Assessment of Motor Planning and Inhibition Performance in Non-Clinical Sample-Reliability and Factor Structure of the Tower of London and Go/No Go Computerized Tasks.

In two studies, we examine the test-retest reliability and factor structure of the computerized Tower of London (TOL) and Go/No Go (GNG). Before analyses, raw results of variables that were not normally distributed were transformed. Study 1 examined the reliability of a broad spectrum of indicators (Initial Time Thinking, ITT; Execution Time, ET; Full Time, FT; Extra Moves, EM; No Go Errors, NGE; Reaction Time for Go Responses, RTGR) across an eight-week delay in a sample of 20 young adults. After correction for multiple comparisons and correlations, our results demonstrate that the tasks have ambiguous test-retest reliability coefficients (non-significant r for all indicators, and interclass correlation (ICC) for TOL; significant ICC for GNG; show lack of reliable change over time for all indicators in both tasks); moreover, ITT exhibits strong practice effects. Study 2 investigated both tasks' factor structure and conducted a more detailed analysis of indicators for each trial (ITT, ET, EM) in the TOL task in the group of 95 young adults. Results reveal a satisfactory 2-factor solution, with the first factor (planning inhibition) defined by ITT, NGE, and RTGR, and the second factor (move efficiency) defined by EM and ET. The detailed analysis identified a 6-factor solution with the first factor defined by ITT for more difficult trials and the remaining five factors defined by EM and ET for each trial, reflecting move efficiency for each trial separately.

Executive Dysfunctions in Schizophrenia: A Critical Review of Traditional, Ecological, and Virtual Reality Assessments.

In recent years, interest has grown in measuring executive function in schizophrenia with ecological and virtual reality (VR) tools. However, there is a lack of critical analysis comparing those tools with traditional ones. This paper aims to characterize executive dysfunction in schizophrenia by comparing ecological and virtual reality assessments with traditional tools, and to describe the neurobiological and psychopathological correlates. The analysis revealed that ecological and VR tests have higher levels of verisimilitude and similar levels of veridicality compared to traditional tools. Both negative symptoms and disorganization correlate significantly with executive dysfunction as measured by traditional tools, but their relationships with measures based on ecological and VR methods are still unclear. Although there is much research on brain correlates of executive impairments in schizophrenia with traditional tools, it is uncertain if these results will be confirmed with the use of ecological and VR tools. In the diagnosis of executive dysfunction, it is important to use a variety of neuropsychological methods-especially those with confirmed ecological validity-to properly recognize the underlying characteristics of the observed deficits and to implement effective forms of therapy.

Relationship of Corpus Callosum Integrity with Working Memory, Planning, and Speed of Processing in Patients with First-Episode and Chronic Schizophrenia.

There is a paucity of reports examining the relationship between the integrity of the corpus callosum (CC) and different aspects of cognitive functioning in patients with first-episode (FES) and chronic schizophrenia (CS) simultaneously; furthermore, what results exist are inconclusive. We used diffusion tensor imaging tractography to investigate differences in integrity in five regions of the CC between FES, CS, and healthy controls (HC). Additionally, we analyzed correlations between these regions' integrity and working memory, planning, and speed of processing. Eighteen patients with FES, 55 patients with CS, and 30 HC took part in the study. We assessed cognitive functions with four tasks from Measurement and Treatment Research to Improve Cognition in Schizophrenia. Patients with CS showed lower fractional anisotropy (FA) in Region 5 (statistical trend) and higher mean diffusivity (MD) in Regions 4 and 5 than HC, and patients with FES had higher MD in Region 3 (statistical trend) than HC. Both clinical groups performed worse on working memory and speed of processing tasks than HC, and patients with CS scored worse than HC on independent planning, and worse than FES and HC on dependent planning. Moreover, in patients with CS, MD in Region 3 was correlated with verbal working memory. Our results suggest that patients with FES and CS are characterized by impaired integrity of the middle and posterior CC, respectively. We confirmed that both clinical groups have cognitive impairments. Moreover, the integrity of the middle CC may influence planning in patients with CS.

The relationship between cingulum bundle integrity and different aspects of executive functions in chronic schizophrenia.

BACKGROUND: Evidence suggests that disruption in the cingulum bundle (CB) may influence executive dysfunctions in schizophrenia, but findings are still inconsistent. Using diffusion tensor imaging tractography, we investigated the differences in fiber integrity between schizophrenia patients and healthy controls together with the association between fiber integrity and executive functions. METHODS: Thirty-two patients with chronic schizophrenia and 24 healthy controls took part in the study. Both groups were matched for age, sex, and years of education. Assessment of cognitive functions was performed using the Berg Card Sorting Test (BCST), the Color Trail Test (CTT), and the Stroop Color-Word Test (SCWT). RESULTS: Results showed group differences, bilaterally (left and right) in fractional anisotropy (FA) of the CB, where patients showed less anisotropy than controls. Moreover, normal asymmetry (left FA > right FA) in the CB in schizophrenia was found. There were no group differences in mean diffusivity (MD). Patients had a similar but reduced profile of executive functions compared to healthy controls. However, when premorbid IQ was controlled for, the differences were no longer statistically significant. In schizophrenia patients, a negative correlation was found between FA of the left CB and perseverative errors in the BCST. CONCLUSIONS: These findings provide evidence that CB disruption appears in schizophrenia patients and might account for impairments of executive processes, including concept formation.