D. Libon - Academia.edu (original) (raw)

Papers by D. Libon

Research paper thumbnail of A quantitative index measuring deficits in semantic knowledge derived from the "animal" word list generation (WLG) task

Archives of Clinical Neuropsychology, 1997

Research paper thumbnail of Neuropsychological Profiles Associated with Subcortical White Matter Alterations and Parkinson's Disease: Implications for the Diagnosis of Dementia

Archives of Clinical Neuropsychology, 2001

Despite the emergence of a number of new classification systems, the diagnosis of cerebrovascular... more Despite the emergence of a number of new classification systems, the diagnosis of cerebrovascular dementia remains controversial. Also controversial is the significance of periventricular and deep white matter alterations (WMA) as seen on magnetic resonance imaging (MRI). To further clarify this issue, MRI scans were used to regroup patients clinically diagnosed with Alzheimer's disease (AD) or subcortical ischemic vascular dementia (IVD) into cohorts presenting with either little versus significant WMA on MRI. These two groups were then compared to demented patients diagnosed with idiopathic Parkinson's disease (PD) using a comprehensive neuropsychological protocol. Neuropsychological assessment failed to distinguish between patients with PD and significant WMA. By contrast, both of these patient groups exhibited disproportionate impairment on tests of executive systems functioning, whereas patients with little WMA showed greater impairment on tests of declarative memory and semantic knowledge. These findings constitute further evidence that the pattern of cognitive impairment associated with significant WMA is distinctly different when compared to AD. These results are discussed within the context of a growing body of literature suggesting that elements of the underlying neuropathologies in AD and IVD are linked. Implications for the diagnosis of dementia are also discussed.

Research paper thumbnail of National Academy of Neuropsychology. Abstracts from the 27th Annual Meeting, Scottsdale, Arizona, November 14-18, 2007

Archives of Clinical Neuropsychology, 2007

Research paper thumbnail of The role of the dynamic body schema in praxis: evidence from primary progressive apraxia

Brain and cognition, 2000

On an influential model of limb praxis, ideomotor apraxia results from damage to stored gesture r... more On an influential model of limb praxis, ideomotor apraxia results from damage to stored gesture representations or disconnection of representations from sensory input or motor output (Heilman & Gonzalez Rothi, 1993; Gonzalez Rothi et al., 1991). We report data from a patient with progressive ideomotor limb apraxia which cannot be readily accommodated by this model. The patient, BG, is profoundly impaired in gesturing to command, to sight of object, and to imitation, but gestures nearly normally with tool in hand and recognizes gestures relatively well. In addition, performance is profoundly impaired on imitation of meaningless gestures and on tasks requiring spatiomotor transformations of body-position information. We provide evidence that BG's apraxia is largely attributable to impairments external to the stored gesture system in procedures coding the dynamic positions of the body parts of self and others; that is, the body schema. We propose a model of a dynamic, interactive p...

Research paper thumbnail of ALS-dementia in a large population of patients with ALS and FTD

Research paper thumbnail of Longitudinal decline in autopsy-defined frontotemporal lobar degeneration

Neurology, 2008

The natural history of patients with pathologically proven frontotemporal lobar degeneration (FTL... more The natural history of patients with pathologically proven frontotemporal lobar degeneration (FTLD) is important from clinical and biologic perspectives, but is not well documented quantitatively. We examine longitudinal decline in cognitive functioning in an autopsy-proven cohort of patients with the clinical diagnosis of a FTLD spectrum disorder or FTLD pathology using a panel of neuropsychological measures. Patients are categorized according to findings at autopsy into tau-positive FTLD, tau-negative FTLD, and frontal variant-Alzheimer disease (fvAD) subgroups. Patients decline significantly over time on all neuropsychological measures. Moreover, several measures differentiate between histopathologically distinct subgroups throughout the course of the disease process. This includes a significant double dissociation involving relative difficulty on a visual constructional measure in tau-positive patients compared to relatively impaired visual confrontation naming in tau-negative patients. Longitudinal measures of FAS naming fluency and animal naming fluency also distinguish tau-positive patients and tau-negative patients with FTLD from patients with fvAD. Other measures show significant decline but do not distinguish between histopathologic groups longitudinally. Our findings suggest different longitudinal patterns of cognitive decline in pathologically defined subgroups of patients. Measures consistently distinguishing between patient subgroups can be used to bolster diagnostic accuracy throughout the course of these diseases, while measures demonstrating undifferentiated longitudinal decline may serve as useful endpoints in treatment trials.

