Dissociation in the recovery from neglect dyslexia and visuospatial unilateral neglect: a case report

The recovery of the ability to read of a patient affected by persistent visuospatial neglect suggests the functional independence of the two phenomena. Neglect dyslexia seems to be an example of a dissociation between an implicit and explicit knowledge of the characteristics of the stimulus.

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Sommario Il recupero della capacità di lettura in un paziente con persistente neglect visuo-spaziale suggerisce l'indipendenza funzionale dei due fenomeni. La neglect dyslexia sembra costituire un esempio di dissociazione tra conoscenza implicita ed esplicita delle caratteristiche dello stimolo.

     

Abnormal line bisection judgements in children with Tourette's syndrome.

Tourette's syndrome (TS) has been associated with loss of normal basal ganglia asymmetry, as well as loss of normal functional asymmetry, including the leftward bias on traditional visuospatial tasks such as line bisection and turning bias tests. The aim of the present study was to examine the lateralisation of visuospatial attention in TS. We examined the effect of an irrelevant moving-dot background on line bisection judgements. Nine children with a DSM IV diagnosis of TS participated, in addition to 9 healthy controls, individually matched for age, sex and IQ. Horizontal lines of varying length were presented on a computer screen with either a blank background, or a moving, random-dot field. The dots moved either leftward or rightward across the screen at 40 or 80 mm/s, and participants were instructed to ignore these distracting stimuli when judging the lines. TS children were found to be abnormally right-biased in line bisection in a similar fashion to unmedicated ADHD children who, in a previous study, showed a similar small, yet significant, right-bias in line bisection. Matched controls showed a small, nonsignificant left bias, consistent with past research. Unlike previous findings with hemineglect patients, the irrelevant moving background had no effect on bisection performance for TS children or healthy controls. The present findings suggest a deficit in visuospatial attention consistent with the emerging picture of a lateralised dysfunction of frontostriatal circuitry in TS.     

Reduced visuospatial performance in children with the D2 dopamine receptor A1 allele

Previous studies suggest a reduced dopaminergic function in subjects with the A1 (minor) allele of the D2 dopamine receptor (DRD2) gene. To explore influences on visuospatial ability as a function of the DRD2 gene, 182 alcohol- and other drug-naive sons (age 10–14) of active alcoholic, recovered alcoholic, and nonalcoholic fathers were administered a visuospatial task (Benton's Judgment of Line Orientation Test) which makes minimal motoric/verbal demands. Visuospatial scores were lower for boys with the A1 allele and for sons of active alcoholics. A1-allele boys made more errors than A2 boys on all 11 of the template lines, with the effect being largest for the rightmost presentations. In contrast, the effect of family history for alcoholism was strongest on both right and left midquadrant presentations. Moreover, separate analyses of the two types of errors produced allele but not family history of alcoholism effects when the two lines were misjudged as farther apart than they actually were and family history but not allele effects where the two lines were misjudged as closer together. These results suggest that polymorphism of the DRD2 gene and family history of alcoholism are dissociable determinants of visuospatial ability and that visuospatial defects previously observed in alcoholics may, in part, be antecedent to their drinking behavior.     

Information processing in long delay memory-guided saccades: further insights from TMS

The performance of memory-guided saccades with two different delays (3 s and 30 s of memorisation) was studied in eight subjects. Single pulse transcranial magnetic stimulation (TMS) was applied simultaneously over the left and right dorsolateral prefrontal cortex (DLPFC) 1 s after target presentation. In both delays, stimulation significantly increased the percentage of error in amplitude of memory-guided saccades. Furthermore, the interfering effect of TMS was significantly higher in the short delay compared to that of the long delay paradigm. The results are discussed in the context of a mixed model of spatial working memory control including two components: First, serial information processing with a predominant role of the DLPFC during the early period of memorisation and, second, parallel information processing, which is independent from the DLPFC, operating during longer delays.     

Specific cerebellar reductions in children with chromosome 22q11.2 deletion syndrome

Children with chromosome 22q11.2 deletion syndrome commonly are found to have morphological brain changes, cognitive impairments, and elevated rates of psychopathology. One of the most commonly and consistently reported brain changes is reduced cerebellar volume. Here, we demonstrate that, in addition to the global cerebellum reductions previously reported, volumetric reductions of the anterior lobule and the vermal region of the neo-cerebellum in the mid-sagittal plane best differentiate children with the deletion from typically developing children. These results suggest that the morphological changes of specific portions of the cerebellum may be an important underlying substrate of cognitive impairments and increased incidence of psychopathology in this group.     

Freezing of gait subtypes have different cognitive correlates in Parkinson's disease

BackgroundFreezing of gait (FOG) is a major concern for Parkinson's disease (PD) patients because it is a leading cause of falls and is associated with poor quality of life. The pathophysiology is unknown but it is hypothesized that it relates to cognitive abnormalities; particularly executive and visuospatial dysfunction. However, prior results have been discrepant. Pharmacologic subtypes of FOG include those that are responsive and unresponsive to levodopa.ObjectiveTo determine whether executive and visuospatial dysfunction are associated specifically with the levodopa unresponsive subtype of FOG.Methods135 PD subjects completed a single assessment included FOG questionnaire, UPDRS motor scale, comprehensive cognitive battery and measure of hallucinations. Analyses compared unresponsive (n = 16), responsive (n = 20) and no FOG (n = 99) subtypes.ResultsThe unresponsive subtype had a significantly older age of onset of PD than the responsive group (p = .03) and had worse motor scores (p = .003) than the no FOG group. Longer disease duration was associated with the responsive group compared to the no FOG group (p = .002). The unresponsive FOG group had significantly poorer visuospatial ability (p = .001) and executive functioning (p = .02) than both the no and responsive FOG subgroups. These latter groups were not significantly different. The responsive FOG group was associated with the presence of hallucinations.ConclusionAside from pharmacological differences, unresponsive FOG is associated with executive and visuospatial dysfunction implicating frontostriatal pathways while responsive FOG is associated with hallucinations suggesting involvement of posterior cortical regions. Further study and treatment of FOG should include appropriate subtype classification.     

