Trait characteristic of impaired visuomotor integration during Trail-Making Test B performance in schizophrenia

Unveiling Trail Making Test: visual and manual trajectories indexing multiple executive processes

The Trail Making Test (TMT) is one of the most popular neuropsychological tests for executive functions (EFs) assessment. It presents several strengths: it is sensitive to executive dysfunction, it is easy to understand, and has a short administration. However, it has important limitations. First, the underlying EFs articulated during the task are not well discriminated, which makes it a test with low specificity. Second, the pen-and-paper version presents one trial per condition which introduces high variability. Third, only the total time is quantified, which does not allow for a detailed analysis. Fourth, it has a fixed spatial configuration per condition. We designed a computerised version of the TMT to overcome its main limitations and evaluated it in a group of neurotypical adults. Eye and hand positions are measured with high resolution over several trials, and spatial configuration is controlled. Our results showed a very similar performance profile compared to the traditional TMT. Moreover, it revealed differences in eye movements between parts A and B. Most importantly, based on hand and eye movements, we found an internal working memory measure that showed an association to a validated working memory task. Additionally, we proposed another internal measure as a potential marker of inhibitory control. Our results showed that EFs can be studied in more detail using traditional tests combined with powerful digital setups. The cTMT showed potential use in older adult populations and patients with EFs disorders.

Neurocognitive Endophenotypes of Schizophrenia and Bipolar Disorder and Possible Associations with FKBP Variant rs3800373

Introduction

Schizophrenia(SCZ) and Bipolar disorder (BD) are frequently occurring and impairing disorders that affect around 1% of the population. Important endophenotypes in the genetic research of SCZ and BD are cognitive functions. Core symptoms for SCZ and BD are impairments in working memory, declarative memory and attention, all of which fulfill the criteria for an endophenotype. The FK506 Binding Protein 5 (FKBP5) gene codes for a co-chaperone of the glucocorticoid receptor and has been reported to be associated with cognition.

Aim

The aims of our research were to determine the degree of cognitive impairment in patients suffering from SCZ and BD and to explore the association of the FKBP5 variant rs3800373 genotype with the cognitive endophenotypes.

Material and Methods

Patients and healthy controls were recruited over a period of two years from the Psychiatric Clinic, Clinical Center University of Sarajevo. Genotyping and neuropsychological assessments were performed for 263 subjects (129 SCZ, 53 BD, and 81 healthy controls [HC]). Neuropsychological assessments were performed for all patients with the Trail Making Test-A&B (TMT-A&B) and Digit-span forward&backwards tasks. The single nucleotide polymorphism (SNP) rs3800373 in the FKBP5 gene was genotyped using Infinium PsychArray Bead Chips.

Results and Conclusion

SCZ and BD patients performed lower than HC in the TMT-A&B and in the Digit-span backwards task, while no differences were observed between SCZ and BD patients. While SCZ patients performed lower than HC in the Digit-span forwards task, there were no differences between BD and HC or between BD and SCZ. Rs 3800373 was not associated with performance in the TMT-A&B or Digit-span forwards&backwards tasks. SCZ and BD share largely overlapping neurocognitive characteristics. Rs3800373 was not associated with performance in the neuropsychological tests. However, given the limited sample size, the results do not exclude an association with the rs3800373 variant in a larger sample. Furthermore, as the analysis was limited to one SNP, the results cannot be generalized to other genetic variants in FKBP5.

Association of DISC1, BDNF, and COMT polymorphisms with exploratory eye movement of schizophrenia in a Chinese Han population

BACKGROUND

Previous studies suggested that exploratory eye movement (EEM) dysfunction appears to be a biological marker specific to schizophrenia, with an unknown molecular mechanism. Genetic studies indicate that disrupted-in-schizophrenia-1 (DISC1), brain-derived neurotrophic factor (BDNF), and catechol-O-methyl transferase (COMT) genes might be implicated in the etiology of schizophrenia, but not in all populations.

OBJECTIVES

The present study aimed to explore associations between these candidate genes and EEM endophenotypes for schizophrenia in a Chinese Han population.

METHODS

EEM recordings were examined in 139 patients with schizophrenia and 143 healthy control participants.

RESULTS

All five EEM parameters, responsive search score, cognitive search score, number of eye fixations, total eye scanning length, and mean eye scanning length, of schizophrenic patients differed significantly from those of healthy controls (P<0.001). The DISC1 SerCys, BDNF ValMet, and COMT ValMet were genotyped in a total sample of 818 schizophrenic patients and 827 healthy control participants, including the above EEM samples. We found that DISC1 Cys and BDNF Met were associated with an increased risk of developing schizophrenia (P<0.001). Furthermore, responsive search score scores of BDNF Met/Met carriers were significantly lower than those of Val allele carriers (P=0.022), which remained modest after Bonferroni correction.

CONCLUSION

The BDNF MetMet polymorphism might be associated with the EEM dysfunction of schizophrenia.

The role of set-shifting in auditory verbal hallucinations

BACKGROUND

Auditory verbal hallucinations (AVHs) are a cardinal characteristic of psychosis. Recent research on the neuropsychological mechanism of AVHs has focused on source monitoring failure, but a few studies have suggested the involvement of attention, working memory, processing speed, verbal learning, memory, and executive functions. In this study we examined the neuropsychological profile of patients with AVHs, assuming that the mechanism underlying this symptom could be a dysfunction of specific cognitive domains.

