Katherine L. Possin

Preliminary evidence of reduced cognitive inhibition in methamphetamine-dependent individuals

Chronic methamphetamine abuse is associated with disruption of frontostriatal function involving serotonin and dopamine circuitry. Clinically, methamphetamine-dependent (MD) individuals are highly distractible and have difficulty focussing. Here, we used a computerized single-trial version of the Stroop Test to examine selective attention and priming in MD. Subject groups comprised eight MD men (31.7+/-7.2 years of age), who had used methamphetamine for 15.75+/-8.4 years but were currently abstinent for 2-4 months, and 12 controls (35.7+9.7 years of age). Compared with the control group, the MD group exhibited significantly greater interference (P<0.05) despite intact priming. Error rates did not differ between the groups. This preliminary finding of reduced cognitive inhibition in MD individuals is consistent with the distractibility they show clinically. Furthermore, the dissociation between explicit attentional performance and priming effects suggests that some attentional functions are not as affected by long-term methamphetamine use as others.

Lewy body dementias

The broad importance of dementia is undisputed, with Alzheimers disease justifiably getting the most attention. However, dementia with Lewy bodies and Parkinsons disease dementia, now called Lewy body dementias, are the second most common type of degenerative dementia in patients older than 65 years. Despite this, Lewy body dementias receive little attention and patients are often misdiagnosed, leading to less than ideal management. Over the past 10 years, considerable effort has gone into improving diagnostic accuracy by refining diagnostic criteria and using imaging and other biomarkers. Dementia with Lewy bodies and Parkinsons disease dementia share the same pathophysiology, and effective treatments will depend not only on successful treatment of symptoms but also on targeting the pathological mechanisms of disease, ideally before symptoms and clinical signs develop. We summarise the most pertinent progress from the past 10 years, outlining some of the challenges for the future, which will require refinement of diagnosis and clarification of the pathogenesis, leading to disease-modifying treatments.

Regional alterations of brain microstructure in Parkinson's disease using diffusion tensor imaging

This study tested the hypothesis that diffusion tensor imaging can detect alteration in microscopic integrity of white matter and basal ganglia regions known to be involved in Parkinsons disease (PD) pathology. It was also hypothesized that there is an association between diffusion abnormality and PD severity and subtype. Diffusion tensor imaging at 4 Tesla was obtained in 12 PD and 20 control subjects, and measures of fractional anisotropy and mean diffusivity were evaluated using both region‐of‐interest and voxel‐based methods. Movement deficits and subtypes in PD subjects were assessed using the Motor Subscale (Part III) of the Unified Parkinsons Disease Rating Scale. Reduced fractional anisotropy (P < .05, corrected) was found in PD subjects in regions related to the precentral gyrus, substantia nigra, putamen, posterior striatum, frontal lobe, and the supplementary motor areas. Reduced fractional anisotropy in the substantia nigra correlated (P < .05, corrected) with the increased rating scale motor scores. Significant spatial correlations between fractional anisotropy alterations in the putamen and other PD‐affected regions were also found in the context of PD subtypes index analysis. Our data suggest that microstructural alterations detected with diffusion tensor might serve as a potential biomarker for PD.

Apolipoprotein E ε4 is associated with disease-specific effects on brain atrophy in Alzheimer's disease and frontotemporal dementia

