Serial and semantic encoding of lists of words in schizophrenia patients with visual hallucinations.

Previous research has suggested that visual hallucinations in schizophrenia are associated with abnormal salience of visual mental images. Since visual imagery is used as a mnemonic strategy to learn lists of words, increased visual imagery might impede the other commonly used strategies of serial and semantic encoding. We had previously published data on the serial and semantic strategies implemented by patients when learning lists of concrete words with different levels of semantic organisation (Brébion et al., 2004). In this paper we present a re-analysis of these data, aiming at investigating the associations between learning strategies and visual hallucinations. Results show that the patients with visual hallucinations presented less serial clustering in the non-organisable list than the other patients. In the semantically organisable list with typical instances, they presented both less serial and less semantic clustering than the other patients. Thus, patients with visual hallucinations demonstrate reduced use of serial and semantic encoding in the lists made up of fairly familiar concrete words, which enable the formation of mental images. Although these results are preliminary, we propose that this different processing of the lists stems from the abnormal salience of the mental images such patients experience from the word stimuli.

Cortical effects of quetiapine in first-episode schizophrenia: a preliminary functional magnetic resonance imaging study.

BACKGROUND: Quetiapine improves both psychotic symptoms and cognitive function in schizophrenia. The neural basis of these actions is poorly understood. METHODS: Three subject groups underwent a single functional magnetic resonance imaging (fMRI) session: drug-naive (n = 7) and quetiapine-treated samples of patients with schizophrenia (n = 8) and a healthy control group (n = 8). The fMRI session included an overt verbal fluency task and a passive auditory stimulation task. RESULTS: In the verbal fluency task, there was significantly increased activation in the left inferior frontal cortex in the quetiapine-treated patients and the healthy control sample compared with the drug-naive sample. During auditory stimulation, the healthy control group and stably treated group produced significantly greater activation in the superior temporal gyrus than the drug-naive sample. CONCLUSIONS: Quetiapine treatment is associated with altered blood oxygen level-dependent responses in both the prefrontal and temporal cortex that cannot be accounted for by improved task performance subsequent to drug treatment.