Editorial Board

Publication date: May 2017
Source:Journal of Human Evolution, Volume 106





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Phytoliths indicate significant arboreal cover at Sahelanthropus type locality TM266 in northern Chad and a decrease in later sites

Publication date: May 2017
Source:Journal of Human Evolution, Volume 106
Author(s): Alice Novello, Doris Barboni, Florence Sylvestre, Anne-Elisabeth Lebatard, Christine Paillès, Didier L. Bourlès, Andossa Likius, Hassane Taisso Mackaye, Patrick Vignaud, Michel Brunet
We analyzed phytolith and diatom remains preserved at 45 Miocene and Pliocene localities dated between 8 and 1 Ma in northern Chad (16–17°N). Some of these localities yielded cranial remains, lower jaws, and teeth of the hominin species Australopithecus bahrelghazali (∼3.6 Ma) and Sahelanthropus tchadensis (∼7 Ma). Of the 111 sediment samples analyzed, 41 yielded phytoliths, 20 yielded diatoms, and seven yielded both phytoliths and diatoms. Freshwater planktonic and tychoplanktonic diatom species, indicative of lacustrine conditions, are dominant (>91%) in the samples. The phytolith assemblages indicate an opening of the vegetation and a general trend toward an expansion of grass-dominated environments during the time spanning the two hominin occurrences in Chad. The phytoliths suggest the presence of a mosaic environment, including closed forest patches, palm groves, and mixed/grassland formations, between 7.5 and 7 Ma, the replacement by palm grove-like vegetation at approximately 6.5–5 Ma, and the presence of exclusive grass-dominated formations after 4.5 Ma. The type-locality of S. tchadensis (TM266) was likely similar to modern palm grove formations with an arboreal cover percentage ≥40%. The type locality of A. bahrelghazali (KT12) was a grass-dominated ecosystem (likely savanna) with an unrated percentage of arboreal cover. Furthermore, the grass phytolith data support the existence of a (recurrent) Sahelian-like dry climate in northern Chad since at least 8 Ma. Therefore the local closed vegetation formations in the Djurab region at 7.5–7 Ma were sustained by aquatic systems (such as lakes or related rivers, marshes) rather than by extensive annual precipitation.



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The affinities of Homo floresiensis based on phylogenetic analyses of cranial, dental, and postcranial characters

Publication date: Available online 21 April 2017
Source:Journal of Human Evolution
Author(s): Debbie Argue, Colin P. Groves, Michael S.Y. Lee, William L. Jungers
Although the diminutive Homo floresiensis has been known for a decade, its phylogenetic status remains highly contentious. A broad range of potential explanations for the evolution of this species has been explored. One view is that H. floresiensis is derived from Asian Homo erectus that arrived on Flores and subsequently evolved a smaller body size, perhaps to survive the constrained resources they faced in a new island environment. Fossil remains of H. erectus, well known from Java, have not yet been discovered on Flores. The second hypothesis is that H. floresiensis is directly descended from an early Homo lineage with roots in Africa, such as Homo habilis; the third is that it is Homo sapiens with pathology. We use parsimony and Bayesian phylogenetic methods to test these hypotheses. Our phylogenetic data build upon those characters previously presented in support of these hypotheses by broadening the range of traits to include the crania, mandibles, dentition, and postcrania of Homo and Australopithecus. The new data and analyses support the hypothesis that H. floresiensis is an early Homo lineage: H. floresiensis is sister either to H. habilis alone or to a clade consisting of at least H. habilis, H. erectus, Homo ergaster, and H. sapiens. A close phylogenetic relationship between H. floresiensis and H. erectus or H. sapiens can be rejected; furthermore, most of the traits separating H. floresiensis from H. sapiens are not readily attributable to pathology (e.g., Down syndrome). The results suggest H. floresiensis is a long-surviving relict of an early (>1.75 Ma) hominin lineage and a hitherto unknown migration out of Africa, and not a recent derivative of either H. erectus or H. sapiens.



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Mechanisms of hemispheric lateralization: A replication study

Publication date: Available online 22 April 2017
Source:Cortex
Author(s): Kim C. Wende, Catherine Thiel, Jens Sommer, Frieder M. Paulus, Sören Krach, Andreas Jansen
It has been shown, using functional magnetic resonance imaging (fMRI), that hemispheric lateralization of brain activity depends on the requirements of the cognitive task performed during the processing of a sensory stimulus rather than on the intrinsic characteristics of that stimulus [Stephan et al. 2003, Science 301(5631): 384-6]. Task-dependent increase in the coupling of the anterior cingulate cortex (ACC), a region involved in cognitive control, and brain areas in the left prefrontal and right parietal cortex, respectively, regions involved in task execution, was proposed as the mechanism underlying this task-dependency of hemispheric lateralization. The aim of the present study was two-fold: First, we aimed for a conceptual replication of these findings in an independent sample of subjects. Second, we investigated the test-retest reliability of the imaging paradigm to assess whether the task can be used to capture reliable measures of inter-individual differences in hemispheric lateralization. We were able to confirm previous findings showing that hemispheric lateralization depends on the nature of the cognitive task rather than on the nature of the processed stimuli. The task-related brain activation patterns were highly reliable across sessions (as indicated by intraclass correlation coefficients, ICCs, ≥0.51). We could, however, not replicate previous results proposing task-dependent changes in the coupling between ACC and brain regions for task execution as the mechanism underlying hemispheric lateralization. This re-opens the question which mechanisms could determine the task-dependent functional asymmetries that were observed previously and replicated in this study.



