Study Biopsychology - Vision Flash Cards

 
Pile Management Card
Biopsychology - Vision

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information that magnocellular system provides?
Color: No
Sensitive to contrast: high
Spatial resolution: LOW (detect very fine details)
Temporal resolution: fast (transient response)
dorsal and ventral streams
hypercomplex cell
neuron in the visual cortex that responds to presence of a line segment with a particular orientation that ends at a particular point within the receptive field

higher abstract level of information
complex cell
neuron in the visual cortex that responds to presence of line segment with a particular orientation located within its receptive field, esp. when the line moves perpendicularly to its orientation
simple cell
an orientation-sensitive neuron in the striate cortex whose receptive field is organized in an opponent fashion
patient with agnosia from ventral stream damage (effect on perception of spatial location?)
patient cannot tell which object is bigger, but CAN adjust fingers properly to pick them up
damage to dorsal stream for perception of spatial location?
person can tell which object is bigger, but trouble adjusting finger width to pick them up
perception of spatial location
parietal lobe "where" pathway: more of a "how pathway"?
-guiding movements base don visual information:
-saccades of eyes
-reaching; grasping
vestibulo-ocular reflex
keeps eyes fixed on one point while head moves: brain stem
componensates for eye movements: a region at junction of temporal and parietal CTX, with vestibular systme input
akinetopsia
inability to see movement - world is in snapshots; caused by damage to area V5 (MST)
TMS to V5 region?
subjects can't tell which stimulus on a computer screen is moving; damage to this region is called AKINETOPSIA
optic flow
in MST area: complex motion of points in visual field caused by relative movement b/w observer and environment; provides info about relative distance of objects from the observer and of the relative direction of movement
V5 or medial temporal (MT):
this region responds to velocity and direction of movement - gets input from V1 and superior colliculus
-fast input; thick, heavily myelinated axons
-humans - V5 located in lateral occiptal cortex (not temporal)
MST (medial superior temporal)
these neurons respond to radial, circular, spiral movement
important function of this region is: optic flow
-some compensation for eye movements
-which direction am I heading?
perception of movement - region(s) that respond to movement?
-V5 or medial temporal (MT)
-MST (medial superior temporal)
parahippocampal place area (PPA)
involved in perception of particular places (scenes and backgrounds)
extrastriate body area (EBA)
invovled in perception of the human body and body parts other than faces...silhouettes stick figures, etc.
-when TMS (transmagnetic stimulation) used to disrupt EBA--> impaired ability to recognize body parts, but not face parts or motorcycles
fusiform face area (FFA)
located in the inferior temporal lobe; involved in perception of faces and other complex objects that require expertise to recognize
prosopagnosia
inability to recognize particular people by the sight of their face -

they can tell something is a face, see and describe features of the face, but can't recognize
lateral occipital complex (LOC)
a region of the extrastriate cortex, involved in perception of objects other than people's bodies and faces (wide variety of objects and shapes)
perception of form
involves ventral stream/inferior temporal cortex - for perception of whole 3D objects and backgrounds
-receptive fields of neurons in this area (TEO) are large - as entire half of visual field
visual agnosia
inability to visually recognize and name a particular category of objects

deficits in visual perception in the absence of blindness; caused by brain damage
cerebral achromatopsia
inability to discriminate among different hues; caused by damage to area V8 of the visual association cortex. damage to central stream, magnocellular system intact
neurons in V4
this area seems to be invovled in the analysis of form as well as color - the color-sensitive neurons had rather unusual secondary receptive field: large region surrounding the primary field.
color constancy
the relatively constant appearance of the colors of objects viewed under varying light conditions
info that the koniocellular system provides?
Color: blue-yellow
Low sensitivity to contrast
Low spatial resolution
Slow temporal resolution
Ventral stream
info that parvocellular system provides?
Color: red-green
Low sensitivity to contrast
High spatial resolution (ability to detect details)
Slow sustained response temporal resolution
Ventral stream
posterior parietal cortex
highest level of dorsal stream of visual association cortex; involved in the perception of movement and spatial location
inferior temporal cortex
highest level of ventral stream of visual association cortex; involved in perception of objects, including people's bodies and faces
ventral stream
a system of interconnected regions of visual cortex involved in the perception of form, beginning with the striate cortex and ending with the inferior temporal cortex.

WHAT the object is; what color?
dorsal stream
a system of interconnected regions of visual cortex invovled in the perception of spatial location, beginning with the striate cortex and ending with the posterior parietal cortex.

