CHapter 4 Flashcards
optic chiasm
x-shaped bundle of fibers on the underside
of the brain
Each hemisphere responds to the ____, or ___, side of the visual field
opposite, contralateral
Lateral geniculate nucleus (LGN)
located in the thalamus of each hemisphere
90 percent of the signals from the retina
Neurons here have center-surround receptive fields
Purposes of the LGN is to regulate neural
information as it flows from the retina to the cortex
Receives more signals from the cortex than from the retina (feedback, “backward”
flow of information)
the information the LGN receives back from the brain may play a role in determining which information is sent up to the brain
Superior colliculus
structure involved in controlling eye movements
10 percent of the signals from the retina
The first thing that happens on the pathway to the brain is
visual signals from both eyes leave the back of the eye in the
optic nerve and meet at a location called the optic chiasm.
Second thing that happens on the pathway to the brain
Approximately 90 percent of the signals from the retina proceed to the lateral geniculate nucleus (LGN) while 10% goes to the superior colliculus
In vision and in other senses as well, the thalamus serves as
relay station where incoming sensory information often makes a stop
before reaching the cerebral cortex.
From the LGN, the visual signal then travels to the______ which is also known as____
occipital lobe, visual receiving area—the place where signals from the retina and LGN first reach the cortex (AKA Striate cortex or V1)
Hubel and Wiesel (1965) state their tactic
for understanding receptive fields as follows:
stimulate the retina with patterns of light while recording from single cells or fibers at various points along the visual pathway. For each cell, the optimum stimulus can be determined, and one can note the characteristics common to cells at each level in the visual pathway, and compare a given level with the next.
Visual Cortex Neuron Receptive Fields
Track effects of processing through different levels of visual system
See which patterns of light generate the largest response in neurons at each level
Measure activation at single cells
Note common patterns of firing within levels and between levels
A neuron’s receptive field is determined by
presenting a stimulus, such as a spot of light, to different places on the retina to determine which areas result in no response, an excitatory response, or an inhibitory response
the receptive field is always on the ____ because that is where the ____are ____.
receptor surface, stimuli , received
Cells in ___ also have excitatory and inhibitory receptive fields, but they are oriented side by side, rather than in circles
Called ___
striate cortex, simple cortical cells
The relationship between orientation and firing is indicated by a neuron’s ___
orientation tuning curve
The orientation tuning curve is
determined by_____
measuring the responses of a simple cortical
cell to bars with different orientations.
there are neurons that respond to ___ that exist in the environment.
all of the orientations
simple, complex, and
end-stopped cells fire in response to specific features of the stimulus, such as orientation or direction of movement, they have also been called____
feature detectors
simple, complex, and
end-stopped cells fire in response to specific features of the stimulus, such as orientation or direction of movement, they have also been called____
feature detectors
Relationship A:
The stimulus-perception relationship
Relationship B:
The stimulus-physiology relationship
Relationship C:
The physiology-perception relationship
To demonstrate a link between physiology and perception, it is necessary to measure
the ___
physiology–behavior relationship (C).
Selective adaptation
firing causes neurons to eventually
become fatigued, or adapt
adaptation causes two physiological
effects
1) the neuron’s firing rate decreases
2) neuron fires less when that stimulus is immediately presented again
Adaptation is _____because only the neurons that were responding to verticals
or near-verticals adapt, and neurons that were not firing do
not adapt.
selective
Measuring the effect of selective adaptation to orientation involves
1- Measure sensitivity to range of one stimulus characteristic
2- Adapt to that characteristic by extended exposure
3- Re-measure the sensitivity to range of the stimulus characteristic
Selective rearing:
animals reared in environments that contain only certain types of stimuli
- Neurons that respond to these stimuli will become more predominate due to neural plasticity
Retinotopic map
an electronic map of the retina as it project on the cortex
Points close together on an object and on the retina will activate neurons close together in the brain (cortex)
Cortical magnification
small area of fovea is represented by large area on visual cortex
Fovea = 0.01% of retina’s area, but 8 – 10% of the retinotopic map on the cortex
How do we determined how points in
the retinal image are represented spatially in the striate cortex
stimulating various places
on the retina and noting where neurons fire in the cortex.
the striate cortex is organized into _____ that are perpendicular to the surface of the cortex, so that all of the neurons
within a location column have their receptive fields at the ____ on the retina.
location columns, same location
Location columns
Receptive fields at the same location on the retina are within a column
Orientation columns
Neurons within columns fire maximally to the same orientation of stimuli
Adjacent columns change preference in orderly fashion
One millimeter across cortex represents entire range of orientation
Hypercolumn:
location column with all of its orientation columns
The cortical representation of a stimulus does not have to ____ the stimulus; it just has
to contain information that represents the stimulus
resemble
Tiling:
columns receiving information about one area cover the entire visual field
The Extrastriate Cortex
other visual areas in the occipital lobe and beyond—areas conveniently known as V2, V3, V4, and V5
From V1 to higher-level areas
gradual increase in receptive field size
Scene representation builds in complexity
More aspects added as you go
Corners, colours, motion, shapes, etc.
What pathway:
also called the ventral pathway
Where pathway:
also called the dorsal pathway
What and where pathways
Originate in retina and continue through two types of ganglion cells in the LGN
Have some interconnections
Receive feedback from higher brain areas
Ablation refers to the
destruction
or removal of tissue in the nervous system
Removal of ____ tissue resulted in problems with the object discrimination task
temporal lobe
What pathway
Removal of_____ tissue resulted in problems with the landmark discrimination task
parietal lobe
Where pathway
Double dissociations:
two functions that involve different mechanisms and operate independently
Inferotemporal (IT) cortex:
IT neurons respond to more complex objects that occupy a larger portion of the visual field
- area in the temporal lobe
1) the pathways are ____but
have connections between them and
(2) signals flow not only
“up” the pathway from the occipital lobe toward the parietal
and temporal lobes but ___ as well
not totally separated ,“back”(feedback)
Median Temporal Lobe (MTL)
Includes the parahippocampal cortex, the entorhinal cortex, and the hippocampus
MTL structures are extremely important for memory
hippocampus is an area associated with
forming and storing memories
The effect of stimulating outside the receptive field is called ___
contextual modulation
Flexible” Receptive Fields
Initially: ____
receptive field is the area of the retina that, when stimulated, influences the firing of the neuron
