Brain artery diameters and risk of dementia and stroke

INTRODUCTION

We tested the association of brain artery diameters with dementia and stroke risk in three distinct population-based studies using conventional T2-weighted brain magnetic resonance imaging (MRI) images.

METHODS

We included 8420 adults > 40 years old from three longitudinal population-based studies with brain MRI scans. We estimated and meta-analyzed the hazard ratios (HRs) of the brain and carotids and basilar diameters associated with dementia and stroke.

RESULT

Overall and carotid artery diameters > 95th percentile increased the risk for dementia by 1.74 (95% confidence interval [CI], 1.13-2.68) and 1.48 (95% CI, 1.12-1.96) fold, respectively. For stroke, meta-analyses yielded HRs of 1.59 (95% CI, 1.04-2.42) for overall arteries and 2.11 (95% CI, 1.45-3.08) for basilar artery diameters > 95th percentile.

DISCUSSION

Individuals with dilated brain arteries are at higher risk for dementia and stroke, across distinct populations. Our findings underline the potential value of T2-weighted brain MRI-based brain diameter assessment in estimating the risk of dementia and stroke.

The Assessment of Situational Judgement Questionnaire: A Novel Instrument to Detect Susceptibility to Financial Scamming

BACKGROUND

Existing measures of scam susceptibility lack ecological validity and situational variability. Evidence suggests that all adults may be susceptible to scams, though a comprehensive fraud victimization theory remains to be explored.

OBJECTIVE

To identify cognitive and sociodemographic variables that differentiate individuals with high scam susceptibility from those less susceptible. This article describes the development and feasibility of the Assessment of Situational Judgment questionnaire (ASJ), a brief tool designed to detect scam susceptibility.

METHODS

The 17-item ASJ was developed using a combination of existing scams reported by the Florida Division of Consumer Services and legitimate scenarios. Participants were presented with scam and legitimate scenarios and queried regarding their willingness to engage. Response options were offered with instructions on a 7-point Likert scale (extremely unlikely to extremely likely). Pilot data from a development sample provided the foundation for the final version of the ASJ.

RESULTS

The final version of the ASJ was administered to 183 online participants. The Scam factor (8 items) explained 50.6% of the variance. The Legit factor (9 items) reported on a 7-point Likert scale explaining 10.6% of the variance. A Scam to Legit ratio provides a proxy for overall scam susceptibility. Cut-off scores of 24 on the Scam factor, 47 on the Legit factor, and 0.62 on the ratio optimize measures of scam susceptibility.

CONCLUSIONS

The ASJ is a brief, ecologically valid measure of scam susceptibility. There is a need for a sensitive and specific tool to detect scam susceptibility in clinical, community, and financial settings.

Neuropsychological Function in Traumatic Brain Injury and the Influence of Chronic Pain

Cognitive dysfunction, pain, and psychological morbidity all present unique challenges to those living with traumatic brain injury (TBI). In this study we examined (a) the impact of pain across domains of attention, memory, and executive function, and (b) the relationships between pain and depression, anxiety, and post-traumatic stress disorder (PTSD) in persons with chronic TBI. Our sample included 86 participants with a TBI and chronic pain (n = 26), patients with TBI and no chronic pain (n = 23), and a pain-free control group without TBI (n = 37). Participants visited the laboratory and completed a comprehensive battery of neuropsychological tests as part of a structured interview. Multivariate analysis of covariance using education as a covariate, failed to detect a significant group difference for neuropsychological composite scores of attention, memory, and executive function (p = .165). A follow-up analysis using multiple one-way analysis of variance (ANOVA) was conducted for individual measures of executive function. Post-hoc testing indicated that those in both TBI groups preformed significantly worse on measures of semantic fluency when compared to controls (p < 0.001, ηρ2 = .16). Additionally, multiple ANOVAs indicated that those with TBI and pain scored significantly worse across all psychological assessments (p < .001). We also found significant associations between measures of pain and most psychological symptoms. A follow-up stepwise linear regression among those in the TBI pain group indicated that post concussive complaints, pain severity, and neuropathic pain symptoms differentially contributed to symptoms of depression, anxiety, and PTSD. These findings suggest deficits in verbal fluency among those living with chronic TBI, with results also reinforcing the multidimensional nature of pain and its psychological significance in this population.

Validity of the NIH toolbox cognitive battery in a healthy oldest-old 85+ sample

OBJECTIVE

To evaluate the construct validity of the NIH Toolbox Cognitive Battery (NIH TB-CB) in the healthy oldest-old (85+ years old).

METHOD

Our sample from the McKnight Brain Aging Registry consists of 179 individuals, 85 to 99 years of age, screened for memory, neurological, and psychiatric disorders. Using previous research methods on a sample of 85 + y/o adults, we conducted confirmatory factor analyses on models of NIH TB-CB and same domain standard neuropsychological measures. We hypothesized the five-factor model (Reading, Vocabulary, Memory, Working Memory, and Executive/Speed) would have the best fit, consistent with younger populations. We assessed confirmatory and discriminant validity. We also evaluated demographic and computer use predictors of NIH TB-CB composite scores.

RESULTS

Findings suggest the six-factor model (Vocabulary, Reading, Memory, Working Memory, Executive, and Speed) had a better fit than alternative models. NIH TB-CB tests had good convergent and discriminant validity, though tests in the executive functioning domain had high inter-correlations with other cognitive domains. Computer use was strongly associated with higher NIH TB-CB overall and fluid cognition composite scores.

CONCLUSION

The NIH TB-CB is a valid assessment for the oldest-old samples, with relatively weak validity in the domain of executive functioning. Computer use's impact on composite scores could be due to the executive demands of learning to use a tablet. Strong relationships of executive function with other cognitive domains could be due to cognitive dedifferentiation. Overall, the NIH TB-CB could be useful for testing cognition in the oldest-old and the impact of aging on cognition in older populations.

Early Amnestic Mild Cognitive Impairment Is Associated with Reduced Total Cerebral Blood Flow with no Brain Tissue Loss

BACKGROUND

Lower cerebral blood flow (CBF) and excessive brain atrophy are linked to Alzheimer's disease (AD). It is still undetermined whether reduced CBF precedes or follows brain tissue loss.

OBJECTIVE

We compared total CBF (tCBF), global cerebral perfusion (GCP), and volumes of AD-prone regions between cognitively normal (CN) and early amnestic mild cognitive impairment (aMCI) and tested their associations with cognitive performance to assess their predictive value for differentiation between CN and early aMCI.

METHODS

A total of 74 participants (mean age 69.9±6.2 years, 47 females) were classified into two groups: 50 CN and 24 aMCI, of whom 88% were early aMCI. tCBF, GCP, and global and regional brain volumetry were measured using phase-contrast and T1-weighted MRI. Neuropsychological tests tapping global cognition and four cognitive domains (memory, executive function, language, and visuospatial) were administered. Comparisons and associations were investigated using analyses of covariance (ANCOVA) and linear regression analyses, respectively.

RESULTS

Women had significantly higher GCP than men. Both, tCBF and GCP were significantly reduced in aMCI compared with CN, while differences in volumes of cerebral gray matter, white matter, and AD-prone regions were not significant. tCBF and GCP were significantly associated with global cognition (standardized beta (stβ) = 0.324 and stβ= 0.326) and with memory scores (stβ≥0.297 and stβ≥0.264) across all participants. Associations of tCBF and GCP with memory scores were also significant in CN (stβ= 0.327 and stβ= 0.284) and in aMCI (stβ= 0.627 and stβ= 0.485).

