Stochastic approaches to understanding dissociations in inflectional morphology

Computer modelling research has undermined the view that double dissociations in behaviour are sufficient to infer separability in the cognitive mechanisms underlying those behaviours. However, all these models employ multi-modal representational schemes, where functional specialisation of processing emerges from the training process. Targeted lesioning of different regions of functional specialisation leads to varied but predictable deficits in model performance. We argue that multi-modal representational schemes are not a necessary condition for the observation of double dissociations in an information processing system that shares resources across multiple tasks. Using a uni-modal representational system, we demonstrate that double dissociations may also result from stochastic processes. Lesioning experiments on a single-route, uni-modal connectionist model of regular and irregular noun and verb morphology confirm and extend earlier work demonstrating that selective impairment across tasks can result from damage to a distributed information processing system. A systematic investigation of the degree to which performance deteriorates across different inflectional classes reveals that simple and double dissociations can occur in this single-route, uni-modal model. An important prediction of the model is that double dissociations between regular and irregular inflection, resulting from stochastic processes should be extremely rare. However, they are particularly likely to occur when the researcher uses test batteries consisting of a small number of items. Given that cognitive neuropsychologists rarely provide details about the distribution of performance in a disordered population, it is concluded that a stochastic interpretation of double dissociations may have wider applicability than is normally supposed.     

Treatment-resistant panic disorder

A substantial number of patients with panic disorder and agoraphobia may remain symptomatic after standard treatment (including selective serotonin reuptake inhibitors, tricyclic antidepressants, benzodiazepines, or irreversible monamine oxidase inhibitors). In this review, recommendations for the treatment of patients with panic disorder and agoraphobia who do not respond to these drugs are provided. Nonresponse to drug treatment could be defined as a failure to achieve a 50% reduction on a standard rating scale after a minimum of 6 weeks of treatment in adequate dose. When initial treatments have failed, the medication should be changed to other standard treatments. In further attempts at treatment, drugs should be used that have shown promising results in preliminary studies, such as venlafaxine. Combination treatments may be used, such as the combination of an selective serotonin reuptake inhibitor and a benzodiazepine. Psychological treatments such as cognitive-behavioral therapy have to be considered in all patients, regardless whether they are nonresponders or not. According to existing studies, a combination of pharmacologic treatment with cognitive-behavioral therapy can be recommended.