Thalamic diffusion differences related to cognitive function in white matter lesions

Cerebral white matter lesions (WMLs) are related to cognitive deficits, probably due to a disruption of frontal–subcortical circuits. We explored thalamic diffusion differences related to white matter lesions (WMLs) and their association with cognitive function in middle-aged individuals. Ninety-six participants from the Barcelona-AsIA Neuropsychology Study were included. Participants were classified into groups based on low grade and high grade of periventricular hyperintensities (PVHs) and deep white matter hyperintensities (DWMHs). Tract-Based Spatial Statistics was used to study thalamic diffusion differences between groups. Mean fractional anisotropy (FA) values in significant areas were calculated for each subject and correlated with cognitive performance. Participants with high-grade PVHs and DWMHs showed lower FA thalamic values compared to those with low-grade PVHs and DWMHs, respectively. Decreased FA thalamic values in high-grade DWMHs, but not high-grade PVH, were related to lower levels of performance in psychomotor speed, verbal fluency, and visuospatial skills. Thalamic diffusion differences are related to lower cognitive function only in participants with high-grade DWMHs. These results support the hypothesis that fronto–subcortical disruption is associated with cognitive function only in DWMHs.     

Familieterapi med familiemedlemmer fordelt på 3 generasjoner

Background: Patients with schizophrenia suffer from wide range of deficits in neurocognitive functions of the brain, including visuospatial working memory. Aims: This study aims at evaluating the effect of short-term smoking abstinence on different components of visuospatial working memory in smoker patients with schizophrenia as well as possible reversal effect of a nicotine patch. Methods: In this trial, 45 male smoker patients with schizophrenia (Razi Hospital, Tabriz, Iran, 2010) were randomly divided into three groups. One group experienced a short time (overnight) smoking abstinence; one group used a single dose of nicotine patch (21 mg) after an overnight smoking abstinence and one group with no intervention or restrain on smoking was considered as control. The function of visuospatial working memory was tested by the brief visuospatial memory test-revised (BVMT-R) at the baseline and after the intervention. Results: The three groups were matched regarding age, educational level and the initial elements of cognitive performance. Between-the-group analysis showed that patients with an overnight smoking abstinence had a significant decrease in percent retained score and an increase in recognition biases compared to patients using nicotine patch and controls. No significant changes were observed in patints using nicotine patch or controls. Conclusions: Smoking abstinence results in visuospatial disabilities in male smoker patients with schizophrenia, including delayed recall and recognition biases.     

Caspase-6 activity predicts lower episodic memory ability in aged individuals

Caspase-6 (Casp6), a cysteinyl protease that induces axonal degeneration, is activated early in Alzheimer Disease (AD) brains. To determine whether Casp6 activation is responsible for early cognitive impairment, we investigated the abundance of Casp6 activity, paired helical filament–1 (PHF-1) phosphorylated Tau and amyloid beta peptide (Aβ) pathology by immunohistochemistry in the hippocampal formation of aged non–cognitively impaired (NCI) individuals. Casp6 activity was restricted to the entorhinal cortex (ERC) and CA1 regions of the hippocampus. Pathology scores were then correlated with cognitive scores obtained within 1 year of death. Regression analyses revealed that ERC and CA1 Casp6 activity were the main contributor to lower episodic memory performance, whereas ERC PHF-1 pathology predicted lower semantic and working memory performance. Aβ did not correlate with any of the cognitive tests. Because Casp6 activity and PHF-1 pathology are intimately associated with AD pathology and memory decline is an early event in AD, we conclude that Casp6 activity and PHF-1 immunoreactivity in ERC identifies aged individuals at risk for developing AD.     

N1pc reversal following repeated eccentric visual stimulation

Early event‐related potential (ERP) hemispheric asymmetries recorded at occipitoparietal sites are usually observed following the sudden onset of a lateral peripheral stimulus. This is usually reflected in an onset‐locked larger N1 over the posterior contralateral hemisphere relative to the ipsilateral hemisphere, an early ERP asymmetry labeled N1pc. When the peripheral sudden onset is followed by a central stimulus, or by a bilaterally balanced visual array of stimuli, these events evoke a reversed N1pc, that is, a larger N1 over the hemisphere ipsilateral to the peripheral sudden onset. This N1pc reversal has been taken as evidence for a remapping of the visual space from an absolute, retinally based frame of reference to a relative, attentionally based frame of reference that codes the spatial positions of objects relative to the peripheral sudden onset, rather than relative to the fovea. Here, we pit the reference frame‐remapping account against an alternative account based on reduced neural reactivity following the peripheral sudden onset. In three experiments, we varied the spatial location of an object relative to a preceding sudden onset, and tested the opposite predictions generated by the frame‐remapping and the reduced neural reactivity accounts. Taken together, the results from the present experiments were consistent with the reduced neural reactivity account and inconsistent with the frame‐remapping account.