IMPAIRMENT OF THE SEMANTIC NETWORK IN SCHIZOPHRENIA

It is well established that patients with schizophrenia display a vari ety of language impairments. Despite considerable research, however, t he underlying mechanisms of the language deficits in schizophrenia rem ain unclear. Representations of semantic networks of 56 patients with schizophrenia and 28 normal comparison (NC) subjects of similar ages a nd educational levels were generated by multidimensional scaling and P athfinder analyses of their responses on the Animal Fluency Test. On t he basis of traditional scoring techniques (i.e., total number of corr ect animal names generated in 60 s), all patients performed significan tly worse than the NC subjects. More detailed analyses of the underlyi ng semantic networks revealed that performance in the patients varied according to age of onset and subtype of schizophrenia. The semantic n etwork of patients with late-onset schizophrenia (i.e., with onset aft er age 45) was virtually identical to that of the NC group. In contras t, the semantic network of patients with a younger age of onset was di sorganized and differed significantly from that of the NC subjects. Fi ndings demonstrated that patients with nonparanoid subtypes displayed greater disorganization in their semantic networks than patients with a paranoid subtype. Although general fluency impairments (e.g., diffic ulties in initiation, retrieval, and search mechanisms) may be sensiti ve to schizophrenia, per se, specific deficits in the structure of sem antic knowledge may be associated with certain characteristics of indi vidual patients with schizophrenia, such as an earlier age of onset an d nonparanoid subtype.