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Cognitive deficits affect a significant proportion of patients with bipolar disorder (BD). Problems with sustained attention have been found independent of mood state and the causes are unclear. We aimed to investigate whether physical parameters such as activity levels, sleep, and body mass index (BMI) may be contributing factors.
Forty-six patients with BD and 42 controls completed a battery of neuropsychological tests and wore a triaxial accelerometer for 21 days which collected information on physical activity, sleep, and circadian rhythm. Ex-Gaussian analyses were used to characterise reaction time distributions. We used hierarchical regression analyses to examine whether physical activity, BMI, circadian rhythm, and sleep predicted variance in the performance of cognitive tasks.
Neither physical activity, BMI, nor circadian rhythm predicted significant variance on any of the cognitive tasks. However, the presence of a sleep abnormality significantly predicted a higher intra-individual variability of the reaction time distributions on the Attention Network Task.
This study suggests that there is an association between sleep abnormalities and cognition in BD, with little or no relationship with physical activity, BMI, and circadian rhythm.
Until the past half-century, all agriculture and land management was framed by local institutions strong in social capital. But neoliberal forms of development came to undermine existing structures, thus reducing sustainability and equity. The past 20 years, though, have seen the deliberate establishment of more than 8 million new social groups across the world. This restructuring and growth of rural social capital within specific territories is leading to increased productivity of agricultural and land management systems, with particular benefits for those previously excluded. Further growth would occur with more national and regional policy support.
We use deep Chandra and HST data to uniquely classify the X-ray binary (XRB) populations in M81 on the basis of their donor stars and local stellar populations (into early-type main sequence, yellow giant, supergiant, low-mass, and globular cluster). First, we find that more massive, redder, and denser globular clusters are more likely to be associated with XRBs. Second, we find that the high-mass XRBs (HMXBs) overall have a steeper X-ray luminosity function (XLF) than the canonical star-forming galaxy XLF, though there is some evidence of variations in the slopes of the sub-populations. On the other hand, the XLF of the prototypical starburst M82 is described by the canonical powerlaw (αcum ∼ 0.6) down to LX ∼ 1036 erg s−1. We attribute variations in XLF slopes to different mass transfer modes (Roche-lobe overflow versus wind-fed systems).
Alzheimer's disease (AD) is considered to be a disorder predominantly affecting memory. It is increasingly recognized that the cognitive profile may be heterogeneous. We hypothesized that it would be possible to define distinct “cognitive phenotypes” in older people with AD.
Participants from three individual studies were included, consisting of 109 patients with a diagnosis of probable AD, and 91 age- and gender-matched control participants. All had demographic and cognitive assessment data available, including the Cambridge Cognitive Examination of the Elderly (CAMCOG). The CAMCOG scores and sub-scores were further analyzed using hierarchical cluster analysis and factor analysis.
Three clusters were identified. The scores loaded onto three factors representing the domains of attention, praxis, calculation, and perception; memory; and language comprehension and executive function. The main difference between the clusters related to degree of memory impairment. The composite score for memory between the clusters remained significantly different despite adjustment for illness duration and age of onset (p < 0.001).
These data suggest clinical heterogeneity within an older group of people with AD. This may have implications for diagnosis, prognosis, response to currently available treatments, and the development of novel therapies.
Recent studies suggest that white matter abnormalities contribute to both motor and non-motor symptoms of Parkinson's disease. The present study was designed to investigate the degree to which diffusion tensor magnetic resonance imaging (DTI) indices are related to executive function in Parkinson's patients. We used tract-based spatial statistics to compare DTI data from 15 patients to 15 healthy, age- and education-matched controls. We then extracted mean values of fractional anisotropy (FA) and mean diffusivity (MD) within an a priori frontal mask. Executive function composite Z scores were regressed against these DTI indices, age, and total intracranial volume. In Parkinson's patients, FA was related to executive composite scores, and both indices were related to Stroop interference scores. We conclude that white matter microstructural abnormalities contribute to cognitive deficits in Parkinson's disease. Further work is needed to determine whether these white matter changes reflect the pathological process or a clinically important comorbidity. (JINS, 2013, 19, 1–6)
The palaeoenvironments associated with Australopithecus (Paranthropus) robustus have generally been reconstructed as habitat mosaics; typically open, arid grasslands in the vicinity of woodlands or forests with a nearby source of permanent water. Disentangling which aspect(s) of these mosaics might have been preferred by the hominins presents a significant challenge. The aim of this study is to enhance our resolution of animal palaeocommunity structure in the Bloubank river valley of South Africa in order to test which ecological conditions might have been favoured or avoided by A. robustus. Faunal assemblage data were collected from a series of hominin-bearing deposits including Kromdraai, Swartkrans, Sterkfontein and Coopers (locality D). Taphonomic data revealed the presence of a potential bias resulting from depositional matrix, though our analysis demonstrated there was no association between taphonomic conditions and taxonomic composition. A selection of environmentally sensitive taxa was assigned to a series of ecological categories based on isotopic, ecomorphological and taxonomic evidence. Correspondence analysis was used to assess changes in faunal composition between assemblages. Results indicate that the more open, arid-adapted taxa there are in a given assemblage, the fewer hominins there tend to be. Rather than reflecting the habitat preference of A. robustus, these data indicate a pattern of habitat avoidance that is inconsistent with a reconstruction of this hominin as an open, arid specialist. We conclude that the hominins were capable of subsisting in sub-optimal habitats as a result of their capacity to significantly alter their dietary patterns in favour of less preferred food items when conditions dictated.
