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Contains fulltext : 293093.pdf (Publisher’s version ) (Open Access), Introduction: Lesion-symptom mapping is a key tool in understanding the relationship between brain structures and behavior. However, the behavioral consequences of lesions from different etiologies may vary because of how they affect brain tissue and how they are distributed. The inclusion of different etiologies would increase the statistical power but has been critically debated. Meanwhile, findings from lesion studies are a valuable resource for clinicians and used across different etiologies. Therefore, the main objective of the present study was to directly compare lesion-symptom maps for memory and language functions from two populations, a tumor versus a stroke population. Methods: Data from two different studies were combined. Both the brain tumor (N = 196) and stroke (N = 147) patient populations underwent neuropsychological testing and an MRI, pre-operatively for the tumor population and within three months after stroke. For this study, we selected two internationally widely used standardized cognitive tasks, the Rey Auditory Verbal Learning Test and the Verbal Fluency Test. We used a state-of-the-art machine learning-based, multivariate voxel-wise approach to produce lesion-symptom maps for these cognitive tasks for both populations separately and combined. Results: Our lesion-symptom mapping results for the separate patient populations largely followed the expected neuroanatomical pattern based on previous literature. Substantial differences in lesion distribution hindered direct comparison. Still, in brain areas with adequate coverage in both groups, considerable LSM differences between the two populations were present for both memory and fluency tasks. Post-hoc analyses of these locations confirmed that the cognitive consequences of focal brain damage varied between etiologies. Conclusion: The differences in the lesion-symptom maps between the stroke and tumor population could partly be explained by differences in lesion volume and topography. Despite

Contains fulltext : 296321.pdf (Publisher’s version ) (Open Access), White matter connections enable the interaction within and between brain networks. Brain lesions can cause structural disconnections that disrupt networks and thereby cognitive functions supported by them. In recent years, novel methods have been developed to quantify the extent of structural disconnection after focal lesions, using tractography data from healthy controls. These methods, however, are indirect and their reliability and validity have yet to be fully established. In this study, we present our implementation of this approach, in a tool supplemented by uncertainty metrics for the predictions overall and at voxel-level. These metrics give an indication of the reliability and are used to compare predictions with direct measures from patients' diffusion tensor imaging (DTI) data in a sample of 95 first-ever stroke patients. Results show that, except for small lesions, the tool can predict fiber loss with high reliability and compares well to direct patient DTI estimates. Clinical utility of the method was demonstrated using lesion data from a subset of patients suffering from hemianopia. Both tract-based measures outperformed lesion localization in mapping visual field defects and showed a network consistent with the known anatomy of the visual system. This study offers an important contribution to the validation of structural disconnection mapping. We show that indirect measures of structural disconnection can be a reliable and valid substitute for direct estimations of fiber loss after focal lesions. Moreover, based on these results, we argue that indirect structural disconnection measures may even be preferable to lower-quality single subject diffusion MRI when based on high-quality healthy control datasets.

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Contains fulltext : 299360.pdf (Publisher’s version ) (Closed access)

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As key element of executive function, cognitive flexibility incorporates multiple component processes, enabling adaptation in response to a constantly changing environment. Preserving cognitive flexibility during surgical resection of a low-grade glioma is of great importance to maintain quality of life and recover optimally from this life event. Dysconnectivity within the fronto-parieto-temporal network of the right parietal lobe has previously been linked to cognitive flexibility deficits, suggesting white matter involvement. To further explore the involvement of white matter in cognitive flexibility, a multicentred international collaboration was established. Nineteen patients, who underwent surgical resection for a low-grade glioma in the right parietal lobe, were assessed pre- and post-surgery, using the Trail Making Test and Stroop-Color-Word-Test to administer cognitive flexibility. Volume measurements and lesion-symptom mapping analyses were performed on postoperative MRI scans. Results showed that the Superior Longitudinal Fasciculus III (SLF III), Arcuate Fasciculus (AF) and Inferior Fronto-Occipital Fasciculus (IFOF) were damaged in both cognitively declined patients (n=4) and cognitively non-declined patients (n=15). Tractographic resection simulations presented similar patterns of dysconnectivity in the right parietal lobe in both groups. In addition, a greater extent of resection was not linked to a decline in cognitive flexibility after surgery. Our findings neither confirm nor deny the proposed involvement of the SLF III, AF and IFOF in cognitive flexibility. Yet, it is clear that cognitive inflexibility is not related to the extent of resection. The integration of DTI and intraoperative monitoring in standard clinical practice is needed for localization and comprehension of cognitive outcomes after neurosurgery.