METHODS

A large neuropsychological battery including set-shifting, working memory, processing speed, attention, fluency, verbal learning and memory, and executive functions was administered to 90 patients with psychotic disorders and 44 healthy controls. The group of patients was divided into two groups: 46 patients with AVHs in the current episode and 44 who denied auditory hallucinations or other modalities in the current episode. AVHs were assessed with the Psychotic Symptom Rating Scales (PSYRATS); the Launay-Slade Hallucination Scale was used to measure long-term propensity to auditory verbal hallucination-like experiences (HLEs) in the sample.

RESULTS

Patients showed poorer performances on all neuropsychological measures compared to the healthy controls' group. In the original dataset without missing data (n=58), patients with AVHs (n=29) presented poorer set shifting and verbal learning, higher levels of visual attention, and marginally significant poorer semantic fluency compared to patients without AVHs (n=29). In the logistic model on the multiple imputed dataset (n=90, 100 imputed datasets), lower capacity of set shifting and semantic fluency distinguished patients with AVHs from those without them.

CONCLUSIONS

Patients experiencing persistent AVHs might fail to shift their attention away from the voices; poorer semantic fluency could be a secondary deficit of set-shifting failure.

Theory of Mind as a potential trait marker of schizophrenia: a family study

INTRODUCTION

Although there is some evidence that Theory of Mind (ToM) deficits may be trait markers of schizophrenia it is not clear yet if ToM deficits are primary deficits, that is, to be independent of deficits in general intellectual abilities and executive function. The aim was to examine if ToM deficits may be trait markers of the illness and the effect of cognitive inhibition, general intellectual abilities and depression on ToM abilities of patients with schizophrenia and their unaffected parents.

METHODS

We assessed ToM abilities (first-order and second-order ToM stories, The Revised Eyes Test), cognitive inhibition (Stroop Task), general intellectual ability (Standard Progressive Matrices Test Plus) in patients with schizophrenia (N=21) and their unaffected fathers (N=21) and mothers (N=21) in comparison with healthy control families (healthy control males, N=21, healthy control fathers, N=21, healthy control mothers, N=21)

RESULTS

Patients showed deficits in first-order ToM tasks but some of these deficits were mediated by general intellectual abilities. Impairments in cognitive inhibition mediated only patients' performance in The Revised Eyes Test. Patients showed deficits in second-order ToM stories independently of deficits in general intellectual abilities and cognitive inhibition. Unaffected parents did not show deficits in first-order ToM tasks, whereas they showed deficits in second-order ToM stories. However, the deficits that unaffected parents showed in second-order ToM stories were mediated by their deficits in general intellectual abilities, and there was an effect of remitted depression on the unaffected mothers' performance.

CONCLUSIONS

The results suggest that intact neurocognitive and general intellectual abilities are necessary in order patients and their unaffected parents to pass successfully ToM tasks. Patients and their unaffected parents show ToM deficits but these deficits are not similar. Patients show ToM deficits but these deficits seem to be a component of the pathophysiology of the illness (e.g., deficits in executive function, general intellectual abilities).

Predictive eye and hand movements are differentially affected by schizophrenia

BACKGROUND

Schizophrenic patients are known to have problems suppressing reflexive eye movements. This is considered to indicate a dysfunction in prefrontal cortex. As the eye and hand motor systems are tightly coupled, we investigated whether predictive hand movements and eye-hand coordination are unimpaired in schizophrenic patients.

METHODS

Saccades and hand movements of 19 patients during an acute schizophrenic episode and 19 controls were measured in a task in which the predictability of target timing was varied.

RESULTS

Schizophrenic patients generated more anticipatory and less visually triggered saccades than controls with both non-predictable and predictable target timing. Anticipatory saccades in the wrong direction were clearly directed towards previous target positions, indicating that they are indicators of erroneous prediction rather than of fixation instability. In contrast to saccades, the number of anticipatory and visually triggered hand movements was the same in patients as in controls. As a consequence, patients took longer to initiate a hand movement after a saccade than controls.

CONCLUSIONS

Schizophrenic patients show increased predictive saccadic activity, but no qualitative changes in predictive saccades. Since prediction itself was not disturbed, the patients' deficit rather lies in the suppression or gating of anticipatory saccades than in their generation. This may be explained by a selective dysfunction of the basal ganglia oculomotor loop. As predictive hand movements were unimpaired, the problems in eye-hand coordination as expressed by a longer initiation time of hand movements relative to saccades are a direct consequence of impaired predictive saccadic behaviour.

Nonequivalence of computerized and paper-and-pencil versions of Trail Making Test

A computerized version of the Trail Making Test, an adaptation of the classical paper-and-pencil form, was compared with the paper-and-pencil form. The testee must connect targets on the screen with the cursor using the mouse instead of a sheet of paper and a pen. The participants were 68 healthy adolescents and young adults. The comparison of scores on the two versions showed that they cannot be considered equivalent; the difference between the two parts of the test (Parts A and B) was greater in the paper-and-pencil version; correlations between the two versions of Part A and of Part B were significant, but too low to consider the two versions parallel. Both versions were accepted by participants. As expected, mean scores were different in Parts A and B in both versions and magnitude of differences was large.

Administration and interpretation of the Trail Making Test

Measurement of cognitive functions is an increasingly important goal for clinicians and researchers. Many neuropsychological test batteries are comprehensive and require specialized training to administer and interpret. The Trail Making Test is an accessible neuropsychological instrument that provides the examiner with information on a wide range of cognitive skills and can be completed in 5-10 min. Its background, psychometric properties, administration procedures and interpretive guidelines are provided in this protocol.