Healthy Adult Controls Research Articles

Anatomy and white matter connections of the orbitofrontal gyrus.

OBJECTIVE The orbitofrontal cortex (OFC) is understood to have a role in outcome evaluation and risk assessment and is commonly involved with infiltrative tumors. A detailed understanding of the exact location and nature of associated white matter tracts could significantly improve postoperative morbidity related to declining capacity. Through diffusion tensor imaging-based fiber tracking validated by gross anatomical dissection as ground truth, the authors have characterized these connections based on relationships to other well-known structures. METHODS Diffusion imaging from the Human Connectome Project for 10 healthy adult controls was used for tractography analysis. The OFC was evaluated as a whole based on connectivity with other regions. All OFC tracts were mapped in both hemispheres, and a lateralization index was calculated with resultant tract volumes. Ten postmortem dissections were then performed using a modified Klingler technique to demonstrate the location of major tracts. RESULTS The authors identified 3 major connections of the OFC: a bundle to the thalamus and anterior cingulate gyrus, passing inferior to the caudate and medial to the vertical fibers of the thalamic projections; a bundle to the brainstem, traveling lateral to the caudate and medial to the internal capsule; and radiations to the parietal and occipital lobes traveling with the inferior fronto-occipital fasciculus. CONCLUSIONS The OFC is an important center for processing visual, spatial, and emotional information. Subtle differences in executive functioning following surgery for frontal lobe tumors may be better understood in the context of the fiber-bundle anatomy highlighted by this study.

Comparing CAT12 and VBM8 for Detecting Brain Morphological Abnormalities in Temporal Lobe Epilepsy.

The identification of the brain morphological alterations that play important roles in neurodegenerative/neurological diseases will contribute to our understanding of the causes of these diseases. Various automated software programs are designed to provide an automatic framework to detect brain morphological changes in structural magnetic resonance imaging (MRI) data. A voxel-based morphometry (VBM) analysis can also be used for the detection of brain volumetric abnormalities. Here, we compared gray matter (GM) and white matter (WM) abnormality results obtained by a VBM analysis using the Computational Anatomy Toolbox (CAT12) via the current version of Statistical Parametric Mapping software (SPM12) with the results obtained by a VBM analysis using the VBM8 toolbox implemented in the older software SPM8, in adult temporal lobe epilepsy (TLE) patients with (n = 51) and without (n = 57) hippocampus sclerosis (HS), compared to healthy adult controls (n = 28). The VBM analysis using CAT12 showed that compared to the healthy controls, significant GM and WM reductions were located in ipsilateral mesial temporal lobes in the TLE-HS patients, and slight GM amygdala swelling was present in the right TLE-no patients (n = 27). In contrast, the VBM analysis via the VBM8 toolbox showed significant GM and WM reductions only in the left TLE-HS patients (n = 25) compared to the healthy controls. Our findings thus demonstrate that compared to VBM8, a VBM analysis using CAT12 provides a more accurate volumetric analysis of the brain regions in TLE. Our results further indicate that a VBM analysis using CAT12 is more robust and accurate against volumetric alterations than the VBM8 toolbox.

A morphometric assessment of type I Chiari malformation above the McRae line: A retrospective case-control study in 302 adult female subjects

PurposeType I Chiari malformation (CMI) is a radiologically-defined structural dysmorphism of the hindbrain and posterior cranial fossa (PCF). Traditional radiographic identification of CMI relies on the measurement of the cerebellar tonsils in relation to the foramen magnum with or without associated abnormalities of the neuraxis. The primary goal of this retrospective study was to comprehensively assess morphometric parameters above the McRea line in a group of female CMI patients and normal controls. Material and methodsTwenty-nine morphological measurements were taken on 302 mid-sagittal MR images of adult female CMI patients (n=162) and healthy controls (n=140). All MR images were voluntarily provided by CMI subjects through an online database and control participant images were obtained through the Human Connectome Project and a local hospital system. ResultsAnalyses were performed on the full dataset of adult female MR images and a restricted dataset of 229 participants that were equated for age, race, and body mass index. Eighteen group differences were identified in the PCF area that we grouped into three clusters; PCF structures heights, clivus angulation, and odontoid process irregularity. Fourteen group differences persisted after equating our CMI and control groups on demographic characteristics. ConclusionPCF structures reliably differ in adult female CMI patients relative to healthy controls. These differences reflect structural abnormalities in the osseous and soft tissue structures of the clivus, odontoid process, and cerebellum. Clinical and pathophysiological implications are discussed.

