یاد گیری کلامی، حافظه و آسیب شناسی روانی در اسکیزوفرنی

Background and aims Verbal learning and memory (VLM) are the most impaired cognitive functions noted in schizophrenia. Though its association with negative symptoms is found consistently, only few have compared this relationship at a drug free/naïve state and on antipsychotic medications. Thus the aim of the study was to compare VLM functions in schizophrenia and normal controls and find its association between negative symptoms at drug free/naïve state and on antipsychotic medication. Method A sample of 78 initially drug naïve/free patients of schizophrenia of either sex, aged between 18 and 45 years, and 30 age, sex and education matched normal controls were assessed for VLM by Rey-Auditory-Verbal-Learning-Test (RAVLT). The schizophrenia group was assessed at baseline and at the end of six weeks treatment with RAVLT and for positive, negative and depressive symptoms. Results The schizophrenia group performed significantly poorly on VLM at both time points compared to normal controls, though significant improvement in the schizophrenia group was noted following six weeks treatment. Only negative symptoms inversely correlated with immediate memory span and verbal learning at baseline and in addition verbal memory at six weeks, while change in any of the dimensions of psychopathology (assessed in terms of positive, negative and depressive symptoms) over six weeks did not correlate with change in measures of cognitive functions. Conclusion For VLM deficits in schizophrenia, though correlated with negative symptoms, improvement with treatment could not be attributed to improvement in psychopathology.

Neurocognitive deficits are a core feature of schizophrenia. Verbal learning and memory (VLM) are one of the most impaired cognitive functions noted among all others (Toulopoulou and Murray, 2004). Evidence for VML deficits being consistent and quantitatively severe has come from reviews (Cirillo and Seidman, 2003 and Heinrichs and Zakzanis, 1998) and meta-analysis (Aleman et al., 1999 and Green, 1996). A profile analysis (using a comprehensive neuropsychological battery) of medication-naïve/free patients with schizophrenia showed that memory function was more severely impaired than other cognitive functions, such as attention, executive function, language, spatial abilities, or sensory and motor functions (Saykin et al., 1991 and Saykin et al., 1994). This deficit is persistent throughout the course of illness without being fully accounted for by duration of illness (Addington and Addington, 2002), changes in illness severity or medication effects. Relationship of psychopathology with VLM deficits shows significant association of negative symptoms (but small effect size) (Aleman et al., 1999) and none with positive symptoms (Addington and Addington, 2002). However, with improvement in symptoms Hughes et al. (2003) found this association was not maintained and concluded the lack of casual association of improvement of cognitive functions with symptom improvement. Contradictory findings have also been reported (Bilder et al., 2000 and Vaz and Heinrichs, 2002). On reviewing the nature of memory deficits in schizophrenia, encoding/learning is found to be primarily impaired (Cirillo and Seidman, 2003) rather than an accelerated rate of forgetting (Gold et al., 2000). Yet some (Tracy et al., 2001) have argued the special case for verbal memory where retrieval processes are also disrupted compared to non-verbal memory. On the other hand meta-analysis (Aleman et al., 1999) has shown differential impairment between verbal and non-verbal material both in delayed recall and recognition memory, though this difference was not statistically significance. In the same analysis immediate and delayed verbal recall scores did not differ. Considering the intricacies related to encoding and retrieval processes in verbal memory functions and the contradictions in literature on VLM's relations with negative symptoms, the present study was undertaken. The objective of the study was to assess VLM in a sample of schizophrenia patients at two time points (one when drug free/naïve and the other after treatment for six weeks) in comparison to normal controls, and evaluate its correlation with psychopathology (assessed in terms of positive, negative and depressive symptoms). A six weeks post-treatment duration for evaluation was considered keeping in mind that most patients show clinical response at four weeks of continuous antipsychotic treatment. Moreover to prevent practice effect on repeating VLM tasks, six weeks time was considered adequate (McCaffrey et al., 2000).

VLM are significantly impaired in schizophrenia. Negative symptoms have inverse correlation with VLM performance. This may be largely contributed by encoding deficits. And improvement in symptoms shows no correlation with improvement in VLM tasks. Though this does not rule out the influence of negative symptoms on other intervening variables that might in turn affect encoding abilities.