CONCLUSION

Reduced tCBF and GCP are sensitive biomarkers of early aMCI that likely precede brain tissue loss.

Structural Basal Ganglia Correlates of Subjective Fatigue in Middle-Aged and Older Adults

OBJECTIVE

Fatigue is among the most common complaints in community-dwelling older adults, yet its etiology is poorly understood. Based on models implicating frontostriatal pathways in fatigue pathogenesis, we hypothesized that smaller basal ganglia volume would be associated with higher levels of subjective fatigue and reduced set-shifting in middle-aged and older adults without dementia or other neurologic conditions.

METHODS

Forty-eight non-demented middle-aged and older adults (M_age = 68.1, SD = 9.4; M_MMSE = 27.3, SD = 1.9) completed the Fatigue Symptom Inventory, set-shifting measures, and structural MRI as part of a clinical evaluation for subjective cognitive complaints. Associations were examined cross-sectionally.

RESULTS

Linear regression analyses showed that smaller normalized basal ganglia volumes were associated with more severe fatigue (β = -.29, P = .041) and poorer Trail Making Test B-A (TMT B-A) performance (β = .30, P = .033) controlling for depression, sleep quality, vascular risk factors, and global cognitive status. Putamen emerged as a key structure linked with both fatigue (r = -.43, P = .003) and TMT B-A (β = .35, P = .021). The link between total basal ganglia volume and reduced TMT B-A was particularly strong in clinically fatigued patients.

CONCLUSION

This study is among the first to show that reduced basal ganglia volume is an important neurostructural correlate of subjective fatigue in physically able middle-aged and older adults without neurological conditions. Findings suggest that fatigue and rapid set-shifting deficits may share common neural underpinnings involving the basal ganglia, and provide a framework for studying the neuropathogenesis and treatment of subjective fatigue.

Measuring the Frailty Phenotype and its Association with Cognition in Mid-Life and Older Age

Background: Frailty is directly linked to physical robustness and cognitive decline in older age. The Fried Frailty phenotype (FP) is a construct composed of five core symptoms that has been studied predominately in older age. There is little research contrasting the psychometric properties of the FP in mid-life versus older age. Objective: We compared the psychometric properties of the FP in mid-life and older age and investigated relationships between the FP and cognition. Methods: Frailty and neuropsychological assessments were completed on 361 adults, between 45 and 92 years of age, without primary neurological disorders. Confirmatory factor analysis was used to examine FP, indicated by Grip Strength, Gait Speed, Physical Activity, Fatigue, and Weight Loss. Measurement invariance was tested in mid-life (45–64 years) versus older age (≥65 years). Associations were examined between FP and language, executive functions, memory, processing speed, and visuospatial domains as well as a Generalized Cognition factor. Age was tested as a moderator of these associations. Results: Weight Loss was a poor indicator of FP. Factor loadings were comparable across age groups; however, Fatigue was disproportionately higher among those in mid-life. FP was negatively associated with all cognitive domains and remained invariant across age groups. Conclusion: Results support the construct validity of the FP and document its stable associations with poorer cognition in middle and older life. Future research investigating central features of frailty earlier in life may offer avenues for developing targeted prevention measures and better characterization of individuals with elevated dementia risk.

Age-related focal thinning of the ganglion cell-inner plexiform layer in a healthy population

Background

Given the aging of the population worldwide, to learn the underlying age-related biological phenomena is important to improve the understanding of the ageing process. Neurodegeneration is an age-associated progressive deterioration of the neuron. Retinal neurodegeneration during aging, such as the reduction in thickness of the retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL) measured by optical coherence tomography (OCT), has been reported, but no studies have provided their specific alteration patterns with age. Therefore, this study is to provide visualization of the evolution of various tomographic intraretinal layer thicknesses during aging and to document age-related changes in focal thickness.

Methods

A total 194 healthy subjects were included in this cross-sectional study. The subjects were divided into four age groups: G1, <35 years; G2, 35-49 years; G3, 50-64 years; and G4 ≥65 years. One eye of each subject was imaged using a custom-built ultrahigh-resolution optical coherence tomography (UHR-OCT). Volumetric data centered on the fovea were segmented to obtain the thickness maps of six intraretinal layers, including the macular retinal nerve fiber layer (mRNFL) and GCIPL.

Results

There were alterations visualized in thickness maps in these intraretinal layers. The GCIPL showed a thickness reduction localized in the inner annulus in elder subjects (G4). Within the inner annulus, the most profound alteration in G4, an oval zone (length 0.76 mm and width 0.52 mm), appeared to be in the inferior sector about 0.61 mm below the fovea, named "A zone". The average thickness reduction of the A zone was 14.4 µm in the elderly group (G4). Age was significantly related to the GCIPL thickness of the inner annulus (ρ =-0.48; P<0.001) and of the A zone (ρ =-0.39, P<0.001).

Conclusions

This is the first study to apply UHR-OCT for visualizing the age-related alteration of intraretinal layers in a general population. The most profound change of the optic nerve fiber is an oval-like focal thinning in GCIPL, which occurred in the inferior sector within the inner annulus and was strongly related to increased age.

Is This Phishing? Older Age Is Associated With Greater Difficulty Discriminating Between Safe and Malicious Emails

OBJECTIVES

As our social worlds become increasingly digitally connected, so too has concern about older adults falling victim to "phishing" emails, which attempt to deceive a person into identity theft and fraud. In the present study, we investigated whether older age is associated with differences in perceived suspiciousness of phishing emails.

METHODS

Sixty-five cognitively normal middle-aged to older adults rated a series of genuine and phishing emails on a scale from definitely safe to definitely suspicious.

RESULTS

Although older age was not related to a shift in overall perception of email safety, older age was related to worse discrimination between genuine and phishing emails, according to perceived suspiciousness.

DISCUSSION

These findings suggest that cognitively normal older adults may be at particular risk for online fraud because of an age-associated reduction in their sensitivity to the credibility of emails.

Peripheral vestibular system: Age-related vestibular loss and associated deficits

Given the interdependence of multiple factors in age-related vestibular loss (e.g., balance, vision, cognition), it is important to examine the individual contributions of these factors with ARVL. While the relationship between the vestibular and visual systems has been well studied (Bronstein et al., 2015), little is known about the association of the peripheral vestibular system with neurodegenerative disorders (Cronin et al., 2017). Further, emerging research developments implicate the vestibular system as an opportunity for examining brain function beyond balance, and into other areas, such as cognition and psychological functioning. Additionally, the bidirectional impact of psychological functioning is understudied in ARVL. Recognition of ARVL as part of a multifaceted aging process will help guide the development of integrated interventions for patients who remain at risk for decline. In this review, we will discuss a wide variety of characteristics of the peripheral vestibular system and ARVL, how it relates to neurodegenerative diseases, and correlations between ARVL and balance, vision, cognitive, and psychological dysfunction. We also discuss clinical implications as well as future directions for research, with an emphasis on improving care for patients with ARVL.

Retinal Microvascular Alterations as the Biomarkers for Alzheimer Disease: Are We There Yet?

