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Search Results: 1 - 10 of 210813 matches for " Sinéad L. Mullally "
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Retrosplenial Cortex Codes for Permanent Landmarks
Stephen D. Auger, Sinéad L. Mullally, Eleanor A. Maguire
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0043620
Abstract: Landmarks are critical components of our internal representation of the environment, yet their specific properties are rarely studied, and little is known about how they are processed in the brain. Here we characterised a large set of landmarks along a range of features that included size, visual salience, navigational utility, and permanence. When human participants viewed images of these single landmarks during functional magnetic resonance imaging (fMRI), parahippocampal cortex (PHC) and retrosplenial cortex (RSC) were both engaged by landmark features, but in different ways. PHC responded to a range of landmark attributes, while RSC was engaged by only the most permanent landmarks. Furthermore, when participants were divided into good and poor navigators, the latter were significantly less reliable at identifying the most permanent landmarks, and had reduced responses in RSC and anterodorsal thalamus when viewing such landmarks. The RSC has been widely implicated in navigation but its precise role remains uncertain. Our findings suggest that a primary function of the RSC may be to process the most stable features in an environment, and this could be a prerequisite for successful navigation.
Suppressing the Encoding of New Information in Memory: A Behavioral Study Derived from Principles of Hippocampal Function
Sinéad L. Mullally, Shane M. O'Mara
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0050814
Abstract: Cognitive processes do not occur in isolation. Interactions between cognitive processes can be observed as a cost in performance following a switch between tasks, a cost that is greatest when the cognitive requirements of the sequential tasks compete. Interestingly, the long-term mnemonic goals associated with specific cognitive tasks can also directly compete. For example, encoding the sequential order in which stimuli are presented in the commonly-utilised 2-Back working memory (WM) tasks is counter-productive to task performance, as this task requires the continual updating of the contents of one's current mental set. Performance of this task consistently results in reduced activity within the medial temporal lobe (MTL), and this response is believed to reflect the inhibitory mnemonic component of the task. Conversely, there are numerous cognitive paradigms in which participants are explicitly instructed to encode incoming information and performance of these tasks reliably increases MTL activity. Here, we explore the behavioural cost of sequentially performing two tasks with conflicting long-term mnemonic goals and contrasting neural profiles within the MTL. We hypothesised that performing the 2-Back WM prior to a hippocampal-dependent memory task would impair performance on the latter task. We found that participants who performed the 2-Back WM task, prior to the encoding of novel verbal/face-name stimuli, recollected significantly fewer of these stimuli, compared to those who had performed a 0-Back control task. Memory processes believed to be independent of the MTL were unaffected. Our results suggest that the inhibition of MTL-dependent mnemonic function persists beyond the cessation of the 2-Back WM task and can alter performance on entirely separate and subsequently performed memory tasks. Furthermore, they indicate that performance of such tasks may induce a temporarily-sustained, virtual lesion of the hippocampus, which could be used as a probe to explore cognitive processes in the absence of hippocampal involvement.
