The nature of learning and memory impairments in schizophrenia

Abstract

The California Verbal Learning Test was used to characterize the learning and memory impairment in schizophrenia (SC) and to evaluate potential clinical and demographic factors associated with this impairment. SC patients (n= 175) performed worse than normal comparison (NC) subjects (n= 229) on all learning, recall, and recognition memory measures. The most important clinical correlates of these impairments were earlier age of onset, more negative symptoms, and greater anticholinergic medication dosage. SC patients showed a prominent retrieval deficit as indicated by disproportionate improvement when tested in a recognition, rather than a free recall, format. A residual impairment seen with recognition testing suggests a mild encoding deficit as well. In contrast, the relative absence of a storage deficit is suggested by the lack of rapid forgetting. Using a discriminant function analysis that differentiates cortical dementia [i.e., Alzheimer's disease (AD)], subcortical dementia [i.e., Huntington's disease (HD)], and normals, it was found that 5070 of the SC patients were classified as having a subcortical memory profile and 35% were classified as having a normal profile, whereas only 15% were classified as having a cortical memory profile. Although these findings reflect the clinical heterogeneity often found in SC, results suggest that most SC patients demonstrate a pattern of learning and memory impairments that resembles the pattern seen in patients with primary subcortical (specifically striatal) pathology. (JINS, 1995,I, 88–99.)

Long-term effects of risperidoneversushaloperidol on verbal memory, attention, and symptomatology in schizophrenia

“…Our observations are in agreement with several studies reporting verbal learning and memory deficits in SC (Aleman et al, 1999;Hill et al, 2004;Paulsen et al, 1995). Most of these studies found that the verbal memory impairment seen in SC resulted from an encoding deficit, probably caused by the use of ineffective learning strategies.…”

“…Mori et al (2002) observed a significant improvement in the immediate memory and verbal working memory of SC patients after anticholinergic treatment had been withdrawn for 2 weeks. Other authors have also reported that higher anticholinergic drug dosages are associated with deficits in free recall (Paulsen et al, 1995) and reduced semantic clustering (Strauss et al, 1990).…”

“…Neurocognitive impairments of verbal learning and memory are among the most severe symptoms of schizophrenia (SC; Aleman et al, 1999;Hill et al, 2004;Paulsen et al, 1995) and have a major impact on patients' everyday activities (Green, 1996). Structural and functional neuroimaging studies in SC have shown evidence of a dysfunction affecting the hippocampus, a brain region that underlies specific memory and learning functions such as conscious recollection of deeply encoded items (Fukuzako et al, 1995;Heckers et al, 1998;Weiss et al, 2004).…”

Efficiency of the CATIE and BACS neuropsychological batteries in assessing cognitive effects of antipsychotic treatments in schizophrenia

“…Verbal learning and memory deficits have become a hallmark of schizophrenia research, and an efficient means for evaluating the overall level of cognitive dysfunction in the disorder (Hill et al, 2004b;Paulsen et al, 1995;Saykin et al, 1991). Despite good reliability and moderate to large factor loadings, verbal list learning was only modestly sensitive to change following atypical antipsychotic treatment in both batteries.…”

Alterations of fronto-temporal connectivity during word encoding in schizophrenia

“…Verbal episodic memory is particularly affected, with impairment relating in part to use of inefficient organizational strategies (Koh and Peterson, 1978;Paulsen et al, 1995;Iddon et al, 1998). Providing a semantic organizational strategy during word encoding normalizes subsequent recognition accuracy in patients with schizophrenia (Ragland et al, 2003).…”