Nonverbal visual attention, but not recognition memory of learning, processes are impaired in motor neurone disease

Signal-detection analysis of the WMS faces subtest: Results in amyotrophic lateral sclerosis patients

About 30% of patients with amyotrophic lateral sclerosis (ALS) suffer from cognitive impairment and 10-15% suffer from frontotemporal dementia (FTD). Due to the patients' reduced motor function, a neuropsychological assessment with a low motor demand can be an advantage when evaluating patients, aiding its application. The present work has studied the usefulness of the Faces subtest of the Wechsler Memory Scale in 42 patients with ALS and 42 healthy volunteers applying Holdnack's Two-High Threshold model. The ALS group performed significantly worse in immediate and delayed discriminability. With respect to the presence of cognitive impairment, it seemed to be independent of the indexes proposed by Holdnack and Delis. On the other hand, motor problems were associated with delayed recognition while behavior alterations were linked to problems with delayed discriminability. ALS patients do not express differences in the bias index, in line with other types of previously studied pathologies.

The Clinical and Radiological Spectrum of Hippocampal Pathology in Amyotrophic Lateral Sclerosis

Hippocampal pathology in Amyotrophic Lateral Sclerosis (ALS) remains surprisingly under recognized despite compelling evidence from neuropsychology, neuroimaging and neuropathology studies. Hippocampal dysfunction contributes significantly to the clinical heterogeneity of ALS and requires structure-specific cognitive and neuroimaging tools for accurate in vivo evaluation. Recent imaging studies have generated unprecedented insights into the presymptomatic and longitudinal processes affecting this structure and have contributed to the characterisation of both focal and network-level changes. Emerging neuropsychology data suggest that memory deficits in ALS may be independent from executive dysfunction. In the era of precision medicine, where the development of individualized care strategies and patient stratification for clinical trials are key priorities, the comprehensive review of hippocampal dysfunction in ALS is particularly timely.

Influence of schooling and age on cognitive performance in healthy older adults

Few studies have examined the influence of a low level of schooling on age-related cognitive decline in countries with wide social and economic inequalities by using the Cambridge Automated Neuropsychological Test Battery (CANTAB). The aim of the present study was to assess the influence of schooling on age-related cognitive decline using unbiased cognitive tests. CANTAB allows cognitive assessment across cultures and education levels with reduced interference of the examiner during data acquisition. Using two-way ANOVA, we assessed the influences of age and education on test scores of old adults (61–84 years of age). CANTAB tests included: Visual Sustained Attention, Reaction Time, Spatial Working Memory, Learning and Episodic Memory. All subjects had a minimum visual acuity of 20/30 (Snellen Test), no previous or current history of traumatic brain/head trauma, stroke, language impairment, chronic alcoholism, neurological diseases, memory problems or depressive symptoms, and normal scores on the Mini Mental State Examination (MMSE). Subjects were grouped according to education level (1 to 7 and ≥8 years of schooling) and age (60–69 and ≥70 years). Low schooling level was associated with significantly lower performance on visual sustained attention, learning and episodic memory, reaction time, and spatial working memory. Although reaction time was influenced by age, no significant results on post hoc analysis were detected. Our findings showed a significantly worse cognitive performance in volunteers with lower levels of schooling and suggested that formal education in early life must be included in the preventive public health agenda. In addition, we suggest that CANTAB may be useful to detect subtle cognitive changes in healthy aging.