Neuromuscular Electrical Stimulation and Anabolic Signaling in Patients with Stroke

Stroke results in limited ability to produce voluntary muscle contraction and movement on one side of the body, leading to further muscle wasting and weakness. Neuromuscular electrical stimulation is often used to facilitate involuntary muscle contraction; however, the effect of neuromuscular electrical stimulation on muscle growth and strengthening processes in hemiparetic muscle is not clear. This study examined the skeletal muscle anabolic response of an acute bout of neuromuscular electrical stimulation in individuals with chronic stroke and healthy older adults. Eleven individuals (59.8 ± 2.7 years old) were divided into a chronic stroke group (n = 5) and a healthy older adult control group (n = 6). Muscle biopsies were obtained before and after stimulation from the vastus lateralis of the hemiparetic leg for the stroke group and the right leg for the control group. The neuromuscular electrical stimulation protocol consisted of a 60-minute, intermittent stimulation train at 60 Hz. Phosphorylation of mammalian target of rapamycin and ribosomal protein S6 kinase beta-1 were analyzed by Western blot. An acute bout of neuromuscular electrical stimulation increased phosphorylation of mammalian target of rapamycin (stroke: 56.0%; control: 51.4%; P = .002) and ribosomal protein S6 kinase beta-1 (stroke: 131.2%; control: 156.3%; P = .002) from resting levels to post-neuromuscular electrical stimulation treatment, respectively. Phosphorylated protein content was similar between stroke and control groups at both time points. Findings suggest that paretic muscles of patients with chronic stroke may maintain ability to stimulate protein synthesis machinery in response to neuromuscular electrical stimulation.

Proteomic analysis of sputum reveals novel biomarkers for various presentations of asthma

BackgroundIt is now recognized that asthma can present in different forms. Typically, asthma present with symptoms of wheeze, breathlessness and cough. Atypical forms of asthma such as cough variant asthma (CVA) or chest tightness variant asthma (CTVA) do not wheeze. We hypothesize that these different forms of asthma may have distinctive cellular and molecular features.Methods30 patients with typical or classical asthma (CA), 27 patients with CVA, 30 patients with CTVA, and 30 healthy control adults were enrolled in this prospective study. We measured serum IgE, lung function, sputum eosinophils, nitric oxide in exhaled breath (FeNO). We performed proteomic analysis of induced-sputum supernatants by mass spectrometry.ResultsThere were no significant differences in atopy and FEV1 among patients with CA, CVA, and CTVA. Serum IgE, sputum eosinophil percentages, FeNO, anxiety and depression scores were significantly increased in the three presentations of asthmatic patients as compared with healthy controls but there was no difference between the asthmatic groups. Comprehensive mass spectrometric analysis revealed more than a thousand proteins in the sputum from patients with CA, CVA, and CTVA, among which 23 secreted proteins were higher in patients than that in controls.ConclusionsPatients with CA, CVA, or CTVA share common clinical characteristics of eosinophilic airway inflammation. And more importantly, their sputum samples were composed with common factors with minor distinctions. These findings support the concept that these three different presentations of asthma have similar pathogenetic mechanism in terms of an enhanced Th2 associated with eosinophilia. In addition, this study identified a pool of novel biomarkers for diagnosis of asthma and to label its subtypes.Trial registrationhttp://www.chictr.org.cn (ChiCTR-OOC-15006221)

The Effects of Tacrolimus on T-Cell Proliferation Are Short-Lived: A Pilot Analysis of Immune Function Testing.

