Gradients of semantic relatedness and their contrasting explanations in refractory access and storage semantic impairments.

We report a study that directly compares the comprehension skills of patients with refractory access and static storage semantic deficits. It has been reported previously, in the context of matching to sample tasks, that the performance of both types of patients may be affected by the semantic relatedness of competing responses. However, it has been hypothesised that such effects of semantic distance may reflect different processes (Warrington & Cipolotti, 1996). More specifically, semantic relatedness effects following refractory access deficits may be explained in terms of the effect of refractoriness on representations that share semantic space, whilst relatedness effects consequent to storage deficits may reflect the preferential sparing of superordinate rather than item-specific information. In this series of experiments, we compare and contrast refractory access and storage patients on word-picture matching tasks that manipulate the semantic relatedness of items within a response array. In particular, the interaction of semantic distance and item frequency is explored. We also provide evidence of gradients of semantic relatedness in our refractory assess patient, and consider what information such patients can provide about extremely fine-grain conceptual organisation.