Prolonged rote learning produces delayed memory facilitation and metabolic changes in the hippocampus of the ageing human brain
Richard AP Roche, Sinéad L Mullally, Jonathan P McNulty, Judy Hayden, Paul Brennan, Colin P Doherty, Mary Fitzsimons, Deirdre McMackin, Julie Prendergast, Sunita Sukumaran, Maeve A Mangaoang, Ian H Robertson, Shane M O'Mara
BMC Neuroscience , 2009, DOI: 10.1186/1471-2202-10-136
Abstract: Results indicate a facilitation of new learning that was evident six weeks after rote learning ceased. This facilitation occurred for verbal/episodic material only, and was mirrored by a metabolic change in left posterior hippocampus, specifically an increase in NAA/(Cr+Cho) ratio.Results suggest that repeated activation of memory structures facilitates anamnesis and may promote neuronal plasticity in the ageing brain, and that compliance is a key factor in such facilitation as the effect was confined to those who engaged fully with the training.The hippocampal formation is a key structure in episodic and spatial memory in humans. Since the original case study of patient H.M. fifty years ago [1], a vast literature has implicated medial temporal lobe structures in memory in both humans and animals [2-4]. Recent decades have seen a delineation of the functions of left and right hippocampi, with left primarily associated with verbally-mediated episodic memory, while the right hippocampus seems crucial for visuo-spatial information [5]. Two features in particular make the hippocampus a unique structure: it was the first region of the brain in which the phenomenon of long-term potentiation [6] was demonstrated in response to pulsed electrical stimulation. LTP remains the most popular neural model of memory formation, and though it has since been shown in other parts of the cortex (E.g. visual cortex: [7,8]; somatosensory cortex: [9]), the hippocampus is still the area in which it is most readily induced [10]. Secondly, the hippocampus is one of the few areas of the brain in which adult neurogenesis occurs; Eriksson et al. [11] have shown that new cells can grow in the dentate gyrus of the hippocampal formation under certain conditions (see also [12,13]). Taken together, these factors suggest the hippocampus may also be a crucial site of plasticity and growth in the mammalian brain (However, several studies point to the importance of entorhinal cortex (EC) rather than hip
Herpes Zoster Vaccine Effectiveness against Incident Herpes Zoster and Post-herpetic Neuralgia in an Older US Population: A Cohort Study
Sinéad M. Langan ,Liam Smeeth,David J. Margolis,Sara L. Thomas
PLOS Medicine , 2013, DOI: 10.1371/journal.pmed.1001420
Abstract: Background Herpes zoster is common and has serious consequences, notably post-herpetic neuralgia (PHN). Vaccine efficacy against incident zoster and PHN has been demonstrated in clinical trials, but effectiveness has not been studied in unselected general populations unrestricted by region, full health insurance coverage, or immune status. Our objective was to assess zoster vaccine effectiveness (VE) against incident zoster and PHN in a general population-based setting. Methods and Findings A cohort study of 766,330 fully eligible individuals aged ≥65 years was undertaken in a 5% random sample of Medicare who received and did not receive zoster vaccination between 1st January 2007 and 31st December 2009. Incidence rates and hazard ratios for zoster and PHN were determined in vaccinated and unvaccinated individuals. Analyses were adjusted for age, gender, race, low income, immunosuppression, and important comorbidities associated with zoster, and then stratified by immunosuppression status. Adjusted hazard ratios were estimated using time-updated Cox proportional hazards models. Vaccine uptake was low (3.9%) particularly among black people (0.3%) and those with evidence of low income (0.6%). 13,112 US Medicare beneficiaries developed incident zoster; the overall zoster incidence rate was 10.0 (9.8–10.2) per 1,000 person-years in the unvaccinated group and 5.4 (95% CI 4.6–6.4) per 1,000 person-years in vaccinees, giving an adjusted VE against incident zoster of 0.48 (95% CI 0.39–0.56). In immunosuppressed individuals, VE against zoster was 0.37 (95% CI 0.06–0.58). VE against PHN was 0.59 (95% CI 0.21–0.79). Conclusions Vaccine uptake was low with variation in specific patient groups. In a general population cohort of older individuals, zoster vaccination was associated with reduction in incident zoster, including among those with immunosuppression. Importantly, this study demonstrates that zoster vaccination is associated with a reduction in PHN. Please see later in the article for the Editors' Summary