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Item does not contain fulltext, De laatste jaren is er een duidelijke toename van wakkere hersenoperaties binnen de functionele (en electieve) neurochirurgie. De belangrijkste reden hiervoor is dat met wakkere hersenoperaties de motoriek en de cognitie van de patiënt bewaakt kunnen worden. Met behulp van corticale stimulaties (Penfield-methoden) of dieptestimulatie kunnen onderliggende functies worden gedetecteerd en kunnen multidisciplinair zogenaamde functionele begrenzingen worden bepaald. Tijdens de pre-, intra- en postoperatieve fasen van de wakkere hersenoperaties heeft de (klinisch) neuropsycholoog een duidelijke en belangrijke rol binnen het multidisciplinaire team. Het psychologisch, cognitief en emotioneel welzijn van de patiënt gelden als belangrijkste verantwoordelijkheid van de neuropsycholoog en laten de neuropsycholoog op het scherpst van de snede van de wetenschappelijke en klinische vaardigheden balanceren. In dit artikel wordt vanuit specialistisch oogpunt ingegaan op deze verschillende neuropsychologische aspecten, zonder een 'receptuur' te willen geven van een ideale testbatterij dan wel afkappunten voor het bepalen van grenzen. Binnen onder andere de werkgroep wakkere OK (WOK) wordt gewerkt aan het tot stand brengen van richtlijnen die als handvat kunnen dienen en richting kunnen geven aan kwalitatief goede zorg en een basis kunnen vormen voor wetenschappelijke onderbouwing van wakkere hersenoperaties.

Item does not contain fulltext, Previous studies have shown that the discrepancy between performance on "fluid" and "crystallized" intelligence measures may serve as an indicator for intellectual decline. The validity of this procedure in older persons is unknown. The present study developed a multiple regression equation, to predict the Raven Advanced Progressive Matrices (APM) score from the National Adult Reading Test (NART) score and demographic variables in a large sample of healthy older persons (n = 270). The discrepancy between the predicted and observed Raven APM scores was transformed into a percentile distribution as an indicator of intellectual decline, which can be used in clinical practice. The validity of the procedure was further examined by comparing the proportion of persons with a significant decline (at the -1 and -1.65 SD level) between two older patient samples (87 patients with cerebral stroke and 387 patients with diabetes mellitus) by means of chi(2) tests. There was a significantly higher rate of intellectual decline at the -1 SD ("below average") and -1.65 SD ("impaired") cutoff levels for patients with stroke compared with patients with diabetes (stroke, 34% and 14%; diabetes, 16% and 5%, p < .05). These findings suggest that the Raven APM-NART discrepancy may be a useful measure of intellectual decline in older persons.

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Contains fulltext : 99600.pdf (publisher's version ) (Closed access), Objective: The ability to make inferences about knowledge, thoughts and feelings of others, i.e. perspective taking, is a key element of social cognition. Clinical observations indicate that Korsakoff patients may have impairments in social cognition, but studies are scarce. Also, executive dysfunction is present in Korsakoff patients, which may hamper perspective taking directly. Methods: Twenty-three patients with Korsakoff's syndrome and 15 healthy matched controls were examined on a story comprehension task, in which inferences had to be made that either relied on perspective taking or not. The effects of task complexity were taken into account and executive function was assessed using an extensive neuropsychological test battery. Results: The performance of Korsakoff patients declined with increasing complexity, but the pattern of decline for perspective-taking and non-perspective-taking stories was similar compared to that of the control group. Furthermore, the performance decline with increasing task complexity was directly related to the overall decline in executive functioning. Conclusion: Executive dysfunction, not deficits in perspective taking per se, appears to underlie difficulties in story comprehension in patients with Korsakoff's syndrome.

