Numeracy Skills in Patients With Degenerative Disorders and Focal Brain Lesions: A Neuropsychological Investigation

Objective: To characterize the numerical profile of patients with acquired brain disorders. Method: We investigated numeracy skills in 76 participants—40 healthy controls and 36 patients with neurodegenerative disorders (Alzheimer dementia, frontotemporal dementia, semantic dementia, progressive aphasia) and with focal brain lesions affecting parietal, frontal, and temporal areas as in herpes simplex encephalitis (HSE). All patients were tested with the same comprehensive battery of paper-and-pencil and computerized tasks assessing numerical abilities and calculation. Degenerative and HSE patients also performed nonnumerical semantic tasks. Results: Our results, based on nonparametric group statistics as well as on the analysis of individual patients, and all highly significant, show that: (a) all patients, including those with parietal lesions—a key brain area for numeracy processing—had intact processing of number quantity; (b) patients with impaired semantic knowledge had much better preserved numerical knowledge; and (c) most patients showed impaired calculation skills, with the exception of most semantic dementia and HSE patients. Conclusion: Our results allow us, for the first time, to characterize the numeracy skills in patients with a variety of neurological conditions and to suggest that the pattern of numerical performance can vary considerably across different neurological populations. Moreover, the selective sparing of calculation skills in most semantic dementia and HSE suggest that numerical abilities are an independent component of the semantic system. Finally, our data suggest that, besides the parietal areas, other brain regions might be critical to the understanding and processing of numerical concepts

Context Memory in Korsakoff’s Syndrome

Memory for contextual information and target-context integration are crucial for successful episodic memory formation and are impaired in patients with Korsakoff’s syndrome. In this paper we review the evidence for the notion that a context memory deficit makes an important contribution to the amnesia in these patients. First, we focus on anterograde memory for contextual (spatial and temporal) information. Next, the use of contextual cues in memory retrieval is examined and their role in retrograde amnesia and confabulation. Evidence on the role of contextual cues and associations in working memory is discussed in relation to the underlying neurocognitive mechanisms and their dissociation from long-term encoding. Finally, we focus on implicit learning of contextual information in Korsakoff patients. It can be concluded that Korsakoff patients are impaired in the explicit processing of contextual information and in target-context binding, both in long-term (retrograde and anterograde) memory and in working memory. These results extend the context memory deficit hypothesis. In contrast, implicit contextual learning is relatively preserved in these patients. These findings are discussed in relation to evidence of dysfunction of the extended diencephalic-hippocampal memory circuit in Korsakoff’s syndrome

Mentalizing the body: : spatial and social cognition in anosognosia for hemiplegia

© The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact [email protected] right-hemisphere damage, a specific disorder of motor awareness can occur called anosognosia for hemiplegia, i.e. the denial of motor deficits contralateral to a brain lesion. The study of anosognosia can offer unique insights into the neurocognitive basis of awareness. Typically, however, awareness is assessed as a first person judgement and the ability of patients to think about their bodies in more 'objective' (third person) terms is not directly assessed. This may be important as right-hemisphere spatial abilities may underlie our ability to take third person perspectives. This possibility was assessed for the first time in the present study. We investigated third person perspective taking using both visuospatial and verbal tasks in right-hemisphere stroke patients with anosognosia (n = 15) and without anosognosia (n = 15), as well as neurologically healthy control subjects (n = 15). The anosognosic group performed worse than both control groups when having to perform the tasks from a third versus a first person perspective. Individual analysis further revealed a classical dissociation between most anosognosic patients and control subjects in mental (but not visuospatial) third person perspective taking abilities. Finally, the severity of unawareness in anosognosia patients was correlated to greater impairments in such third person, mental perspective taking abilities (but not visuospatial perspective taking). In voxel-based lesion mapping we also identified the lesion sites linked with such deficits, including some brain areas previously associated with inhibition, perspective taking and mentalizing, such as the inferior and middle frontal gyri, as well as the supramarginal and superior temporal gyri. These results suggest that neurocognitive deficits in mental perspective taking may contribute to anosognosia and provide novel insights regarding the relation between self-awareness and social cognition.Peer reviewe

