Visual encoding impairment in patients with schizophrenia: contribution of reduced working memory span, decreased processing speed, and affective symptoms.

OBJECTIVE: Previous research has revealed the contribution of decreased processing speed and reduced working memory span in verbal and visual memory impairment in patients with schizophrenia. The role of affective symptoms in verbal memory has also emerged in a few studies. The authors designed a picture recognition task to investigate the impact of these factors on visual encoding. METHOD: Two types of pictures (black and white vs. colored) were presented under 2 different conditions of context encoding (either displayed at a specific location or in association with another visual stimulus). It was assumed that the process of encoding associated pictures was more effortful than that of encoding pictures that were presented alone. Working memory span and processing speed were assessed. RESULTS: In the patient group, working memory span was significantly associated with the recognition of the associated pictures but not significantly with that of the other pictures. Controlling for processing speed eliminated the patients' deficit in the recognition of the colored pictures and greatly reduced their deficit in the recognition of the black-and-white pictures. The recognition of the black-and-white pictures was inversely related to anxiety in men and to depression in women. CONCLUSIONS: Working memory span constrains the effortful visual encoding processes in patients, whereas processing speed decrement accounts for most of their visual encoding deficit. Affective symptoms also have an impact on visual encoding, albeit differently in men and women.

Abnormal functioning of the semantic network in schizophrenia patients with thought disorganization. An exemplar production task.

Numerous studies have indicated that thought disorganization in schizophrenia is associated with an enhanced semantic priming effect. This suggests abnormal functioning of the semantic network in these patients, with disinhibited spreading of semantic activation. We investigated whether thought disorganization is also associated with atypical responses in the production of semantic category exemplars. An exemplar production task was administered to 43 patients with schizophrenia and 24 healthy controls. The names of 16 semantic categories were provided, and the participants were requested to produce an exemplar for each category. The typicality of the response was rated according to norms. Higher ratings of thought disorganization were associated with the production of more atypical exemplars. In addition, the patients with high thought disorganization scores were significantly more atypical in their responses than were the healthy controls. In contrast, the patients with low thought disorganization scores were equivalent to the healthy controls. Higher ratings of affective flattening were associated with the production of less atypical exemplars. The results corroborate, within a different paradigm than semantic priming, the theory that thought disorganization is associated with faster and more distant connections within the semantic network. This effect is counteracted by affective flattening.