Executive Dysfunctions and Event-Related Brain Potentials in Patients with Amyotrophic Lateral Sclerosis

A growing body of evidence implies psychological disturbances in amyotrophic lateral sclerosis (ALS). Specifically, executive dysfunctions occur in up to 50% of ALS patients. The recently shown presence of cytoplasmic aggregates (TDP-43) in ALS patients and in patients with behavioral variants of frontotemporal dementia suggests that these two disease entities form the extremes of a spectrum. The present study aimed at investigating behavioral and electrophysiological indices of conflict processing in patients with ALS. A non-verbal variant of the flanker task demanded two-choice responses to target stimuli that were surrounded by flanker stimuli which either primed the correct response or the alternative response (the latter case representing the conflict situation). Behavioral performance, event-related potentials (ERP), and lateralized readiness potentials (LRP) were analyzed in 21 ALS patients and 20 controls. In addition, relations between these measures and executive dysfunctions were examined. ALS patients performed the flanker task normally, indicating preserved conflict processing. In similar vein, ERP and LRP indices of conflict processing did not differ between groups. However, ALS patients showed enhanced posterior negative ERP waveform deflections, possibly indicating increased modulation of visual processing by frontoparietal networks in ALS. We also found that the presence of executive dysfunctions was associated with more error-prone behavior and enhanced LRP amplitudes in ALS patients, pointing to a prefrontal pathogenesis of executive dysfunctions and to a potential link between prefrontal and motor cortical functional dysregulation in ALS, respectively.

Uncinate fasciculus microstructure and verbal episodic memory in amyotrophic lateral sclerosis: a diffusion tensor imaging and neuropsychological study

The present study evaluates the integrity of uncinate fasciculus (UF) and the association between UF microstructure and verbal episodic memory (as one of the cognitive functions linked to UF) in non-demented patients with amyotrophic lateral sclerosis (ALS) using diffusion tensor imaging (DTI). We studied 21 patients with ALS and 11 healthy, demographically-comparable volunteers. Fractional anisotropy, apparent diffusion coefficient, axial and radial diffusivity were the DTI metrics examined. Episodic memory was evaluated with Babcock Story Recall Test and Rey Auditory Verbal Learning Test (RAVLT) for patients; measures of immediate and delayed recall and retention for both tests and sum of words recalled through five learning trials for RAVLT were considered. Patients with ALS showed significant bilateral reduction of axial diffusivity in the UF as compared to controls. Furthermore, there were several significant relations between various DTI metrics (mostly in left hemisphere) and memory measures (specifically for the RAVLT). UF microstructural changes may contribute to ALS-related memory impairment, with word-list learning performance relying more upon the integrity of frontal and temporal connections than memory components associated with story recall.

Cognitive performance improvement in Canadian Armed Forces personnel during deployment

Introduction: Chronic stress can decrease resilience and diminish cognitive adaptability; thus, operational stressors related to military deployment can pose significant risks to cognitive functioning. Numerous studies have aimed to assess the effects of deployment on cognitive functioning on the basis of cognitive performance measures administered before and after deployment. However, to the best of our knowledge, no studies have measured neurocognitive performance of military personnel while they were deployed to a combat zone. Methods: Canadian Armed Forces military troops ( N = 85) were tested during pre-deployment training and during deployment in Afghanistan. At both time points, the participants completed a detailed demographic form and performed touch-screen neurocognitive tests using the Cambridge Neuropsychological Test Automated Battery (CANTAB). The CANTAB measurements included executive function (Attention Switching Task [AST] and Spatial Working Memory [SWM] test), decision making and response control (Stop Signal Task [SST]), and attention (Reaction Time [RTI] test). Two-tailed, paired t-tests were used to compare pre-deployment and deployment CANTAB results. Results: On average, all participants significantly improved their performance on all neurocognitive tests during deployment compared with pre-deployment. At both pre-deployment and deployment time points, the participants demonstrated excellent performance on the AST and RTI test and less-than-optimal performance on the SWM test and SST. Discussion: The influence of training, social factors, and emotional status, among many others, on cognitive adaptability should be taken into account to fully understand soldiers’ capability to improve and maintain high cognitive functioning during deployment.