The discovery of the first species of African hominin, Australopithecus africanus, from Taung, South Africa in 1924, launched the study of fossil man in Africa. New discoveries continue to confirm the importance of this region to our understanding of human evolution. Outlining major developments since Raymond Dart's description of the Taung skull and, in particular, the impact of the pioneering work of Phillip V. Tobias, this book will be a valuable companion for students and researchers of human origins. It presents a summary of the current state of palaeoanthropology, reviewing the ideas that are central to the field, and provides a perspective on how future developments will shape our knowledge about hominin emergence in Africa. A wide range of key themes are covered, from the earliest fossils from Chad and Kenya, to the origins of bipedalism and the debate about how and where modern humans evolved and dispersed across Africa.
It is generally accepted that archaic humans of the African later Early and early Middle Pleistocene constituted the source population for anatomically modern humans. Due to limited fossil and archaeological records, however, relatively little is known about the morphology, behaviour and ecology of these presumed ancestors of modern humans. Fragmentary fossils (variously attributed to Homo heidelbergensis, H. rhodesiensis and H. helmei) from across Africa suggest that these archaic humans were both taller and more massive than their extant modern human descendants in this region, and perhaps had a body shape that was stockier and less ‘nilotic’ than seen among extant sub-Saharan Africans. Fragmentary fossils attributed to Homo sapiens, on the other hand, appear to represent individuals closer in body size to the means of recent sub-Saharan Africans. Since body size and shape are critical to the ecology, energetics and thermoregulatory adaptations of early humans, these differences in morphology may signal important adaptive changes at the time of the origins of modern humans. Comparative analyses of femoral and orbital dimensions support the claim that Middle Pleistocene Africans were of greater body size (both stature and mass) and had greater mass/stature ratios than modern Africans, and support the claim that early African H. sapiens were of smaller body size than their Middle Pleistocene ancestors.
Since Raymond Dart named Australopithecus africanus in 1925, palaeoanthropology has been advanced by the discovery of numerous additional australopithecine and other fossil hominins, as well as applications of medical imaging technology for reconstructing and measuring their remains. Although improved dates for some fossils and a better understanding of their developmental trajectories have helped to modify some earlier beliefs about hominin evolution, the now much-enlarged fossil record of South African australopithecines is of key importance for understanding human evolution. This chapter details how the accumulated advances in palaeoanthropology, in general, and the South African record of endocasts, in particular, impact on our understanding of the nature and timing of hominin brain evolution. Three-dimensional computed tomography (3D-CT) of certain South African australopithecines has led to new reconstructions in the form of virtual endocasts as well as revised cranial capacity estimates that impact the overview of the tempo and mode of hominin brain evolution during the Plio-Pleistocene. The recent discovery and reaction to Homo floresiensis is discussed and compared with the earlier reception of Taung’s discovery by scientists and the public. The endocasts of Taung and LB1 are briefly reviewed within the context of the ongoing debate about the respective evolutionary roles of brain size and neurological reorganisation during human evolution.
In this chapter, I survey ideas of the concept of species, as they apply to the human evolutionary record. I discuss the question of the meaning of a genus, concluding that all species since the separation of the human line from that of the chimpanzee (and possibly including the chimpanzee lineage as well) should be placed in a single genus, for which the prior available name is Homo. How new species arise is a yet more controversial topic, and I list the variety of modes of speciation that have been proposed, with predictions as to what the results of some of these modes might look like, making suggestions as to how they might apply in palaeoanthropology.
The current chapter examines allometric exponents as they apply to the evolution of the size, or mass, of the modern human brain relative to the mass of the body. The mass of the brain is considered as a single level of organisation of the nervous system and is treated separately to other levels of organisation. A comprehensive dataset is used to examine the relationship between brain and body mass in primates and hominids. This analysis allows us to postulate that the evolution of the size of the human brain can, for the most part, be accounted for by scaling with body size. There appears to be a minimum of two potential adaptive events that have led to alterations in the scaling laws that help explain the actual mass of the human brain. These two events occur at the origin of primates and the origin of the hominid lineage. These scaling laws appear to obviate much of the need for adaptationist explanations in terms of the evolution of the mass of the human brain.