BACKGROUND

Alzheimer disease (AD) is a heterogeneous and multifactorial disorder with an insidious onset and slowly progressive disease course. To date, there are no effective treatments, but biomarkers for early diagnosis and monitoring of disease progression offer a promising first step in developing and testing potential interventions. Cerebral vascular imaging biomarkers to assess the contributions of vascular dysfunction to AD are strongly recommended to be integrated into the current amyloid-β (Aβ) [A], tau [T], and neurodegeneration [(N)]-the "AT(N)" biomarker system for clinical research. However, the methodology is expensive and often requires invasive procedures to document cerebral vascular dysfunction. The retina has been used as a surrogate to study cerebral vascular changes. There is growing interest in the identification of retinal microvascular changes as a safe, easily accessible, low cost, and time-efficient approach to enhancing our understanding of the vascular pathogenesis associated with AD.

EVIDENCE ACQUISITION

A systemic review of the literature was performed regarding retinal vascular changes in AD and its prodromal stages, focusing on functional and structural changes of large retinal vessels (vessels visible on fundus photographs) and microvasculature (precapillary arterioles, capillary, and postcapillary venules) that are invisible on fundus photographs.

RESULTS

Static and dynamic retinal microvascular alterations such as retinal arterial wall motion, blood flow rate, and microvascular network density were reported in AD, mild cognitive impairment, and even in the preclinical stages of the disease. The data are somewhat controversial and inconsistent among the articles reviewed and were obtained based on cross-sectional studies that used different patient cohorts, equipment, techniques, and analysis methods.

CONCLUSIONS

Retinal microvascular alterations exist across the AD spectrum. Further large scale, within-subject longitudinal studies using standardized imaging and analytical methods may advance our knowledge concerning vascular contributions to the pathogenesis of AD.

Systolic Blood Pressure and Cognition in the Elderly: The Northern Manhattan Study

BACKGROUND

Increasing evidence suggests that hypertension is a risk factor for cognitive impairment and dementia. The relationship between blood pressure and cognition in a racially and ethnically diverse population remains unclear.

OBJECTIVE

To study association of blood pressure with cognition cross-sectionally and longitudinally in the elderly.

METHODS

Participants are stroke-free individuals from the racially and ethnically diverse Northern Manhattan Study (NOMAS) (n = 1215). General linear models are constructed to examine blood pressure in relation to cognition cross-sectionally and longitudinally at a five-year follow-up.

RESULTS

We found a cross-sectional association of systolic blood pressure (SBP) with word fluency/semantic memory, executive function, and processing speed/visual motor integration (VMI) function. This association was independent of demographics, vascular risk factors, white matter hyperintensity volume (WMHV), and carotid intima-media thickness (cIMT). The cross-sectional association of SBP with processing speed/VMI and executive function was attenuated after adjusting anti-hypertension medications in the models. Baseline SBP was associated with the change of processing speed/VMI function after adjusting vascular risk factors, WMHV, and cIMT at a 5-year follow-up. This longitudinal association was not found after adjusting anti-hypertension medications in the models. Further analyses revealed that individuals with category SBP from < 120 mmHg to≥140 mmHg had a linear decline in processing speed/VMI function at a 5-year follow-up.

CONCLUSION

We show that SBP is negatively associated with cognition cross-sectionally and longitudinally in the elderly. Anti-hypertension treatment eliminates the negative association of SBP with processing speed/VMI function longitudinally. Our findings support the treatment of stage 1 systolic hypertension in the elderly.

Distinctive Convergence Eye Movements in an Acquired Neurosensory Dysfunction

In late 2016, diplomats in Havana, Cuba, began presenting with a unique symptom complex after perceiving a strange noise and/or feeling a pressure field in their domicile. This report is a retrospective, quantitative analysis of video-oculography data of pupillary light reflex performance and binocular disparity-driven eye and pupil movements during the acute time period after the reported exposure. The patterns of response in these 19 individuals are markedly different than those seen in a group of individuals with the usual acute mild traumatic brain injury (17 subjects) and from 62 control subjects (21-60 years old) with no injury. Non-linear least squares regression was used to estimate the model parameters from the eye movement and the pupil measurements (1). Linear discriminant analysis was then used to identify a classifier for an objective discrimination of the groups with >91% accuracy and no confusion between the acute neurosensory findings among the members of the Havana diplomatic community and the subjects with acute mild traumatic brain injury. This pattern difference in eye and pupil behavior may be a useful screen to help objectively distinguish blunt trauma from Havana-type effects in the future and to guide the affected individuals to appropriate care.

1144 Actigraphy-defined Sleep And Neurocognitive Decline In Middle-age Hispanic/Latino Adults

Introduction

Few studies have evaluated objective sleep measures and longitudinal neurocognitive decline, particularly in middle-age or Hispanic/Latino adults. We evaluated prospective associations between actigraphy-defined sleep and 7-year neurocognitive change among Hispanic/Latino adults. We hypothesized that sleep duration would be associated with neurocognitive decline.

Methods

We analyzed data from 1,036 adults 45-64 years of age from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), a multi-center prospective cohort study of diverse community-dwelling Hispanic/Latino adults. At Visit 1 (2008-2011), participants underwent neurocognitive assessments, 7-days of actigraphy, home sleep testing, and sleep questionnaires (including the Insomnia Severity Index). Seven years later, participants repeated neurocognitive assessments. The neurocognitive battery included the Six-Item Screener, Brief Spanish-English Verbal Learning Test, phonemic word fluency test, and Digit Symbol Subtest. Survey linear regression was used to evaluate prospective associations between actigraphy-defined or self-reported sleep variables and neurocognitive change. Final models adjusted for objectively-defined variables (age, body-mass index, Field Center, and time between neurocognitive assessments), and self-reported variables (sex, education, Hispanic/Latino background, alcohol consumption, physical activity, heart failure, cerebrovascular events, depression and anxiety symptoms, and antidepressant use).

Results

At Visit 1, the sample was 55% female and mean age was 54.9±2.2 years. The mean sleep duration was 402.6±27.6 minutes, mean sleep-onset latency was 11.3±9.7 minutes, mean number of days with naps of ≥ 15 minutes duration was 1.1±0.7, and mean sleep-time per nap was 51±14.1 minutes. Increased sleep-onset latency was associated with 7-year declines in global neurocognitive function (β=-0.0026, p&lt;0.01), verbal learning (β=-0.0028, p&lt;0.001) and verbal memory (β=-0.036, p&lt;0.05). Increased sleep-time per nap predicted better verbal memory (β=0.0038, p&lt;0.05). In contrast, sleep duration, sleep fragmentation, and self-reported sleep measures were not associated with neurocognitive change.

Conclusion

Among middle-age adults, sleep-onset latency and nap duration were associated with neurocognitive change. These findings may serve as targets for intervention of neurocognitive decline.

Support

This work is supported by the National Institute on Aging: R01AG048642, RF1AG054548, R01AG061022, R21AG056952, and R21HL140437 (AR).

Focal alteration of the intraretinal layers in neurodegenerative disorders

Focal intraretinal alterations have been studied to advance our understanding of the pathology of neurodegenerative diseases. The current literature involving focal alterations in the intraretinal layers was reviewed through PubMed using the search terms "focal alteration", "region of interest", "optical coherence tomography", "glaucoma", "multiple sclerosis", "Alzheimer's disease", "Parkinson disease", "neurodegenerative diseases" and other related items. It was found that focal alterations of intraretinal layers were different in various neurodegenerative diseases. The typical focal thinning might help differentiate various ocular and cerebral diseases, track disease progression, and evaluate the outcome of clinical trials. Advanced exploration of focal intraretinal alterations will help to further validate their clinical and research utility.