WHERE in space the object is; what direction of movement?
extrastriate cortex
region of visual association cortex that surrounds the striate cortex; receives fibers from the striate cortex and from the superior colliculi and projects to the inferior temporal cortex
Visual association cortex
Role is to combine individual modules from perceived objects and entire visual scenes.
hierarchy of info flow.
direction of info flow tends to be up the hierarchy ('bottom-up" processing)
Also some info travels down the hierarchy ("top-down" processing...V1->LGN)
modular organization of V1
there is a very organized way that the striate CTX is set up - so that there is a map of different neurons
-each module~ 150,000 neurons
-each module processes info from one small part of visual field
-2 CO (cytochrome oxidase) blobs
-Neurons in CO blobs respond to color and low spatial frequencies; not orientation or movement; monocular
binocular depth cues
perceiving depth...
-stereopsis - sense of depth we get from both of our eyes
-most striate CTX neurons respond to info from both eyes
-many respond to retinal disparity
-these neurons contribute to perception of depth
monocular depth cues
perceiving depth...
-relative size
-relative movement (i.e. driving in a cae - things moving slower in the distance are farther away)
-color/detail (atmospheric haze; less detailed, dimmer things are farther away)
spatial frequencies
instead of detecting lines and edges, it is now thought that V1 neurons are responding to spatial frequencies. any visual pattern can be decomposed mathematically into several different sine waves (Fourier analysis)
higher-level feature detectors
simple, complex, and hypercomplex neurons; each level is integrating input from many neurons on the previous level
feature detectors
cells in the striate cortex selectively respond to particular features in the visual field; e.g. orientation
striate cortex
aka primary visual cortex aka V1
6 layers of neurons
"map" of left visual field on right V1, vice versa
Distorted map: 25% corresponds to fovea of retina
Feature detector neurons - fire more when they see certain types of lines/movemnet
color constancy
colors looks the same to us under different lighting conditions; cortex compares information from different parts of the retina to determine the color you perceive. It's not all in the retina!
opponent color theory
we have 2 types of receptors, red-green and blue-yellow. we perceive yellow as absence of blue stimulation, etc.
Trichromatic theory
we have 3 types of color receptors, each sensitive to one hue; other colors formed by blending
"center-surround" receptor fields
help us detect edges
color of squares look lighter up against the darker square - on edges - center surround organization emphasizes illuminiation - higher rate of firing on edges -- look lighter on edge
"OFF" cells
light in center-->decreased firing; light in surround-->increased firing
"ON" cells
light in center of field --> increased firing; light in surround-->decreased firing
receptive field of a cell =
portion of the visual field that that cell responds to
the "non-conscious" visual pathway preserved in blindsight...
axons from retinal ganglion cells that terminate in the superior colliculus in the brainstem
6 layers of LGN
Parvocellular and magnocellular layers with koniocellular sub-layers in between.
Parvo and Konio - input from color-responsive retinal ganglion cells
LGN layers 2,3, 5 - from ipsilaterla eye
1, 4, 6 - from contralateral eye
striate cortex
where LGN neurons' axons terminate (aka primary visual cortex; V1)
lateral geniculate nucleus of the thalamus (LGN)
where axons from all ganglion cells gathered into the optic nerve or crossed over to other side of optic chiasm terminate; LGN neurons' axons terminate in the striate cortex
How do photoreceptors work in information transmission in the retina?
Light exposure--> Rhodopsin breaks down into opsin and retinal photopigments; hyperpolarization of photoreceptor membrane-->less neurotransmitter (inhibitory effects on bipolar cells) released; Light-->disinhibition of bipolar cells.
Bipolar cells excite ganglion cells--increase their rate of firing.
3 layers in the retina
photoreceptors (info in)
bipolar cells
ganglion cells (info out to brain)

also there are horizontal cells; amacrine cells
optic disk
place where optic nerve exits the retina; we have a blind spot - where the optic disk is, the brain "fills in" that missing portion of the visual field
rods
120 mil.
Black and white, greater sensitivity (respond to lower levels of light)
cones
5 mil.
Color vision, higher acuity
fovea
The central part of retina, has the highest density of cones = high acuity.
retina
contains photoreceptors
smooth pursuit movements
we can't make smooth movements unless following somehting. following object vs. vestibulo-ocular reflex
saccadic
fast movements of the eye
vergence
movement of eye to focus
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