Selective attention and the three-process memory model for the interpretation of verbal free recall in amyotrophic lateral sclerosis

The present study investigates selective attention and verbal free recall in amyotrophic lateral sclerosis (ALS) and examines the contribution of selective attention, encoding, consolidation, and retrieval memory processes to patients' verbal free recall. We examined 22 non-demented patients with sporadic ALS and 22 demographically related controls using Stroop Neuropsychological Screening Test (SNST; selective attention) and Rey Auditory Verbal Learning Test (RAVLT; immediate & delayed verbal free recall). The item-specific deficit approach (ISDA) was applied to RAVLT to evaluate encoding, consolidation, and retrieval difficulties. ALS patients performed worse than controls on SNST (p < .001) and RAVLT immediate and delayed recall (p < .001) and showed deficient encoding (p = .001) and consolidation (p = .002) but not retrieval (p = .405). Hierarchical regression analysis revealed that SNST and ISDA indices accounted for: (a) 91.1% of the variance in RAVLT immediate recall, with encoding (p = .016), consolidation (p < .001), and retrieval (p = .032) significantly contributing to the overall model and the SNST alone accounting for 41.6%; and (b) 85.2% of the variance in RAVLT delayed recall, with consolidation (p < .001) and retrieval (p = .008) significantly contributing to the overall model and the SNST alone accounting for 39.8%. Thus, selective attention, encoding, and consolidation, and to a lesser extent of retrieval, influenced both immediate and delayed verbal free recall. Concluding, selective attention and the memory processes of encoding, consolidation, and retrieval should be considered while interpreting patients' impaired free recall. (JINS, 2012, 18, 1-10).

ALS and Frontotemporal Dysfunction: A Review

Though once believed to be a disease that was limited to the motor system, it is now apparent that amyotrophic lateral sclerosis (ALS) may be associated with cognitive changes in some patients. Changes are consistent with frontotemporal dysfunction, and may range from mild abnormalities only recognized with formal neuropsychological testing, to profound frontotemporal dementia (FTD). Executive function, behavior, and language are the most likely areas to be involved. Screening helpful in detecting abnormalities includes verbal or categorical fluency, behavioral inventories filled out by the caregiver, and evaluation for the presence of depression and pseudobulbar affect. Patients with cognitive dysfunction have shortened survival and may be less compliant with recommendations regarding use of feeding tubes and noninvasive ventilation. Evolving knowledge of genetic and pathological links between ALS and FTD has allowed us to better understand the overlapping spectrum of ALS and FTD.

The on-freezing phenomenon: cognitive and behavioral aspects

Freezing of gait is a warning sign of Parkinson's disease. One could distinguish off-freezing, which is associated with dopaminergic therapy and to its titration, and it is clinically related to wearing-off phenomenon. Differently, the on-freezing phenomenon seems to be related to a neural disruption of the frontal-parietal-basal ganglia-pontine projections; clinically, it does not respond to therapy modifications or to different drug titration. In a group of patients with on-freezing, we have detected an alteration of focusing attention, an impairment of set-shifting, in addition to poor abstract reasoning and a reduction of planning. These aspects have been even more evident, when compared with the results obtained by a group of PD patients, without freezing.

Altered patterns of cortical activation in ALS patients during attention and cognitive response inhibition tasks

Since amyotrophic lateral sclerosis (ALS) can be accompanied by executive dysfunction, it is hypothesised that ALS patients will have impaired performance on tests of cognitive inhibition. We predicted that ALS patients would show patterns of abnormal activation in extramotor regions when performing tests requiring the inhibition of prepotent responses (the Stroop effect) and the inhibition of prior negatively primed responses (the negative priming effect) when compared to healthy controls. Functional magnetic resonance imaging was used to measure activation during a sparse sequence block design paradigm investigating the Stroop and negative priming effects in 14 ALS patients and 8 healthy age- and IQ-matched controls. Behavioural measures of performance were collected. Both groups' reaction times (RTs) reflected the Stroop effect during scanning. The ALS and control groups did not differ significantly for any of the behavioural measures but did show significant differences in cerebral activation during both tasks. The ALS group showed increased activation predominantly in the left middle temporal gyrus (BA 20/21), left superior temporal gyrus (BA 22) and left anterior cingulate gyrus (BA 32). Neither group's RT data showed clear evidence of a negative priming effect. However the ALS group showed decreased activation, relative to controls, particularly in the left cingulate gyrus (BA 23/24), left precentral gyrus (BA 4/6) and left medial frontal gyrus (BA 6). Greater cerebral activation in the ALS group accompanying the performance of the Stroop effect and areas of decreased activation during the negative priming comparison suggest altered inhibitory processing in ALS, consistent with other evidence of executive dysfunction in ALS. The current findings require further exploration in a larger study.