Sleep quality mediates the relationship between frailty and cognitive dysfunction in non-demented middle aged to older adults

ABSTRACTObjectives:Frailty is associated with cognitive decline in older adults. However, the mechanisms explaining this relationship are poorly understood. We hypothesized that sleep quality may mediate the relationship between frailty and cognition.

PARTICIPANTS

154 participants aged between 50-90 years (mean = 69.1 years, SD = 9.2 years) from the McKnight Brain Registry were included.

MEASUREMENTS

Participants underwent a full neuropsychological evaluation, frailty and subjective sleep quality assessments. Direct relationships between frailty and cognitive function were assessed using linear regression models. Statistical mediation of these relationships by sleep quality was assessed using nonparametric bootstrapping procedures.

RESULTS

Frailty severity predicted weaker executive function (B = -2.77, β = -0.30, 95% CI = -4.05 - -1.29) and processing speed (B = -1.57, β = -0.17, 95% CI = -3.10 - -0.16). Poor sleep quality predicted poorer executive function (B = -0.47, β = -0.21, 95% CI = -0.79 - -0.08), processing speed (B = -0.64, β = -0.28, 95% CI = -0.98 - -0.31), learning (B = -0.42, β = -0.19, 95% CI = -0.76 - -0.05) and delayed recall (B = -0.41, β = -0.16, 95% CI = -0.80 - -0.31). Poor sleep quality mediated the relationships between frailty severity and executive function (B = -0.66, β = -0.07, 95% CI = -1.48 - -0.39), learning (B = -0.85, β = -0.07, 95% CI = -1.85 - -0.12), delayed recall (B = -0.47, β = -0.08, 95% CI = -2.12 - -0.39) and processing speed (B = -0.90, β = -0.09, 95% CI = -1.85 - -0.20).

CONCLUSIONS

Relationships between frailty severity and several cognitive outcomes were significantly mediated by poor sleep quality. Interventions to improve sleep quality may be promising avenues to prevent cognitive decline in frail older adults.

Neuropsychological correlates of subjective fatigue in non-demented older adults and the moderating effect of physical activity

This study examined the association between self-reported fatigue and neuropsychological performance in 167 middle-aged and older (age range: 50-91 years) adults without dementia. Participants completed the Fatigue Symptom Inventory, a comprehensive neuropsychological evaluation, and frailty assessment. Higher levels of fatigue were significantly associated with poorer attention/information processing, executive functioning, and psychomotor speed, even after controlling for depression, sleep quality, physical weakness, and other covariates. Participants endorsing moderate-severe fatigue faced higher odds (OR = 6.6, 95% CI = 1.1, 39.1) of exhibiting clinical attention/information processing impairments than those without. Moderation analyses showed that fatigue was related to select cognitive deficits among those reporting mean or lower levels of activity, but not high levels. These findings highlight fatigue as an important clinical marker of select cognitive deficits in non-demented older adults that is distinct from the common confounding conditions examined in this study. High levels of physical activity may buffer this relationship.

Acute findings in an acquired neurosensory dysfunction

Background

In the Autumn of 2016, diplomatic personnel residing in Havana began to present with symptoms of dizziness, ear pain, and tinnitus that emerged after perception of high frequency noise and/or a pressure sensation. Understanding the acute symptoms of this disorder is important for better defining the disorder and developing optimal diagnostic, preventive, and treatment algorithms.

Objectives

To define the presenting symptoms in a cohort of patients in the acute time period after perceiving a noise/pressure exposure in Havana.

Design/Settings/Participants

Review of 25 symptomatic individuals who reported a localized sensation of noise/pressure and 10 asymptomatic individuals (roommates of those affected) who did not experience the sound/pressure.

Results

Immediately after the exposure, the majority of individuals reported intense ear pain in one or both ears and experienced tinnitus. All of the individuals noticed unsteadiness and features of cognitive impairment. On presentation to our center, dizziness (92%) and cognitive complaints (56%) were the most common symptoms. Formal testing revealed that 100% of individuals had an otolithic abnormality and evidence of cognitive dysfunction.

Conclusion and Relevance

This study focuses on the acute presentation of a phenomenon in which symptoms emerge after perception of a localized noise/pressure and in which the acute symptomology includes the universal nature of vestibular injuries and select cognitive deficits. The findings presented in this acute group of patients begin to provide a better picture of the initial injury pattern seen after this exposure and may allow for more accurate diagnosis of this disorder in future cases.

Level of Evidence

Retrospective review

Subacute Pain after Traumatic Brain Injury Is Associated with Lower Insular N-Acetylaspartate Concentrations

Persistent pain is experienced by more than 50% of persons who sustain a traumatic brain injury (TBI), and more than 30% experience significant pain as early as 6 weeks after injury. Although neuropathic pain is a common consequence after CNS injuries, little attention has been given to neuropathic pain symptoms after TBI. Magnetic resonance spectroscopy (MRS) studies in subjects with TBI show decreased brain concentrations of N-acetylaspartate (NAA), a marker of neuronal density and viability. Although decreased brain NAA has been associated with neuropathic pain associated with spinal cord injury (SCI) and diabetes, this relationship has not been examined after TBI. The primary purpose of this study was to test the hypothesis that lower NAA concentrations in brain areas involved in pain perception and modulation would be associated with greater severity of neuropathic pain symptoms. Participants with TBI underwent volumetric MRS, pain and psychosocial interviews. Cluster analysis of the Neuropathic Pain Symptom Inventory subscores resulted in two TBI subgroups: The Moderate Neuropathic Pain (n = 17; 37.8%), with significantly (p = 0.038) lower insular NAA than the Low or no Neuropathic Pain group (n = 28; 62.2%), or age- and sex-matched controls (n = 45; p < 0.001). A hierarchical linear regression analysis controlling for age, sex, and time post-TBI showed that pain severity was significantly (F = 11.0; p < 0.001) predicted by a combination of lower insular NAA/Creatine (p < 0.001), lower right insular gray matter fractional volume (p < 0.001), female sex (p = 0.005), and older age (p = 0.039). These findings suggest that neuronal dysfunction in brain areas involved in pain processing is associated with pain after TBI.

Physiological and pathophysiological implications of lipid sensing in the brain

Fatty acid (FA)-sensitive neurons are present in the brain, especially the hypothalamus, and play a key role in the neural control of energy homeostasis. Through neuronal output, FA may modulate feeding behaviour as well as insulin secretion and action. Subpopulations of neurons in the ventromedial and arcuate hypothalamic nuclei are selectively either inhibited or activated by FA. Molecular effectors of these FA effects probably include chloride or potassium ion channels. While intracellular metabolism and activation of the ATP-sensitive K⁺ channel appear to be necessary for some of the signalling effects of FA, at least half of the FA responses in ventromedial hypothalamic neurons are mediated by interaction with FAT/CD36, an FA transporter/receptor that does not require intracellular metabolism to activate downstream signalling. Thus, FA or their metabolites can modulate neuronal activity as a means of directly monitoring ongoing fuel availability by brain nutrient-sensing neurons involved in the regulation of energy and glucose homeostasis. Recently, the role of lipoprotein lipase in FA sensing has also been shown in animal models not only in hypothalamus, but also in hippocampus and striatum. Finally, FA overload might impair neural control of energy homeostasis through enhanced ceramide synthesis and may contribute to obesity and/or type 2 diabetes pathogenesis in predisposed subjects.