A case of selective impairment of encyclopaedic numerical knowledge or ‘when December 25th is no longer Christmas day, but ‘20 + 5’ is still 25

This study investigates encyclopaedic numerical knowledge in a patient with a presumed left temporal dysfunction, associated with temporal lobe epilepsy. Encyclopaedic numbers are those used as nominal labels (such as in ‘British Broadcasting Corporation – BBC 1’ or ‘Levis 501’) to express familiar or historical dates (e.g., our birthday or the French revolution, 1789) and to indicate other general or autobiographical numerical information (e.g., Personal Identification numbers – PINs, post-codes, telephone numbers). We showed a dissociation between impaired processing of encyclopaedic numbers and preserved processing of non-encyclopaedic numbers (e.g., the larger between 54 and 65 or the result of ‘6 × 9’). This dissociation complements the existing data showing the reverse pattern of performance, namely an advantage for encyclopaedic compared to nonencyclopaedic numbers. These data add important information on an aspect of numerical processing that has not yet been systematically explored and reinforce the distinction between numerical and non-numerical knowledge in the semantic system

Numerical Observation of Disorder-Induced Anomalous Kinetics in the A + A -> 0 Reaction

We address via numerical simulation the two-dimensional bimolecular annihilation reaction $A + A \to \emptyset$ in the presence of quenched, random impurities. Renormalization group calculations have suggested that this reaction displays anomalous kinetics at long times, $c_{A}(t) \sim at^{\delta -1}$, for certain types of topological or charged reactants and impurities. Both the exponent and the prefactor depend on the strength of disorder. The decay exponents determined from our simulations agree well with the values predicted by theory. The observed renormalization of the prefactor also agrees well with the values predicted by theory.Comment: 16 pages, 5 figures, uses Elsevier style elsart. To appear in Physica

Psychogenic amnesia: syndromes, outcome, and patterns of retrograde amnesia

There are very few case series of patients with acute psychogenic memory loss (also known as dissociative/functional amnesia), and still fewer studies of outcome, or comparisons with neurological memory-disordered patients. Consequently, the literature on psychogenic amnesia is somewhat fragmented and offers little of prognostic value for individual patients. In the present study, we reviewed the case records and neuropsychological findings in 53 psychogenic amnesia cases (3M:1F), in comparison with 21 consecutively recruited neurological memory-disordered patients and 14 healthy controls. In particular, we examined the pattern of retrograde amnesia on an assessment of autobiographical memory (the Autobiographical Memory Interview). We found that our patients with psychogenic memory loss fell into four distinct groups, which we categorised as: (i) fugue state, (ii) fugue-to-focal retrograde amnesia, (iii) psychogenic focal retrograde amnesia following a minor neurological episode, and (iv) patients with gaps in their memories. While neurological cases were characterised by relevant neurological symptoms, a history of a past head injury was actually more common in our psychogenic cases (p=0.012), perhaps reflecting a ‘learning episode’ predisposing to later psychological amnesia. As anticipated, loss of the sense of personal identity was confined to the psychogenic group. However, clinical depression, family/relationship problems, financial/employment problems, and failure to recognise the family were also statistically more common in that group. The pattern of autobiographical memory loss differed between the psychogenic groups: fugue cases showed a severe and uniform loss of memories for both facts and events across all time-periods, whereas the two focal retrograde amnesia groups showed a ‘reversed’ temporal gradient with relative sparing of recent memories. After 3-6 months, the fugue patients had improved to normal scores for facts and near-normal scores for events. By contrast, the two focal retrograde amnesia groups showed a lesser improvement and continued to show a reversed temporal gradient. In conclusion, the outcome in psychogenic amnesia, particularly those characterised by fugue, is better than generally supposed. Findings are interpreted in terms of Markowitsch’s and Kopelman’s models of psychogenic amnesia, and with respect to Anderson’s neuroimaging findings in memory inhibition

A case of selective impairment of encyclopaedic numerical knowledge or 'when December 25th is no longer Christmas day, but "20 + 5" is still 25