Apolipoprotein ε4 (apoE4) has been strongly linked with Alzheimers disease (AD) and contributes to several other neurological disorders. We investigated the influence of ε4 allele carrier status on the pattern of gray matter atrophy and disease severity in 51 patients with probable AD and 31 patients with behavioral variant frontotemporal dementia (bvFTD), compared with 56 healthy controls. Voxel-based morphometry was performed by using statistical parametric mapping. The ε4 allele frequency was higher in the AD group (P < 0.001) than the controls but not in the bvFTD group. No differences in demographic or cognitive profiles were observed between ε4 allele carriers and noncarriers within any of the diagnostic groups. However, ε4 carrier status was associated with more severe brain atrophy in disease-specific regions compared with noncarriers in both AD and bvFTD. AD ε4 carriers showed greater atrophy in the bilateral parietal cortex and right hippocampus, and bvFTD ε4 carriers demonstrated greater atrophy in the bilateral medial, dorsolateral, and orbital frontal cortex, anterior insula, and cingulate cortex with right predominance. This regional ε4 effect is consistent with the hypothesis that apoE may affect the morphologic expression uniquely in different neurodegenerative diseases. The atrophy patterns in ε4 carriers may indicate that they are at greater risk for clinical progression.

Symptoms of frontotemporal dementia provide insights into orbitofrontal cortex function and social behavior.

Abstract:  Recent investigations into the brain substrates of behavioral changes in frontotemporal dementia (FTD) demonstrate that the orbitofrontal cortex (OFC) plays a crucial role in normal social and emotional behavior. The initial symptoms of FTD reflect the early involvement of OFC as well as the disruption of an associated network involving the insula, striatum, and medial frontal lobes. As predicted by patients with other types of OFC lesions, FTD patients show impairments involving stimulus‐reward reversal learning, response inhibition, and ability to judge the appropriateness of their behavior in the social context. While the natural reward system remains intact in these patients, that is, patients will seek out directly rewarding stimuli, such as food and sex, with progressive OFC dysfunction they lose the ability to process complex stimulus‐reward contingencies. These abnormalities are apparent in their social interactions, which break down early in the disease. Also, deficits in emotion recognition and empathy have been directly linked to OFC atrophy in these patients. In contrast, some patients with early FTD show intact cognitive skills, including memory and executive functioning. Here, we review the behavioral and neuropsychological changes that accompany OFC atrophy in FTD and argue that phylogenetically new neurons found in this region, called von Economo neurons, are selectively vulnerable in FTD.

Low N-acetyl-aspartate and high choline in the anterior cingulum of recently abstinent methamphetamine-dependent subjects: a preliminary proton MRS study

Studies based on animal models report that methamphetamine (MA) abuse diminishes dopamine (DA) and serotonin innervation in frontal brain regions. In this in vivo human study, we used proton magnetic resonance spectroscopy (MRS), which yields measures of N-acetyl-aspartate (NAA), a marker of living neurons, to examine frontal brain regions possibly affected by methamphetamine dependence (MD). We tested the hypothesis that MD subjects would exhibit abnormally low levels of NAA, referenced to creatine (Cr), in anterior cingulate gray matter. We further hypothesized that the primary visual cortex, which receives relatively less DA innervation than the frontal brain regions, would show normal NAA/Cr ratios in MD subjects. Subjects included nine MD men (mean+/-standard deviation (S.D.)=32.5+/-6.4 years) and nine age-matched control men (mean+/-S.D.=32.7+/-6.8 years). The MD subjects were MA-free for 4-13 weeks. Proton MRS metabolites were expressed as ratios of creatine; the absolute values of which did not distinguish controls and MD subjects. With regard to metabolite ratios, the MD men had significantly lower NAA/Cr in the cingulum (mean+/-standard error (S.E.): control=1.46+/-0.03; MD=1.30+/-0.03; Mann-Whitney P=0.01) but not in the visual cortex (mean+/-S.E.: control=1.64+/-0.06; MD=1.69+/-11; Mann-Whitney P=0.52) relative to controls. These results provide evidence for NAA/Cr deficit that is selective to the anterior cingulum, at least with respect to visual cortex, in MD subjects. The neuronal compromise that these changes reflect may contribute to the attentional deficits and dampened reward system in MD.