Centrally administered urocortin 2 decreases gorging on high-fat diet in both diet-induced obesity-prone and -resistant rats

Objective

Obesity is a costly, deadly public health problem for which new treatments are needed. Individual differences in meal pattern have been proposed to play a role in obesity risk. The present study tested the hypothesis that i) the microstructure of chronic high-fat diet intake differs between genetically selected Diet-Induced Obesity (DIO) and Diet Resistant (DR) rats, and ii) central administration of urocortin 2 (Ucn 2), a corticotropin-releasing factor type 2 (CRF₂) agonist, decreases high-fat diet intake not only in lean DR rats, but also in obese DIO rats.

Design

Male, selectively bred DIO and DR rats (n=10/genotype) were chronically fed a high-fat diet. Food and water intake as well as ingestion microstructure were then compared under baseline conditions and following third intracerebroventricular injection of Ucn 2 (0, 0.1, 0.3, 1, 3 µg).

Results

Irrespective of genotype, Ucn 2 reduced nocturnal food intake with a minimum effective dose of 0.3 µg, suppressing high-fat diet intake by ~40% at the 3 µg dose. Ucn 2 also made rats of both genotypes eat smaller and briefer meals, including at doses that did not reduce drinking. Obese DIO rats ate fewer but larger meals than DR rats, which they ate more quickly and consumed with 2/3^rd less water.

Conclusions

Unlike leptin and insulin, Ucn 2 retains its full central anorectic efficacy to reduce high-fat diet intake even in obese, genetically-prone DIO rats, which otherwise show a “gorging” meal pattern. These results open new opportunities of investigation towards treating some forms of diet-induced obesity.

Whole-brain proton MR spectroscopic imaging in Parkinson's disease

BACKGROUND AND PURPOSE

To examine the distributions of proton magnetic resonance spectroscopy (MRS) observed metabolites in Parkinson's disease (PD) throughout the whole brain.

METHODS

Twelve PD patients and 18 age-matched controls were studied using neuropsychological testing, MRI and volumetric MR spectroscopic imaging. Average values of signal normalized metabolite values for N-acetyl-aspartate, total-creatine, and total-choline (NAA, total-Cre, total-Cho, respectively) and their ratios were calculated for gray matter (GM) and white matter (WM) in each lobar brain region.

RESULTS

Analyses revealed altered metabolite values in PD subjects relative to controls within the GM of the temporal lobe (right: elevated Cre, P = .027; decreased NAA/Cre, P = .019; decreased Cho/Cre, P = .001 and left: decreased NAA/Cre; P = .001, decreased Cho/Cre, P = .007); the right occipital lobe (decreased NAA, P = .032 and NAA/Cre, P = .016); and the total cerebrum GM (decreased NAA/Cre, P = .029). No meaningful correlations were obtained between abnormal metabolite values and the neuropsychological measures.

CONCLUSIONS

PD is associated with widespread alterations of brain metabolite concentrations, with a primary finding of increased creatine. Higher creatine values in our PD sample may reflect greater neuronal energy expenditure early in the disease process that is compensatory. This is the first whole brain MRS study of PD that has examined metabolite changes across a large fraction of the brain volume, including the cortical mantle.

Chronic alterations in rat brain α-adrenoceptors following traumatic brain injury

Norepinephrine (NE) has been implicated in cerebral plasticity and recovery of function after brain injury. To examine the status of noradrenergic mechanisms in the brain following traumatic brain injury (TBI), male Sprague-Dawley rats underwent right sensorimotor cortex contusions and were observed for the next 30 days for recovery of motor function by measurement of the time taken to perform a modified beam walking task! At 30 days, their brains were assayed by receptor autoradiography for αr- and α2-adrenoceptor binding with 1 nM [3H]prazosin and 1 nM [3H]paraminoclonidine, respectively. One day after contusion, TBI rats took 60% longer to run the beam than sham-lesioned controls. Run times were directly proportional (r = 0.784; P = 0.012) to lesion volume determined at 30 days. The motor deficit persisted for 8 days, after which TBI and control rats had similar run times, largely due to increased run times in sham rats. At 30 days, TBI rats had a generalized, bilateral decrease in [3H]prazosin binding across all brain areas read (F[l,13] = 9.23; P = 0.009) with specific 12%-21% decreases in the cortex contralateral to the lesion and bilaterally in the dorsomedial hypothalamic and three thalamic nuclei. On the other hand, [3H]paraminoclonidine binding did not differ from sham lesion controls in any brain area of TBI rats. Thus, unilateral TBI is followed by widespread, bilateral changes in α1-adrenoceptor binding which would leave the animal vulnerable to any factors which reduced the access of NE to its postsynaptic adrenoceptors. This is compatible with the observation that α1-antagonists and α2-agonists can transiently reinstate the motor deficit after recovery has occurred.

Challenges and opportunities for characterizing cognitive aging across species

The gradual decline of cognitive ability with age, even in the absence of overt brain disease, is a growing problem. Although cognitive aging is a common and feared accompaniment of the aging process, its underlying mechanisms are not well understood and there are no highly effective means to prevent it. Additional research on cognitive aging is sorely needed, and methods that enable ready translation between human subjects and animal models stand to provide the most benefit. Here and in the six companion pieces in this special issue, we discuss a variety of challenges and opportunities for studying cognitive aging across species. We identify tests of associative memory, recognition memory, spatial and contextual memory, and working memory and executive function as cognitive domains that are age-sensitive and amenable to testing with parallel means in both humans and animal models. We summarize some of the important challenges in using animal models to test cognition. We describe unique opportunities to study cognitive aging in human subjects, such as those provided by recent large-scale initiatives to characterize cognition in large groups of subjects across the lifespan. Finally, we highlight some of the challenges of studying cognitive aging in human subjects.

Characterizing healthy samples for studies of human cognitive aging

Characterizing the cognitive declines associated with aging, and differentiating them from the effects of disease in older adults, are important goals for human neuroscience researchers. This is also an issue of public health urgency in countries with rapidly aging populations. Progress toward understanding cognitive aging is complicated by numerous factors. Researchers interested in cognitive changes in healthy older adults need to consider these complexities when they design and interpret studies. This paper addresses important factors in study design, patient demographics, co-morbid and incipient medical conditions, and assessment instruments that will allow researchers to optimize the characterization of healthy participants and produce meaningful and generalizable research outcomes from studies of cognitive aging. Application of knowledge from well-designed studies should be useful in clinical settings to facilitate the earliest possible recognition of disease and guide appropriate interventions to best meet the needs of the affected individual and public health priorities.

