145 research outputs found
A step towards non-invasive characterization of the human frontal eye fields of individual subjects
No full textBackground: Identifying eye movement related areas in the frontal lobe has a long history, with microstimulation in monkeys producing the most clear-cut results. For humans, however, there is still no consensus about the location and the extent of the frontal eye field (FEF). There is also no simple non-invasive method for unambiguously defining the FEF in individual subjects, a prerequisite for clinical applications. Here we explore the use of magnetoencephalography (MEG) for the non-invasive identification and characterization of FEF activity in an individual subject.Methods: We mapped human brain activity before, during and after saccades by applying tomographic analysis to MEG data. Statistical parametric maps and circular statistics produced plausible FEF loci, but no unambiguous definition for individual subjects. Here we first computed the spectral decomposition and correlation with electrooculogram (EOG) of the tomographic brain activations. For each of these two measures statistical comparisons were made between different saccades.Results: In this paper, we first review the frontal cortex activations identified in earlier animal and human studies and place the putative human FEFs in a well-defined anatomical framework. This framework is then used as reference for describing the results of new Fourier analysis of the tomographic solutions comparing active saccade tasks and their controls. The most consistent change in the dorsal frontal cortex was at the putative left FEF, for both saccades to the left and right. The asymmetric result is consistent with the 1-way callosal traffic theory. We also showed that the new correlation analysis had its most consistent change in the contralateral putative FEF. This result was obtained for EOG latencies before saccade onset with delays of a few hundreds of milliseconds (FEF activity leading the EOG) and only for visual cues signaling the execution of a saccade in a previously defined saccade direction.Conclusions: The FEF definition derived from microstimulation describes only one of the areas in the dorsal lateral frontal lobe that act together to plan, prepare and execute a saccade. The definition and characterization of these areas in an individual subject can be obtained from non-invasive MEG measurements.<br/
MEG identifies dorsal medial brain activations during sleep
No full textAll sleep stages contain epochs with high-amplitude electrophysiological phasic events, alternating with quieter “core periods.” High-amplitude and core state properties cannot be disentangled with PET and fMRI. Here from high temporal resolution magnetoencephalography data, regional changes in neuronal activity were extracted during core periods in different frequency bands for each sleep stage and waking. We found that gamma-band activity increases in precuneus during light sleep (stages 1/2) and in the left dorso–medial prefrontal cortex (L-DMPFC) during deep sleep (stages 3/4). The L-DMPFC activated area expands laterally during rapid eye movement (REM) sleep, into a volume of about 5 cm3 bounded by regions attributed to Theory of Mind (ToM) and default systems, both involved in introspection. Gamma band activity in this area was higher during REM sleep than other sleep stages and active wakefulness. There is a tantalizing correspondence between increased wide-band activity (dominated by low frequencies) in early non-REM (NREM) sleep stages and increases in gamma-band activity in late NREM and REM periods that we attribute to a lateral disinhibition mechanism. The results provide a description of regional electrophysiological changes in awake state, light and deep sleep, and REM sleep. These changes are most pronounced in the L-DMPFC and the other areas around the dorsal midline that are close to, but do not overlap with areas of the default and ToM systems, suggesting that the DMPFC, particularly in the left hemisphere, plays an important role in late NREM stages, in REM and possibly in dreaming.<br/
Interocular yoking in human saccades examined by mutual information analysis
No full textBackground: Saccadic eye movements align the two eyes precisely to foveate a target. Trial-by-trial variance of eye movement is always observed within an identical experimental condition. This has often been treated as experimental error without addressing its significance. The present study examined statistical linkages between the two eyes’ movements, namely interocular yoking, for the variance of eye position and velocity.Methods: Horizontal saccadic movements were recorded from twelve right-eye-dominant subjects while they decided on saccade direction in Go-Only sessions and on both saccade execution and direction in Go/NoGo sessions. We used infrared corneal reflection to record simultaneously and independently the movement of each eye. Quantitative measures of yoking were provided by mutual information analysis of eye position or velocity, which is sensitive to both linear and non-linear relationships between the eyes’ movements. Our mutual information analysis relied on the variance of the eyes movements in each experimental condition. The range of movements for each eye varies for different conditions so yoking was further studied by comparing GO-Only vs. Go/NoGo sessions, leftward vs. rightward saccades.Results: Mutual information analysis showed that velocity yoking preceded positional yoking. Cognitive load increased trial variances of velocity with no increase in velocity yoking, suggesting that cognitive load may alter neural processes in areas to which oculomotor control is not tightly linked. The comparison between experimental conditions showed that interocular linkage in velocity variance of the right eye lagged that of the left eye during saccades.Conclusions: We conclude quantitative measure of interocular yoking based on trial-to-trial variance within a condition, as well as variance between conditions, provides a powerful tool for studying the binocular movement mechanism<br/
Detection and characterization of Bartonella species in Western Australia
No full textIn this study, the prevalence and genetic diversity of Bartonella species in various arthropod vectors from both wild and domestic animals in Australia were investigated using nested-polymerase chain reaction (PCR) assays and multilocus sequence analysis (MLSA). Previous studies on Bartonella species in Australia have been confined to mammalian hosts, including humans, cats, native rodents and eastern grey kangaroos. However, little is known about the status of bartonellae in arthropod vectors, which is essential in understanding the transmission dynamics of the organisms.
