must be a gap in the receptor layer; this gap is

   called the blind spot.

How are the two problems associated with the five different layers of the Retina resolved? (use fovea and completion) 

1. The thinning of the retinal ganglion cell layer at the fovea reduces the distortion of incoming light

2. Completion: The visual system uses information provided by the receptors around the blind spot to fill in the gaps in your retinal images.

True/False: The Fovea contains only cones

True

What do the cones specialize in?

Photopic vision: fine details and color (acuity)

What do the rods specialize in?

Scotopic vision: movement, less fine-detail (sensitivity)

What is the photopic spectral sensitivity curve?

The graph of the sensitivity of cone-mediated vision to different wavelengths of light.

What is a spectral sensitivity curve?

a graph of the relative brightness of lights of the same intensity presented at different wavelengths is called a spectral sensitivity curve.

What is the Purkinje effect? 

(cones) In intense light, red and yellow wavelengths look brighter than blue or green wavelengths of equal intensity; (rods) in dim light, blue and green wavelengths look brighter than red and yellow wavelengths of equal intensity.

What is binocular disparity? 

The difference in the position of the same image on the two retinas

What is binocular disparity used for?

builds a 3rd worldview and depth perception 

What does connectic mean?

movement

What is better in low light? (cones or rods)

rods

What is better in bright light? (cones or rods)

cones

What is a saccade?

small jerky movements from one fixation point to another 

True/False: The positions of the images on your two retinas can never correspond exactly because your two eyes do not view the world from exactly the same position

True

What is inattentional blindess?

failing to notice a fully visible unexpected object to due to a lack of attention even in plain sight

What are fixations?

occurs when a person tries to fix their gaze on (i.e., stare at) a point.

What is a blind spot?

a gap in the receptor layer

The area on the retina where the bundle of axons from the retinal ganglion cells leave the eye as the optic nerve.

What is the retina-geniculate-striate system?

the neural projections from the retinas through the lateral geniculate nuclei to the left and right primary visual cortex (striate cortex).

What is the retina-geniculate pathways?

conduct signals from each retina to the primary visual cortex (also known

as striate cortex) through the lateral geniculate nuclei of the thalamus.

What is the primary visual cortex or striate cortex?

What is the lateral geniculate nuclei?

receives visual input from receptors

True/False: All signals from the left visual field reach the right primary visual cortex

True 

What is the function of the optic chiasm?

it flips images right-side up

What are the bottom two layers of the lateral-geniculate?

Magnocellular

What does the magnocellular respond to?

movement 

What are the top four layers of the lateral-geniculate?

Parvocellular

What does the parvocellular respond to?

fine detail

What is retinotopic organization?

organized like a map of the retina

True/False: The retina-geniculate-striate system is not retinotopic

False

What are mach bands?

the nonexistent stripes of brightness and darkness running adjacent to the edges

What are edges?

the place where two different areas of a visual system meet

How do contrast enhancements occur using lateral inhibition?

Neurons in the retina that are more strongly activated, inhibit their neighbors from firing when stimulated by light, causing the darker area to appear even darker and the lighter area to appear even lighter where they meet. 

How do match bands occur using contrast enhancement?

the intensification of the perception of edges

What are on-center cells?

respond to lights shone in the central region of their receptive fields with “on” firing and to lights shone in the periphery of their receptive fields with inhibition, followed by “off” firing when the light is turned off.

What are off-center cells?

respond with inhibition and “off” firing in response to lights in the center of their receptive fields and with “on” firing to lights in the periphery of their receptive fields.

What are simple cortical cells?

they are rectangular

True/False: Our visual system respond most to circles

False

How are complex cortical cells different from simple complex cortical cells?

has larger receptors

cannot be divided by “on” and “off” regions

complex = binocular (respond to stimulation of either eye) while simple = monocular (respond to stimulation of only one of the the eyes)

True or False: We have more complex cortical cells.

True

What is an on-response?

a neuron fires when light is on

What is an off response?

a neuron is inhibited from firing when light is on, but fires when light is turned off.

What is component theory?

the relative amount of activity produced in three different classes of cones by light determines its perceived color 

What is opponent processing theory?

there are two different classes of cell in the visual system for encoding color and one class of brightness each of the three classes of cells encodes two complementary colors

What is color constancy? 

the tendency for an object to stay the same color despite major changes in the wavelengths of the light that it reflects

What is retinex theory?

the color of an object is determined by its reflection the proportion of light of different wavelengths that surface reflects

What are the three cones?

red

green

blue

What is the primary visual cortex?

area of cortex that receives most of its input from the

visual relay nuclei of the thalamus

What is the secondary visual cortex?

are of the visual cortex that receives most of their input from the primary visual cortex

What is the association cortex?  

areas of visual cortex are that receive input from areas of secondary visual cortex as well as from the secondary areas of other sensory systems

What is a scotoma?

an area of blindness

What is blindsight?

the ability to respond to visual stimuli in a scotoma with no conscious awareness of them

Damage to an area of the primary visual cortex produces a______.

scotoma

What is conscious awareness?

What is the Dorsal Stream?

involved in the perception of “where” objects

What is Ventral Stream?

involved in the perception of “what” objects are

What stream mediates “control of behavior?” or behavioral interactions with objects

dorsal stream

Which stream mediates “conscious perception”?

ventral stream

What is Visual Agnosia?

can see things, but they don’t know what they are

What is Prosopagnosia?

refers to a difficulty in recognizing faces