Research paper thumbnail of The Contribution of White Matter Neuroimaging to Multimodal Diagnosis of Frontotemporal Lobar Degeneration (P03.096)

Research paper thumbnail of White matter imaging contributes to the multimodal diagnosis of frontotemporal lobar degeneration

Objective: To evaluate the distribution of white matter (WM) disease in frontotemporal lobar dege... more Objective: To evaluate the distribution of white matter (WM) disease in frontotemporal lobar degeneration (FTLD) and Alzheimer disease (AD) and to evaluate the relative usefulness of WM and gray matter (GM) for distinguishing these conditions in vivo.

Research paper thumbnail of Screening for Frontotemporal Dementias and Alzheimer’s Disease with the Philadelphia Brief Assessment of Cognition: A Preliminary Analysis

Dementia and Geriatric Cognitive Disorders, 2007

A neuropsychological screening instrument sensitive to neuropsychological deficits associated wit... more A neuropsychological screening instrument sensitive to neuropsychological deficits associated with Alzheimer's disease (AD) and patients with frontotemporal dementia (FTD) would be valuable for diagnostic evaluation. The Philadelphia Brief Assessment of Cognition (PBAC) assesses working memory/executive control, language, visuospatial operations, verbal/visual episodic memory, and behavior/social comportment and can be administered and scored in 15-20 min. Participants included 149 patients with AD and four groups of FTD patients - i.e., patients with a decline in social comportment, personality, and executive functioning (SOC/EXEC), semantic dementia (SemD), progressive nonfluent aphasia (PNFA), and corticobasal syndrome (CBS). The total PBAC score correlated with the Mini-Mental State Examination. Between-group analysis of PBAC subscales and the results of logistic regression analyses produced substantial between-group differences, emphasizing the sensitivity of the test to differentiate dementia subtypes. AD patients were impaired on tests of episodic memory, SOC/EXEC patients were impaired on a measure of social comportment/behavioral disturbance, PNFA patients obtained low scores on tests of working memory/executive control, SemD patients obtained lower scores on language-mediated measures, and CBS patients were impaired on visuospatial/visual memory tests. These data support the usefulness of the PBAC as a relatively brief screening test of overall dementia severity across a wide range of dementia patients.

Research paper thumbnail of Distinct Antemortem Profiles in Patients With Pathologically Defined Frontotemporal Dementia

Archives of Neurology, 2007

Clinical-pathologic studies are crucial to understanding brain-behavior relations and improving d... more Clinical-pathologic studies are crucial to understanding brain-behavior relations and improving diagnostic accuracy in neurodegenerative diseases. To establish clinical, neuropsychological, and imaging features of clinically diagnosed patients with frontotemporal dementia (FTD) that help discriminate between pathologically determined tau-positive FTD, tau-negative FTD, and frontal-variant Alzheimer disease. Retrospective clinical-pathologic survey. Academic medical center. Patients Sixty-one participants with the clinical diagnosis of a frontotemporal spectrum disorder who underwent a neuropsychological evaluation and had an autopsy-confirmed disease. Neuropsychological performance and high-resolution structural magnetic resonance imaging (MRI). Distinguishing features of patients with tau-positive FTD include visual perceptual-spatial difficulty and an extrapyramidal disorder significantly more often than other patients, significant cortical atrophy in the frontal and parietal regions as evidenced on MRI, and the burden of pathology is greatest in the frontal and parietal regions. Patients with tau-negative FTD are distinguished by their greater difficulties with social, language, and verbally mediated executive functions, significant cortical atrophy in the frontal and temporal regions as evidenced on MRI, and significant frontal and temporal pathology. Patients with Alzheimer disease at autopsy have significantly impaired delayed recall during episodic memory testing; atrophy that involves temporal areas, including the hippocampus, as evidenced on MRI; and widely distributed pathology including the medial temporal structures. A discriminant function analysis grouped patients on the basis of clinical and neuropsychological features with 87.5% accuracy. Clinical, neuropsychological, and imaging profiles can contribute to accurate antemortem diagnosis in FTD.

