Dorsal stream dysfunction results
from posterior parietal damage
and is associated with cerebral palsy, periventricular white matter injury, premature birth, hydrocephalus and Williams syndrome, and similar visual difficulties are becoming apparent in children with autistic spectrum disorder.
What happens if your dorsal stream is damaged?
If either the dorsal or ventral stream is damaged, this leads to
dissociable behavioural deficits
. For example, patients with optic ataxia have lesions in parietal areas, which are part of the dorsal stream. They have deficits in reaching and grasping objects, but are able to visually discriminate different objects.
What is the dorsal stream responsible for?
Firstly, the dorsal stream, which is generally accepted to be responsible for
motion perception, spatial awareness, and vision for action
, includes areas V5, V3a, and V6, and terminates in parietal cortex.
What does dorsal stream mean?
The dorsal stream,
or where pathway
, describes a hierarchy of areas that support visually-guided behaviors and localizing objects in space. It involves two main groups of areas, which receive separate, strong projections from V1. The lateral group in the dorsal stream consists of areas MT, MTc, MST, and FST.
What happens if your ventral stream is damaged?
Patients with damage to the ventral stream are
typically unable to perceive the size, shape, and orientation of objects
. Remarkably, however, some of these patients continue to show normal preshaping and rotation of the hand when they reach out to grasp the very objects whose forms they fail to see.
What is form agnosia?
Visual form agnosia is
a severe disorder of visual recognition resulting from extrastriate lesions in occipital and temporal cortex
. Despite preserved visual acuity and minor visual field defects, patients with visual form agnosia are severely impaired in shape and form discrimination.
What is object agnosia?
Object agnosia (
an inability to recognize objects in the environment
) • Prosopagnosia (poor face recognition) • Simultanagnosia (inability to recognize whole visual scenes)
Where is the dorsal stream located?
Dorsal stream
Also known as the parietal stream, the “where” stream, or the “how” stream, this pathway stretches
from the primary visual cortex (V1) in the occipital lobe forward into the parietal lobe
.
What is the difference between ventral and dorsal stream?
The ventral stream (or “vision-for-perception” pathway) is believed to mainly subserve recognition and discrimination of visual shapes and objects, whereas the dorsal stream (or “vision-for-action” pathway) has been primarily associated with
visually guided reaching and grasping
based on the moment-to-moment analysis …
What is a dorsal stream in psychology?
a series of cortical maps that originate in the striate cortex (primary visual cortex) of the occipital lobe and project forward and upward into the parietal lobe
. Known informally as the “where” or “how” pathway, the dorsal stream is involved in processing object motion and location in space.
What is dorsal vision?
The dorsal visual pathway is
a functional stream originating in primary visual cortex and terminating in
the superior parietal lobule that is responsible for the localization of objects in space and for action-oriented behaviors that depend on the perception of space.
What are the function of ventral and dorsal stream?
The ventral stream is likely not contributing toward object vision alone but is involved in the processing of a number of visual features; the ventral stream is not solely responsible for object recognition;
the dorsal stream is responsible for spatial vision as well as for spatial attention
, and is responsible for …
How does the ventral stream work?
a pathway that carries visual information from the primary visual cortex to the temporal lobe
. According to one widely-accepted hypothesis, the ventral stream (so named because of the path it takes along the ventral side of the brain) carries information related to object form and recognition.
What is visual agnosia in dementia?
General Discussion. Primary visual agnosia is
a rare neurological disorder characterized by the total or partial loss of the ability to recognize and identify familiar objects and/or people by sight
. This occurs without loss of the ability to actually see the object or person.
What is an example of a patient’s experience of agnosia?
This condition can also be described by only seeing one object at a time. An example is
having two cups in your visual field and only being able to see one at a time
. Impaired ability to recognize or identify objects by touch alone.
What is associative agnosia mean?
Associative visual agnosia refers
to difficulty with understanding the meaning of what they are seeing
. They can draw or copy but do not know what they have drawn. They correctly perceive the form and know the object when tested with verbal or tactile information, but cannot identify the object.