A longitudinal study of the evolution of cognitive function and affective state in patients with amyotrophic lateral sclerosis

OBJECTIVES

The study aimed to evaluate cognitive function and emotional reactivity in 18 patients with ALS, compared to 19 matched controls, and assess their evolution over a 12-month period.

METHODS

18 ALS patients and 19 matched controls were included, and assessed at inclusion, six months and twelve months later. Depression was evaluated with the Geriatric Depression Scale, and cognitive function with the Folstein Mini Mental State. A battery of psychometric tests (Wisconsin Card Sorting Test (WCST), the numerical Empan test, the Trail-making test, the Boston Naming Test, the 15-word Rey memory test, the Benton visual retention test and the Raven Progressive Matrix) was used to measure frontal processing and non-frontal function. Emotional reactivity was measured with the film-evoked emotions test.

RESULTS

ALS patients were significantly more depressed than controls, as measured on the Geriatric Depression Scale, and depression increased over the study period. There was a very mild defect in cognitive function, and a performance deficit in the Trail-making test, a measure of frontal processing. These deficits, unlike neuromuscular function and depression, did not aggravate over the 12 months of the study. There was no observable change in non-frontal function. Emotional reactivity did not differ significantly between ALS patients and controls.

CONCLUSIONS

This study provides further evidence for a mild defect in frontal cognitive processing in ALS patients that evolves only slowly, if at all, with time.

Cognition and amyotrophic lateral sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS) is classically described as a pure motor disease; however, there is growing evidence of a range of cognitive impairment. Cognitive abnormalities include deficiencies in frontal executive skills, varying from mild deficits to meeting criteria for diagnosis of frontotemporal dementia (FTD). Cognitive impairment occurs in sporadic and familial forms of ALS. Patients may present with cognitive deficits before, after, or at the onset of motor neuron disease. Structural and functional imaging studies have shown extramotor cortical degeneration corresponding to levels of frontal executive impairment on neuropsychologic testing. In addition, ALS and a subset of FTD patients display common pathological findings on immunohistochemistry staining. It is believed that these disorders represent a continuum between motor and nonmotor cortical degeneration. The purpose of this article is to review the literature on cognitive deficits in ALS. Identifying changes in cognition is critical for physicians and caregivers of ALS patients, as cognitive decline may interfere with patient compliance. Diagnosis and treatment of cognitive symptoms in ALS patients may improve quality of life.

Increased prepulse inhibition of the acoustic startle response is associated with better strategy formation and execution times in healthy males

Prepulse inhibition (PPI) refers to the attenuation of the amplitude of the startle reflex in response to sudden intense stimuli (pulse) if preceded by a weaker sensory stimulus (prepulse). PPI reflects the ability to filter out irrelevant information in the early stages of processing so that attention can be directed to more salient environmental features. Inhibition at this early stage of information processing appears modulated by the prefrontal cortex in a "top-down" fashion and this may account for the normal inter-individual variability in PPI and in cognitive performance. PPI data were calculated from 82 healthy male subjects who were also tested in problem solving (Stockings of Cambridge; SoC), spatial working memory (SWM) and 5-choice reaction time (RT) tests from the Cambridge Neuropsychological Test Automated Battery. Correlations between PPI scores and cognitive test variables were examined. In addition PPI scores were divided in quartiles which were used as grouping factors in examining cognitive test performance. Compared to individuals in the lowest quartile those in the highest had (a) shorter execution but not reaction times on the 5-choice RT, (b) shorter subsequent but not initial thinking times in the SoC where they also solved more problems correctly with the minimum number of moves, and (c) better strategy but not errors scores in the SWM. Our findings suggest that greater PPI is associated with superior abilities in strategy formation and execution times. We suggest that this is due to more efficient early information processing.