To facilitate the investigation, ectoparasites (ticks and fleas) were collected from both wild and domestic animals from various locations in Australia. All ectoparasites were screened for Bartonella species using newly designed nested-PCRs targeting the gltA gene (citrate synthase) and the ribosomal internal transcribed spacer (ITS) region, developed as part of the present study. Multilocus sequence analysis of the 16S ribosomal RNA (rRNA), citrate synthase (gltA),cell division protein (ftsZ) and RNA polymerasebeta-subunit (rpoB) genes and the ribosomal ITS region was applied to identify and confirm the status of all Bartonella species identified in this study. Multilocus sequence analysis of the cytochrome oxidase subunit I (COI) and 18S ribosomal RNA (rRNA) genes of flea vectors harbouring a diversity of Bartonella species were analysed to characterize the extent of genetic diversity in the flea vectors and to elucidate vector-parasite associations.
A phylogenetic analysis of the 5 concatenated loci identified 3 novel Bartonella species in flea vectors from marsupials in Western Australia. Candidatus Bartonella antechini was detected in fleas (Acanthopsylla jordani) from mardos (Antechinus flavipes - also called the yellow-footed antechinus). Candidatus Bartonella woyliei was detected in fleas (Pygiopsylla hilli), from brush-tailed bettongs (Bettongia penicillata– also called woylies), and Candidatus Bartonella bandicootii was detected in Pygiopsylla tunneyi fleas from western barred bandicoots (Perameles bougainville). Furthermore, a potential novel species, Bartonella sp. strain WC2 was detected in ticks (Ixodes australiensis) from woylies based on the criterion of a genetic similarity of less than 96% of the gltA locus compared with other validated Bartonella species. In the present study, the grouping of marsupial-derived Bartonella species confirmed the existence of a marsupial cluster of Bartonella species in Australia, which appears to have evolved separately to Bartonella species in other mammals.
The detection of the known zoonotic Bartonella species, B. henselae and B. clarridgeiae in red foxes and their fleas (Ctenocephalides felis), indicated that red foxes could be an important reservoir of Bartonella infections for other animals and humans in the same geographical locality. Bartonella henselae and B. clarridgeiae DNA were also detected from fleas collected from pet cats in the same area. The genetic association of these zoonotic Bartonella species detected in wildlife and pet animals has demonstrated and confirmed the distribution of zoonotic Bartonella species in fleas from both wild and domestic animals in this region and a possible ecological association between the animal species.