Acute Cardiovascular Events after Herpes Zoster: A Self-Controlled Case Series Analysis in Vaccinated and Unvaccinated Older Residents of the United States
Caroline Minassian?,Sara L. Thomas?,Liam Smeeth?,Ian Douglas?,Ruth Brauer?,Sinéad M. Langan
PLOS Medicine , 2015, DOI: 10.1371/journal.pmed.1001919
Abstract: Background Herpes zoster is common and can have serious consequences. Additionally, emerging data suggest an increased risk of acute cardiovascular events following herpes zoster. However, to our knowledge, existing association studies compare outcomes between individuals and are therefore vulnerable to between-person confounding. In this study, we used a within-person study design to quantify any short-term increased risk of acute cardiovascular events (stroke and myocardial infarction [MI]) after zoster and to assess whether zoster vaccination modifies this association. Methods and Findings The self-controlled case series method was used to estimate rates of stroke and acute MI in defined periods after herpes zoster compared to other time periods, within individuals. Participants were fully eligible Medicare beneficiaries aged ≥65 y with a herpes zoster diagnosis and either an ischemic stroke (n = 42,954) or MI (n = 24,237) between 1 January 2006 and 31 December 2011. Age-adjusted incidence ratios (IRs) for stroke and MI during predefined periods up to 12 mo after zoster relative to unexposed time periods were calculated using conditional Poisson regression. We observed a marked increase in the rate of acute cardiovascular events in the first week after zoster diagnosis: a 2.4-fold increased ischemic stroke rate (IR 2.37, 95% CI 2.17–2.59) and a 1.7-fold increased MI rate (IR 1.68, 95% CI 1.47–1.92), followed by a gradual resolution over 6 mo. Zoster vaccination did not appear to modify the association with MI (interaction p-value = 0.44). We also found no evidence for a difference in the IR for ischemic stroke between vaccinated (IR 1.14, 95% CI 0.75–1.74) and unvaccinated (IR 1.78, 95% CI 1.68–1.88) individuals during the first 4 wk after zoster diagnosis (interaction p-value = 0.28). The relatively few vaccinated individuals limited the study’s power to assess the role of vaccination. Conclusions Stroke and MI rates are transiently increased after exposure to herpes zoster. We found no evidence for a role of zoster vaccination in these associations. These findings enhance our understanding of the temporality and magnitude of the association between zoster and acute cardiovascular events.
Nahm's conjecture and coset models
Sinéad Keegan,Werner Nahm
Physics , 2011,
Abstract: When is a $q$-series modular? This is an interesting open question in mathematics that has deep connections to conformal field theory. In this paper we define a particular $r$-fold $q$-hypergeometric series $f_{A,B,C}$, with data given by a matrix $A$, a vector $B$, and a scalar $C$, all rational, and ask when $f_{A,B,C}$ is modular. In the past much work has been done to predict which values of $A$ give rise to modular $f_{A,B,C}$, however there is no straightforward method for calculating corresponding values of $B$. We approach this problem from the point of view of conformal field theory, by considering $(2n+3,2)$--minimal models, and coset models of the form $\hat{su}(2)_k /\hat{u}(1)$. By calculating the characters of these models and comparing them to the functions $f_{A,B,C}$, we succeed in computing appropriate $B$-values in many cases.
NK Cells and Psoriasis
Sinéad Dunphy,Clair M. Gardiner
Journal of Biomedicine and Biotechnology , 2011, DOI: 10.1155/2011/248317
Abstract: Psoriasis is a chronic condition of the skin characterised by distinctive scaly plaques. The immune system is now thought to play a major role in the development and pathogenesis of psoriasis with immune cells and cytokines influencing keratinocyte function. Keratinocytes in turn, can activate and recruit immune cells leading to a positive feedback loop in disease. Natural Killer (NK) cells are lymphocytes that are best known for killing virally infected and cancer cells. However, evidence is emerging to support a role for NK cells in psoriasis. NK cells are found in the inflammatory infiltrate in psoriatic skin lesions. They can produce a range of inflammatory cytokines, many of which are important in the pathogenesis of psoriasis. Recent genetic studies have identified a range of potential molecules relating to NK cell biology that are known to be important in psoriasis. This paper will discuss the evidence, both cellular and genetic, for NK cell involvement in psoriasis.