Plasticity of Brain α-Adrenoceptors During the Development of Diet-Induced Obesity in the Rat

Male Sprague-Dawley rats, which are prone to develop diet-induced obesity (DIO) on a high energy (HE) diet can be separated from rats which are diet-resistant (DR) by several prospective tests. Using such tests, chow-fed DRl-prone rats have higher binding of 3H paraminoclonidine (PAC) to brain alpha2-adrenoceptors than do DIO-prone rats. These differences disappear after 3 months on a HE diet. To study the predictive value of these tests and possible associated changes in presynaptic membrane composition, brain alpha3(1-) (1nM 3H prazosin) and (alpha2-adrenoceptor (1nM) 3-H PAC) binding and synaptosomal fatty acid composition were assessed in 3-month-old male rats separated by weight gain into DR and DIO groups after 1 month on a HE diet. DIO had comparable total caloric intake but gained 30% and 43% more weight and were hyperinsulinemic compared to DR and chow-fed rats, respectively. After 1 month on a HE diet, DR rats still had 15%-53% higher 3H PAC binding than DIO and/or chow-fed rats in 14 of 16 brain areas assessed. A phenotype effect was present primarily in the amygdala where DR rats had higher 3H PAC binding than DIO rats. A diet effect was seen in some hypothalamic nuclei where both DR and DIO rats had higher 3H PAC binding than chow-fed rats. Conversely, DIO rats had 14%-21% higher 3H prazosin binding than DR rats in 3 brain areas. Changes in brain synaptosomal membranes' fatty acids reflected both phenotype and diet effects. Thus, while diet composition affects presynaptic membrane composition and alpha2-adrenoceptor binding in both DR and DIO rats, the predominance of plasticity of these parameters is limited to the brains of DR rats. This suggests that such plasticity may be an important determinant of the ability to resist the development of diet-induced obesity on a HE diet.

Postshunt cognitive and functional improvement in idiopathic normal pressure hydrocephalus

BACKGROUND

Improvement in gait after shunt placement has been well documented in idiopathic normal pressure hydrocephalus (iNPH); however, controversy remains regarding the extent and pattern of postsurgical cognitive changes. Conflicting findings may be explained by variability in both test selection and follow-up intervals across studies. Furthermore, most investigations lack a control group, making it difficult to disentangle practice effects from a true treatment effect.

OBJECTIVE

To examine postshunt changes in a sample of well-characterized iNPH participants compared with a group of age- and education-matched healthy control subjects.

METHODS

We identified 12 participants with iNPH undergoing shunt placement and 9 control participants. All participants were evaluated with comprehensive neuropsychological testing and standardized gait assessment at baseline and were followed up for 6 months.

RESULTS

Repeated-measures analysis of variance revealed a significant group- (iNPH and control) by-time (baseline and 6 months) interaction for Trailmaking Test B: (P < .003) and Symbol Digit Modalities (P < .02), with greater improvement in iNPH participants relative to control subjects. In addition, the iNPH group showed greater improvement in gait (P < .001) and caregivers reported improved activities of daily living (P < .01) and reduced caregiver distress (P < .01).

CONCLUSION

This study demonstrates improvements in mental tracking speed and sustained attention 6 months after shunt placement in iNPH. The present investigation is the first study to use a controlled design to show that cognitive improvement in iNPH is independent of practice effects. Furthermore, these findings indicate functional and quality-of-life improvements for both the shunt responder and their caregiver.

Brain lipid sensing and nervous control of energy balance

Nutrient sensitive neurons (glucose and fatty acids (FA)) are present in many sites throughout the brain, including the hypothalamus and brainstem, and play a key role in the neural control of energy and glucose homeostasis. Through neuronal output, FA may modulate feeding behaviour as well as both insulin secretion and action. For example, central administration of oleate inhibits food intake and glucose production in rats. This suggests that daily variations in plasma FA concentrations might be detected by the central nervous system as a signal which contributes to the regulation of energy balance. At the cellular level, subpopulations of neurons in the ventromedial and arcuate hypothalamic nuclei are selectively either inhibited or activated by FA. Possible molecular effectors of these FA effects likely include chloride or potassium ion channels. While intracellular metabolism and activation of the ATP-sensitive K(+) channel appear to be necessary for some of the signaling effects of FA, at least half of the FA responses in ventromedial hypothalamic neurons are mediated by interaction with FAT/CD36, a FA transporter/receptor that does not require intracellular metabolism to activate downstream signaling. Thus, FA or their metabolites can modulate neuronal activity as a means of directly monitoring ongoing fuel availability by brain nutrient-sensing neurons involved in the regulation of energy and glucose homeostasis. Besides these physiological effects, FA overload or metabolic dysfunction might impair neural control of energy homeostasis and contribute to obesity and/or type 2 diabetes in predisposed subjects.

Objective quantification of neuromotor symptoms in Parkinson's disease: implementation of a portable, computerized measurement tool

Quantification of neuromotor symptoms with device-based measures provides a useful supplement to clinical evaluation. Research using the CATSYS has established its utility as a computerized measurement system to quantify neuromotor function. The primary objective of this study is to provide technical guidance on the use of the CATSYS in Parkinson's disease (PD). Forty-four patients with idiopathic PD and 28 healthy controls were prospectively recruited and evaluated with CATSYS, a portable, Windows-based system consisting of a data logger and four different sensors (tremor pen, touch recording plate, reaction time handle, and force plate for balance recording) for quantification of neuromotor functions. CATSYS discriminated between PD and controls on measurements of rest/postural tremor, pronation/supination, finger tapping, simple reaction time, and postural sway intensity and velocity. CATSYS measurements using the proposed test battery were associated with relevant clinician-rated Unified Parkinson's disease rating scale (UPDRS) items assessing tremor and bradykinesia. More work is warranted to establish CATSYS as a diagnostic/monitoring instrument in movement disorders using the proposed technical approaches.

PTSD Symptoms and Onset of Neurologic Disease in Elderly Trauma Survivors

In this case study, we present two Holocaust survivors who appeared to have adapted well post-trauma, but developed severe PTSD symptomatology following the onset of neurologic illness in later life. These individuals were referred fro neuropsychological evaluations by their treating neurologists to assess their levels of cognitive functioning. We present the neuropsychological findings, and discuss possible mechanisms for emergence of PTSD symptoms. These case studies demonstrate the need for systematic research to further investigate the potential relationship between aging, degenerative disease, and PTSD symptoms in elderly trauma survivors.

Subthreshold depression in Parkinson's disease

OBJECTIVE

It is estimated that 40% of patients with Parkinson's disease (PD) are clinically depressed, however, little is known about the frequency and associated features of subthreshold depression in PD. The current study sought to determine the prevalence of subthreshold depression (sD) and to further characterize the associated features in a sample of 111 nondemented patients with moderate to severe PD.

METHODS

Patients were classified into the following groups: diagnostic depression (DD), subthreshold depression (sD), or nondepressed (ND) by applying the Diagnostic and Statistical Manual, 4th edn criteria for depression and previously reported criteria for sD to items from the Beck Depression Inventory, 2nd edn. These groups were compared on clinical and demographic variables. The symptom profile of the sD group is also described.

RESULTS

Fifty participants (45.0%) were classified as ND, 32 (28.8%) as sD, and 29 (26.1%) as DD. Patients with sD were younger (approximately 5 yrs) than nondepressed patients, but did not differ in disease stage or any other demographic variables. Patients with sD tended to endorse mood symptoms that overlap with PD, including fatigue, sleep difficulties, appetite dysfunction, and concentration difficulties. These symptoms were also endorsed with high frequency by the other groups.

CONCLUSIONS

These findings suggest that sD is not uncommon in PD and may be more prevalent among younger patients. The finding that sD patients report mood symptoms that overlap with the PD symptomatology suggests that these two entities share common features and may be difficult to disentangle.

Differential effects of exercise on body weight gain and adiposity in obesity-prone and -resistant rats

OBJECTIVE

To determine the effect of exercise on weight gain and adiposity in obesity-prone and -resistant rats.

DESIGN

Body weight gain, fat pad weights, food intake, plasma leptin and insulin levels were assessed in outbred male Sprague-Dawley rats, which remained sedentary or were given unrestricted access to running wheels either before or after they developed diet-induced obesity (DIO) or diet-resistance (DR) on a high energy (HE; 31% fat) diet.