The genetic clustering of Bartonella species and flea vectors with their Australian fauna hosts suggests co-evolution of hosts, fleas and Bartonella species in Australia. In conclusion, the close association between Australian fauna, Australian fleas and Bartonella species suggests adaptation by Bartonella species to a specific ecological niche, comprised of specific mammalian hosts and specific flea vectors in particular environments
Beyond ‘Needy’ Individuals: Conceptualizing Information Behavior
No full textUnderstanding information users and their behavior is a question of central importance for information
research and practice. The paper challenges several aspects of existing approaches to understanding information behavior, including: the focus on individual cognition at the expense of social and affective factors; the construction of information users as defined by their areas of ignorance and uncertainty, rather than their expertise; and the focus on purposive rather than non-purposive information behavior. It argues that only by addressing these weaknesses and developing new research strategies and theoretical frameworks which focus attention on the social processes and relationships which underpin users’ information behavior can we hope to develop a truly holistic understanding of the relationship between people and information. The paper uses the author’s study of information behavior researcher’s constructions of an author (Brenda Dervin) to illustrate how a social constructivist approach can both build on existing approaches to information behavior research and address some of their weaknesses. It argues that social constructivist approaches provide a theoretical lens through which information researchers can gain a clearer picture of information users not as ‘needy’ individuals to be ‘helped’, but as social beings, experts in their own life-worlds
Indo-European vocabulary in Old Chinese : a new thesis on the emergence of Chinese language and civilization in the late Neolithic age
No full textThis study is a much expanded version of the paper I read at the XXXII International Congress for Asian and North African Studies on August 28, 1986 in Hamburg (Germany). Contents 1. Recent developments in the field of historical linguistics 2. Monosyllabic structure of Chinese words and Indo-European stems 3. Tonal accents of Middle Chinese 4. Preliminaries on the comparison of consonants and vowels 5. Some IE stems corresponding to Chinese words of entering tone 6. Middle Chinese tones and final consonants of IE stems 7. Some IE stems corresponding to Chinese words of rising tone 8. Some IE stems corresponding to Chinese words of vanishing tone 9. Some IE stems corresponding to Chinese words of level tone 10. Reconstruction of Middle Chinese vocalism according to Yün-ching 11. Old Chinese vocalism 12. Vocalic correspondences between Chinese and IE 13. Initials of Old Chinese 14. Initial consonant clusters in Old Chinese as seen from IE-stems 15. Proximity of Chinese to Germanic 16. Relation of Old Chinese to neighboring languages 17. Emergence of Chinese Empire and language in the middle of the third millennium B.C. Appendix * Abbrevations * Bibliography * Rhyme Tables of Early Middle Chinese (600) * Rhyme Tables of Early Mandarin (1300) * Word Index o English o Pinyin In 1786, just over two hundred years ago, comparative historical linguistics was born, when Sir William Jones (1746-1794) discovered the relationship between Old-Indian Sanskrit, Greek, and Latin. Since then, the emerging Indo-European philology has thrown much light on the early history of mankind in Eurasia. During the past two hundred years, many suggestions were also made in regard to relationships of Indo-European to other languages such as Semitic, Altaic, Austronesian, Korean etc., but Indo-Europeanists commonly rejected such attempts for want of convincing evidence. As to Chinese, Joseph Edkins was the first to advance the thesis of its proximity to Indo-European. In his work China's Place in Philology. An Attempt to show that the Language of Europe and Asia have a Common Origin (1871) he presented a number of Chinese words similar to those of Indo-European. In his time, Edkins' thesis seemed bold and extravagant. But today, more than a hundred years later, we are in a much better position to carry out a comprehensive and well-founded comparative study. Since the end of the nineteenth century, many Sinologists have been engaged in reconstruction of the mediaeval and archaic readings of Chinese characters. Among them, Karlgren (1889-1978) was the most successful, and in 1940 he published a comprehensive phonological and etymological dictionary entitled Grammata Serica. In the meantime, the Indo-Europeanists Alois Walde (1869-1924) and Julius Pokorny (1887-1970) were devoting themselves to the compilation of a useful etymological dictionary. The result was the Indogermanisches Etymologisches Wörterbuch by Pokorny (1959) which provides a solid basis for our lexical comparisons. Soon thereafter, some Sinologists made use of the two dictionaries by Karlgren and Pokorny to compare Chinese and Indo-European words. In 1967, an unaffiliated German scholar, Jan Ulenbrook, published an article "Einige Übereinstirnrnungen