Apraxia after a superior parietal lesion.

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neurobiology

Background:

• Unilateral limb apraxia is a complex motor disorder affecting skilled movements.
• The superior parietal lobes, including Brodmann areas 5 and 7, are implicated in sensorimotor integration.
• Hand-manipulation neurons in monkeys suggest a role for these areas in proprioceptive guidance.

Observation:

• A patient with a right superior and inferior parietal lobe lesion presented with left limb apraxia.
• The patient's performance in pantomime, imitation, and object use significantly worsened without visual guidance.
• Despite intact proprioception and no optic ataxia, the patient struggled with visual-to-somatosensory spatial transcoding.

Findings:

• The lesion affected the right superior parietal lobe (Brodmann areas 5 and 7) and inferior parietal lobe.
• Visual guidance is critical for performing skilled limb movements in patients with parietal lobe damage.
• The patient demonstrated deficits in transcoding visual spatial information to somatosensory spatial coordinates.

Implications:

• The superior parietal lobe is crucial for transcoding visual-spatial information into somatosensory-spatial codes.
• This region also plays a vital role in translating spatial-temporal representations of skilled movements into somatosensory-spatial formats.
• Understanding these pathways is essential for diagnosing and treating apraxia and related sensorimotor disorders.