This study investigates encyclopaedic numerical knowledge in a patient with a presumed left temporal dysfunction, associated with temporal lobe epilepsy. Encyclopaedic numbers are those used as nominal labels (such as in ‘British Broadcasting Corporation – BBC 1’ or ‘Levis 501’) to express familiar or historical dates (e.g., our birthday or the French revolution, 1789) and to indicate other general or autobiographical numerical information (e.g., Personal Identification numbers – PINs, post-codes, telephone numbers). We showed a dissociation between impaired processing of encyclopaedic numbers and preserved processing of non-encyclopaedic numbers (e.g., the larger between 54 and 65 or the result of ‘6 × 9’). This dissociation complements the existing data showing the reverse pattern of performance, namely an advantage for encyclopaedic compared to nonencyclopaedic numbers. These data add important information on an aspect of numerical processing that has not yet been systematically explored and reinforce the distinction between numerical and non-numerical knowledge in the semantic system

A Feasibility Study of Quantifying Longitudinal Brain Changes in Herpes Simplex Virus (HSV) Encephalitis Using Magnetic Resonance Imaging (MRI) and Stereology.

OBJECTIVES: To assess whether it is feasible to quantify acute change in temporal lobe volume and total oedema volumes in herpes simplex virus (HSV) encephalitis as a preliminary to a trial of corticosteroid therapy. METHODS: The study analysed serially acquired magnetic resonance images (MRI), of patients with acute HSV encephalitis who had neuroimaging repeated within four weeks of the first scan. We performed volumetric measurements of the left and right temporal lobes and of cerebral oedema visible on T2 weighted Fluid Attenuated Inversion Recovery (FLAIR) images using stereology in conjunction with point counting. RESULTS: Temporal lobe volumes increased on average by 1.6% (standard deviation (SD 11%) in five patients who had not received corticosteroid therapy and decreased in two patients who had received corticosteroids by 8.5%. FLAIR hyperintensity volumes increased by 9% in patients not receiving treatment with corticosteroids and decreased by 29% in the two patients that had received corticosteroids. CONCLUSIONS: This study has shown it is feasible to quantify acute change in temporal lobe and total oedema volumes in HSV encephalitis and suggests a potential resolution of swelling in response to corticosteroid therapy. These techniques could be used as part of a randomized control trial to investigate the efficacy of corticosteroids for treating HSV encephalitis in conjunction with assessing clinical outcomes and could be of potential value in helping to predict the clinical outcomes of patients with HSV encephalitis

The affective modulation of motor awareness in anosognosia for hemiplegia : Behavioural and lesion evidence

© 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).The possible role of emotion in anosognosia for hemiplegia (i.e., denial of motor deficits contralateral to a brain lesion), has long been debated between psychodynamic and neurocognitive theories. However, there are only a handful of case studies focussing on this topic, and the precise role of emotion in anosognosia for hemiplegia requires empirical investigation. In the present study, we aimed to investigate how negative and positive emotions influence motor awareness in anosognosia. Positive and negative emotions were induced under carefully-controlled experimental conditions in right-hemisphere stroke patients with anosognosia for hemiplegia (n = 11) and controls with clinically normal awareness (n = 10). Only the negative, emotion induction condition resulted in a significant improvement of motor awareness in anosognosic patients compared to controls; the positive emotion induction did not. Using lesion overlay and voxel-based lesion-symptom mapping approaches, we also investigated the brain lesions associated with the diagnosis of anosognosia, as well as with performance on the experimental task. Anatomical areas that are commonly damaged in AHP included the right-hemisphere motor and sensory cortices, the inferior frontal cortex, and the insula. Additionally, the insula, putamen and anterior periventricular white matter were associated with less awareness change following the negative emotion induction. This study suggests that motor unawareness and the observed lack of negative emotions about one's disabilities cannot be adequately explained by either purely motivational or neurocognitive accounts. Instead, we propose an integrative account in which insular and striatal lesions result in weak interoceptive and motivational signals. These deficits lead to faulty inferences about the self, involving a difficulty to personalise new sensorimotor information, and an abnormal adherence to premorbid beliefs about the body.Peer reviewedFinal Published versio