Item does not contain fulltext, Recent functional magnetic resonance imaging (fMRI) studies addressing healthy subjects point towards posterior parietal cortex (PPC) involvement in episodic memory tasks. This is noteworthy, since neuropsychological studies usually do not connect parietal lesions to episodic memory impairments. Therefore an inventory of the possible factors behind this apparent paradox is warranted. This review compared fMRI studies which demonstrated PPC activity in episodic memory tasks, with findings with studies of patients with PPC lesions. A systematic evaluation of possible explanations for the posterior parietal paradox indicates that PPC activation in fMRI studies does not appear to be attributable to confounding cognitive/psychomotor processes, such as button pressing or stimulus processing. What may be of more importance is the extent to which an episodic memory task loads on three closely related cognitive processes: effort and attention, self-related activity, and scene and image construction. We discuss to what extent these cognitive processes can account for the paradox between lesion and fMRI results. They are strongly intertwined with the episodic memory and may critically determine in how far the PPC plays a role in a given memory task. Future patient studies might profit from specifically taking these cognitive factors into consideration in the task design.

Item does not contain fulltext, We present two cases (A.C. and W.J.) with navigation problems resulting from parieto-occipital right hemisphere damage. For both the cases, performance on the neuropsychological tests did not indicate specific impairments in spatial processing, despite severe subjective complaints of spatial disorientation. Various aspects of navigation were tested in a new virtual reality task, the Virtual Tubingen task. A double dissociation between spatial and temporal deficits was found; A.C. was impaired in route ordering, a temporal test, whereas W.J. was impaired in scene recognition and route continuation, which are spatial in nature. These findings offer important insights in the functional and neural architecture of navigation.

Item does not contain fulltext, The relative contribution of dominant and non-dominant language networks to recovery from aphasia is a matter of debate. We assessed with functional magnetic resonance imaging (fMRI) to what extent the left and right hemispheres are associated with recovery from aphasia after stroke. fMRI with three language tasks was performed in 13 aphasic stroke patients and in 13 healthy subjects. Severity of aphasia was examined within 2 months after stroke and after at least 1 year. Recovery of naming ability and scores on the Token Test were correlated with data from fMRI in the chronic phase. A breath-hold paradigm was used to investigate hemodynamic responsiveness. Overall language performance in the chronic phase correlated with higher relative activation of left compared to right perisylvian areas. Recovery of naming ability was positively correlated with activation in the left inferior frontal gyrus (IFG) for semantic decision and verb generation. Recovery on the Token Test was positively correlated with activation in both left and right IFG during semantic decision and verb generation. Hemodynamic response to the breath-hold task was similar in patients and controls. Our study suggests that in the chronic stage after stroke left IFG activity is associated with improvement of picture naming and sentence comprehension, whereas activity in the right IFG may reflect up-regulation of non-linguistic cognitive processing. Altered hemodynamic responsiveness seems an unlikely confounder in the interpretations of fMRI results. (C) 2009 Elsevier Inc. All rights reserved.

Item does not contain fulltext, Impairments in executive functioning frequently occur after acquired brain damage, in psychiatric disorders, and in relation to aging. The Brixton Spatial Anticipation Test is a relatively new measure for assessing the ability to detect and follow a rule, an important aspect of executive functioning. To date, normative data on this task are limited, particularly concerning the elderly. This study presents age- and education-adjusted regression-based norms obtained in a group of healthy older participants (n = 283; mean age 67.4 +/- 8.5 years). The applicability and validity of these norms were further examined in different groups of patients with stroke (n = 106), diabetes mellitus (n = 376), MCI/early dementia (n = 70), psychiatric disorders (n = 63), and Korsakoff's syndrome (n = 41). The results showed that patients with Korsakoff's syndrome, stroke, and psychiatric disorders performed significantly worse than healthy controls. Test-retest correlation (n = 83), learning effects, and correlations with other neuropsychological tests were also explored. Based on the present study, the Brixton test appears a useful addition to existing measures of executive functioning. Moreover, the test can be reliably applied in different groups of clinical patients.

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Item does not contain fulltext, Human neuropsychology suggests that there are two distinct body representations. Body image and body schema are, respectively, thought to be involved in conscious perceptual judgments and unconscious sensorimotor guidance. The evidence is based on the double dissociation between disorders of perceptual detection and sensorimotor guidance. Until now, research focused on cases that had impaired tactile pressure sensitivity and comparisons of performance were of cases suffering from different types of lesions (peripheral and central). Here, we report a unique double dissociation in two stroke patients with intact basic somatosensory processing (tactile detection). One patient was poor at identifying the position of where she had been touched on a line drawing of a hand, but was able to point accurately towards the actual position on her/his hand itself. The reverse pattern was observed in the other patient. This finding provides further support for separate Processing for body image and body scheme.