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Impaired peripheral reaching and on-line corrections in patient DF: optic ataxia with visual form agnosia

Publication date: Available online 22 April 2017
Source:Cortex
Author(s): Stéphanie Rossit, Monika Harvey, Stephen H. Butler, Larissa Szymanek, Stéphanie Morand, Simona Monaco, Robert D. McIntosh
An influential model of vision suggests the presence of two visual streams within the brain: a dorsal occipito-parietal stream which mediates action and a ventral occipito-temporal stream which mediates perception. One of the cornerstones of this model is DF, a patient with visual form agnosia following bilateral ventral stream lesions. Despite her inability to identify and distinguish visual stimuli, DF can still use visual information to control her hand actions towards these stimuli. These observations have been widely interpreted as demonstrating a double dissociation from optic ataxia, a condition observed after bilateral dorsal stream damage in which patients are unable to act towards objects that they can recognize. In Experiment 1, we investigated how patient DF performed on the classical diagnostic task for optic ataxia, reaching in central and peripheral vision. We replicated recent findings that DF is remarkably inaccurate when reaching to peripheral targets, but not when reaching in free vision. In addition we present new evidence that her peripheral reaching errors follow the optic ataxia pattern increasing with target eccentricity and being biased towards fixation. In Experiments 2 and 3, for the first time we examined DF's on-line control of reaching using a double-step paradigm in fixation-controlled and free-vision versions of the task. DF was impaired when performing fast on-line corrections on all conditions tested, similarly to optic ataxia patients. Our findings question the long-standing assumption that DF's dorsal visual stream is functionally intact and that her on-line visuomotor control is spared. In contrast, in addition to visual form agnosia, DF also has visuomotor symptoms of optic ataxia which are most likely explained by bilateral damage to the superior parietal occipital cortex. We thus conclude that patient DF can no longer be considered as an appropriate single-case model for testing the neural basis of perception and action dissociations.



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Long-term effects of angiotensin-(1–7) on lipid metabolism in the adipose tissue and liver

Publication date: Available online 22 April 2017
Source:Peptides
Author(s): Carolina Campos Lima Moreira, Fabíola Cesário Lourenço, Érica Guilhen Mario, Robson Augusto Souza Santos, Leida Maria Botion, Valéria Ernestânia Chaves
The angiotensin (Ang) converting enzyme 2/Ang-(1–7)/Mas axis has been described to have a beneficial role on metabolic disorders. In the present study, the use of a transgenic rat model that chronically overexpresses Ang-(1–7) enabled us to investigate the chronic effects of this peptide on lipid accumulation in the liver and adipose tissue. The transgenic group showed a marked tendency toward increased expression of peroxisome proliferator-activated receptor-γ (PPARγ) and decreased lipoprotein lipase (LPL) expression and activity in epididymal adipose tissue. We also showed that Mas receptor-knockout mice had decreased PPARγ expression in adipose tissue, accompanied by an increase in LPL activity. These results confirm the regulation of adipose tissue LPL activity by Ang-(1–7) and suggest that this occurs independent of PPARγ expression. The reduced adiposity index of transgenic rats, due to the effect of Ang-(1–7), was accompanied by a decrease in lipogenesis. These findings suggest a direct effect of Ang-(1–7) on lipogenesis, independent of the stimulatory effect of insulin. Furthermore, the decreased concentration of triacylglycerol in the liver of transgenic rats may result from increased activity of cytosolic lipases and decreased fatty acid uptake from the adipose tissue, determined from fatty acid-binding protein expression, and hepatic de novo fatty acid synthesis, evaluated by fatty acid synthase expression. The data clearly show that Ang-(1–7) regulates lipid metabolism in the adipose tissue and liver.



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Instruments for evaluating pharmacotherapy intervention efficacy in violent and aggressive behavior and conduct disorder in youth

Publication date: Available online 22 April 2017
Source:Aggression and Violent Behavior
Author(s): Jessica L. Hambly, Sohil Khan, Brett McDermott, William Bor, Alison Haywood
There is a need to identify the most appropriate standardized instruments for research evaluating pharmacotherapy for youth with violent and aggressive behaviors. Youth violence and aggression are heterogeneous behaviors which differ depending on age and gender.Instruments used in randomised controlled trials evaluating efficacy of pharmacotherapy in conduct disorder and its comorbidities were reviewed for psychometric, administrative and practicality evidence. Evidence was rated on a 3-point scale, adapted from the Scientific Advisory Committee's Instrument Review Criteria.Of the nine included instruments, the Nisonger Child Behavior Rating Form (NCBRF), Conners' 3rd Edition, and Behavior Problems Inventory (BPI-01) were rated the highest for their psychometric properties. The Children's Aggression Scale (CAS), Aberrant Behavior Checklist (ABC) and Disruptive Behavior Disorder Rating Scale (DBDRS) were rated moderate, and the Child Behavior Checklist (CBCL), Modified Overt Aggression Scale (MOAS) and Swanson, Nolan, and Pelham Rating Scale (SNAP-IV) were rated lowest. The NCBRF, BPI-01 and CAS were the only instruments that could be used to measure both frequency and severity of aggressive behaviors. The CAS and MOAS featured the most items pertaining to violence and aggression.The broad-band scales, the NCBRF and Conners' 3rd Edition, rated highest for their psychometric properties, however their usefulness in youth violence and aggression research is limited. The heterogeneity of aggressive and violent behaviors, age, gender, functional level, situational context and the type of informant should be taken into account when considering an appropriate instrument. All items in the CAS and the MOAS can be used to measure violent and/or aggressive behaviors. Further research into the psychometric properties of the MOAS in violent and aggressive youth is required before its use can be recommended. The CAS was found to be the most psychometrically sound and useful instrument that exclusively measures aggressive behaviors in youth.

Graphical abstract

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