BackgroundOptimal immunosuppression after organ transplant should balance the risks of rejection, infection, and malignancy while minimizing barriers to adherence including frequent or time-sensitive dosing. There is currently no reliable immune function assay to directly measure the degree of immunosuppression after transplantation.MethodsWe developed an immune function assay to mea//sure T-cell proliferation after exposure to immunosuppression in vivo. We tested the assay in mice, and then piloted the approach using single time point samples, 11 pediatric kidney transplant recipients prescribed tacrolimus, mycophenolate, and prednisone 6 months to 5 years posttransplant, with no history of rejection, opportunistic infection, or cancer. Twelve healthy adults were controls.ResultsWe demonstrated that our assay can quantify suppression of murine T-cell proliferation after tacrolimus treatment in vivo. In humans, we found a mean 25% reduction in CD4 and CD8 T-cell proliferation in pediatric renal transplant recipients on triple immunosuppression compared with adult healthy controls, but the pilot results were not statistically significant nor correlated with serum tacrolimus levels. We observed that cell processing and washing reduced the effects of tacrolimus on T-cell proliferation, as did discontinuation of tacrolimus treatment shortly before sampling.ConclusionsT-cell proliferation is currently not suitable to measure immunosuppression because sample processing diminishes observable effects. Future immune function testing should focus on fresh samples with minimal washing steps. Our results also emphasize the importance of adherence to immunosuppressive treatment, because T-cell proliferation recovered substantially after even brief discontinuation of tacrolimus.

A wearable vibrotactile biofeedback system improves balance control of healthy young adults following perturbations from quiet stance

Maintaining postural equilibrium requires fast reactions and constant adjustments of the center of mass (CoM) position to prevent falls, especially when there is a sudden perturbation of the support surface. During this study, a newly developed wearable feedback system provided immediate vibrotactile clues to users based on plantar force measurement, in an attempt to reduce reaction time and CoM displacement in response to a perturbation of the floor. Ten healthy young adults participated in this study. They stood on a support surface, which suddenly moved in one of four horizontal directions (forward, backward, left and right), with the biofeedback system turned on or off. The testing sequence of the four perturbation directions and the two system conditions (turned on or off) was randomized. The resulting reaction time and CoM displacement were analysed. Results showed that the vibrotactile feedback system significantly improved balance control during translational perturbations. The positive results of this preliminary study highlight the potential of a plantar force measurement based biofeedback system in improving balance under perturbations of the support surface. Future system optimizations could facilitate its application in fall prevention in real life conditions, such as standing in buses or trains that suddenly decelerate or accelerate.

Manual tracking impairs postural stability in older adults

Introduction Older adults show increased postural sway and a greater risk of falls when completing activities with high cognitive demands. While dual-task approaches have clarified an association between cognitive processes and postural control, it is unclear how manual ability, which is also required for the successful completion of cognitively demanding tasks (such as putting a key into a lock), affects this relationship. Method Kinematic technology was used to explore the relationship between postural sway and manual control in healthy younger and older adults. Participants ( n = 82) remained standing to complete a visual-motor tracking task on a tablet computer. Root mean square tracking error measured manual performance, and a balance board measured deviations in centre of pressure as a marker of postural sway. Results Older adults displayed poorer manual accuracy and increased postural sway across all testing conditions. Conclusions Cognitive capacity can interact with multiple task demands, and in turn affect postural sway in older adults. Improving our understanding of factors that influence postural control will assist falls-prevention efforts and inform clinical practice.

Do you see what I see? Mobile eye-tracker contextual analysis and inter-rater reliability

Mobile eye-trackers are currently used during real-world tasks (e.g. gait) to monitor visual and cognitive processes, particularly in ageing and Parkinson’s disease (PD). However, contextual analysis involving fixation locations during such tasks is rarely performed due to its complexity. This study adapted a validated algorithm and developed a classification method to semi-automate contextual analysis of mobile eye-tracking data. We further assessed inter-rater reliability of the proposed classification method. A mobile eye-tracker recorded eye-movements during walking in five healthy older adult controls (HC) and five people with PD. Fixations were identified using a previously validated algorithm, which was adapted to provide still images of fixation locations (n = 116). The fixation location was manually identified by two raters (DH, JN), who classified the locations. Cohen’s kappa correlation coefficients determined the inter-rater reliability. The algorithm successfully provided still images for each fixation, allowing manual contextual analysis to be performed. The inter-rater reliability for classifying the fixation location was high for both PD (kappa = 0.80, 95% agreement) and HC groups (kappa = 0.80, 91% agreement), which indicated a reliable classification method. This study developed a reliable semi-automated contextual analysis method for gait studies in HC and PD. Future studies could adapt this methodology for various gait-related eye-tracking studies.

