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Biomedical subjects

Robert C Welsh

Publications and source records attributed to Robert C Welsh.

32 records · Page 2Linked to original sources
PubMed2004

Neural correlates of individual ratings of emotional salience: a trial-related fMRI study.

Accurate appraisal of meaningful environmental signals involves the interpretation of salient information for their intrinsic emotional value and personal relevance. We examined the neural basis for these components of endogenous salience during such appraisals using trial-related functional magnetic resonance imaging (fMRI). Subjects viewed affective pictures and assessed either the emotional intensity or extent of self-relatedness of the content of those pictures. In a parametric factorial design, individualized subjective ratings of these two dimensions were correlated with brain activity. The nucleus accumbens (NAcc) responded to both increasing emotional intensity and self-relatedness. Activity in the amygdala was specifically related to affective judgments and emotional intensity. The volitional act of appraising the extent of personal association specifically engaged the ventral medial prefrontal cortex (MPFC), and additionally recruited dorsal medial frontal regions and insula as the extent of self-relatedness increased. The findings highlight both overlapping and segregated neural representations of intrinsic value and personal relevance during the appraisal of emotional stimuli.

Adolescent↗
PubMed2004

A functional neuroimaging study of motivation and executive function.

Executive functions, such as working memory, must intersect with functions that determine value for the organism. Functional imaging work in humans and single-unit recordings in non-human primates provide evidence that PFC might integrate motivational context with working memory. With functional magnetic resonance imaging (fMRI), we addressed the question of motivation and working memory, using a trial-related design in an object-working memory task. The design permitted the analysis of BOLD signal at separate stages, corresponding to encoding, maintenance, and retrieval. Subjects were motivated by a financial incentive during the task, such that they could gain a high or a low reward. The two different levels of reward also entailed greater or lesser risk of losing money for incorrect responses. In the high, relative to the low, reward condition, subjects shifted response bias, and showed a trend to greater sensitivity. We found main effects in fMRI BOLD signal for reward, which overlapped with BOLD effects for maintenance of information, in the right superior frontal sulcus and bilateral intraparietal sulcus. We also found an interaction between reward and retrieval from working memory in the right dorsolateral prefrontal cortex. Main effects of load and reward occurred in adjacent regions of the ventrolateral PFC during retrieval. The data demonstrate that when subjects perform a simple working memory task, financial incentives motivate performance and interact with some of the same neural networks that process various stages of working memory. Areas of overlap and interaction may integrate information about value, or they may represent a general effect of motivation increasing neural effort.

Adult↗
PubMed2004

Variations in pre-hospital fibrinolysis process of care: insights from the Assessment of the Safety and Efficacy of a New Thrombolytic 3 Plus international acute myocardial infarction pre-hospital care survey.

The Assessment of the Safety and Efficacy of a New Thrombolytic 3 (ASSENT 3 PLUS) Plus trial (n=1639) was an international trial of pre-hospital fibrinolysis with tenecteplase randomly assigned to enoxaparin or unfractionated heparin, involving 106 sites in 12 countries. Given the potential impact of process of care delivery in various healthcare systems, we undertook a comprehensive validated survey of population demographics, geographical factors, emergency medical services, methods of electrocardiogram interpretation and pre-hospital fibrinolysis administration. The potential study population was 42.4 x 10(6) with 70% urban. The land areas of individual emergency medical services sites varied from 6 to 20000/km(2). Three emergency medical services personnel (range 2-5) attended each ambulance with the highest level of training, consisting of a physician (65%), registered nurse (20%) or paramedic. Before the initiation of the study, 72% of sites administered pre-hospital fibrinolysis (range 1-20 years). Electrocardiograms were interpreted on the scene in 60% and transmitted for physician's interpretation in the remainder; 41% of patients (679/1639) were enrolled at sites without a physician at the scene. The ASSENT 3 Plus trial incorporated a wide variation in population density, emergency medical services resources, and physician's interpretation of ECG and administering pre-hospital fibrinolysis. Understanding this diversity will help in evaluating the general applicability and feasibility of pre-hospital fibrinolysis in various health systems, as well as the pre-hospital care of ST elevation myocardial infarction patients regardless of reperfusion strategies.

Canada↗
PubMed2004

A marriage of enhancement: fibrinolysis and conjunctive therapy.

