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 visual stream do?
The dorsal stream is involved in spatial awareness and guidance of actions (e.g., reaching). In this it has two distinct functional characteristics—it contains a detailed map of the visual field, and is also good at detecting and analyzing movements.
What happens when there is damage to the ventral stream?
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.
Which visual features are processed by the 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 happens when optic chiasm is damaged?
If the optic nerve is damaged in the optic chiasm level, it causes bitemporal hemianopia. This may occur in expanding pituitary adenoma (Figure 1). If optic nerve is damaged posterior to the optic chiasm (optic tract, optic radiation), it causes a visual field defect on the opposite side to the damage [5-7].
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 the most likely deficit resulting from a dorsal stream lesion?
The dorsal stream processes information about the “where” of the visual stimulus (Figure 15.10). Damage the dorsal visual association cortex results in deficits in spatial orientation, motion detection and in guidance of visual tracking eye movements.
What is ventral pathway responsible for?
What happens optic chiasm?
In the optic chiasm, the fibers of the nasal retina (i.e., the temporal visual field) of each eye cross, whereas the fibers of the temporal retina (i.e., the nasal visual field) of each eye proceed uncrossed. Thus, each optic tract contains visual fibers from the same hemifield of each eye.
What is the symptom complex of dorsal stream dysfunction?
The symptom complex of dorsal stream dysfunction, which is associated with a range of pathologies affecting the posterior parietal area, ranges in character and severity. It may be associated with slightly or significantly impaired visual acuities and visual fields, and may also be associated with varying degrees of cerebral palsy.
How does damage to the ventral stream affect visual processing?
Damage to the ventral stream can cause inability to recognize faces or interpret facial expression. Along with the visual ventral pathway being important for visual processing, there is also a ventral auditory pathway emerging from the primary auditory cortex.
Is the dorsal stream system automatic or unconscious?
The dorsal stream system is automatic and unconscious. It is ‘on-line’ and is not memory based. Damage in this brain territory is associated with a range of visual behaviours described in Table I .
Where does the dorsal stream lead to in the brain?
The ventral stream (also known as the “what pathway”) leads to the temporal lobe, which is involved with object and visual identification and recognition. The dorsal stream (or, “where pathway”) leads to the parietal lobe, which is involved with processing the object’s spatial location relative to the viewer and with speech repetition.