Relationship between the serum level of transglutaminase 2-specific IgE and disease condition in patients with atopic dermatitis

Objective To detect the serum level of transglutaminase 2 (TG2) -specific IgE (sIgE) in patients with atopic dermatitis (AD) , and to analyze its correlation with the disease condition. Methods A total of 77 patients with AD were enrolled into this study, including 44 patients aged ≥ 12 years and 33 patients aged < 12 years. Of the 77 patients, 20 were diagnosed with intrinsic AD, which was characterized by the absence of sIgE and total serum IgE values < 150 kU/L, and 49 with extrinsic AD characterized by positive (++) or even strongly positive sIgE for more than 1 kind of exogenous allergens, or total serum IgE values ≥ 150 kU/L. Immunocapture-biotinylated detector enzyme immunoassay was performed to detect the serum level of TG2-sIgE in 77 patients with AD, 40 adult patients with psoriasis vulgaris (PV) and 30 healthy adult controls. Clinical data on the AD patients were recorded, including age, disease duration, SCORAD score, blood eosinophil count, levels of total IgE and TG2-sIgE. Results The serum levels of TG2-sIgE in AD patients aged ≥ 12 years, AD patients aged 0.05) . Conclusion The serum level of TG2-sIgE obviously increases in AD patients, so TG2 may be one kind of autoantigen in AD patients, but there is no significant correlation between the TG2-sIgE level and AD severity. Key words: Dermatitis, atopic; Transglutaminases; Immunoglobulin E; Autoantigens; Severity of illness index

A cross-sectional comparison of brain glucose and ketone metabolism in cognitively healthy older adults, mild cognitive impairment and early Alzheimer's disease

IntroductionDeteriorating brain glucose metabolism precedes the clinical onset of Alzheimer's disease (AD) and appears to contribute to its etiology. Ketone bodies, mainly β-hydroxybutyrate and acetoacetate, are the primary alternative brain fuel to glucose. Some reports suggest that brain ketone metabolism is unchanged in AD but, to our knowledge, no such data are available for MCI. ObjectiveTo compare brain energy metabolism (glucose and acetoacetate) and some brain morphological characteristics in cognitively healthy older adult controls (CTL), mild cognitive impairment (MCI) and early AD. Methods24 CTL, 20 MCI and 19AD of similar age and metabolic phenotype underwent a dual-tracer PET and MRI protocol. The uptake rate constants and cerebral metabolic rate of glucose (KGlu, CMRGlu) and acetoacetate (KAcAc, CMRAcAc) were evaluated with PET using [18F]-fluorodeoxyglucose ([18F]-FDG), a glucose analogue, and [11C]-acetoacetate ([11C]-AcAc), a ketone PET tracer. Regional brain volume and cortical thickness were evaluated by T1-weighted MRI. ResultsIn AD compared to CTL, CMRGlu was ~11% lower in the frontal, parietal, temporal lobes and in the cingulate gyrus (p<0.05). KGlu was ~15% lower in these same regions and also in subcortical regions. In MCI compared to CTL, ~7% glucose hypometabolism was present in the cingulate gyrus. Neither regional nor whole brain CMRAcAc or KAcAc were significantly different between CTL and MCI or AD. Reduced gray matter volume and cortical thinning were widespread in AD compared to CTL, whereas, in MCI compared to CTL, volumes were reduced only in the temporal cortex and cortical thinning was most apparent in temporal and cingulate regions. DiscussionThis quantitative kinetic PET and MRI imaging protocol for brain glucose and acetoacetate metabolism confirms that the brain undergoes structural atrophy and lower brain energy metabolism in MCI and AD and demonstrates that the deterioration in brain energy metabolism is specific to glucose. These results suggest that a ketogenic intervention to increase energy availability for the brain is warranted in an attempt to delay further cognitive decline by compensating for the brain glucose deficit in MCI and AD.

