The Parietal Lobes

The parietal lobes have two functional regions:

1. Sensation and perception - integrates sensory information to form a single perception ([cognition]
2. Integrating sensory input - primarily with the visual system. It constructs a spatial coordinate system to represent the world around us, including our body image and spatial relations.

In this way, our bodies possess an inner sensory map, with a spatial connection to each finger, arm, toe, foot etc. This is why amputees often still feel as though the missing limb is still attached - as the mind map still associates its presence in relation to the rest of the body.

Video - Brain Mind Lecture 4: The Parietal Lobes

An Introductory Overview: Body Image, Phantom Limbs, Phantom Limb Pain, Apraxia, Agnosia, Language, by Rhawn Joseph, Ph.D.

NOTE: To reduce confusion, all CT images have been reversed so damage on the left appears on the left, and right sided damage appear on the right.

Damage to Left Parietal Lobe

Damage to the left parietal lobe can result in "Gerstmann's Syndrome." This results in right-left confusion and is associated with:

• Difficulty with Writing - agraphia
• Difficulty with Mathematics - acalculia
• Disorders of language - aphasia
• Inability to perceive objects normally - agnosia

Left parietal-temporal lesions can effect verbal memory and the ability to recall strings of digits.

Damage to Right Parietal Lobe

Damage to the right parietal lobe can result in neglecting part of the body or space affecting grooming and dressing. It can also cause:

• Difficulty in making things - constructional apraxia
• Denial of deficits - anosagnosia
• Difficulty drawing

The right parietal-temporal lobe is concerned with non-verbal memory. Right parietal-temporal lesions can produce significant changes in personality.

Damage to Both Parietal Lobes

Bi-lateral damage, for example due to large lesions, can cause a visual attention and motor syndrome called 'Balint's Syndrome'. This is characterized by:

• Inability to voluntarily control the gaze - ocular apraxia
• Inability to integrate components of a visual scene - simultanagnosia
• Inability to accurately reach for an object with visual guidance - optic ataxia

Memory and personality deficits can also occur if there is damage to the area between the parietal and temporal lobes.

Next: The Temporal Lobe of the Brain

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