LECTURE 26 - closed loop control - - visual pathways Flashcards
what are the two streams of the visual pathway ?
dorsal and ventral stream
where does the dorsal stream travel ?
V1 (primary visual cortex) to PPC (posterior parietal cortex)
where does the ventral stream travel ?
V1 to inferotemporal cortex
what does the dorsal stream support ?
vison for action
what does the ventral stream support ?
vision for perception
what is prosopagnosia ?
- face blindness is a neurological disorder characterized by the inability to recognize familiar faces
- people with prosopagnosia may have difficulty distinguishing between faces, remembering faces, or associating faces with names or identities
what is the important case study of the closed-loop control : visual pathway and prosopgnosia ?
- the monkey study
- had names associated with each chimpanzee based on the features of the face
- can see features but cant put it all together
what is one piece of evidence that shows we have a dorsal and ventral aspect
study by Ungerleider and Mishkin in the 1980s, the researchers trained monkeys to perform two different tasks: one involving the perception of the location of an object and the other involving the perception of the object’s identity
what is a region of ventral visual pathway which is responsible for this now process ?
fusiform face region
what is visual agnosia ?
a neurological condition characterized by the inability to recognize or interpret visual information, despite normal functioning of the eyes and optic nerves
can DF identify different shapes or object features ?
cannot
can DF reach out and grasp objects properly
yes
does object agnosia use vision for motor contact ?
yes, fully intact use of vision for motor contact (movement)
what is the first classic and simple study looking at DF’s visual abilities ?
model, copy and memory drawing of apple and book (milner and goodie)
describe the visual agnosia and DF study :
- DF was asked to look at an object (so these would be paper drawings) and then in response, DF is asked to copy them using paper and pencil in order to copy the image
what is the main point of the DF study ?
- that DF has an idea, she has a memory of what these objects look like, however when she is physically looking at those things she’s only unable to recognize these elements
what is DF ?
Patient DF is a woman with visual apperceptive agnosia
what are the two tasks in visual agnosia ?
PT and AT
what does PT and AT stand for ?
PT = perception task
AT = action task
what is the perception task ?
involves presenting a patient with a series of simple geometric shapes, and asking them to identify or match the shapes
what is action task ?
involves presenting a patient with a series of common objects, such as a pen, a key, or a watch, and asking them to identify or name the objects
what are milner and goodale responsible for ?
- visual agnosia
- primarily involved in the early studies of DS processing abilities and they came up with this very simple task in order to provide a very explicit demonstration of what DF can and cannot do
what was the PT asked to do for the closed-loop control : visual agnosia ?
- was asked to pick up and orientate it to the slot
- slot on the door can change orientation
what was the AT asked to do fro the closed-loop control : visual agnosia ?
has to physically put in the slot
do we have separate visual pathways for perception and action ?
yes
what does LOC stand for ?
lateral occipital cortex
what area has leison of patients with DF ?
LOC
the leison in a visual agnosia DF patient ?
lesion will lead to an impairment in the use of vision for perception, but not in the use of vision to control action
what is optic ataxia ?
an ataxia in which patients have difficulty completing visually guided reaching tasks in the absence of other sensory cues
which ataxia has a double dissociation ?
optic ataxia
can AT (ataxia) recognize shapes, sized and object features ?
yes without a problem
can AT (ataxia) reach out and grasp objects with visual control ?
no they cannot
can DF (agnosia) recognize shapes, sizes and objejct features ?
no they cannot
can DF (agnosia) reach out and grasp objects properly ?
yes
describe patient Anne :
- has bilateral posterior parietal cortex lesions
- has dysmetria / misreading errors
- looking @ object through peripheral vision and is reaching out grasping it
- in right peripheral visual field the cant catch pen but on the left side she can
- improved performance = closed eyes
fill in the two blanks “someone who has an optic ataxia will have a challenge in using _____ in order to control _____ , and so this represents the double dissociation that supports this duplex model of vision control”
vision and action
when does patient Anne have improved performance ?
when she closes her eyes
what is the ponzo illusion ?
visual illusion that demonstrates how our perception of the size of an object is influenced by the context in which it appears (scale)
which visual pathway is egocentric responsible for ?
dorsal visual pathway
which visual pathway is allocentric responsible for ?
ventral visual pathway
between egocentric and allocentric which is relative and absolute ?
egocentric = absolute
allocentric = relative
describe the muller-layer figure ?
type of visual illusion in which two lines of the same length appear to be different lengths due to the addition of arrow-like fins at the ends of the lines (arrows can be oriented inwards or outwards)
what are muller-layer figures used for ?
closed loop controls : visual frames of reference
what is the muller-layer figured an example of ?
pictorial illusion
what is the “lee’s moving room experiment” ?
an experiment in sensory psychology that investigates how the brain uses visual and vestibular (balance-related) cues to perceive motion and orientation in space
describe lee’s moving room experiment :
- subjects asked to maintain static posture while facing the front wall
- experimenter gradually moved wall forwards or backward
- postural sway measured
- moving wall FOWARD resulted in a dramatic forward lean
- moving wall BACKWARD resulted in a dramatic forward lean
- visual information is a source of afferent information controlling balance
moving wall FOWARD resulted ______________
in a dramatic forward lean
moving wall BACKWARD resulted ________________
resulted in a dramatic forward lean
was lee’s moving room experiment easier/more difficult for adults/kids ?
easier = adults
harder = kids
why was lee’s moving room experiment more difficult for kids ?
kids dont have sophisticated nervous systems yet therefore they call on their bums
