[Influence of attention on an auditory-verbal learning test in schizophrenic patients]

Schizophrenic patients are known to feature alterations in their cognitive performances, principally in executive functions, attention and memory. In this last domain, studies have shown a relatively severe and global deficit, which can be assessed in chronic and first episode patients. It seems that the memory dysfunction is independent of age and intellectual level, but does correlate with negative psychopathology and global functioning. In the study of memory dysfunction, attentional capacities, information processing and symptomatology have to be considered as determining factors. It has been shown that patients with schizophrenia perform poorly in selective attention tasks and that this deficit may interfere with learning. In the same way, the slowing of information processing contributes to a superficial and incomplete learning. The impact of symptomatology has also to be considered, as negative and depressive symptoms are linked to mnesic performances. The majority of studies bearing on working memory and schizophrenia show an alteration of performances, but studies on long term memory are more equivocal. Procedural memory seems to be preserved, while declarative memory is impaired. These results support the hypothesis that in schizophrenia, memory processes that are consciously controlled are impaired, contrary to implicit learning which may be intact. Nevertheless, studies bearing on semantic memory and episodic memory show controversial results. Still, many authors argue that schizophrenic patients have difficulties in recalling learned material, specially when a delay or a interfering task are introduced in the test. Besides, the schizophrenic subjects do not use the semantic properties of the words, as well as the control subjects, when they have to learn a words list for example. The main goal of the present study was to examine the auditory-verbal learning capacities of 31 schizophrenic patients (20 men and 11 women, 19-56 years old), compared to 27 healthy subjects (11 men and 16 women, 23-56 years old). All subjects received an evaluation including the Rey Auditory-Verbal Learning Test, used to study the progressive acquisition of 15 disyllabic words which are successively orally presented five times to the subject. About forty-five minutes after the last of the five immediate recalls, the delayed recall is assessed and a percentage of retention is also calculated. Visual reasoning and attention capacities were studied with the Progressive Matrix and the d2 encumbrance test respectively. Global psychiatric symptomatology of the patients group was assessed with the Brief Psychiatric Rating Scale. Considering the literature existing on the verbal learning capacities of schizophrenic patients, it was expected that the patients would perform poorly and learn slower than controls. The initial learning of the material, which is a critical stage for schizophrenic patients, was studied with particular attention as well as the effect of the introduction of a delay upon the recall of the words list. A secondary objective of the study was to investigate the role of visual reasoning and attention upon auditory-verbal learning process. According to published studies, it is expected that schizophrenic patients manifest some impairment in the domains of visual reasoning and attention. The question is to know whether it alters performances in the auditory-verbal learning test or not. Finally, the links between clinical characteristics of the patients, like age and illness duration, and their learning performances were explored. Statistical analysis included first a descriptive analysis of data to examine differences between the two groups. Second, ANCOVAs were used in order to control the respective impact of educational level, attention capacities and verbal reasoning capacities upon learning performances. Third, Spearman's correlations were used to detect links between clinical characteristics of the patients and learning performances. The comparisons between patients and controls confirmed that schizophrenic patients scored less in the attentional and visual reasoning tasks. They also featured a lower educational level compared to the healthy subjects. In the auditory-verbal learning test, the patients showed altered performances in the five recalls, as well as in the delayed recall and for the retention percentage. In order to control the impact of educational level, attentional and visual reasoning capacities, these parameters were introduced in the statistical analyses. Educational level did not influence memory alterations in the schizophrenic group. However, attention and, to a lesser extend, visual reasoning had an impact on the comparison of memory scores: when controlling attention, almost no significant group effect remained. Finally, the exploratory analyses of links between clinical characteristics and memory only revealed the presence of a significant negative correlation between illness duration and learning performances. Thus, the analyze of data showed that schizophrenic subjects featured poor performances in the domains of attention, verbal reasoning and auditory-verbal memory. Further analyses taking into account group differences on attention suggest that the impairment featured by schizophrenic patients in the domain of verbal memory strongly relies on an attentional deficit. These results are discussed according to the existing literature and methodological limitations. Clinical implications are also discussed.