Contains fulltext : 70108.pdf (publisher's version ) (Closed access), Several neuropsychological studies have suggested parallel processing of somatosensory input when localising a tactile stimulus on one's own by pointing towards it (body schema) and when localising this touched location by pointing to it on a map of a hand (body image). Usually these reports describe patients with impaired detection, but intact sensorimotor localisation. This study examined three patients with a lesion of the angular gyrus with intact somatosensory processing, but with selectively disturbed finger identification (finger agnosia). These patients performed normally when pointing towards the touched finger on their own hand but failed to indicate this finger on a drawing of a hand or to name it. Similar defects in the perception of other body parts were not observed. The findings provide converging evidence for the dissociation between body image and body schema and, more importantly, reveal for the first time that this distinction is also present in higher-order cognitive processes selectively for the fingers.

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Item does not contain fulltext, Scene recognition can be enhanced by appropriate colour information, yet the level of visual processing at which colour exerts its effects is still unclear. It has been suggested that colour supports low-level sensory processing, while others have claimed that colour information aids semantic categorization and recognition of objects and scenes. We investigated the effect of colour on scene recognition in a case of colour agnosia, M.A.H. In a scene identification task, participants had to name images of natural or non-natural scenes in six different formats. Irrespective of scene format, M.A.H. was much slower on the natural than on the non-natural scenes. As expected, neither M.A.H. nor control participants showed any difference in performance for the non-natural scenes. However, for the natural scenes, appropriate colour facilitated scene recognition in control participants (i.e., shorter reaction times), whereas M.A.H.'s performance did not differ across formats. Our data thus support the hypothesis that the effect of colour occurs at the level of learned associations.

Item does not contain fulltext, An important aspect of research into the link between genes and behaviour concerns the identification of familial determination. There is evidence for familial factors in selective deficits, such as developmental dyslexia and developmental prosopagnosia. Colour agnosia concerns a selective neuropsychological condition in which colour perception is intact, while the identification and naming of colour is disrupted. We recently demonstrated that this deficit can occur as a developmental deficit. Here, we show that there is a familial factor in the development of colour agnosia by reporting the colour processing abilities of the mother and the daughters of a man with developmental colour agnosia.

Item does not contain fulltext, Background: Although cognitive impairment early after stroke is a powerful predictor of long-term functional dependence and dementia, little is known about the characteristics and determinants of cognitive dysfunction in acute stroke. Methods: We administered a neuropsychological examination covering 7 cognitive domains to 190 patients within 3 weeks after a first stroke. We also assembled lesion characteristics, clinical factors at admission, demographic characteristics and vascular risk factors. Multivariate logistic regression adjusted for age, gender and education was performed to examine determinants of acute cognitive impairment. Results: Overall, 74% of patients with a cortical stroke, 46% with a subcortical stroke and 43% with an infratentorial stroke demonstrated acute cognitive impairment.Disorders in executive functioning (39%) and visual perception/construction (38%) were the most common. The prevalence and severity of deficits in executive functioning, language, verbal memory and abstract reasoning was more pronounced following left compared to right cortical stroke (all p < 0.05). Intracerebral haemorrhage (OR = 5.6; 95% CI = 1.2-25.4) and cortical involvement of the stroke (OR = 3.6; 95%, CI = 1.3-9.9) were independent determinants of acute cognitive impairment, whereas premorbid moderate alcohol consumption exerted a protective effect (OR = 0.4; 95% CI = 0.1-1.1). Conclusions: Cognitive impairment is common in the first weeks after stroke, with executive and perceptual disorders being the most frequent. Intracerebral haemorrhage, cortical involvement of the lesion and premorbid moderate alcohol consumption are independently associated with acute cognitive impairment.

Item does not contain fulltext, Colour agnosia concerns the inability to recognise colours despite intact colour perception, semantic memory for colour information, and colour naming. Patients with selective colour agnosia have been described and the deficit is associated with left hemisphere damage. Here we report a case study of a 43-year-old man who was referred to us with a stroke in his right cerebellar hemisphere. During the standard assessment it transpired that he was unable to name coloured patches. Detailed assessment of his colour processing showed that he suffers from a selective colour agnosia. As he claimed to have had this problem all his life, and the fact that the infratentorial infarct that he had incurred was in an area far away from the brain structures that are known to be involved in colour processing, we suggest that he is the first reported case of developmental colour agnosia.

