Apraxia, mechanical problem solving and semantic knowledge

Abstract

To investigate the nature of the apraxia in corticobasal degeneration (CBD) five patients with CBD and five matched controls were compared on tests of: i) meaningless and symbolic gesture production, ii) a battery of semantic tasks based on 20 everyday items (involving naming and picture-picture matching according to semantic attributes, matching gestures-to-objects, object usage from name and with the real object) and iii) a novel tool test of mechanical problem solving. All five patients showed severe impairment in the production of meaningless and symbolic gestures from command, and by imitation, and were also impaired when using real objects. Deficits were not, however, restricted to action production: four were unable to match gestures to objects and all five showed impairment in the selection and usage of novel tools in the mechanical problem solving task. Surprising was the finding of an additional semantic knowledge breakdown in three cases, two of whom were markedly anomic. The apraxia in CBD is, therefore, multifactorial. There is profound breakdown in the organisation and co-ordination of motor programming. In addition, patients show central deficits in action knowledge and mechanical problem solving, which has been linked to parietal lobe pathology. General semantic memory may also be affected in CBD in some cases and this may then contribute to impaired object usage. This combination of more than one deficit relevant for object use may explain why CBD patients are far more disabled by their dyspraxia in everyday life than any other patient group.

When objects lose their meaning: What happens to their use?

“…Zangwill (1960) noted that difficulties in using real objects may be related to a severe production disorder. In concordance with this, we have reported a group of patients with ideomotor apraxia owing to corticobasal degeneration,who had difficulties demonstrating the use of real objects (Spatt et al, 2002). Ochipa, Rothi, and Heilman (1989) reported a lefthanded patient who, following a right-hemisphere stroke, was able to name objects but was unable to point to them when their functions were described or to describe their functions himself.…”

“…There is no doubt that the ability to use objects can be disrupted when conceptual knowledge about them is preserved (Rumiati et al, 2001;Spatt et al, 2002). All such reported cases can, we think, be explained by frank nonsemantic apraxic disorders.…”

“…Several patients have been reported in the literature who were unable to use real objects correctly despite having preserved knowledge about those same objects (Rumiati, Zanini, Vorano, & Shallice, 2001;Spatt, Bak, Bozeat, Patterson, & Hodges, 2002). These patients invariably had some level of ideomotor apraxia associated with damage to parietal regions, which left them unable to produce the movements appropriate for object use.…”

A Model-Based Approach to Understanding Apraxia in Corticobasal Syndrome

“…Peigneux and colleagues (2001) showed that imitation was more impaired than pantomime irrespective of the gesture type in 18 patients with CBS. Two other studies, with smaller sample sizes provide further evidence that imitation is more impaired than pantomime in CBS Spatt et al 2002). Other studies fail to provide information on both pantomime and imitation tasks and therefore do not elucidate this issue (Monza et al 2003;Leiguarda et al 1994;Salter et al 2004).…”

“…Kinematic abnormalities in object (tool) use in CBS have been reported in the past (Merians et al 1999;Leiguarda et al 2000). In addition, studies comparing pantomime and actual tool use have shown that patients improve when manipulating tools, which theoretically should translate in better performance in actual life Spatt et al 2002;Leiguarda et al 2000).…”