More haste less speed: A meta-analysis of thinking latencies during planning in people with psychosis

Cognitive impairment is a core feature of psychosis, with slowed processing speed thought to be a prominent impairment in schizophrenia and first-episode psychosis. However, findings from the Stockings of Cambridge (SOC) planning task suggest changes in processing speed associated with the illness may include faster responses in early stages of planning, though findings are inconsistent. This review uses meta-analytic methods to assess thinking times in psychosis across the available literature. Studies were identified by searching PubMed, Web of Science and Google Scholar. Eligibility criteria: 1) included a sample of people with non-affective psychosis according to DSM III, DSM IV, DSM V or ICD-10 criteria; 2) employed the SOC task; 3) included a healthy control group; and 4) published in English. We identified 11 studies that employed the SOC task. Results show that people with psychosis have significantly faster initial thinking times than non-clinical participants, but significantly slower subsequent thinking times during problem execution. These findings indicate that differences in processing speed are not limited to slower responses in people with psychosis but may reflect a preference for step-by-step processing rather than planning before task execution. We suggest this style of responding is adopted to compensate for working memory impairment

The effect of 'masking' on picture naming

Original article can be found at: http://www.cortex-online.org/ Copyright Masson S.p.A.It is frequently assumed that because compared to nonliving things, living things are less familiar, have lower name frequency, and are more visually complex, this makes them more difficult to name by patients and normal subjects. This has also been implicitly accepted as an explanation for the greater incidence of living thing disorders. Patient studies do not, however, typically contain any premorbid data and so, we do not know that the same variables would have necessarily predicted their ‘normal’ performance. To examine this issue, we measured picture-naming latencies in normal subjects presented with unmasked and masked versions of the same line drawings. In accord with other recent studies, living things were named faster than nonliving things. Furthermore, contrary to some theories of category naming, the living thing advantage persisted regardless of whether stimuli were undegraded, degraded or the density of degradation. Finally, multiple simultaneous regression analyses showed that one visual variable (Euclidean Overlap) and one linguistic variable (Age of Acquisition) predicted naming latencies across all masked and unmasked conditions. Other variables either had no predictive value (Contour Overlap; Name Frequency; Category); predicted only high masking (Visual Complexity; Familiarity), or normal and low masking (Number of Phonemes). These findings imply that the more commonly documented deficits for living things do not reflect an exaggeration of the normal profile (be it with masked or unmasked stimuli) or the influence of the same variables that affect normal naming.Peer reviewe

A domain specific deficit for foodstuffs in patients with Alzheimer's disease

Original article can be found at: http://journals.cambridge.org/--Copyright Cambridge University PressAlthough some studies have reported a category specific naming deficit in Alzheimer’s patients (invariably for living things), others have failed to replicate this finding (Laws et al., in press). Inconsistencies may partly stem from the fact that category effects are hidden in group analyses because individual Alzheimer’s patients show category deficits in opposing directions, namely, some living and some nonliving (Gonnerman et al., 1997). Additionally, category effects may depend upon the specific composition of living things, such as the ratio of animals to fruits and vegetables, though this has never been explicitly examined. To examine this, we conducted a more detailed fractionation of living and nonliving categories for individual patients.Peer reviewe

When is category specific in Alzheimer's disease

Original article can be found at : http://www.cortex-online.org/--Copyright Masson S.p.A.Mixed findings have emerged concerning whether category-specific disorders occur in Alzheimer's disease. Factors that may contribute to these inconsistencies include: ceiling effects / skewed distributions for control data in some studies; differences in the severity of cognitive deficit in patients; and differences in the type of analysis (in particular, if and how controls are used to analyse single case data).We examined picture naming in Alzheimer's patients and matched elderly healthy normal controls in three experiments. These experiments used stimuli that did and did not produce ceiling effects / skewed data in controls. In Experiment 1, we examined for category effects in individual DAT patients using commonly used analyses for single cases (χ2 and z-scores). The different techniques produced quite different outcomes. In Experiment 2a, we used the same techniques on a different group of patients with similar outcomes. Finally, in Experiment 2b, we examined the same patients but (a) used stimuli that did not produce ceiling effects / skewed distributions in healthy controls, and (b) used statistical methods that did not treat the control sample as a population. We found that ceiling effects in controls may markedly inflate the incidence of dissociations in which living things are differentially impaired and seriously underestimate dissociations in the opposite direction. In addition, methods that treat the control sample as a population led to inflation in the overall number of dissociations detected. These findings have implications for the reliability of category effects previously reported both in Alzheimer patients and in other pathologies. In particular, they suggest that the greater proportion of living than nonliving deficits reported in the literature may be an artifact of the methods used.Peer reviewe