RESULTS

When fed a low fat (4.5%) chow diet, rats which would later develop DIO (n=6) after 3 weeks on HE diet ran the same amount as DR rats (n=6). Other rats were first made DIO (n=12) or DR (n=12) after 10 weeks on HE diet and then either kept sedentary or given running wheels for 4 weeks on HE diet. DIO and DR rats ran comparable amounts but only the DIO rats reduced their body weight gain, fat pad relative to body weights and plasma leptin levels significantly, compared to their sedentary controls. Exercise had no effect on food intake in either DIO or DR rats but reduced feed efficiency (weight gain/caloric intake) in both.

CONCLUSION

Although DIO and DR rats ran similar amounts, the greater reduction in body weight gain and adiposity of exercising DIO rats suggests that they are more sensitive to some metabolic or physiologic system that prevents them from increasing their intake sufficiently to compensate for their net reduction in energy stores.

Premorbid personality characteristics of patients with ALS

Experienced neurologists caring for patients with amyotrophic lateral sclerosis (ALS) have commented that these patients commonly exhibit similar personality features. Previous research studies on the premorbid personality characteristics of ALS patients have however not clearly substantiated this observation. In the present study, caregivers of newly diagnosed ALS patients provided ratings of patients' premorbid personality traits, and these ratings were compared with those of caregivers of patients newly diagnosed with other chronic, progressive diseases. Results indicated that ALS patients were rated as significantly lower than the other medical patients in the Openness trait on the NEO-Personality Inventory. This finding is discussed in relation to past research findings, prevailing clinical characterizations of ALS patients, and current research on cognitive and behavioral changes in ALS.

Sympathetic activity, age, sucrose preference, and diet-induced obesity

Only half the adult male Sprague-Dawley rats which are placed on a diet relatively high in calories, fat, and sucrose (HE diet) develop diet-induced obesity (DIO). The rest are diet-resistant (DR). Some chow-fed rats prone to develop DIO on an HE diet have greater initial food intake of this diet and all have greater glucose-induced plasma norepinephrine (NE) increases than DR-prone rats. Here we looked for a relationship of sucrose preference or 24-hour urinary catecholamine excretion as possible phenotypic markers of the DIO- and DR-prone states before HE diet exposure as a function of age. When begun on an HE diet at 3 months of age, DIO-prone rats gained 30% more weight over 3 months than DR-prone rats and had 35% heavier retroperitoneal fat pads. While still on chow, sucrose preferences were similar, but 24 hour urine NE levels were 29% higher in DIO- than in DR-prone rats. The slope of the curve of urine NE versus body weight gain after 3 months on HE diet was 4-fold greater in DIO- than in DR-prone rats. After 3 months on the HE diet, there was no statistical relationship between 24-hour urine NE and body weight or prior body weight gain in DIO or DR rats. Six-month-old DIO-prone rats had 126% and 128% more urine NE and gained 112% and 232% more weight after 3 months on HE diet than DR-prone and chow-fed rats, respectively. Only DIO-prone rats showed a correlation (r=0.879; p=0.05) between urine NE levels and subsequent weight gain on HE diet. Thus, 3- or 6-month-old DIO- and DR-prone rats can be identified by their 24-hour basal urine NE levels but not sucrose preference prior to HE diet exposure. While this may suggest higher basal sympathetic activity in DIO-prone rats, other explanations are possible.

Side and type of motor symptom influence cognition in Parkinson's disease

It is well known that many patients with Parkinson's disease experience neuropsychological decline. However, the nature and extent of mental status change varies widely, with some patients showing mild or no cognitive impairments and others exhibiting frank dementia. Research has shown that several clinical disease parameters may differentially correlate with patterns of neuropsychological dysfunction. The present study examined side and type of motor symptom at disease onset and their relationship to cognition in idiopathic Parkinson's disease (PD). We identified 58 patients who initially presented with one of the following symptom profiles: right-side tremor onset (RSO-T; n = 15), right-side bradykinesia/rigidity onset (n = 12), left-side tremor onset (n = 19), and left-side bradykinesia/rigidity onset (n = 12). There were no differences between groups in disease duration, overall mental status, education, or depression severity. We administered a battery of neuropsychological measures to the four PD subgroups and a group of matched control subjects (n = 40). MANCOVAs controlling for age revealed patients with RSO-T performed significantly better than the other three PD subgroups across the entire neuropsychological battery. Further, the RSO-T subgroup performed comparably to controls. In contrast, the other three PD subgroups showed widespread cognitive deficits. These findings suggest an intricate relationship between motor symptom and side of disease onset and it is the combination of these factors that may influence the disease course and extent of cognitive deterioration. Furthermore, patients who develop tremor on the right side of their body represent a distinct subgroup of PD patients who exhibit relative sparing of cognitive function.

Neurobehavioral effects of harmful algal bloom (HAB) toxins: a critical review

Human exposure to naturally occurring marine toxins has been associated with a range of neurobehavioral abnormalities. The toxins are produced by harmful algal blooms (HABs) and are typically contracted through seafood consumption. The primary target of many of the HAB toxins is the neurologic system, and the neurobehavioral symptoms associated with the HAB illnesses have influenced public health policy. The HAB-related illnesses most frequently linked to neuropsychological disturbance are Amnesic Shellfish Poisoning, Ciguatera Fish Poisoning, and Possible Estuarine Associated Syndrome, which is associated with exposure to the Pfiesteria piscicida organism. Although the neurophysiologic mechanisms underlying many of the HAB illnesses have been well delineated, the literature examining the neuropsychological impairments is unclear and needs to be defined. This review is intended to introduce an emerging area of study linking HAB illnesses with neuropsychological changes.

Early cognitive changes and nondementing behavioral abnormalities in Parkinson's disease

Early cognitive changes in patients with PD are often subtle and influenced by factors that interact with the disease process, including age of disease onset, medication, and the specific constellation of motor symptoms. These factors notwithstanding, ample evidence exists that specific cognitive changes occur early in the course of PD. This evidence does not imply that cognitive deficits are pervasive during the early stages. To the contrary, they are usually subtle and often difficult to detect without formal neuropsychological testing. Executive-function deficits are the most frequently reported cognitive problems and, given that executive skills are an integral part of many tasks, it follows that subtle difficulties may be seen on a wide range of cognitive measures, particularly in working memory and visuospatial dysfunction, two areas that rely heavily on executive skills. Whereas apraxia and language processing deficits occur infrequently, subtle changes in olfaction and contrast sensitivity have also been repeatedly observed. Finally, depressive symptoms are also common in the early stages of the disease. The significance of the early behavioral changes and their prognostic implications are largely unknown. Prospective studies are needed to understand the longitudinal course of early cognitive changes to determine whether they remain as circumscribed impairments or represent a precursor to a more widespread dementia.

Beta oxidation in the brain is required for the effects of non-esterified fatty acids on glucose-induced insulin secretion in rats

AIMS/HYPOTHESIS

NEFA play a key role in the setting of insulin resistance and hyperinsulinaemia, which are both features of the prediabetic state. In addition to the direct effects on pancreas and peripheral tissues, NEFA have been reported to act via changes in autonomic nervous system activity. The present study was aimed at studying the effects of a local increase in NEFA in the brain on glucose-induced insulin secretion (GIIS) and on insulin action. We hypothesised that cerebral NEFA beta oxidation is a prerequisite for these central effects.

