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