Cognitive functioning in sporadic amyotrophic lateral sclerosis: a six month longitudinal study

OBJECTIVE

To observe changes in cognition over six months in subjects with recently diagnosed sporadic amyotrophic lateral sclerosis (ALS).

METHODS

The study used a between-group and within-group longitudinal design. Nineteen ALS subjects and eight matched caregivers were recruited to participate in baseline neuropsychological assessments that were repeated six months later. Between group comparisons for these variables were undertaken at baseline and six months later. Within group/across time comparisons for these variables were carried out for both groups. Individual analyses for the neuropsychological variables using z scores were done for the ALS subjects using their baseline performance as the basis for comparison with their six month performance.

RESULTS

The between-group and within-group comparisons did not show significant differences in cognitive function over time. In individual analyses, however, seven of 19 ALS subjects (36.84%) developed abnormal neuropsychological performance over six months.

CONCLUSIONS

Early in the disease course, over one third of the ALS subjects developed cognitive deficits over six months. These findings support the hypothesis that cognitive deficits in ALS become more prominent over time.

Cognitive function in healthy older European adults: the ZENITH study

OBJECTIVE

Baseline data are reported from a study of the effects of zinc supplementation on cognitive function in older adults as assessed by the CANTAB computerised test battery.

DESIGN

This is a multicentre prospective intervention study employing a randomised double-blind design.

SETTING

European community-based study.

PARTICIPANTS

There are 387 healthy adults aged 55-87 y from centres in France, Italy and Northern Ireland.

INTERVENTIONS

Measures of visual memory, working memory and attention were obtained at baseline (prior to supplementation).

RESULTS

Younger adults (<70 y) performed significantly better than older adults (>70 y) on all tests, with minimal differences between centres. In addition, men outperformed women on tests of spatial span, pattern recognition memory and reaction times, although these gender differences varied somewhat between centres.

CONCLUSIONS

The results are generally consistent with previous age- and gender-related effects on cognitive functioning.

Only subtle cognitive deficits in non-bulbar amyotrophic lateral sclerosis patients

Neuropsychological investigations of amyotrophic sclerosis (ALS) patients revealed considerable discrepancies regarding neurocognitive functions. Some, but not all studies have suggested executive dysfunctioning and memory impairment, and there is a wide range of applied neuropsychological tests and results. In this study, we investigated the neuropsychological performance of 15 non-bulbar ALS patients, 14 patients with neuromuscular symptoms, and 15 healthy controls. To avoid confounding effects of motor disability, performance was assessed using exclusively motor-free tests of frontal lobe functioning (specific memory functions, conditional-associative learning, attention, and executive functions). ALS patients exhibited poorer performance in two conditions (semantic and alternating condition, respectively) of the Verbal Fluency Test, suggesting a subtle executive deficit. No deficits were found in tests of memory, conditional-associative learning, or attention. Assessed mood status was not related to neuropsychological performance. Verbal memory (CVLT) and verbal fluency (lexical condition) were positively associated with duration of disease. Our results support the view that there are only subtle cognitive deficits in ALS patients and we assume a possible effect of practice on cognitive tasks following reduced daily motor activity.

