Ideomotor apraxia and functional ability.

The impact of ideomotor apraxia (IMA) on functional ability has been a relatively neglected topic in research. This has been due to the continued focus on performance on gesture imitation and pantomime of tool-use, together with widespread acceptance of anecdotal evidence that IMA has no effect when directly manipulating objects. An increasing number of studies have shown that IMA does in fact result in increased clumsiness when handling objects and may contribute to disability in everyday life. However the effect seems relatively mild compared to the stark abnormalities on gesture imitation and pantomime. The conventional explanation for this is that the cues provided by naturalistic contexts improve retrieval of action representations, but an alternative account concerns task-specific cognitive demands. Performance on simple prehensile tasks can be successfully guided by physical affordances whereas motor tasks may be failed if they require the support of memory or problem solving ability. A central deficit in IMA may be impaired postural representation causing inability to solve the problem of how to manipulate objects where neither affordance nor memory can dictate action. However, this account still fails to explain fully the patterns of error seen on complex naturalistic tasks such as dressing. Future research needs to further our understanding of how IMA maps on to disability, which will have implications for theory building and for therapeutic intervention.