Pharmacologic reperfusion of patients with acute ST segment elevation myocardial infarction is designed to achieve prompt high-quality reperfusion, prevent recurrent ischemia and reinfarction, maintain long-term patency, and to enhance patient survival and quality of life. Because monotherapy with fibrinolytics is by itself unable to achieve all of these objectives, antithrombotic, anti-platelet, and other novel agents are required. We discuss herein the role of unfractionated and enoxaparin, the potential added value of direct thrombin inhibitors, and the importance of aspirin. Despite the promise of glycoprotein IIb/IIIa inhibitors, risks associated with intracranial hemorrhage in the elderly have led to restraint in their application to broad populations. Facilitation of urgent percutaneous coronary intervention with combination reduced-dose fibrinolytic and glycoprotein IIb/IIIa inhibitors remains a promising potential future path. The future is likely to emphasize greater application of the already effective therapies at our disposal and the development of novel anti-platelet and anti-thrombin agents as well as those directed toward inflammation.

Animals↗
PubMed2004

Low cardiorespiratory fitness is associated with elevated C-reactive protein levels in women with type 2 diabetes.

OBJECTIVE: The purpose of this study was to examine differences in novel markers of cardiovascular disease (CVD) in women with type 2 diabetes stratified according to cardiorespiratory fitness. RESEARCH DESIGN AND METHODS: A total of 28 women (mean age 57 +/- 6 years) with type 2 diabetes who were free from overt CVD were placed into low cardiorespiratory fitness (LCF) or average cardiorespiratory fitness (ACF) groups based on a graded exercise test to exhaustion. A group of eight women without type 2 diabetes were also examined and served as healthy control subjects. The median VO(2peak) value was used as a cutoff for group determination. We assessed both conventional CVD risk factors, including blood pressure, BMI, and lipid profile, as well as novel CVD risk factors, such as left ventricular filling dynamics, arterial stiffness, fasting insulin, and C-reactive protein (CRP). RESULTS: VO(2peak) values were 69 +/- 14 and 91 +/- 24% of predicted values for sedentary age-matched healthy individuals in the LCF and ACF groups, respectively. BMI was significantly greater in the LCF group (P < 0.05); however, no differences were observed in age, lipid profile, or resting hemodynamics. CRP was 3.3-fold higher in the LCF group (6.3 +/- 41. vs. 1.9 +/- 1.7 mg/l, P < 0.05), whereas other novel markers of CVD were not significantly different between the groups. Significant negative relationships were observed between VO(2peak) and both CRP (r = -0.49) and the homeostasis model assessment index (r = -0.48) (P < 0.05). CONCLUSIONS: The novel finding of this investigation is that low cardiorespiratory fitness is associated with elevated CRP and reduced fasting glucose control in women with type 2 diabetes.

Age of Onset↗
PubMed2003

Working memory for complex scenes: age differences in frontal and hippocampal activations.

Age differences in frontal and hippocampal activations in working memory were investigated during a maintenance and subsequent probe interval in an event-related fMRI design. Younger and older adults either viewed or maintained photographs of real-world scenes (extended visual or maintenance conditions) over a 4-sec interval before responding to a probe fragment from the studied picture. Behavioral accuracy was largely equivalent across age and conditions on the probe task, but underlying neural activations differed. Younger but not older adults showed increased left anterior hippocampal activations in the extended visual compared with the maintenance condition. On the subsequent probe interval, however, older adults showed more left and right inferior frontal activations than younger adults. The increased frontal activations at probe in older adults may have been compensatory for the decreased hippocampal activations during maintenance, but alternatively could have reflected the increased difficulty of the probe task for the older subjects. Thus, we demonstrate qualitatively different engagement of both frontal and hippocampal structures in older adults in a working memory task, despite behavioral equivalence.

Adult↗
PubMed2003

Habituation of rostral anterior cingulate cortex to repeated emotionally salient pictures.

Habituation of the neural response to repeated stimuli has been well demonstrated for subcortical limbic regions responding to emotionally salient stimuli. Although the rostral or affective division of the anterior cingulate cortex (rACC) is also engaged during emotional processing, little is known about the temporal dynamics of this region in sustained evaluation of emotional salience. Using a test/retest design, the present study assessed habituation in the human brain with functional magnetic resonance imaging. Eight healthy subjects were exposed to two repeated runs of aversive, neutral, and blank images. Activation of the rACC to negatively valenced pictures occurred only in the first session, and this activation was significantly greater in the first relative to the second session. Additionally, medial prefrontal cortex, hippocampal, and amygdalar activations were noted during the first, but not second, presentation of aversive pictures. These findings highlight the phasic activity of the rACC in emotional processing consistent with habituation.

Adult↗
PubMed2003

Activation of the medial prefrontal cortex and extended amygdala by individual ratings of emotional arousal: a fMRI study.

