Syntactic processing in sentence comprehension under dual-task conditions in aphasic patients

The functional architecture of the verbal processing resource system was studied by testing aphasic patients for their abilities to use syntactic structure in sentence comprehension in isolation and under dual-task conditions. Patients who showed evidence for a reduction in the resources available for syntactic processing in sentence comprehension were tested on a sentence-picture matching task that required syntactic processing in a no-interference condition and while recalling a series of digits that was one less than or equal to their span. Patients showed equivalent effects of syntactic complexity in comprehension in the three conditions; that is, the effect of syntactic complexity did not increase under digit load conditions. This result supports the conclusion that the processing resource system that underlies syntactic processing is substantially separate from the one that is used for some other verbally mediated functions.