Postural knowledge of transitive pantomimes and intransitive gestures.

Patients with apraxia are more impaired when performing transitive pantomimes than intransitive gestures. This dissociation might be related to the differences in movement complexity. Alternatively, the programs for intransitive gestures might be better defined, more widely distributed, or easier to activate than are those for transitive pantomimes. The purpose of this study was to test the complexity versus representational hypotheses. Twenty right-handed normal subjects both performed and discriminated correct from incorrect transitive pantomimes and intransitive gestures. The discrimination was performed by having subjects point at illustrations of hand postures. The subjects performed better when discriminating postures than when performing gestures or pantomimes. On both the production and discrimination tests, subjects performed better with intransitive gestures than transitive pantomimes. Although the finding that even normal subjects had more difficulty performing transitive pantomimes than intransitive gestures might appear to support the complexity hypothesis, that subjects also had more difficulty discriminating transitive than intransitive postures supports the representational activation hypothesis.