Visual Spatial Cognition in Neurodegenerative Disease

Visual spatial impairment is often an early symptom of neurodegenerative disease; however, this multi-faceted domain of cognition is not well-assessed by most typical dementia evaluations. Neurodegenerative diseases cause circumscribed atrophy in distinct neural networks, and accordingly, they impact visual spatial cognition in different and characteristic ways. Anatomically-focused visual spatial assessment can assist the clinician in making an early and accurate diagnosis. This article will review the literature on visual spatial cognition in neurodegenerative disease clinical syndromes, and where research is available, by neuropathologic diagnoses. Visual spatial cognition will be organized primarily according to the following schemes: bottom-up/top-down processing, dorsal/ventral stream processing, and egocentric/allocentric frames of reference.

The Early Neuropsychological and Behavioral Characteristics of Frontotemporal Dementia

Frontotemporal lobar degeneration (FTLD) represent a constellation of disorders that may be overlooked or misdiagnosed, despite being fairly common presenile neurodegenerative diseases. Although the cognitive disorder can be difficult to document, particularly early in the dementia course, neuropsychological evaluation can assist in the diagnosis. Neuropsychologists are in an excellent position to draw from related disciplines like personality theory and social psychology to better assess the types of changes that characterize the prodromal and early phases of the disease. This review summarizes the current state of the field in the diagnosis of FTLD and discusses the emerging role of neuropsychology in elucidating the brain organization of complex processes including empathy, behavioral control and inhibition, reward systems, appetitive behaviors, emotional regulation, and goal-orientation. As this review underscores, frontotemporal dementia remains a powerful model for studying brain–behavior relationships.

Quinacrine treatment trial for sporadic Creutzfeldt-Jakob disease

Objective: To determine whether oral quinacrine increases survival in sporadic Creutzfeldt-Jakob disease (sCJD). Methods: This NIH/National Institute on Aging–funded, double-blinded, placebo-controlled, stratified randomization treatment trial was conducted at the University of California, San Francisco from February 2005 through May 2009 (ClinicalTrials.gov, NCT00183092). Subjects were randomized (50:50) to quinacrine (300 mg daily) or placebo with inpatient evaluations at baseline, and planned for months 2, 6, and 12. Subjects returning for their month-2 visit were offered open-label quinacrine. The primary outcome was survival from randomization to month 2. Results: Of 425 patients referred, 69 subjects enrolled, 54 subjects were randomized to active drug or placebo, and 51 subjects with sCJD were included in survival analyses. Survival for the randomized portion of the trial (first 2 months) showed no significant difference between the 2 groups (log-rank statistic, p = 0.43; Cox proportional relative hazard = 1.43, quinacrine compared with placebo, 95% confidence interval = 0.58, 3.53). The quinacrine-treated group, however, declined less on 2 of 3 functional scales, the modified Rankin and Clinical Dementia Rating, than the placebo group during the first 2 months. Conclusion: This interventional study provides Class I evidence that oral quinacrine at 300 mg per day does not improve 2-month survival of patients with sCJD, compared with placebo. Importantly, this study shows that double-blinded, placebo-controlled, randomized treatment trials are possible in prion disease. Furthermore, the quantitative data collected on the course of sCJD will be useful for future trials. Classification of evidence: This study provides Class I evidence that quinacrine does not improve survival for people with sCJD when given orally at a dose of 300 mg per day for 2 months.

White matter atrophy in Alzheimer's disease variants

In comparison with late‐onset Alzheimers disease (LOAD, onset, >65 years), early‐age‐of‐onset Alzheimers disease (EOAD, onset, <65 years) more often presents with language, visuospatial, and/or executive impairment, often occurring earlier than a progressive memory deficit. The logopenic variant of primary progressive aphasia (lv‐PPA) and posterior cortical atrophy (PCA) have recently been described as possible atypical variants of EOAD. Lv‐PPA is characterized by isolated language deficit, whereas PCA is characterized by predominant visuospatial deficits. Severe hemispheric gray matter (GM) atrophy associated with EOAD, lv‐PPA, and PCA has been described, but regional patterns of white matter (WM) damage are still poorly understood.