Executive inhibition and semantic association in schizophrenia

Original article can be found at: http://www.sciencedirect.com/science/journal/09209964 Copyright Elsevier B. V.Research indicates that some patients with schizophrenia display aberrant inhibition of semantic memory, which may underpin formal thought disorder (FTD). We administered a novel Stroop-like paradigm to three groups of participants: 15 schizophrenic patients with formal thought disorder (FTD), 16 with low FTD ratings, and 15 healthy matched controls. They were required to inhibit a prepotent response for a (previously instructed) required response. Four conditions examined the effect of executive demands by manipulating the relatedness between prepotent and required responses (i.e., identical, semantically related, or unrelated). Two further conditions examining executive function working memory demands required the naming of real or abstract pictures that did and did not necessitate inhibition, respectively. Patients with and without FTD experienced increased difficulty when executive function working memory was required. Moreover, those with FTD also showed increased executive inhibition, but the pattern of errors suggested that the result of this was an automatic activation of semantically related representations. The findings support the notion that increased inhibition underpins the disorganised access to semantic memory in patients with FTD.Peer reviewe

Domain-specific deficits in schizophrenia

MEDLINE® is the source for the MeSH terms of this document.Introduction. Object recognition deficits are well documented in certain neurological disorders (e.g., Alzheimer's disease, herpes simplex encephalitis). Although agnosic problems have been documented in some patients with schizophrenia (Gabrovska et al., 2003), no study has investigated whether such deficits differentially affect specific categories of information (as they sometimes do in neurological cases). Method. In Part I of this study, we compared object recognition in 55 patients with chronic schizophrenia and 22 age- and NART IQ-matched healthy controls. In Part II, we present a detailed case study of one patient with schizophrenia (DH) who displays a severe category specific semantic knowledge for living things. Results. Of the patients with schizophrenia, 75% had object recognition below the 5th percentile, and in 11% of cases, a highly specific classical category dissociation emerged (5 cases with nonliving deficit and 1 with living deficit); and two other patients showed strong dissociation for living things. These findings provide convincing evidence of a classical double dissociation across the two categories. In Part II, the in-depth case study of one schizophrenic patient (DH), documented a profound agnosia for living things. While DH displayed intact low level perceptual and spatial ability and could copy drawings, he was severely impaired at naming, picture-name matching, semantic fluency, and could not describe or draw items from memory. Conclusions. The presence of impaired object recognition in most schizophrenic patients, along with highly selective category specific deficits in a minority, is discussed with reference to similar findings in neurological patients.Peer reviewe

Basic-level visual similarity and category specificity

Original article can be found at: http://www.sciencedirect.com/science/journal/02782626 Copyright Elsevier Inc. DOI: 10.1016/S0278-2626(03)00115-5 [Full text of this article is not available in the UHRA]The role of visual crowding in category deficits has been widely discussed (e.g., [Humphreys et al., 1988]; [Laws and Gale, 2002]; [Tranel et al., 1997]). Most studies have measured overlap at the superordinate level (compare different examples of ‘animal’) rather than at the basic level (compare different examples of ‘dog’). In this study, we therefore derived two measures of basic-level overlap for a range of categories. The first was a computational measure generated by a self-organising neural network trained to process pictures of living and non-living things; the second was a rating of perceived visual similarity generated by human subjects to the item names. The computational measure indicated that the pattern of crowded/uncrowded does not honour a living/non-living distinction. Nevertheless, different superordinates showed varied degrees of basic-level overlap, suggesting that specific token choice affects some superordinates more than others e.g., individual fruit and vegetable tokens show greater variability than any other items, while tools and vehicles produce more reliable or overlapping basic-level visual representations. Finally, subject ratings correlated significantly with the computational measures indicating that the neural model represents structural properties of the objects that are psychologically meaningful.Peer reviewe

What happens to semantic memory when formal thought disorder remits? : Revisiting a case study

Original article can be found at: http://www.informaworld.com Copyright Informa / Taylor & Francis Group [Full text of article is not available in the UHRA]Introduction: Laws, Kondel, and McKenna (1999) previously reported a case study analysis of a schizophrenic patient (TC) with severe formal thought disorder (FTD). Examining consistency across item and modality of input, Laws et al. documented an impairment of access to semantic knowledge in TC. Method: Following substantial improvement in his FTD, we readministered the same extensive battery of neuropsychological tests tapping semantic memory functioning. Results: Whilst TC's naming remained relatively good, it also became more consistent across both time and modality. Tasks tapping language comprehension and understanding of semantic association revealed some significant improvements. Nevertheless, TC showed a residual propensity to verify false information. Conclusion: Improvement in FTD in schizophrenia was accompanied by a better and more stable semantic memory performance in TC. The findings are consistent with, and expand upon the original suggestion that thought disorder reflects disorganised access to semantic memory.Peer reviewe