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 the 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 does the dorsal stream do?
According to one widely-accepted hypothesis, the dorsal stream (so named because of the path it takes along the dorsal side of the brain)
carries information related to movement and spatial relationships between objects in the visual field
. It is sometimes called the “where” pathway. See also: ventral stream.
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 do the dorsal and ventral streams do?
From their model, the
ventral stream processes visual information for the purpose of visual perception
(“vision for perception”), while the dorsal stream processes visual information for the purpose of executing movements (“vision for action”).
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 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 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 makes up the dorsal stream?
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 is dorsal language stream?
C: The dorsal language stream (SLF and AF) is
the most superficial long association fiber tract in the cerebrum
. … The middle fiber pathway in the suprasylvian area is the SLF II, which connects the angular gyrus or middle portion of the occipital lobe to the middle frontal gyrus.
What is the ventral stream responsible for?
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 object agnosia?
Object agnosia (
an inability to recognize objects in the environment
) • Prosopagnosia (poor face recognition) • Simultanagnosia (inability to recognize whole visual scenes)
What is the dorsal visual pathway?
Dorsal visual pathway: this pathway
extends from the primary visual cortex (V1) in the occipital lobe to the parietal lobe
. The dorsal pathway is subdivided by the intraparietal sulcus (IPS) into several main sectors including the superior parietal lobule, inferior parietal lobule, and the supramarginal gyrus.
What is dorsal and ventral side?
In general,
ventral refers to the front of the body, and dorsal refers to the back
. These terms are also known as anterior and posterior, respectively. … Similarly, for the feet, the dorsal side is the top of the foot, or the area facing upwards when standing upright.
What are the two visual pathways?
This provides information about the depth of objects. In addition to the primary visual pathways, two other major visual pathways can be distinguished:
the tectal, or collicular, pathway and the pretectal nuclei pathway
. Thus fibers from the optic tracts do not all go to the lateral geniculate body.
