Module 6.2 Flashcards
Axons of which cell form the optic nerve?
ganglion cells
What is the name of the site which the right and left optic nerves meet?
optic chiasm
Where do most axons in optic nerves synapse?
lateral geniculate nucleus
What is the destination of axons from the later geniculate nucleus?
other parts of the thalamus and the occipital cortex
What is lateral inhibition?
Lateral inhibition is when one cell inhibits another cell’s activity.
How does lateral inhibition enhance contrast?
It enhances contrast by increasing sensory perception.
Describe parvocellular ganglion cells.
Parvocellular gangion cells have small receptive fields and are sensitive to color and details.
How do parvocellular ganglion cells differ from magnocellular ganglion cells?
Magnocellular ganglion cells have larger receptive fields and are movement sensitive, and are not color sensitive.
What is a receptive field of a cell in the visual system?
the part of the field that inhibits or excites it
What happens at the optic chiasm?
Half of the axons from ganglion cells cross to the opposite hemisphere
Describe the evidence that Area V1 is necessary for conscious vision.
People with damage to the Area V1, report no conscious vision, no visual imagery, and no visual images.
What is blindsight?
the ability for a person to respond to visual info that they report not seeing
What are two potential explanations for blindsight?
One explanation is that the other branches of the optic nerve deliver visual info to the supior colliculus and other areas, so maybe one of those parts controls the blindsight responses. Another explanation is that tiny bits of healthy tissue remain within an otherwise damaged visual cortex that provides enough perception for blindsight
In what cortical area does the dorsal stream end?
parietal cortex
What is the dorsal stream’s functional contribution to vision?
It helps the motor area find and use objects
For what accomplishment did Hubel and Wiesel win the Nobel Prize?
They used microelectrode recordings to to study individual cells and they distinguished several types of cells in the visual cortex.
Describe the receptive fields of simple cells.
they have fixed inhibitory and excitatory zones
What is the major difference between the responses of simple and complex visual cortical cells?
Simple cells respond to the exact location of a stimulus, complex cells do not.
Describe the receptive field of a hypercomplex cell.
It has a strong inhibitory area at one end of its receptive field.
What is a feature detector?
Neurons whose responses indicate the presence of a particular feature
Are neurons in area V1 feature detectors?
No
Describe the evidence for and against area V1 neurons being feature detectors.
The evidence suggesting Area V1 neurons are feature detectors is that they respond strongly to bar- or edge-shaped patterns. The evidence against area V1 neurons being feature detectors is cortical cells, who also respond well to a single bar or line, responds more strongly to a spatial frequency
Which areas, beyong V1, are important for shape analysis? What are their contributions?
The inferior temporal cortex is important for shape analysis. It detects objects, but not the amount of light or dark on the retina.
What is shape constancy?
the ability to recognize an object’s shape even as it changes position, angle, and lighting
What is visual agnosia?
an inability to recognize objects despite otherwise good visioin
What is prosopagnosia?
the inability to recognize faces
What area in the inferior temporal lobe increases its activity when people with intact brains recognize faces?
fusiform gyrus
What appears to be a special function of V4?
color constancy
Which 2 areas of the cortex are specialized for motion perception?
MT (middle-temporal cortex or area V5) and MST (medial superior temporal cortex)
How do MT cells respond?
When something moves at a particular speed in a particular direction
What are the preferred stimuli for cells in the dorsal part of area MST?
complex stimuli
What is the role of ventral MST cells?
To repsond to an object that moves relative to its background
Why don’t we see a blur when we move our eyes?
Because several of the visual areas of your brain decrease their activity during voluntary eye movements
What is a saccade?
a ballistic movement of the eyes from one fixation point to another
Describe motion blindess.
the ability to see objects but not being able to see if they are moving or how fast and in what direction an object is moving
What causes motion blindness?
damage to the MT
