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Parietal Lobe
Aka: Parietal Lobe, Parietal Lobe Function, Cerebral Parietal Lobe, Homunculus, Primary Somatosensory Cortex, Primary Somesthetic Area, Brodmann Area 3 1 2, Secondary Somatosensory Cortex, Secondary Somesthetic Area, Brodmann Area S2, Superior Parietal Lobule, Brodmann Area 5, Visuo-Motor Coordination Area, Brodmann Area 7, Angular Gyrus, Brodmann Area 39, Supramarginal Gyrus, Brodmann Area 40, Brodmann Areas of Parietal Lobe, Posterior Paracentral Gyrus, Precuneus, Post Central Gyrus
- Definitions
- Parietal Lobe
- Parietal Lobe receives sensory input and performs language processing
- As with motor centers in the Frontal Lobe, the Parietal Lobe is organized in the form of the cortical humunculus
- Disproportionately large region devoted to the face and hands, in contrast with the torso and legs
- Sensory functionality is primarily contained in Brodmann Areas 3,1,2
- Also in adjacent seconday somatic area (for pain and TemperatureSensation)
- Brain Lesions result in Receptive Aphasia, sensory loss, hemianopia and and spatial Disorientation.
- Anatomy: Brodmann Areas of Parietal Lobe
- Images


- Primary Somatosensory Cortex or Somesthetic Area (Area 3,1,2)
- Lesions in this region affect contralateral sensory loss in light touch, pressure and proprioception
- Pain and Temperature sense are received in a region inferior to Area 3,1,2, known as the Secondary Somesthetic Area.
- Secondary Somatosensory Cortex or Somesthetic Area (Area S2)
- Lesions in this region affect pain and Temperature sense
- These fibers are inferior to Primary Somesthetic Area (Area 3,1,2)
- Superior Parietal Lobule (Anterior, Area 5)
- Involved in spatial orientation
- Visuo-Motor Coordination (Posterior, Area 7)
- Involved in spatial orientation
- Angular Gyrus (Area 39)
- When in the dominant hemisphere, a lesion in the Angular Gyrus affects the ability to read (alexia) and write (agraphia).
- Supramarginal Gyrus (Area 40)
- Dominant hemisphere lesions in the Supramarginal Gyrus cause Agnosia of tactile Sensation and proprioception
- The patient may have difficulty with left-right discrimination and Apraxia (difficulty with skilled movement)
- It also affects the interpretation of gestures made by other people.
- Physiology: Homunculus
- Homunculus is a graphical representation of sensory and motor control
- Man standing at the midline between the two Cerebral Hemispheres
- Legs are above the falx cerebri at the medial Parietal Lobe (Anterior Cerebral Artery)
- Legs are relatively small compared to arms and head
- Represents fewer overall Neurons dedicated to leg motor and sensory control
- Man is bending at the waist over the top of the Parietal Lobe
- Legs and head extend over the lateral Parietal Lobe (Middle Cerebral Artery)
- Arms and head are relatively large
- Represents greater overall Neurons dedicated to arm/head motor and sensory control
- Signs: Brain Lesions
- Receptive Aphasia (Area 39)
- Sensory loss (Area 3,1,2 and Area S2 following Homunculus distribution)
- Spatial Disorientation (Area 5, 7)
- Hemianopia (loss of half of Visual Field in each eye)
- Agnosia of tactile Sensation and proprioception (Area 40, dominant hemisphere)
- Apraxia (difficulty with skilled movement) and altered left-right discrimination (Area 40)
- Exam
- Cognitive Dominant
- Names fingers
- Knows left and right
- Performs calculations on paper
- Reading
- Cognitive Non-Dominant
- Constructs copy of matchstick figure made by examiner
- References
- Newton (1994) Am Fam Physician 49(4): 787-97 [PubMed]