Voluntary finger movement in man: Cerebral potentials and theory

Three different brain potentials preceeding voluntary rapid finger flexion can be recorded from the skull surface by time reversed averaging. The early cortical activity preceding unilateral movement is bilateral and widespread (Bereitschaftspotential, BP). The same applies for the second potential (pre-motion positivity, PMP). Only the third potential (motor potential, MP) is unilateral and restricted to the contralateral motor cortex. In a total of 87 experiments with 39 subjects, the BP started on the average 750 ms (SD 360, SE 38.5) prior to rapid finger flexion. Its largest amplitude was found mid-parietally and averaged-5.3 V (SD 2.32, SE 0.4). Such amplitudes were found with averages of 800 and more movements per experiment. However, at the beginning of an experiment the BP is larger. Preceding finger movement, the BP was found bilaterally over the parietal and precentral cortex and over the midline. Over the frontal cortex, either no potential or positivity was recorded. In normal subjects, the BP always begins bilaterally and symmetrically. At parietal leads, it remains bilaterally-symmetrical. A slight contralateral preponderance begins about 400 ms prior to movement only over motor cortex, which becomes statistically significant at 150 ms. When comparing the parietal BP amplitude with the precentral amplitude on the ipsilateral side, where no superposition of the MP occurs, there is more negativity parietally than precentrally, although the parietal skull is about 11% thicker than the precentral. The BP is a negative shift of the cortical DC potential probably representing a preparatory process in the dendritic network of those cortical areas that are involved in the intended movement.The PMP is the next potential occurring 90–80 ms ( , SD 34.2, SE 2.95) prior to the first action potential in the contracting muscle (EMG). It was found in 85% of our subjects. The PMP has at its maximum, mid-parietally, a mean amplitude of +1.7 V (SD 1.6, SE 0.28). Like the BP, the PMP is bilateral and widespread in parietal and precentral leads of both sides and in the midline with a maximum at the anterior parietal region, despite the parietal skull being thicker than precentral. The short and the relatively constant onset time suggests that the PMP might reflect cortical activity (motor command) related to initiation of the tactually guided rapid finger movement under study.The MP starting 60–50 ms ( , SD 19.4, SE 3.1) prior to first activity in the agonist EMG is the last potential to occur and is the only unilateral potential: its localisation is limited to the hand area of the motor cortex contralateral to the moving finger. In bipolar recordings, contralateral versus ipsilateral precentral or contralateral precentral versus vertex, it appears as a sharp additional negativity. This additional negativity averaged-1.3 V (SD 0.64, SE 0.08). The MP reflects the motor cortical activity immediately preceding the movement.After movement onset, a complex potential is recorded, that is also seen with passive finger movement, largely representing a somatosensory (proprioceptive) evoked response. The possible meaning of the movement-related potentials is discussed in relation to a theory of central motor function.Supported by the Deutsche ForschungsgemeinschaftHabilitationsschrift of L.D. submitted to the Faculty of Clinical Medicine, University of Ulm (1974)     

Genomic divergence of zebu and taurine cattle identified through high-density SNP genotyping

Background

Natural selection has molded evolution across all taxa. At an arguable date of around 330,000 years ago there were already at least two different types of cattle that became ancestors of nearly all modern cattle, the Bos taurus taurus more adapted to temperate climates and the tropically adapted Bos taurus indicus. After domestication, human selection exponentially intensified these differences. To better understand the genetic differences between these subspecies and detect genomic regions potentially under divergent selection, animals from the International Bovine HapMap Experiment were genotyped for over 770,000 SNP across the genome and compared using smoothed F_ST. The taurine sample was represented by ten breeds and the contrasting zebu cohort by three breeds.

Results

Each cattle group evidenced similar numbers of polymorphic markers well distributed across the genome. Principal components analyses and unsupervised clustering confirmed the well-characterized main division of domestic cattle. The top 1% smoothed F_ST, potentially associated to positive selection, contained 48 genomic regions across 17 chromosomes. Nearly half of the top F_ST signals (n = 22) were previously detected using a lower density SNP assay. Amongst the strongest signals were the BTA7:~50 Mb and BTA14:~25 Mb; both regions harboring candidate genes and different patterns of linkage disequilibrium that potentially represent intrinsic differences between cattle types. The bottom 1% of the smoothed F_ST values, potentially associated to balancing selection, included 24 regions across 13 chromosomes. These regions often overlap with copy number variants, including the highly variable region at BTA23:~24 Mb that harbors a large number of MHC genes. Under these regions, 318 unique Ensembl genes are annotated with a significant overrepresentation of immune related pathways.

Conclusions

Genomic regions that are potentially linked to purifying or balancing selection processes in domestic cattle were identified. These regions are of particular interest to understand the natural and human selective pressures to which these subspecies were exposed to and how the genetic background of these populations evolved in response to environmental challenges and human manipulation.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-14-876) contains supplementary material, which is available to authorized users.     

Assessing signatures of selection through variation in linkage disequilibrium between taurine and indicine cattle

Background

Signatures of selection are regions in the genome that have been preferentially increased in frequency and fixed in a population because of their functional importance in specific processes. These regions can be detected because of their lower genetic variability and specific regional linkage disequilibrium (LD) patterns.