METHODS

Male Wistar rats were infused with Intralipid/heparin for 24 h through the carotid artery towards the brain (IL rats), after which we performed the GIIS test, a euglycaemic-hyperinsulinaemic clamp and c-fos immunochemistry. In another series of experiments, Intralipid/heparin infusion was coupled with lateral ventricular infusion of etomoxir, a CPT1 inhibitor, which was initiated 5 days previously.

RESULTS

During the infusion period, there were no changes in plasma NEFA, insulin or glucose concentrations. IL rats displayed an increased GIIS compared with control rats (C rats) infused with saline/heparin, and their liver insulin sensitivity was decreased. Furthermore, lipid infusion induced a significant decrease in c-fos-like immunoreactive neurons in medial hypothalamic nuclei, and an increase in lateral hypothalamus. Neuronal activation profile was almost normalised in IL rats infused with etomoxir, and GIIS was strongly decreased, possibly because of the concomitant normalisation of hepatic glucose output.

CONCLUSIONS/INTERPRETATION

These results strongly suggest that beta oxidation is required for the central effects of NEFA on GIIS.

The regulation of glucose-excited neurons in the hypothalamic arcuate nucleus by glucose and feeding-relevant peptides

Glucosensing neurons in the hypothalamic arcuate nucleus (ARC) were studied using electrophysiological and immunocytochemical techniques in neonatal male Sprague-Dawley rats. We identified glucose-excited and -inhibited neurons, which increase and decrease, respectively, their action potential frequency (APF) as extracellular glucose levels increase throughout the physiological range. Glucose-inhibited neurons were found predominantly in the medial ARC, whereas glucose-excited neurons were found in the lateral ARC. ARC glucose-excited neurons in brain slices dose-dependently increased their APF and decreased their ATP-sensitive K+ channel (KATP channel) currents as extracellular glucose levels increased from 0.1 to 10 mmol/l. However, glucose sensitivity was greatest as extracellular glucose decreased to <2.5 mmol/l. The glucokinase inhibitor alloxan increases KATP single-channel currents in glucose-excited neurons in a manner similar to low glucose. Leptin did not alter the activity of ARC glucose-excited neurons. Although insulin did not affect ARC glucose-excited neurons in the presence of 2.5 mmol/l (steady-state) glucose, they were stimulated by insulin in the presence of 0.1 mmol/l glucose. Neuropeptide Y (NPY) inhibited and alpha-melanocyte-stimulating hormone stimulated ARC glucose-excited neurons. ARC glucose-excited neurons did not show pro-opiomelanocortin immunoreactivity. These data suggest that ARC glucose-excited neurons may serve an integrative role in the regulation of energy balance.

Convergence of pre- and postsynaptic influences on glucosensing neurons in the ventromedial hypothalamic nucleus

Glucosensing neurons in the ventromedial hypothalamic nucleus (VMN) were studied using visually guided slice-patch recording techniques in brain slices from 14- to 21-day-old male Sprague-Dawley rats. Whole-cell current-clamp recordings were made as extracellular glucose levels were increased (from 2.5 to 5 or 10 mmol/l) or decreased (from 2.5 to 0.1 mmol/l). Using these physiological conditions to define glucosensing neurons, two subtypes of VMN glucosensing neurons were directly responsive to alterations in extracellular glucose levels. Another three subtypes were not directly glucose-sensing themselves, but rather were presynaptically modulated by changes in extracellular glucose. Of the VMN neurons, 14% were directly inhibited by decreases in extracellular glucose (glucose-excited [GE]), and 3% were directly excited by decreases in extracellular glucose (glucose-inhibited [GI]). An additional 14% were presynaptically excited by decreased glucose (PED neurons). The other two subtypes of glucosensing neurons were either presynaptically inhibited (PIR; 11%) or excited (PER; 8%) when extracellular glucose was raised to > 2.5 mmol/l. GE neurons sensed decreased glucose via an ATP-sensitive K(+) (K(ATP)) channel. The inhibitory effect of increased glucose on PIR neurons appears to be mediated by a presynaptic gamma-aminobutyric acid-ergic glucosensing neuron that probably originates outside the VMN. Finally, all types of glucosensing neurons were both fewer in number and showed abnormal responses to glucose in a rodent model of diet-induced obesity and type 2 diabetes.

Glucosensing neurons do more than just sense glucose

The brain regulates energy homeostasis by balancing energy intake, expenditure and storage. To accomplish this, it has evolved specialized neurons that receive and integrate afferent neural and metabolic signals conveying information about the energy status of the body. These sensor-integrator-effector neurons are located in brain areas involved in homeostatic functions such as the hypothalamus, locus coeruleus, basal ganglia, limbic system and nucleus tractus solitarius. The ability to sense and regulate glucose metabolism is critical because of glucose's primacy as a metabolic substrate for neural function. Most neurons use glucose as an energy substrate, but glucosensing neurons also use glucose as a signaling molecule to regulate neuronal firing and transmitter release. There are two types of glucosensing neurons that either increase (glucose responsive, GR) or decrease (glucose sensitive, GS) their firing rate as brain glucose levels rise. Little is known about the mechanism by which GS neurons sense glucose. However, GR neurons appear to function much like the pancreatic beta-cell where glycolysis regulates the activity of an ATP-sensitive K(+) (K(ATP)) channel. The K(ATP) channel is composed of four pore-forming units (Kir6.2) and four sulfonylurea binding sites (SUR). Glucokinase (GK) appears to modulate K(ATP) channel activity via its gatekeeper role in the glycolytic production of ATP. Thus, GK may serve as a marker for GR neurons. Neuropeptide Y (NPY) and pro-opiomelanocortin (POMC) neurons in the hypothalamic arcuate nucleus are critical components of the energy homeostasis pathways in the brain. Both express Kir6.2 and GK, as well as leptin receptors. They also receive visceral neural and intrinsic neuropeptide and transmitter inputs. Such metabolism-related signals can summate upon K(ATP) channel activity which then alters membrane potential, neuronal firing rate and peptide/transmitter release. The outputs of these neurons are integral components of effector systems which regulate energy homeostasis. Thus, arcuate NPY and POMC neurons are probably prototypes of this important class of sensor-integrator-effector neurons.

Application of the multilingual aphasia examination-spanish in the evaluation of Hispanic patients post closed-head trauma

Despite the rapid increase of Hispanics in the U.S., there continues to be a lack of adequate psychological assessment tools to examine Spanish-speaking patients with cognitive or neuropsychological disturbances. We investigated the clinical utility of the Multilingual Aphasia Examination-Spanish (MAE-S) in the evaluation of language functions of Hispanic subjects post-traumatic brain injury (TBI). The performance of 40 TBI patients was compared to that of 40 age-, gender-, and education-matched normal controls. Subject groups differed on the Visual Naming (VN), Controlled Oral Word Association (COWA), and Token Test subtests. The VN and COWA subtests were the best discriminators of group membership. Distribution of scores for the patient group on the Rating of Articulation scale additionally indicate subtle articulatory difficulties post-TBI. For all subtests, trauma severity per Glasgow Coma Scale was the best predictor of language performance, over and above the contribution of other clinical and demographic variables. These results are consistent with prior reports of dysphasia post-TBI and suggest that the MAE-S is a sensitive and accurate measure to assess language disturbances in Hispanic populations.