The apraxias are higher-order defects of sensorimotor integration

The classical features of motor disorders due to neurological disease affecting the pyramidal pathways, cerebellum and basal ganglia in humans are well known. What is less understood is the clinical world of apraxia--'inability to perform purposeful skilled movements in the absence of any elementary motor (weakness, akinesia, abnormal posture or tone) or sensory deficits, or impaired comprehension or memory'. Much of what clinicians call apraxia is a failure of gesture production to command, due to problems of transcoding language into motor action, without motor deficit in ordinary life. However, damage to premotor regions and superior parietal lobules provokes devastating spontaneous higher-order motor deficits, including limb-kinetic apraxia, diagnostic apraxia, visuomotor apraxia and ideational apraxia.