Maria Gabriella Vita

Neuropsychological Predictors of Conversion from Mild Cognitive Impairment to Alzheimer's Disease

The construct of mild cognitive impairment (MCI) has been proposed to identify patients at risk of developing Alzheimers disease (AD) in the pre-clinical stage. Although subjects with MCI have an increased risk of progressing to dementia, most remain stable or return to normality. The new criteria for diagnosing prodromal AD assume that, to increase the predictive value of the MCI, in addition to a defect of delayed recall there must also be the presence of abnormal biomarkers, investigating structural and molecular neuroimaging and cerebrospinal fluid (CSF) analysis of amyloid-β or tau proteins. Although acknowledging that the use of CSF degeneration biomarkers is advisable not only for research, but also for clinical purposes, the present review is centered upon the neuropsychological markers of conversion to AD, which are equally clinically important. In particular, results of this review suggest the following: (a) measures of delayed recall are the best neuropsychological predictors of conversion from MCI to AD; (b) memory tests providing controlled encoding and cued recall are not necessarily better predictors than free recall tests; (c) stringent cut-off points are necessary to increase the specificity of these predictors; (d) multi-domain amnestic MCI patients are the best candidates for clinical trials, but not for treatment with disease-modifying drugs; and (e) not only episodic but also semantic memory is significantly impaired in patients who will convert to AD. These data and the underlying neural mechanisms will be discussed, trying to distinguish results obtained in MCI patients from those obtained in a pre-MCI stage of the AD progression.

Human brain networks in cognitive decline: a graph theoretical analysis of cortical connectivity from EEG data

The aim of this study was to investigate the neuronal network characteristics in physiological and pathological brain aging. A database of 378 participants divided in three groups was analyzed: Alzheimers disease (AD), mild cognitive impairment (MCI), and normal elderly (Nold) subjects. Through EEG recordings, cortical sources were evaluated by sLORETA software, while graph theory parameters (Characteristic Path Length λ, Clustering coefficient γ, and small-world network σ) were computed to the undirected and weighted networks, obtained by the lagged linear coherence evaluated by eLORETA software. EEG cortical sources from spectral analysis showed significant differences in delta, theta, and alpha 1 bands. Furthermore, the analysis of eLORETA cortical connectivity suggested that for the normalized Characteristic Path Length (λ) the pattern differences between normal cognition and dementia were observed in the theta band (MCI subjects are find similar to healthy subjects), while for the normalized Clustering coefficient (γ) a significant increment was found for AD group in delta, theta, and alpha 1 bands; finally, the small world (σ) parameter presented a significant interaction between AD and MCI groups showing a theta increase in MCI. The fact that AD patients respect the MCI subjects were significantly impaired in theta but not in alpha bands connectivity are in line with the hypothesis of an intermediate status of MCI between normal condition and overt dementia.

Patterns of cognitive decline and rates of conversion to dementia in patients with degenerative and vascular forms of MCI.

According to recent criteria, Mild Cognitive Impairment (MCI) represents a clinical condition with multiple cognitive presentations (amnesic and non amnesic) that can be supported by different types of brain lesions (mainly vascular and atrophic). In order to asses if the cognitive presentation and the rate of progression differ according to the type of brain pathology, two populations of MCI patients, characterized by hippocampal atrophy (n: 39) and vascular subcortical pathology (n: 36) respectively, on the basis of MRI findings, were investigated. Patients underwent an extensive neuropsychological test battery twice (at baseline and at two years follow-up), which is made up of the MMSE and various tests of episodic memory, short-term memory, visual-spatial abilities, executive functions, language, attention, praxis and psychomotor speed. Atrophic and vascular MCI patients showed a remarkably different pattern of impairment at the baseline. The former were significantly more impaired in episodic memory tasks. The latter were more impaired in an action naming task. At the follow up examination, the rate of progression to dementia was higher in atrophic (14/39) than in vascular (5/36) MCI patients. The comparison between neuropsychological scores obtained at the baseline and at the follow-up showed that atrophic MCI patients underwent a severe decline in several cognitive domains, whereas vascular MCI patients showed a significant decline only in those tasks requiring executive abilities. Our results confirm that a selective and severe defect of episodic memory is associated with hippocampal atrophy and that MCI patients with atrophic lesions are more likely to convert to Alzheimers type dementia while MCI patients with vascular lesions are characterized by a slight decline in executive function over time and by a tendency to develop probable vascular forms of dementia.

