Chapter 14: The Parietal Lobes

Functional Zones of Parietal Lobes

- Anterior Zone- 1,2,3, and 43 -somatosensory cortex -posterior zone - remaining areas -posterior parietal cortex

Symptoms of parietal lobe damage that are not visuomotor

- difficulty with arithmetic -difficulty with certain aspects of language -difficulty with movement sequences

Balint's Syndrome

-Can't fixate on visual stimulus -neglect of objects -Optic Ataxia

Spatial Navigation

-Cognitive Spatial Map -route knowledge, unconcious knowledge of how to reach a destination -Medial parietal region (MPR) - neurons show responses associated with making a specific movement at a specific location

Somatosensory symptoms of Parietal-Lobe Lesions

-Lesions to the post-central gyrus produce: -abnormally high sensory thresholds -Impaired position sense - Deficits in stereognosis - or tactile perception - afferent paresis -- clumsy finger movements due to lack of feedback about finger position

Disorders of Spatial Cognition

-Mental rotation requires: -Mental imaging of the stimulus -manipulation of the image -left hemisphere deficit may result from the inability to generate the image -right hemisphere deficit may result in the inability to manipulate the image -the inability to use topographic information is associated with right hemisphere damage

Contralateral Neglect

-Neglect for visual, auditory, and somesthetic stimulation on one side of the body or space -During recovery patients go through allesthesia, begin to respond to the neglected stimuli as if they were on the other side of the body or space, and then simultaneous extinction -Lesion most often in the right inferior parietal lobe -right intraparietal sulcus and the right angular gyrus -Occasionally noted after lesions to the frontal lobe and cingulate cortex -Defective sensation or perception -Defective attention or orientation

The Parietal Lobes

-Process and integrate Somatosensory and Visual information. -Anatomy of the Parietal Lobes. - Anterior border- central fissure - Ventral border- Sylvan Fissure - Dorsally by the cingulate gyrus - posterior border- Parieto-occipital sulcus

Simultaneous extinction

-Two stimuli are applied simultaneously to opposite sides of the body -A failure to report a stimulus on one side is referred to as extinction

theory of Parietal Lobe Function

-anterior zones- process somatic sensations and perceptions -posterior zones- integrate information from vision with somatosensory information for movement

Constructional Apraxia

-can not copy pictures, build puzzles, or copy a series of facial movements -associated with right and left parietal lesion **

Ideomotor apraxia

-cannot copy serial movements -more likely to be associated with left parietal lesions

Left and Right Parietal Lobes Compared

-clear asymmetry, but some overlap -overlap may be due to preferred cognitive mode of individual

Left parietal symptoms

-disturbed language function -Apraxia -dyscalculia -difficulty with arithmetic -poor recall inability to discriminate right and left -right hemianopia

Gerstmann Syndrome

-finger agnosia -right/left confusion -agraphia -acalculia -results from a left parietal lobe lesion

Spatial Attention

-function of the parietal lobe to selectively attend to different stimuli -Disengagement -shifting attention from one stimulus to the next

Acalculia

-inability to do arithmetic -noted in parietal lobe patients -might result from the spatial properties of addition and subtraction -two digit number occupy different spaces -"borrowing" during subtraction

Apraxia

-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

Sensorimotor Transformation

-neural calculations of the relative position of the body with respect to sensory feedback from movements being made and planned

Area PG

-receives complex connections including visual, somesthetic, proprioceptive, auditory, vestibular, oculomotor, and cingulate connections -Parieto-temporo-occipital cross roads - part of the dorsal stream

Guidance of movement

-sensitive to eye movements -posterior parietal cortex

Area PE

-somatosensory -inputs from the somatosensory strip -outputs to primary motor cortex, supplementary motor cortex, premotor regions, and area PF

Object Recognition

-viewer centered object identification -determines the location, location orientation, and motion of an object -posterior parietal cortex -After Right parietal lobe lesions patients are poor at recognizing objects in unfamiliar views

Language problems in parietal patients

-words have spatial organization "tap" vs. "pat"

Blind Touch

Cannot feel stimuli, but can report their location

Subdivisions of the Parietal Lobes

Postcentral Gyrus -Brodmann's areas 1,2,3 Superior Parietal Lobule -Brodmann's areas 5 and 7 Parietal Operculum -Brodmann's area 43 **Inferior Parietal Lobule** Supramarginal Gyrus - Brodmann's area 40 Angular Gyrus -Brodmann's area 39

von Economo

Posterior parietal Areas -PE -PF -PG - polymodal and symmetrical - larger in right hemisphere

Asymbolia for pain

absence of normal reactions to pain

Right parietal lobe damage

deficits in drawings, have tendency to omit key details

Agnosia

inability to interpret sensations

Asterognosis

inability to recognize an object by touch

Anosodiaphoria

indifference to illness

movement sequence problems in parietal patients

individual elements of the movement may have spatial organization

Area PF

input from somatosensory, primary motor cortex, and small visual input through area PG

Asomatognosia

loss of knowledge or sense of one's own body

Finger agnosia

unable to point to the fingers or show them to the examiner

Anosognosia

unawareness or denial of illness