Cortical selective vulnerability in motor neuron disease: a morphometric study

Neuroimaging and neuropsychological studies have revealed that the primary motor cortex (PMC) and the extramotor cortical areas are functionally abnormal in motor neuron disease (MND, amyotrophic lateral sclerosis), but the nature of the cortical lesions that underlie these changes is poorly understood. In particular, there have been few attempts to quantify neuronal loss in the PMC and in other cortical areas in MND. We used SMI-32, an antibody against an epitope on non-phosphorylated neurofilament heavy chain, to analyse the size and density of SMI-32-positive cortical pyramidal neurons in layer V of the PMC, the dorsolateral prefrontal cortex (DLPFC) and the supragenual anterior cingulate cortex (ACC) in 13 MND and eight control subjects. There was a statistically significant reduction in the density of SMI-32-immunoreactive (IR) pyramidal neurons within cortical layer V in the PMC, the DLPFC and the ACC in MND subjects compared with controls [t (19) = 2.91, P = 0.009; estimated reduction 25%; 95% CI = 8%, 40%]. In addition, we studied the density and size of interneurons immunoreactive for the calcium-binding proteins calbindin-D(28K) (CB), parvalbumin (PV) and calretinin (CR) in the same areas (PMC, DLPFC and ACC). Statistically significant differences in the densities of CB-IR neurons were observed within cortical layers V (P = 0.003) and VI (P = 0.001) in MND cases compared with controls. The densities of CR- and PV-IR neurons were not significantly different between MND and control cases, although there were trends towards reductions of CR-IR neuronal density within the same layers and of PV-IR neuronal density within cortical layer VI. Loss of pyramidal neurons and of GABAergic interneurons is more widespread than has been appreciated and is present in areas associated with neuroimaging and cognitive abnormalities in MND. These findings support the notion that MND should be considered a multisystem disorder.

Neuropsychological changes after subthalamic nucleus stimulation: a 12 month follow-up in nine patients with Parkinson's disease

Deep brain stimulation of the subthalamic nucleus has been recognized as one of the most promising techniques to decrease 'off' motor symptoms and motor fluctuations, allowing a reduction of drug therapy and limiting side effects of drug therapy. However, there is still open debate on the possible consequences of chronic subthalamic stimulation on general cognitive performance. A general amelioration of cognitive performance, in particular of executive functions has been reported but results are not homogeneous. We studied nine patients with Parkinson's Disease for 12 months following surgery for deep stimulation, studying their cognitive performances, paying particular attention to linguistic tests and selective alternating words production. Our results may be consistent with a slowing of cognitive activity, with a reduction of quantitative production, but with an increase in control of linguistic production, which is more precise and definite. We discuss the possible significance of these results, fully aware that only nine patients were involved, and that the potential for generalization is seriously limited, with a particular overview on the frontal-subthalamic pathway, which in our opinion is responsible for the results we observed.

Cognitive changes following subthalamic nucleus stimulation in two patients with Parkinson disease

The limits of a drug therapy in severe forms of Parkinson disease have led to refining neurosurgery on the basal ganglia. Deep brain stimulation of the subthalamic nucleus has been recognized as one of the most promising techniques to decrease "off" motor symptoms and motor fluctuations, allowing a reduction of drug therapy and limiting side effects of the drugs. There is still open debate on the possible consequences of chronic subthalamic stimulation in other ways, apart from motor symptoms, of general cognitive performance. We examined and followed two patients with Parkinson disease for 9 mo. after surgery for deep stimulation, studying their cognitive performances. There is a general amelioration of cognitive performances, in particular as far as linguistic capabilities is concerned. We discuss the possible significance of these results, reminding strenuously that only two patients were involved, so the potential for generalization is seriously limited.

Complex cognitive disruption in frontal dementia related to motor neuron disease

We describe a patient in whom motor neuron disease and frontal dementia showed concomitant development. This patient underwent a detailed and sequential neurolinguistic assessment, which indicated an alteration in language planning, language comprehension, and morphosyntactic operations. He showed also attention deficit, abstract reasoning disturbances, and prosopoagnosia which became worse during the year follow-up. We suggest that a more specific and sensitive neurolinguistic and neuropsychological test battery must be used to detect and study the entire disruption of cognitive processes in frontal dementia related to motor neuron disease.