Patterns of neuropsychological impairment in MCI patients with small subcortical infarcts or hippocampal atrophy

We investigated whether MCI patients with hippocampal atrophy or multiple subcortical infarcts demonstrate neuropsychological patterns and markers considered typical of Alzheimers disease (AD) and of vascular dementia (VD), respectively. An extensive neuropsychological battery, including tests of memory, visual-spatial and executive functions, language, attention, praxis and psychomotor speed, was administered to 36 mild cognitive impairment (MCI) patients with hippocampal atrophy and 41 MCI patients with multiple subcortical infarcts. Both groups of MCI patients were very mildly impaired and well matched in terms of MMSE scores. A clear, disproportionately severe, episodic memory disorder was observed in MCI patients with hippocampal atrophy. A less specific neuropsychological profile, consisting of impairment on an Action Naming task that is sensitive to frontal lobe lesions, was observed in MCI patients with multiple subcortical infarcts. In MCI patients, a disproportionately severe episodic memory impairment strongly points to an Alzheimers type brain pathology, whereas the prevalence of executive deficits and other frontal lobe symptoms are a much weaker diagnostic marker of small vessel subcortical disease.

Cerebellar degeneration associated with mGluR1 autoantibodies as a paraneoplastic manifestation of prostate adenocarcinoma

Subacute cerebellar degeneration associated with metabotropic glutamate receptor type 1 (mGluR1) autoantibodies is an uncommon syndrome known to be part of the spectrum of paraneoplastic cerebellar degenerations associated with neuronal autoantibodies. We describe a patient with prostate adenocarcinoma who developed a subacute cerebellar ataxia. Autoantibodies specific to mGluR1 were detected in patients serum and cerebrospinal fluid (CSF). Immunohistochemistry analyses of patients prostate adenocarcinoma revealed abundant mGluR1 expression in luminal acinar epithelial cells and binding of patients IgGs to tumoral mGluR1. These findings suggest that cerebellar degeneration associated with mGluR1 antibodies can be a paraneoplastic accompaniment of prostate adenocarcinoma.

Selective impairment of action-verb naming and comprehension in progressive supranuclear palsy

Some previous studies in brain-damaged patients suggested that neural systems in the left temporal lobe might be crucial in the production and comprehension of nouns, while analogous systems in posterior frontal cortical areas might be involved in the production and comprehension of verbs. We assessed performance on neuropsychological tasks of production and comprehension of nouns and action-verbs in 10 patients with progressive supranuclear palsy (PSP) and in 10 age-matched healthy controls. PSP patients also underwent measurements of regional cerebral blood flow by means of single photon emission computed tomography (SPECT), using 99mTc-Ethyl Cysteinate Dimer. In all PSP patients, SPECT showed a significant hypoperfusion in the inferior frontal gyrus (IFG). PSP patients performed significantly worse than controls on all lexical-semantic tasks, except for the auditory lexical decision task on nouns. Within PSP patients, however, a significantly lower performance was observed on action-verbs as compared to nouns on various lexical-semantic tasks (oral and written confrontation naming, auditory and visual single-word comprehension). Analysis of individual performance revealed heterogeneous patterns of neuropsychological impairment in different PSP patients. Despite some difficulty in drawing clear-cut conclusions about the locus of functional damage, we hypothesise that in most of our PSP patients such selective impairment in the production and in the comprehension of action-verbs could be due to semantic deficits affecting the conceptual category of actions. These findings are consistent with the hypothesis that in PSP a dysfunction of neural systems in posterior frontal cortical areas (mainly involving the IFG) critical for processing the conceptual category of actions might result in a selective impairment of production and comprehension of action-verbs.

Brain tissue modifications induced by cholinergic therapy in Alzheimer's disease.

A previous preliminary investigation based on a novel MRI approach to map anatomical connectivity revealed areas of increased connectivity in Alzheimers disease (AD) but not in mild cognitive impairment patients. This prompted the hypothesis tested here, that these areas might reflect phenomena of brain plasticity driven by acetylcholinesterase inhibitors (AChEIs). Thirty‐eight patients with probable AD (19 under medication with AChEIs and 19 drug‐naïve) were recruited together with 11 healthy controls. All subjects had MRI scanning at 3T, including volumetric and diffusion‐weighted scans. Probabilistic tractography was used to initiate streamlines from all parenchymal voxels, and anatomical connectivity maps (ACMs) were obtained by counting, among the total number of streamlines initiated, the fraction passing through each brain voxel. After normalization into standard space, ACMs were used to test for between‐group comparisons, and for interactions between the exposure to AChEIs and global level of cognition. Patients with AD had reduced ACM values in the fornix, cingulum, and supramarginal gyri. The ACM value was strongly associated with the AChEI dosage‐x‐duration product in the anterior limb (non‐motor pathway) of the internal capsule. Tractography from this region identified the anterior thalamic radiation as the main white matter (WM) tract passing through it. The reduced connectivity in WM bundles connecting the hippocampi with the rest of the brain (fornix/cingulum) suggests a possible mechanism for the spread of AD pathology. An intriguing explanation for the interaction between AChEIs and ACM is related to the mechanisms of brain plasticity, partially driven by neurotrophic properties of acetylcholine replacement. Hum Brain Mapp 34:3158–3167, 2013.

