The role of the dynamic body schema in praxis: Evidence from primary progressive apraxia

Author(s): Giovannetti, T., Libon, D.

Journal/Book: Brain Cognition. 2000; 44: 525 B St, Ste 1900, San Diego, CA 92101-4495, USA. Academic Press Inc. 166-191.

Abstract: On an influential model of limb praxis, ideomotor apraxia results from damage to stored gesture representations or disconnection of representation?, from sensory input or motor output (Heilman & Gonzalez Rothi, 1993: Gonzalez Rothi ct al., 1991). We report data From a patient with progressive ideomotor limb apraxia which cannot be readily accommodated by this model. The patient, BG, is profoundly impaired in gesturing to command, to sight of object, and to imitation, but gestures nearly normally with tool in hand and recognizes gestures relatively well. In addition, performance is profoundly impaired on imitation of meaningless gestures and on tasks requiring spatiomotor transformations of body-position information. We provide evidence that BG's apraxia is largely attributable to impairments external to the stored gesture system in procedures coding the dynamic positions of the body parts of self and others: that is, the body schema. We propose a model of a dynamic, interactive praxis system subserved by posterior parietal cortex in which stored representational elements, when present, provide ''top-down'' support to spatiomotor procedures computed on-line. In addition to accounting fur BG's performance, this model accommodates a common pattern of ideomotor apraxia more readily than competing accounts.

Note: Article Buxbaum LJ, Moss Rehabil Res Inst, 1200 W Tabor Rd, Philadelphia,PA 19141 USA

Keyword(s): body schema; body representation; body-centered coding; praxis; apraxia; ideomotor apraxia; gesture; IDEOMOTOR APRAXIA; PARIETAL CORTEX; SELECTIVE IMPAIRMENT; IMITATING GESTURES; NEURONAL-ACTIVITY; PREMOTOR CORTEX; LEFT-HEMISPHERE; OPTIC ATAXIA; OBJECTS; RECOGNITION

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