Research paper thumbnail of Syntactic comprehension deficits are associated with MRI white matter alterations in dementia

Journal of the International Neuropsychological Society, 2008

Comprehension difficulties associated with periventricular and deep white matter alterations (WMA... more Comprehension difficulties associated with periventricular and deep white matter alterations (WMA) in mild dementia were investigated using portions of the Boston Diagnostic Aphasia Examination (BDAE) Complex Ideation subtest and Syntax subtests. Mild dementia participants were grouped according to the extent of their WMA as observed on magnetic resonance imaging (mild WMA n 5 45 vs. moderate to severe WMA n 5 52). Correlation and regression analyses also were performed to examine the link between WMA and comprehension abilities, as well as the link between comprehension abilities and neuropsychological measures of executive functioning, language, episodic memory, and overall dementia severity. Results showed that the WMA groups differed on the BDAE-Syntax subtests, with the severe WMA group demonstrating more impairment. Correlation and regression analyses including the entire sample also demonstrated that the extent of WMA was significantly linked to Syntax test scores but not Complex Ideation scores. Regression analyses including neuropsychological measures showed that the BDAE-Complex Ideation score was marginally predicted by only overall dementia severity, whereas the BDAE-Syntax scores were significantly predicted by independent measures of working memory0executive functioning. In conclusion, greater subcortical WMA and executive deficits are associated with greater difficulties in syntactic comprehension in individuals with mild dementia. (JINS, 2008, 14, 542-551.)

Research paper thumbnail of A quantitative index measuring deficits in semantic knowledge derived from the "animal" word list generation (WLG) task

Archives of Clinical Neuropsychology, 1997

Research paper thumbnail of Neuropsychological Profiles Associated with Subcortical White Matter Alterations and Parkinson's Disease: Implications for the Diagnosis of Dementia

Archives of Clinical Neuropsychology, 2001

Despite the emergence of a number of new classification systems, the diagnosis of cerebrovascular... more Despite the emergence of a number of new classification systems, the diagnosis of cerebrovascular dementia remains controversial. Also controversial is the significance of periventricular and deep white matter alterations (WMA) as seen on magnetic resonance imaging (MRI). To further clarify this issue, MRI scans were used to regroup patients clinically diagnosed with Alzheimer's disease (AD) or subcortical ischemic vascular dementia (IVD) into cohorts presenting with either little versus significant WMA on MRI. These two groups were then compared to demented patients diagnosed with idiopathic Parkinson's disease (PD) using a comprehensive neuropsychological protocol. Neuropsychological assessment failed to distinguish between patients with PD and significant WMA. By contrast, both of these patient groups exhibited disproportionate impairment on tests of executive systems functioning, whereas patients with little WMA showed greater impairment on tests of declarative memory and semantic knowledge. These findings constitute further evidence that the pattern of cognitive impairment associated with significant WMA is distinctly different when compared to AD. These results are discussed within the context of a growing body of literature suggesting that elements of the underlying neuropathologies in AD and IVD are linked. Implications for the diagnosis of dementia are also discussed.