Item does not contain fulltext, We used functional magnetic resonance imaging to examine the neuroanatomical correlates of visual hallucinations in a patient with a left visual field defect who had suffered bilateral occipital infarction. By cross-correlating the functional magnetic resonance imaging data with the hallucination events, we were able to identify the cerebral activity underlying the hallucinations. Bilateral activation was observed during visual stimulation in the calcarine fissure and the same activation was found medially in the left and right occipital cortex adjacent to the infarcted areas. This pattern of perilesional visual cortex activation is consistent with the suggestion that primary sensory areas may be involved in visual hallucinations after stroke.

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Item does not contain fulltext, This study examines the applicability of the modified Location Learning Test (mLLT) as a test of spatial memory in neuropsychological patients. Three groups of participants were examined: stroke patients, patients with diabetes mellitus and healthy participants (N=411). Three error measures were computed, the Total Score (index of overall performance), the Learning Index (the learning curve over subsequent trials) and the Delayed Recall Score, measuring decay over time. The Learning Index was the most sensitive measure, showing differences between the three groups as well as lateralization effects within the stroke group. Also, the mLLT correlated significantly with the Rey Auditory Verbal Learning Test, as well as with age and education level. Regression-based normative data were computed based on the healthy participants. In all, the mLLT appears to be a sensitive and valid test for the detection of object-location memory impairments in clinical groups.

Item does not contain fulltext, Objective: To examine whether intravenous recombinant tissue plasminogen activator (rt–PA) treatment given in the acute phase of ischaemic stroke has a favourable effect on cognitive and functional outcome at six months post–stroke. Methods: The present study included 92 patients with a first–ever symptomatic infarct, of whom 25 (27%) were subjected to rt–PA treatment in the first three hours post–stroke. Multivariate logistic regression analyses adjusted for stroke severity, education, age, and sex were performed to examine whether rt–PA treatment influenced cognitive outcome (assessed with a neuropsychological examination covering 7 cognitive domains), basic ADL independence (modified Barthel Index >= 19), and instrumental ADL independence (Frenchay Activities Index >= 15) after six months. Results: The adjusted odds ratio for intact cognition was 1.0 (95% CI 0.2 to 4.3), that for basic ADL outcome 13.5 (95 % CI 1.4 to 129.4) and for instrumental ADL 7.1 (95 % CI 1.2 to 42.2). Conclusion: Our findings suggest that rt–PA treatment is associated with a favourable basic and instrumental ADL outcome, but not with a beneficial cognitive outcome after 6 months.

Item does not contain fulltext, Patients with colour agnosia can perceive colours and are able to match coloured patches on hue, but are unable to identify or categorise colours. It is a rare condition and there is as yet no agreement on the clinical definition or a generally accepted explanation. In line with observations from object agnosia and prosopagnosia, we hypothesised that (some of) these patients might still be able to process colour information at an implicit level. In this study, we investigated this possibility of implicit access to colour semantics and colour names in a man (MAH) who suffers from developmental colour agnosia. We designed two experimental computer tasks: an associative colour priming task with a lexical decision response and a reversed Stroop task. The results of these experiments suggest that there is indeed automatic processing of colour, although MAH was unable to explicitly use colour information.

Item does not contain fulltext, Purpose of review This review of the cognitive status following stroke and vascular cognitive impairment starts by questioning the concept of vascular dementia and related concepts. Our position is that in many cases these labels promote a superficial conceptualization of an inherently complex and heterogeneous phenomenon hampering a more detailed understanding. Recent findings After stroke or disease of the cerebral vasculature, the cognitive and emotional outcome is dependent on a combination of three factors with the relative importance differing between causes. First, focal damage may lead to selective impairments that are dependent on the localization of the (grey matter) lesion. Second, diffuse neuronal dysfunction produces a more uniform profile of a decrease in mental speed, memory problems, and reduced executive functioning. Third, cognitive outcome is further modulated - notably in terms of severity - by patient variables such as age, sex, premorbid level of functioning, and comorbidity (e.g. hypertension). Summary The complex character of the cognitive repercussions of stroke can be better harnessed by employing modern neuropsychological assessment procedures. This allows both a detailed categorization of the patients for the selection and effectiveness of therapeutic intervention, as well as the construction of reliable prognostic models.