Occipital and Parietal Lobes Org and Function

Question 1

Functions of Area V1

Answer 1

color perception

form and motion perception

Question 2

Functions of Area V2

Answer 2

more detailed/ integrated color, form, and motion perception

Question 3

Functions of Area V4

Answer 3

primarily involved in color perception (fine-tuned)

Question 4

Dorsal Stream (visual)

Answer 4

the “where” pathway
sends info to the parietal lobe
visual info to locate objects, detect movement, orient attention, and coordinate for action/ grasping

Question 5

Ventral Stream (visual)

Answer 5

the “what” pathway
Sends info to inferior temporal lobe
object perception and detection, process color and form

Question 6

What is the STS stream?

Answer 6

Located in the parietal and temporal lobes
Neurons are responsive to both auditory and visual input
Interaction between the visual and dorsal streams

Question 7

What is visual dysfunction?

Answer 7

Dysfunction in visual pathway before it reaches the occipital cortex will result in total loss of visual perception for the parcel of associated information

Question 8

What is apperceptive agnosia?

Answer 8

Damage to bilateral lateral occipital lobes

Failure in object recognition but basic visual functions (acuity, color, motion) preserved

Question 9

What is associative agnosia?

Answer 9

Damage to anterior temporal/association areas

Inability to recognize an object despite its apparent perception (e.g. Can copy a drawing, but cannot identify it)

Question 10

What is prosopagnosia?

Answer 10

Face blindness
Damage to the fusiform gyrus
Inability to recognize faces (even own face)

Question 11

What is pure alexia?

Answer 11

Damage to the splenic might of the corpus callousness and left visual cortex
Inability to read/ perceive letters/ words with intact speech, hearing and wiring

Question 12

Somatosensory agnosias:

Answer 12

Asomatognosia: loss of sense of one’s own body, most commonly affects left side of body

Anosognosia: unawareness or denial of illness

Anosodiaphoria: indifference to illness

Asymbolia for pain: absence of normal reactions to pain such as withdrawal

Autopagnosia: finger agnosia
Usually results from left parietal cortex lesions

Question 13

What is contralateral neglect?

Answer 13

Neglect for visual, auditory, and somesthetic stimulation on one side of the body or space
Lesion most often in the right inferior parietal lobe (left neglect)

Question 14

What do right parietal lobe lesions sometimes impair?

Answer 14

Patients can be impaired at recognizing familiar objects in unfamiliar views

Question 15

What is apraxia?

Answer 15

Movement disorder in which the loss of movement is not caused by weakness, inability to move, abnormal muscle tone, intellectual deterioration, poor comprehension, or other disorders of movement

Question 16

What is Bálint’s Syndrome?

Answer 16

Bilateral damage to the occipito-parietal region
Simultagnosia: can’t perceive while visual field
Oculomotor apraxia: difficulty fixating eyes (gaze paralysis)
Optic apraxia / dysmetria: difficulty with hand-eye coordination

Question 17

What is Gerstmann Syndrome?

Answer 17

Finger agnosia of fingers on either hand
Right-left confusion
Agraphia: inability to write
Acalculia: inability to do simple math problems
Disturbed language function
Results from a left parietal lobe lesion (angular gyrus)

Question 18

What is spatial disorientation?

Answer 18

Distortions in spatial perception
Out of body experiences (imagine that they have more than one body, feel that they are occupying a space distant from their bodies, see people or objects that are not there)

Question 19

What are some of the functions of the parietal lobes?

Answer 19

Anterior zones- process somatic sensations and perceptions

Posterior zones- integrate information from vision with somatosensory information for movement and spatial function, play significant role in mental imagery, especially object rotation and navigation through space

Functions also when no movement is required (concept of left and right, cognitive spatial maps in the brain, mental rotation of objects)

Other functions include arithmetic (more complex math requiring spatial manipulation) language (because words have spatial organization) and movement sequencing (individual elements of the movement have a spatial organization)

Question 20

What are some somatoperceptual disorders?

Answer 20

Astereognosis: disorder of tactile perception (inability to recognize nature of an object by touch)

Simultaneous extinction: two stimuli applied simultaneously to opposite sides of the body, a failure to report a stimulus on one side is referred to as extinction

Numb touch: cannot feel stimuli and cannot feel touch, but can report the location of the touch, complete anesthesia on one side

Question 21

What symptoms do lesions to the sensory strip (postcental gyrus) typically produce?

Answer 21

Abnormally high sensory thresholds
Impaired position sense
Deficits in stereognosis (or tactile perception)
Afferent paresis (clumsy finger movements due to lack of kinesthetic feedback about finger position)

Question 22

What are some of the behavioral uses of spatial information?

Answer 22

Object recognition/ identification

Guidance of movement to objects

Sensorimotor transformation (perception of the body’s position relative to novelty being made and planned)

Question 23

What are the subdivisions of the parietal cortex?

Answer 23

Postcentral gyrus (somatosensory cortex)

Superior parietal lobule (guides movement, info on limb position)

Parietal operculum

Supramarginal gyrus

Angular gyrus (input from somatosensory and visual areas)