BACKGROUND: Significant differences between individual responses to emotional stimuli can be important for the study of emotion. We investigated whether incorporating individual ratings of emotional arousal in the analysis of functional magnetic resonance imaging (fMRI) data improves the detection of activation in the medial prefrontal cortex (MPFC) and sublenticular extended amygdala (SLEA), areas implicated in the processing of emotional salience. METHODS: Healthy subjects viewed counterbalanced blocks of aversive, nonaversive, and blank images. Outside the scanner, they rated the intensity of emotional arousal (salience) of each presented picture. RESULTS: Incorporating the subject's response to each stimulus by using individualized regressors produced more robust activations within MPFC and SLEA compared with a simple boxcar regressor, identical for all subjects. CONCLUSIONS: Our findings demonstrate that individual behavioral data are useful in improving detection of activation in block-design functional imaging studies.

Adult↗
PubMed2003

Prehospital management of acute ST-elevation myocardial infarction: a time for reappraisal in North America.

Although the medical and technologic revolution in the last 3 decades has improved clinical outcome in patients sustaining acute ST-elevation myocardial infarction (STEMI), residual morbidity and mortality remain major health concerns. The critical roles of temporal delay and optimal sustained patency as modulators of successful reperfusion have been repeatedly demonstrated, and investigation into the ideal interface between pharmacologic and mechanical reperfusion continues. Despite physician awareness and patient education programs, time from symptom onset to treatment in STEMI remains stalled at approximately 3 hours for pharmacologic reperfusion, as documented in major clinical trials. Multifaceted improvements with advanced paramedic training, transmittable 12-lead electrocardiograms, and bolus fibrinolytics facilitate potential prehospital diagnosis and treatment. Thus, as we proceed into the 21st century, it is essential to reexamine strategies for addressing these and other issues relating to the process of delivering optimal care to most patients with STEMI. Especially notable are the opportunities provided through prehospital management with initiation of therapy, triage to appropriate hospitals, or both as major potential avenues to further enhance patient outcomes. We review past research in prehospital therapy for STEMI and practical impediments to implementation to establish a framework for interpretation of future developments.

Clinical Trials as Topic↗
PubMed2003

Late potentials in female triathletes before and after prolonged strenuous exercise.

The objectives of this study were to evaluate the prevalence of late potentials (LP) in female triathletes before and after prolonged strenuous exercise (PSE), and to determine whether LP are related to greater left ventricular (LV) dimensions and/or mass. Thirteen female triathletes were examined immediately before (Pre), one hour after (Post), and 24 to 48 hours after PSE (Recovery) using signal-averaged electrocardiography (SAECG). Late potentials were evaluated by two or more standard SAECG anomalies. Left ventricular dimensions and mass were measured Pre using two-dimensional echocardiography. Results revealed that no significant differences existed between Pre, Post, and Recovery in the SAECG parameters. Four athletes displayed LP during Pre. The incidence of LP during did not increase Post. There were no significant relationships between LV dimensions or mass and SAECG parameters. In conclusion, a small portion of female triathletes display LP before and after PSE, which are not worsened by PSE nor related to increased LV dimensions and/or mass.

Action Potentials↗
PubMedDate not supplied

Multiparametric color-encoded brain MR imaging in Talairach space.

Clinical magnetic resonance (MR) imaging of the brain is typically performed in the standard three orthogonal planes of the magnet, with little regard to head positioning. Multiple sequences with different imaging parameters are performed, and gray-scale images are obtained and displayed separately. The authors have implemented, and currently advocate, the routine acquisition of coregistered transverse images after roll, yaw, and pitch correction to Talairach space. Talairach, anterior commissure (AC)-posterior commissure (PC) referenced, stereotactic space has been widely embraced by the neuroscience community. This standardization should lead to more reproducible and readily interpretable MR examinations. A method is described to obtain direct AC-PC referenced (Talairach space) MR images. Sample protocols are provided. Coregistered T1-weighted, T1-weighted with contrast material administration, T2-weighted, fluid-attenuated inversion recovery (FLAIR), MR angiography, fractional anisotropy, and functional MR imaging sequences are presented, depicting a wide range of imaging parameters applied to normal brain anatomy in Talairach space. Illustrative examples of pathology are also provided. Color encoding is discussed and exploited to display and integrate multiparameter MR imaging contrast and white-matter-tract direction (anisotropy). The color composites may reduce the number of images needed for review by a factor of three or four and facilitate interpretation.

Brain↗