Cognitive change in motor neurone disease/amyotrophic lateral sclerosis (MND/ALS)

A motor neuronopathy complicating frontotemporal dementia (FTD) has been recognised and designated FTD/motor neurone disease (MND). FTD is characterised by profound character change and altered social conduct, and executive deficits, reflecting focal degeneration of the frontal and temporal neocortex. The motor neuronopathy comprises bulbar palsy and limb amyotrophy. The major histological change is typically of microvacuolation of the cerebral cortex, with atrophy of the bulbar neurones and anterior horn cells of the spinal cord. Ubiquitinated inclusion bodies occur in large pyramidal cortical neurones and in surviving cranial nerve nuclei and anterior horn cells. Evidence is emerging that some patients with classical MND/amyotrophic lateral sclerosis (ALS), who are thought not to be demented, develop cognitive deficits in the realm of frontal executive functions. Moreover, frontal lobe abnormalities have been demonstrated by neuroimaging. The findings point to a link between FTD/MND and cMND/ALS and suggest that a proportion of patients with cMND/ALS go on to develop FTD. Patients with cMND/ALS may not be equally vulnerable. The hypothesis is that patients who present with bulbar palsy and amyotrophy, rather than corticospinal and corticobulbar features, may be most susceptible to the development of FTD.

A neuropsychological investigation of dementia in motor neurone disease (MND)

Different clinical criteria for diagnosing dementia were compared in a sample of 69 patients with motor neurone disease (MND). Participants' performances on a computerised battery of neuropsychological tests were evaluated to assess the usefulness of these tests in predicting dementia in MND. The results indicated that when diagnostic criteria for frontotemporal (FTD) were used as part of a questionnaire method of diagnosing dementia the incidence of dementia in MND was considerably greater than traditional estimates suggest. Through a series of logistic and multiple regressions the results demonstrated that neuropsychological test performance related well to diagnostic classifications of dementia. MND patients with a clinical diagnosis of dementia were likely to demonstrate impaired new learning; poor working memory and planning; slowness in information processing and rigidity in thinking. These features, which are typical of cases of FTD, suggest that the dementia of MND is usefully characterised as a form of FTD. The finding that neuropsychological impairment correlated with behavioural features of dysexecutive impairment in daily living, indicates that the management focus in MND must be broadened to include cognitive/behavioural issues.

Extramotor involvement in ALS: PET studies with the GABA(A) ligand [(11)C]flumazenil

We used the benzodiazepine GABA(A) marker [(11)C] flumazenil to study cerebral dysfunction in amyotrophic lateral sclerosis (ALS) with PET. Seventeen non-demented patients with clinically definite or probable ALS were scanned and statistical parametric maps were derived to localize changes in regional flumazenil volumes of distribution (FMZVD), which correlate closely with receptor density (B(max)), and the results were compared with those of 17 controls. The ALS group showed statistically significant decreases in relative FMZVD in the prefrontal cortex (areas 9 and 10 bilaterally), parietal cortex (area 7 bilaterally), visual association cortex (area 18 bilaterally) and left motor/premotor cortex (including area 4) (P < 0.001). Relative reductions in FMZVD were also seen in the left ventrolateral and dorsolateral prefrontal cortex (areas 45, 46 and 47), Broca's area and the right temporal (area 21) and right visual association cortex (area 19). These observations suggest that cerebral dysfunction in ALS involves motor/premotor and extramotor areas, particularly the prefrontal regions.

