Multiple task demands in action disorganization syndrome

We present novel evidence for specific, disruptive effects of multi-step task demands on the production of everyday life tasks in two patients with Action Disorganization Syndrome (ADS). Experiment 1 demonstrated that the patients were impaired at carrying out everyday life tasks but improved when they instructed the examiner to perform the tasks. Experiments 2 and 3 showed that the patients improved in their own performance when the demands were reduced - by eliminating the need to use their own task schema (Experiment 2) and by reducing the need for error monitoring (Experiment 3). Experiment 4 reduced sequential effects in task performance further by having patients perform the same individual actions as before but now out of the task context. The data indicate that ADS patients are vulnerable to multiple demands made during the performance of everyday life tasks and show abnormal, disruptive effects of three specific factors: (i) using a self-driven schema, (ii) error monitoring and (iii) the activation of prior actions from the same task. The implications for understanding ADS are discussed.