Expanding Assessment of Fear of Falling among Older Adults with an Intellectual Disability: A Pilot Study to Assess the Value of Proxy Responses
Sinéad Foran,Mary McCarron,Philip McCallion
ISRN Geriatrics , 2013, DOI: 10.1155/2013/493042
Abstract: Introduction. Fear of falling (FOF) has emerged as an important health concern in older adults, yet it has rarely been investigated in people with intellectual disabilities (ID). Valid and reliable measurement approaches are a particular challenge. Scales that have been developed to measure FOF have not been validated for use with older people with ID and are not routinely used with proxy respondents. Method. 63 people comprised purposeful samples of 3 groups, people with ID , their nominated key workers , and additional support workers . Test-retest reliability and interrater reliability were assessed for using a dichotomous, single-item FOF screening measure. The degree of FOF and activity restriction due to FOF were also investigated. Results. Inter-rater reliability was found to be moderate to excellent with Kappa?=?0.77 on ratings of the FOF item. Test-retest reliability for each group of reviewers for the FOF item were also found to be excellent (0.95). Conclusion. The global item is a suitable screening measure for FOF in older adults with ID and can assist in identification of individuals requiring further assessment. Proxies, if carefully selected, can provide consistent and reliable reports of the presence of FOF in people with ID. 1. Introduction Fear of falling (FOF) has emerged as an important health concern in all older adults given its demonstrated association with restrictions in daily activity and in many cases activity avoidance [1]. The substantial body of literature that has emerged addresses prevalence, risk factors, and consequences [2–4]. Reported prevalence of FOF in the general elderly population is as high as 85% [3]; identified risk factors include having had a previous fall [5], increasing age [4], female gender [6], dizziness, depression and anxiety [7], and balance and gait disorders [8] and documented consequences of FOF include a decline in physical and mental performance, activity avoidance, and a loss of health-related quality of life [9, 10]. A consequence of FOF is an increased risk of falling [5, 11] and there is a likelihood of additional falls, given reported rates of 29% and 92% of FOF among recent fallers with previous falls [3, 12]. Studies suggest that FOF is a psychological experience resulting in reduced physical activity leading to poor balance, mobility impairment, and social isolation [13]. Such consequences may lead to increased likelihood for falling in the future. By comparison very little is known about FOF among older people with ID despite studies showing that older people with ID have higher rates
Ab initio investigation of FeAs/GaAs heterostructures for potential spintronic and superconducting applications
Sinéad M. Griffin,Nicola A. Spaldin
Physics , 2011, DOI: 10.1103/PhysRevB.85.155126
Abstract: Ultra-thin FeAs is of interest both as the active component in the newly identified pnictide superconductors, and in spintronic applications at the interface between ferromagnetic Fe and semiconducting GaAs. Here we use first-principles density functional theory to investigate the properties of FeAs/GaAs heterostructures. We find that the Fermi surface is modified from that characteristic of the pnictide superconductors by interactions between the FeAs layer and the As atoms in the GaAs layers. Regardless of the number of FeAs layers, the Fe to As ratio, or the strain state, the lowest energy magnetic ordering is always antiferromagnetic, suggesting that such heterostructures are not promising spintronic systems, and offering an explanation for the failure of spin injection across Fe/GaAs interfaces.
A density functional theory study of FeAs comparing LDA+U, GGA+U and hybrid functionals
Sinéad M. Griffin,Nicola A. Spaldin
Physics , 2014,
Abstract: We use density functional theory within the local density approximation (LDA), LDA+U, generalized gradient approximation (GGA), GGA+U, and hybrid-functional methods to calculate the properties of iron monoarsenide. FeAs, which forms in the MnP structure, is of current interest for potential spintronic applications as well as being the parent compound for the newly-identified pnictide superconductors. We compare the calculated structural, magnetic and electronic properties obtained using the different functionals to each other and to experiment, and investigate the origin of a recently-reported magnetic spiral. Our results indicate the appropriateness or otherwise of the various functionals for describing FeAs and the related Fe-pnictide superconductors.
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