Phonological Working Memory for Words and Nonwords in Cerebral Cortex.

The primary purpose of this study was to identify the brain bases of phonological working memory (the short-term maintenance of speech sounds) using behavioral tasks analogous to clinically sensitive assessments of nonword repetition. The secondary purpose of the study was to identify how individual differences in brain activation were related to participants' nonword repetition abilities. We used functional magnetic resonance imaging to measure neurophysiological response during a nonword discrimination task derived from standard clinical assessments of phonological working memory. Healthy adult control participants (N = 16) discriminated pairs of real words or nonwords under varying phonological working memory load, which we manipulated by parametrically varying the number of syllables in target (non)words. Participants' cognitive and phonological abilities were also measured using standardized assessments. Neurophysiological responses in bilateral superior temporal gyrus, inferior frontal gyrus, and supplementary motor area increased with greater phonological working memory load. Activation in left superior temporal gyrus during nonword discrimination correlated with participants' performance on standard clinical nonword repetition tests. These results suggest that phonological working memory is related to the function of cortical structures that canonically underlie speech perception and production.

Dissociable Effects of Aging and Mild Cognitive Impairment on Bottom-Up Audiovisual Integration.

Effective audiovisual sensory integration involves dynamic changes in functional connectivity between superior temporal sulcus and primary sensory areas. This study examined whether disrupted connectivity in early Alzheimer's disease (AD) produces impaired audiovisual integration under conditions requiring greater corticocortical interactions. Audiovisual speech integration was examined in healthy young adult controls (YC), healthy elderly controls (EC), and patients with amnestic mild cognitive impairment (MCI) using McGurk-type stimuli (providing either congruent or incongruent audiovisual speech information) under conditions differing in the strength of bottom-up support and the degree of top-down lexical asymmetry. All groups accurately identified auditory speech under congruent audiovisual conditions, and displayed high levels of visual bias under strong bottom-up incongruent conditions. Under weak bottom-up incongruent conditions, however, EC and amnestic MCI groups displayed opposite patterns of performance, with enhanced visual bias in the EC group and reduced visual bias in the MCI group relative to the YC group. Moreover, there was no overlap between the EC and MCI groups in individual visual bias scores reflecting the change in audiovisual integration from the strong to the weak stimulus conditions. Top-down lexicality influences on visual biasing were observed only in the MCI patients under weaker bottom-up conditions. Results support a deficit in bottom-up audiovisual integration in early AD attributable to disruptions in corticocortical connectivity. Given that this deficit is not simply an exacerbation of changes associated with healthy aging, tests of audiovisual speech integration may serve as sensitive and specific markers of the earliest cognitive change associated with AD.

Neural correlates of atomoxetine improving inhibitory control and visual processing in Drug-naïve adults with attention-deficit/hyperactivity disorder.

Atomoxetine improves inhibitory control and visual processing in healthy volunteers and adults with attention-deficit/hyperactivity disorder (ADHD). However, little is known about the neural correlates of these two functions after chronic treatment with atomoxetine. This study aimed to use the counting Stroop task with functional magnetic resonance imaging (fMRI) and the Cambridge Neuropsychological Test Automated Battery (CANTAB) to investigate the changes related to inhibitory control and visual processing in adults with ADHD. This study is an 8-week, placebo-controlled, double-blind, randomized clinical trial of atomoxetine in 24 drug-naïve adults with ADHD. We investigated the changes of treatment with atomoxetine compared to placebo-treated counterparts using the counting Stroop fMRI and two CANTAB tests: rapid visual information processing (RVP) for inhibitory control and delayed matching to sample (DMS) for visual processing. Atomoxetine decreased activations in the right inferior frontal gyrus and anterior cingulate cortex, which were correlated with the improvement in inhibitory control assessed by the RVP. Also, atomoxetine increased activation in the left precuneus, which was correlated with the improvement in the mean latency of correct responses assessed by the DMS. Moreover, anterior cingulate activation in the pre-treatment was able to predict the improvements of clinical symptoms. Treatment with atomoxetine may improve inhibitory control to suppress interference and may enhance the visual processing to process numbers. In addition, the anterior cingulate cortex might play an important role as a biological marker for the treatment effectiveness of atomoxetine. Hum Brain Mapp 38:4850-4864, 2017. © 2017 Wiley Periodicals, Inc.