Cognitive and Behavioral Determinants of Psychotic Symptoms in Alzheimer's Disease

Aims: To investigate the relationship between psychotic symptoms and cognitive impairment in Alzheimers disease (AD). Methods: A total of 108 subjects affected by AD were subdivided into subjects without delusions (ND), subjects with paranoid delusions (PD), subjects with delusional misidentifications (DM), subjects with both DM and PD (DM+PD), subjects with visual hallucinations (v-HALL), and subjects without visual hallucinations (N-HALL). Results: PD and ND subjects performed similarly on neuropsychological tests, while DM patients performed significantly worse than PD and ND patients. v-HALL patients performed worse than N-HALL patients on memory, visuospatial, and executive functions. As for behavioral features, DM and v-HALL subjects reported higher scores on the abnormal motor behavior subscale of the neuropsychiatric inventory (NPI); PD subjects reported higher scores on the disinhibition subscale of the NPI. The severity of PD was predicted by the severity of disinhibition (B = 0.514; p = 0.016) but not by neuropsychological performances. The severity of DM was predicted by age (B = 0.099; p = 0.048) and MMSE (B = -0.233; p = 0.001). The severity of v-HALL was predicted by age (B = 0.052; p = 0.037) and scores on an immediate visual memory task (B = -0.135; p = 0.007). Conclusions: The occurrence of PD may require the relative sparing of cognitive functions and be favored by frontal lobe dysfunction, while DM is associated with the overall level of cognitive impairment. Finally, v-HALL are associated with the impairment of visuospatial abilities.

Typicality of words produced on a semantic fluency task in amnesic mild cognitive impairment: Linguistic analysis and risk of conversion to dementia

Semantic and, to a lesser extent, phonological verbal fluency tasks are impaired in Alzheimers disease (AD) and in amnesic mild cognitive impairment (aMCI). Furthermore, both fluency tasks have been considered as possible markers of conversion from aMCI to AD. Up to recent years, the use of fluency tasks has been limited to word count, but, more recently, linguistic variables, such as word frequency, age of acquisition, familiarity, and typicality, have also been considered. In particular, attention has been focused on typicality of words produced on semantic verbal fluency tasks, because the tendency to produce only the more typical members of various categories points to an impoverishment of semantic memory. The aim of our study was to compare in aMCI, AD, and control subjects a lexical (word frequency) and a lexical-semantic variable (item typicality) in a semantic verbal fluency task, and to evaluate the possible value of these variables in predicting conversion from aMCI to AD during a 2 years follow-up period. We found no difference in mean typicality of words produced by aMCI and AD subjects whereas both groups produced words of higher mean typicality than control subjects. Furthermore, to assess the relationship between typicality values and risk of conversion to AD, the aMCI group was split in two subgroups, including subjects who obtained a mean typicality value lower or higher than the median value of the whole aMCI group. Consistent with our hypothesis, conversion to AD was significantly more frequent in high typicality than in low typicality subjects.

Standardization, Clinical Validation, and Typicality Norms of a New Test Assessing Semantic Verbal Fluency

OBJECTIVE Semantic verbal fluency (SVF) tests are widely used in clinical neuropsychology. We propose the standardization and clinical validation of a new SVF test based on the production of names of birds and articles of furniture (Birds and Articles of Furniture test-BAF). METHODS A sample of 268 subjects aged 40 years or more underwent the test. The clinical validation was conducted on subjects affected by amnesic Mild Cognitive Impairment (aMCI; N = 106), mild (N = 178), and moderate (N = 114) Alzheimers disease (AD). RESULTS The BAF total score was influenced by both age and education, whereas the single scores obtained on BAF were also influenced by gender. The percentage of subjects with pathological score on BAF increased from aMCI (19%) to mild (45.5%) and moderate (71.1%) AD, and receiver operating characteristic curves analysis showed that the BAF may be highly reliable in distinguishing aMCI and AD patients from healthy subjects. We also provide typicality norms for birds and articles of furniture that could be useful in the assessment of qualitative features of words produced in semantic fluency tests. CONCLUSIONS The BAF test could be a valid and reliable tool in both clinical practice and research on subjects affected by cognitive impairment.