Methods

By comparing the differences in regional LD variation between dairy and beef cattle types, and between indicine and taurine subspecies, we aim at finding signatures of selection for production and adaptation in cattle breeds. The VarLD method was applied to compare the LD variation in the autosomal genome between breeds, including Angus and Brown Swiss, representing taurine breeds, and Nelore and Gir, representing indicine breeds. Genomic regions containing the top 0.01 and 0.1 percentile of signals were characterized using the UMD3.1 Bos taurus genome assembly to identify genes in those regions and compared with previously reported selection signatures and regions with copy number variation.

Results

For all comparisons, the top 0.01 and 0.1 percentile included 26 and 165 signals and 17 and 125 genes, respectively, including TECRL, BT.23182 or FPPS, CAST, MYOM1, UVRAG and DNAJA1.

Conclusions

The VarLD method is a powerful tool to identify differences in linkage disequilibrium between cattle populations and putative signatures of selection with potential adaptive and productive importance.     

Humpback whales interfering when mammal‐eating killer whales attack other species: Mobbing behavior and interspecific altruism?

Humpback whales (Megaptera novaeangliae) are known to interfere with attacking killer whales (Orcinus orca). To investigate why, we reviewed accounts of 115 interactions between them. Humpbacks initiated the majority of interactions (57% vs. 43%; n = 72), although the killer whales were almost exclusively mammal‐eating forms (MEKWs, 95%) vs. fish‐eaters (5%; n = 108). When MEKWs approached humpbacks (n = 27), they attacked 85% of the time and targeted only calves. When humpbacks approached killer whales (n = 41), 93% were MEKWs, and ≥87% of them were attacking or feeding on prey at the time. When humpbacks interacted with attacking MEKWs, 11% of the prey were humpbacks and 89% comprised 10 other species, including three cetaceans, six pinnipeds, and one teleost fish. Approaching humpbacks often harassed attacking MEKWs (≥55% of 56 interactions), regardless of the prey species, which we argue was mobbing behavior. Humpback mobbing sometimes allowed MEKW prey, including nonhumpbacks, to escape. We suggest that humpbacks initially responded to vocalizations of attacking MEKWs without knowing the prey species targeted. Although reciprocity or kin selection might explain communal defense of conspecific calves, there was no apparent benefit to humpbacks continuing to interfere when other species were being attacked. Interspecific altruism, even if unintentional, could not be ruled out.     

Impact of temperature on Na2Sr(PO4)F:Eu3+ phosphor

In this article, we report the synthesis of Na₂Sr_1‐x(PO₄)F:Eu_x phosphor via a combustion method. The influence of different annealing temperatures on the photoluminescence properties was investigated. The phosphor was excited at both 254 and 393 nm. Na₂Sr_1‐x(PO₄)F:Eu_x³⁺ phosphors emit strong orange and red color at 593 and 612 nm, respectively, under both excitation wavelengths. Na₂Sr_1‐x(PO₄)F:Eu_x³⁺ phosphors annealed at 1050°C showed stronger emission intensity compared with 600, 900 and 1200°C. Moreover, Na₂Sr_1‐x(PO₄)F:Eu_x³⁺ phosphor was found to be more intense when compared with commercial Y₂O₃:Eu³⁺ phosphor. Copyright © 2013 John Wiley & Sons, Ltd.     

Dialect change in resident killer whales: implications for vocal learning and cultural transmission

Variation in vocal signals among populations and social groups of animals provides opportunities for the study of the mechanisms of behavioural change and their importance in generating and maintaining behavioural variation. We analysed two call types made by two matrilineal social groups of resident killer whales, Orcinus orca, over 12-13 years. We used a neural network-based index of acoustic similarity to identify mechanisms of call differentiation. A test for structural modification of the calls detected significant changes in one call type in both groups, but not in the other. For the modified call type, the rate of divergence between the two groups was significantly lower than the rate of modification within either group showing that calls were modified in a similar fashion in the two groups. An analysis of structural parameters detected no strong directionality in the change. The pattern of call modification could have been caused by maturational changes to the calls or, if killer whale dialects are learned behavioural traits, cultural drift in the structure of the calls together with horizontal transmission of modifications between the two groups. Such vocal matching between members of different matrilines would suggest that vocal learning is not limited to vertical transmission from mother to offspring, which has important implications for models of gene-culture coevolution. Copyright 2000 The Association for the Study of Animal Behaviour.     

Geographic variation in the time‐frequency characteristics of high‐frequency whistles produced by killer whales (Orcinus orca)

Investigating intraspecific variation in acoustic signals can indicate the extent of isolation and divergence between populations and adaptations to local environments. Here we analyze the variation in killer whale high‐frequency (>17 kHz) whistles recorded off Norway, Iceland, and in the North Pacific. We used a combination of methods including multivariate comparisons of spectral and temporal parameters and categorization of contours to types. Our results show that spectral and temporal characteristics of high‐frequency whistles recorded in the North Pacific show significant differences from whistles recorded in the Northeast Atlantic, being generally stereotyped, lower in frequency, and slightly longer in duration. Most high‐frequency whistles from the North Pacific were downsweeps, whereas this was one of the least common types recorded in the Northeast Atlantic. The repertoire of whistles recorded in Norway was similar to Iceland, but whistles produced in Norway had significantly lower maximum frequency and frequency range. Most methods were able to discriminate between whistles of the North Pacific and the Northeast Atlantic, but were unable to consistently distinguish whistles from Iceland and Norway. This suggests that macro‐ and microgeographic differences in high‐frequency whistles of killer whales may reflect historical geographic isolation between ocean basins and more recent divergence between adjacent populations.