You'll feel better in the morning: slow wave activity and overnight mood regulation in interepisode bipolar disorder.

Sleep disturbances are prominent correlates of acute mood episodes and inadequate recovery in bipolar disorder (BD), yet the mechanistic relationship between sleep physiology and mood remains poorly understood. Using a series of pre-sleep mood inductions and overnight sleep recording, this study examined the relationship between overnight mood regulation and a marker of sleep intensity (non-rapid eye movement sleep slow wave activity; NREM SWA) during the interepisode phase of BD. Adults with interepisode BD type 1 (BD; n = 20) and healthy adult controls (CTL; n = 23) slept in the laboratory for a screening night, a neutral mood induction night (baseline), a happy mood induction night, and a sad mood induction night. NREM SWA (0.75-4.75 Hz) was derived from overnight sleep EEG recordings. Overnight mood regulation was evaluated using an affect grid pleasantness rating post-mood induction (pre-sleep) and the next morning. Overnight mood regulation did not differ between groups following the sad or happy inductions. SWA did not significantly change for either group on the sad induction night compared with baseline. In BD only, SWA on the sad night was related to impaired overnight negative mood regulation. On the happy induction night, SWA increased relative to baseline in both groups, though SWA was not related to overnight mood regulation for either group. These findings indicate that SWA disruption may play a role in sustaining negative mood state from the previous night in interepisode BD. However, positive mood state could enhance SWA in bipolar patients and healthy adults.

Effect of Cervical Kinesthetic Motor Imagery on Postural Control of Healthy Young Adults with Fear of Falling

Motor imagery (MI) is the act of coding the mental aspect of an intended task without executing it. Fear consists of an anxiogenic response to a previous event, which provides a state of alertness to the individual in the face of a threat. These two conditions (imagery and fear) may modulate orthostatic postural control, but their combined effect is still unknown. To investigate whether cervical kinesthetic motor imagery induces modulations in postural control and in the fear of falling (FoF) sensation in healthy young adults. Participants (n = 20) were placed on the Wii Balance Board® and oriented to perform and imagine three tasks for 60 s: (1) closed eyes; (2) cervical flexion; and (3) cervical inclination. The number of performed and imagined repetitions were recorded, and participants responded to a question at the end of each task regarding the FoF. There were four relevant effects: (1) there was no difference between the number of performed and imagined repetitions (p &gt; 0.05) indicating similarities; (2) there was a greater sensation of FoF induced by kinesthetic MI tasks (p &lt; 0.001); (3) there was a greater modulation of the center of pressure (mean velocity and amplitude) in the anteroposterior direction in phobic subjects (p &lt; 0.05); and (4) there was no modulation between the non-phobic subjects in the anteroposterior direction (p &gt; 0.05). The FoF during kinesthetic MI tasks may influence the orthostatic postural control, favoring the reduction in postural stability.

Developing clinically practical transcranial direct current stimulation protocols to improve saccadic eye movement control.

Recent research indicates that anodal transcranial direct current stimulation (tDCS) applied over the frontal eye field (FEF) can improve saccadic eye movement control in healthy young adults. The current research set out to determine whether similar results can be produced using a clinically practical protocol, whether tDCS applied over the dorsolateral prefrontal cortex (DLPFC) might also afford benefits, and whether benefits extend to older adults. Twenty young and 10 older adults completed two active (FEF and DLPFC) and one sham stimulation session. To aid clinical translation, the method of positioning the electrodes entailed simple measurements only. Saccadic performance following anodal tDCS applied over the FEF or DLPFC did not differ from the sham condition in either age group. Additionally, saccadic performance contralateral to the active electrodes showed no evidence of benefits over ipsilateral performance. These results call into question whether the protocol utilized can be applied effectively using only simple measurements to localize the relevant frontal subregion. Future efforts to develop a clinically practical tDCS protocol to improve saccadic eye movement control should include a sham control condition and consider adjusting the tDCS electrode montage and current strength to optimize the chances of conferring benefits in the population under study.