Verbal fluency and executive dysfunction in amyotrophic lateral sclerosis (ALS)

Neuropsychological investigations of amyotrophic lateral sclerosis (ALS) patients have revealed variable results on specific tests, despite a similar overall cognitive profile of predominantly executive dysfunction with some evidence of memory impairment. The most striking and consistent deficit is found using tests of verbal fluency. The current investigation explored why verbal fluency is particularly sensitive to the impairment in ALS, by investigating some of the underlying cognitive processes: (i) intrinsic response generation; (ii) phonological loop functions; and (iii) simple word retrieval. Twenty-two ALS patients and 25 healthy controls were investigated. The battery included: (i) written and spoken letter-based fluency, category fluency, design fluency; (ii) the Phonological Similarities effect and Word Length Effect; and (iii) computerised sentence completion and confrontational naming. The tests were designed to control for motor speed and to accommodate for the range of disabilities that are present in ALS patients. Significant impairments were found on some tests of intrinsic response generation, namely the Written Verbal Fluency Test, Category Fluency Test (generation of animal names) and Design Fluency Test. Phonological loop functions appeared to be intact with evidence of both the Phonological Similarities and Word Length Effects, but the ALS patients displayed significantly reduced working memory capacity. No deficits were found on tests of simple word retrieval. The findings indicate that verbal fluency impairments in ALS patients result from a higher order dysfunction, implicating deficits in the supervisory attentional system or central executive component of working memory, and are not caused or exaggerated by an impairment in phonological loop functions or in primary linguistic abilities. The study also demonstrates the importance of controlling for differences in motor speed, which may have served to exaggerate the presence of cognitive deficits in ALS patients reported by some other studies.

Molecular factors underlying selective vulnerability of motor neurons to neurodegeneration in amyotrophic lateral sclerosis

Current research evidence suggests that genetic factors, oxidative stress and glutamatergic toxicity, with damage to critical target proteins and organelles, may be important contributory factors to motor neuron injury in amyotrophic lateral sclerosis (ALS). Various molecular and neurochemical features of human motor neurons may render this cell group differentially vulnerable to such insults. Motor neurons are large cells with long axonal processes which lead to requirements for a high level of mitochondrial activity and a high neurofilament content compared to other neuronal groups. The lack of calcium buffering proteins parvalbumin and calbindin D28k and the low expression of the GluR2 AMPA receptor subunit may render human motor neurons particularly vulnerable to calcium toxicity following glutamate receptor activation. Motor neurons also have a high perisomatic expression of the glutamate transporter protein EAAT2 and a very high expression of the cytosolic free radical scavenging enzyme Cu/Zn superoxide dismutase (SOD1) which may render this cell group vulnerable in the face of genetic or post-translational alterations interfering with the function of these proteins. More detailed characterisation of the molecular features of human motor neurons in the future may allow the strategic development of better neuroprotective therapies for the benefit of patients afflicted by ALS.

Test/re-test reliability of the CANTAB and ISPOCD neuropsychological batteries: theoretical and practical issues. Cambridge Neuropsychological Test Automated Battery. International Study of Post-Operative Cognitive Dysfunction

Neuropsychological test batteries are repeatedly administered to evaluate changes over time or the effects of clinical interventions. Relationships between scores on different tests within batteries are also examined to test models for associations between functional deficits. These comparisons may be misleading unless Test/Re-test reliability for individual tests is satisfactory. Interpretations of repeated measurements also depend on the extent to which improvement with practice varies between tasks and between more and less able individuals. Test/Re-test correlations and practice effects for two neuropsychological test batteries (CANTAB, ISPOCD) and from laboratory tasks commonly used in cognitive assessments of older people were obtained from large groups of healthy elderly. Tests in neuropsychological batteries varied markedly in test/re-test reliability which, in some cases, fell below levels considered methodologically acceptable. Putative measures of 'frontal' or 'executive' function, in which performance may be markedly improved by abrupt discovery of an appropriate strategy, were especially likely to show low reliability. Most tests showed significant practice effects, and on some these are substantial enough to compromise comparisons on repeated testing. On a minority of tests practice effects were counter-intuitive, in that less able showed significantly more gains than more able individuals.