Location in the Visual World Flashcards
region of the visual world that is seen by ones eyes
-
visual field
info in the left visual field goes to what hemisphere?
right
each __ responds to a stimulation on just a small circular patch of the retina- the cells receptive field
retinal ganglion cell
Light falling on one place on the retina will activate one ganglion cell, and light falling on another place will activate a different ganglion cell
-this is?
coding location
cells in the ___ also have a visual field
lateral geniculate nucleus
each LGN cell represents?
a particular place
receptive fields of cells in the cortex are typically _____ than those of the retinal ganglion cells
larger
is more cortical tissue devoted to cells in the fovea or in the periphery
the fovea
the ore information that is being sent along a pathway, the more?
cortical tissue is devoted to it
where are the central and periphery visual fields represented in V1
central part of visual field= posteriorly
periphery= anterior
the upper part of the visual field is represented where in V1? and the lower part?
- upper part= bottom of V1
- bottom part= upper V1
what is the best in the central part of the visual field?
acuity (from cones)
what has a larger receptive field: retinal ganglion cells or cells in the cortex
cortex cells
the receptive field of a corticol neuron must be composed of ?
the receptive field of many RGCs
what brain structures are almost all connected by corpus callosum and what ones are not connected
most of the frontal lobes are connect to each other and the occipital lobe has NO callosal connections
what is the one exception to the occipital lobe having no callosal connection
cells that lie along the midline of the visual field are connected to one another via the corpus callosum to that their receptive fields overlap
cells response to a particular stimulus is?
selective
place a straight line positioned at 45 degrees angle in front of the eyes is how we see?
shape
retinal ganglion cells only respond to?
absence of light, not to shape
concentric circle arrangement of retinal ganglion cells
look this up
RGC have on center cells so they are excited when?
and inhibited when?
light falls on the center portion of the receptive field
- inhibited when light falls on the periphery of the receptive field
(concentric circle arrangement)
if light crosses the whole receptive field of a RGC on center cell there is?
weak excitation
RGCs have off center cells so these are excited when? and inhibited when?
= excited when light falls on the periphery of the receptive field and
- inhibited when light falls in the center of receptive field
light across the whole receptive field of a off center cell produces
weak inhibition
what tells the brain about the amount of light hitting a certain spot on the retina compared with the rest or the retina
each retinal ganglion cell
neighboring retinal ganglion cells recieve there inputs from?
an overlapping set of photoreceptors b/c there receptive field overlap
a small spot of light shining on the retina is likely to produce activity in off center or on center cells
both
the amount of light reflected by an object relative to its surroundings
luminance contrast
luminance contrast allows for?
input from the RGCs to tell the brain about shape
V1 neurons receive in put from multiple? and have much larger receptive fields than them
RGCs
how do cells behave like orientation detectors
excited by bars of light orientated in particular directions
simple cells have a receptive field with a ?
rectangular on-off arrangement
simple cells either prefer __ or ___?
horizontal orientation or oblique (slanted) orientation
maximally excited by bars of light moving on a particular direction through the receptive field
complex cells
maximally responsive to moving bars, also have a strong inhibitory area at one end of the receptive field
hypercomplex cells
hypercomplex cells help detect
edge detection and motion
neurons are organized into functional columns (0.5 mm strip or cortex)
- -> columns comprise of neurons with similar?
- -> inputs arrive in layer ___, and then connect ___ with other layers
- functions
- layer 4, vertically
ocular dominance columns recieve input from ?
left or right eye
adjacent columns house neruons that are responsive to slightly different?
orientations,
forming an array of 180 degrees
every neuron in the same column has?
the same orientation bias (ex 45 degrees)
in temporal cortex, cells are maximally excited by complex visual stimuli
- examples?
May be selective to particular faces seen head on, to faces viewed in profile, to the posture of the head, even to certain facial expressions
recognizing that na object is the same across different viewing orientations
stimulus equivalence
what is necessary for activation of most neurons on the temporal lobe?
complex features
complex features that are necessary for activation of temporal lobe neurons include?
size
colour
texture
orientation
neurons in Temporal coretx that have similar bot not identical responsiveness to particular features cluster where in accordance with each other? How does this happen?
cluster in columns
- -> experience! to tell it what is related and what is not
- -> harder to tell differences between shapes you have not seen
the preferred stimulus of neurons in the temporal lobe are able to alter their preference with?
experience
obtains entire range of colours in visual world by mixing 3 colours
subtractive colour mixing
subtractive colour mixing is property of the ?
cones in the retina
increases light to make colour
additive color mixing
the lighter the colour , the more ___ it contains
light
why does a white surface reflects entire visible spectrum
because the lighter the colour the more light it contains
Explanation of color vision based on the coding of three primary colors, red, green, and blue
trichomatic theory
the colour we see is determined by the relative responses of
different cone types
what are the 4 basic colours
red green yellow blue
what can explain colour blindness
trichomatic theory
- some ppl are born without cones for a specific colour
can the trichomatic theory explain afterimages? (red-green; blue-yellow)
no
Explanation of color vision that emphasizes the importance of the opposition of colors
opponent process theory
in the oppon process theory what colour oppose each other
- red- green
- blue - yellow
where does opponent processing occur?
- what kind of receptive fields
in about 60% retinal ganglion cells
–> on and off center surround receptive fields
explain the opponent color contrast response with respect to receptive fields
- center of receptive field in excitatory to some colours and inhibitory to other colours
- stimulation to the periphery has the opposite effect (center is responsive to one wave length and the surround the other)
colour sensitive cells are found in ___ in V1 which also respond in a _____ manner
- blobs
- opponent process manner
neurons in V1 respond to wavelength of colour whereas neurons in V4 respond to?
- various perceived colours
_ center is excited by a certain colour and the surround in inhibited)
what may be important for colour constancy and why
neurons in corticol region V4, b/c perceived colour is constant relative to other colours regardless of the change in illumination
involved in processing visual info for action
dorsal steam
Neurons in this area are silent to visual stimulation when a person is under anesthesia
dorsal stream
Some cells in this area process the visual appearance of an object to be grasped
dorsal stream ( fire even when watching other pick up object)
Destruction of the retina or optic nerve of one eye, producing loss of sight in that eye
monocular blindness
Blindness of an entire left or right visual field
homonymous hemianopia
Blindness of one quadrant of the visual field
quadrantanopia
Small blind spot in the visual field caused by a small lesion or migraines of the visual cortex
scotoma
damage to the visual stream causes what? (3)
- visual form agnosia: can recognize objects or drawing of objects
- color agnosia (achromatopsia)
- face agnosia (propagnosia)
copy objects and even draw objects from memory. However, they cannot later recognize these copied objects. – still appropriately shape their hands when grasping for objects, despite not being able to recognize those object
visual form agnosia, damage to ventral stream
correct grasp of object due to
ventral stream
injury to dorsal stream =
optic ataxia: defecit to visual control of reaching and other movements