Antioxidant defense system in familial hypercholesterolemia and the effects of lipoprotein apheresis

Oxidative stress is thought to play an important role in the pathogenesis of disorders associated with atherosclerosis. Alpha-tocopherol is considered to be an effective lipophilic antioxidant, which protects lipid membranes against peroxidation and thus prevents cell damage by reaction with free radicals. However, measurement of alpha-tocopherol concentration in serum does not reflect the content of α-tocopherol in membranes whereas erythrocyte alpha-tocopherol may be good indicator of antioxidative status. Therefore a simple isocratic reversed phase HPLC method has been developed and validated for the determination of alpha-tocopherol in human erythrocytes in a clinical setting. The content of alpha-tocopherol in human erythrocyte membrane and lipoperoxidation were studied in patients with severe hypercholesterolemia treated by lipoprotein apheresis. The group of hypercholesterolemic patients (n = 14) treated by lipoprotein apheresis was compared to healthy adult normolipidemic controls. After lipoprotein apheresis, the content of in membrane alpha-tocopherol did not change significantly despite decreased tocopherol in serum and lipoprotein fractions. We observed significantly decreased lipoperoxidation as revealed by serum TBARS, representing end products of lipid peroxidation, which increased from third day afterwards and remained significantly higher in comparison to controls until the next LDL-apheresis. We conclude that aggressive lipid lowering procedure with lipoprotein apheresis was associated with favorable transient decrease of lipoperoxidation. Simultaneously the cell membrane bound antioxidative defense mechanisms as reflected by the content of alpha-tocopherol in human erythrocyte membrane where not depressed in spite of its decreased plasma lipid carrier. Another variables involved remain to be investigated.

Memory-guided force control in healthy younger and older adults.

Successful performance of a memory-guided motor task requires participants to store and then recall an accurate representation of the motor goal. Further, participants must monitor motor output to make adjustments in the absence of visual feedback. The goal of this study was to examine memory-guided grip force in healthy younger and older adults and compare it to performance on behavioral tasks of working memory. Previous work demonstrates that healthy adults decrease force output as a function of time when visual feedback is not available. We hypothesized that older adults would decrease force output at a faster rate than younger adults, due to age-related deficits in working memory. Two groups of participants, younger adults (YA: N=32, mean age 21.5years) and older adults (OA: N=33, mean age 69.3years), completed four 20-s trials of isometric force with their index finger and thumb, equal to 25% of their maximum voluntary contraction. In the full-vision condition, visual feedback was available for the duration of the trial. In the no vision condition, visual feedback was removed for the last 12s of each trial. Participants were asked to maintain constant force output in the absence of visual feedback. Participants also completed tasks of word recall and recognition and visuospatial working memory. Counter to our predictions, when visual feedback was removed, younger adults decreased force at a faster rate compared to older adults and the rate of decay was not associated with behavioral performance on tests of working memory.

Minimum toe clearance: probing the neural control of locomotion

Minimum toe clearance (MTC) occurs during a highly dynamic phase of the gait cycle and is associated with the highest risk of unintentional contact with obstacles or the ground. Age, cognitive function, attention and visual feedback affect foot clearance but how these factors interact to influence MTC control is not fully understood. We measured MTC in 121 healthy individuals aged 20–80 under four treadmill walking conditions; normal walking, lower visual field restriction and two Stroop colour/word naming tasks of two difficulty levels. Competition for cognitive and attentional resources from the Stroop task resulted in significantly lower mean MTC in older adults, with the difficult Stroop task associated with a higher frequency of extremely low MTC values and subsequently an increased modelled probability of tripping in this group. While older adults responded to visual restriction by markedly skewing MTC distributions towards higher values, this condition was also associated with frequent, extremely low MTC values. We reveal task-specific, age-dependent patterns of MTC control in healthy adults. Age-related differences are most pronounced during heavy, distracting cognitive load. Analysis of critically-low MTC values during dual-task walking may have utility in the evaluation of locomotor control and fall risk in older adults and patients with motor control deficits.