Research paper thumbnail of National Academy of Neuropsychology. Abstracts from the 27th Annual Meeting, Scottsdale, Arizona, November 14-18, 2007

Archives of Clinical Neuropsychology, 2007

Research paper thumbnail of The role of the dynamic body schema in praxis: evidence from primary progressive apraxia

Brain and cognition, 2000

On an influential model of limb praxis, ideomotor apraxia results from damage to stored gesture r... more On an influential model of limb praxis, ideomotor apraxia results from damage to stored gesture representations or disconnection of representations from sensory input or motor output (Heilman & Gonzalez Rothi, 1993; Gonzalez Rothi et al., 1991). We report data from a patient with progressive ideomotor limb apraxia which cannot be readily accommodated by this model. The patient, BG, is profoundly impaired in gesturing to command, to sight of object, and to imitation, but gestures nearly normally with tool in hand and recognizes gestures relatively well. In addition, performance is profoundly impaired on imitation of meaningless gestures and on tasks requiring spatiomotor transformations of body-position information. We provide evidence that BG's apraxia is largely attributable to impairments external to the stored gesture system in procedures coding the dynamic positions of the body parts of self and others; that is, the body schema. We propose a model of a dynamic, interactive p...

Research paper thumbnail of ALS-dementia in a large population of patients with ALS and FTD

Research paper thumbnail of Longitudinal decline in autopsy-defined frontotemporal lobar degeneration

Neurology, 2008

The natural history of patients with pathologically proven frontotemporal lobar degeneration (FTL... more The natural history of patients with pathologically proven frontotemporal lobar degeneration (FTLD) is important from clinical and biologic perspectives, but is not well documented quantitatively. We examine longitudinal decline in cognitive functioning in an autopsy-proven cohort of patients with the clinical diagnosis of a FTLD spectrum disorder or FTLD pathology using a panel of neuropsychological measures. Patients are categorized according to findings at autopsy into tau-positive FTLD, tau-negative FTLD, and frontal variant-Alzheimer disease (fvAD) subgroups. Patients decline significantly over time on all neuropsychological measures. Moreover, several measures differentiate between histopathologically distinct subgroups throughout the course of the disease process. This includes a significant double dissociation involving relative difficulty on a visual constructional measure in tau-positive patients compared to relatively impaired visual confrontation naming in tau-negative patients. Longitudinal measures of FAS naming fluency and animal naming fluency also distinguish tau-positive patients and tau-negative patients with FTLD from patients with fvAD. Other measures show significant decline but do not distinguish between histopathologic groups longitudinally. Our findings suggest different longitudinal patterns of cognitive decline in pathologically defined subgroups of patients. Measures consistently distinguishing between patient subgroups can be used to bolster diagnostic accuracy throughout the course of these diseases, while measures demonstrating undifferentiated longitudinal decline may serve as useful endpoints in treatment trials.

Research paper thumbnail of The Contribution of White Matter Neuroimaging to Multimodal Diagnosis of Frontotemporal Lobar Degeneration (P03.096)

Research paper thumbnail of White matter imaging contributes to the multimodal diagnosis of frontotemporal lobar degeneration

Objective: To evaluate the distribution of white matter (WM) disease in frontotemporal lobar dege... more Objective: To evaluate the distribution of white matter (WM) disease in frontotemporal lobar degeneration (FTLD) and Alzheimer disease (AD) and to evaluate the relative usefulness of WM and gray matter (GM) for distinguishing these conditions in vivo.

Research paper thumbnail of Screening for Frontotemporal Dementias and Alzheimer’s Disease with the Philadelphia Brief Assessment of Cognition: A Preliminary Analysis

Dementia and Geriatric Cognitive Disorders, 2007

A neuropsychological screening instrument sensitive to neuropsychological deficits associated wit... more A neuropsychological screening instrument sensitive to neuropsychological deficits associated with Alzheimer's disease (AD) and patients with frontotemporal dementia (FTD) would be valuable for diagnostic evaluation. The Philadelphia Brief Assessment of Cognition (PBAC) assesses working memory/executive control, language, visuospatial operations, verbal/visual episodic memory, and behavior/social comportment and can be administered and scored in 15-20 min. Participants included 149 patients with AD and four groups of FTD patients - i.e., patients with a decline in social comportment, personality, and executive functioning (SOC/EXEC), semantic dementia (SemD), progressive nonfluent aphasia (PNFA), and corticobasal syndrome (CBS). The total PBAC score correlated with the Mini-Mental State Examination. Between-group analysis of PBAC subscales and the results of logistic regression analyses produced substantial between-group differences, emphasizing the sensitivity of the test to differentiate dementia subtypes. AD patients were impaired on tests of episodic memory, SOC/EXEC patients were impaired on a measure of social comportment/behavioral disturbance, PNFA patients obtained low scores on tests of working memory/executive control, SemD patients obtained lower scores on language-mediated measures, and CBS patients were impaired on visuospatial/visual memory tests. These data support the usefulness of the PBAC as a relatively brief screening test of overall dementia severity across a wide range of dementia patients.

Research paper thumbnail of Distinct Antemortem Profiles in Patients With Pathologically Defined Frontotemporal Dementia

Archives of Neurology, 2007

Clinical-pathologic studies are crucial to understanding brain-behavior relations and improving d... more Clinical-pathologic studies are crucial to understanding brain-behavior relations and improving diagnostic accuracy in neurodegenerative diseases. To establish clinical, neuropsychological, and imaging features of clinically diagnosed patients with frontotemporal dementia (FTD) that help discriminate between pathologically determined tau-positive FTD, tau-negative FTD, and frontal-variant Alzheimer disease. Retrospective clinical-pathologic survey. Academic medical center. Patients Sixty-one participants with the clinical diagnosis of a frontotemporal spectrum disorder who underwent a neuropsychological evaluation and had an autopsy-confirmed disease. Neuropsychological performance and high-resolution structural magnetic resonance imaging (MRI). Distinguishing features of patients with tau-positive FTD include visual perceptual-spatial difficulty and an extrapyramidal disorder significantly more often than other patients, significant cortical atrophy in the frontal and parietal regions as evidenced on MRI, and the burden of pathology is greatest in the frontal and parietal regions. Patients with tau-negative FTD are distinguished by their greater difficulties with social, language, and verbally mediated executive functions, significant cortical atrophy in the frontal and temporal regions as evidenced on MRI, and significant frontal and temporal pathology. Patients with Alzheimer disease at autopsy have significantly impaired delayed recall during episodic memory testing; atrophy that involves temporal areas, including the hippocampus, as evidenced on MRI; and widely distributed pathology including the medial temporal structures. A discriminant function analysis grouped patients on the basis of clinical and neuropsychological features with 87.5% accuracy. Clinical, neuropsychological, and imaging profiles can contribute to accurate antemortem diagnosis in FTD.

Research paper thumbnail of Syntactic comprehension deficits are associated with MRI white matter alterations in dementia

Journal of the International Neuropsychological Society, 2008

Comprehension difficulties associated with periventricular and deep white matter alterations (WMA... more Comprehension difficulties associated with periventricular and deep white matter alterations (WMA) in mild dementia were investigated using portions of the Boston Diagnostic Aphasia Examination (BDAE) Complex Ideation subtest and Syntax subtests. Mild dementia participants were grouped according to the extent of their WMA as observed on magnetic resonance imaging (mild WMA n 5 45 vs. moderate to severe WMA n 5 52). Correlation and regression analyses also were performed to examine the link between WMA and comprehension abilities, as well as the link between comprehension abilities and neuropsychological measures of executive functioning, language, episodic memory, and overall dementia severity. Results showed that the WMA groups differed on the BDAE-Syntax subtests, with the severe WMA group demonstrating more impairment. Correlation and regression analyses including the entire sample also demonstrated that the extent of WMA was significantly linked to Syntax test scores but not Complex Ideation scores. Regression analyses including neuropsychological measures showed that the BDAE-Complex Ideation score was marginally predicted by only overall dementia severity, whereas the BDAE-Syntax scores were significantly predicted by independent measures of working memory0executive functioning. In conclusion, greater subcortical WMA and executive deficits are associated with greater difficulties in syntactic comprehension in individuals with mild dementia. (JINS, 2008, 14, 542-551.)