zwischen dem Chinesischen und dem Indogermanischen", in which he claimed that 57 words are related. Shortly afterwards, Tor Ulving of the University of Goteborg, Sweden, wrote a review of this article framing the title as a question: "Indo-European elements in Chinese?" While working on his thesis on word families in Chinese, Ulving compiled for his own use two dictionaries: "Archaic Chinese - English" and "English - Archaic Chinese", and discovered thereby 238 Chinese words similar to Indo-European roots. In spite of this considerable number of word equivalents, however, Mr. Ulving became discouraged and, as he told me in his letter of April, 1986, has given up his researches in this field. The skepticism, common among Indo-Europeanists in regard to comparative studies with other languages, is largely based on the dogmatic opinion that only morphology is relevant but not vocabulary. Since the typology of Chinese seems to preclude a cognate relation to Indo-European, they are inclined to discard any lexical correspondences as merely accidental or onomatopoetic. Besides, prehistorical contacts and mixtures between these languages seem not conceivable, as the Indo-Europeans are supposed to have originated in Northern Europe or at best in the Central Asian steppe, thousands of miles away from East Asia. Hence, any research into a relationship between Old Chinese and Indo-European languages would be but futile from the outset. Yet there are also opposing views among Indo-Europeanists. Investigations into Germanic languages and the oldest Indo-European language, Hittite, led some of them to a critical revision of the prevailing conception about a Proto-Indo-European. Hermann Hirt (1934) for instance states: "Inflexion of Indo-European languages is due to a relatively late development, and its correct comprehension can be achieved only by proceeding from the time of non-inflexion." And Carl Karstien (1936) holds the opinion that "Chinese corresponds most ideally to the hypothetic prototype of Indo-European." Regarding vocabulary, there are striking similarities in the monosyllabic structure of the basic words. In modern German and English, all the words of everyday speech are monosyllabic and their stereotypical structure is: initial consonant(s) + vowel(s) + final consonant(s). The same word structure is valid for Chinese as well. It is fundamentally different from the disyllabic structure of Altaic words and from the triconsonantal-disyllabic structure of Semitic words. Characteristic of the monosyllabic word structure is, besides, the complexity of the syllable nucleus, which consists of different vowels and vowel clusters in contrast to the monophthongal vocalism of polysyllabic words. Another objection raised to comparisons between Chinese and Indo-European is the existence of tonal accents in Chinese. Since most modern Indo-European languages have only expiratory accents, Chinese is considered to be a highly exotic language. Yet, even in Chinese, the use of tonal accents as a means of lexical differentiation is a result of comparatively recent development in the long history of Chinese language, the earliest monuments of which date back to 1300 B.C. (cf. Chang 1970, p.21). Unknown to Old Chinese, the existence of tonal accents was for the first time mentioned in the 5th century by Shen Yüeh (441-513). In Middle Chinese (Mch.) there were four tone categories: A P'ing-sheng 平 a level tone (which developed into Mandarin tone 1 or 2). B Shang-sheng 上 a rising tone (Mandarin tone 3). C Ch'u-sheng 去 a vanishing, i.e. falling tone (Mandarin tone 4). D Ju-sheng 入 an entering tone with a staccato effect, the word being abruptly stopped by a final consonant -p, -t, -k. (In Early Mandarin the words of this tone lost their final consonant and were distributed among the tones 2, 3 and 4, respectively according to the phonation of initials). In Middle Chinese, words of the entering tone were the only group which still preserved the final stops and therefore a close syllabic structure. So they are most appropriate for convincing comparisons with monosyllabic Indo-European word stems. The final stops -p, -t, -k of the entering tone are nowadays still extant in daily speech of several dialects in South China as well as in Chinese borrowings in Japanese, Vietnamese and Korean. As a speaker of a Taiwan dialect of Minnan origin, I could immediately identify some Indo-European stems with corresponding Chinese words. Besides, the command of Japanese and German was also a great help for this study. In the following lists I have chosen a number of Indo-European stems which are phonetically and semantically equivalent to Chinese words. Correspondences in initial and final consonants refer to the points of articulation, thus we have equations: IE labials = Old Chinese labials, IE dentals = dentals, IE l, r = dentals (cf. p. 31); Ø, i (final and medial) IE velars = velars and laryngeals, and occasionally (the so-called "satem"-forms) IE velars = dental sibilants and affricates. Regarding the manner of articulation, there are no regular correspondences between Indo-European and Chinese consonants like Grimm's law which is valid among Indo-European dialects to a certain extent. But this is not astonishing, since in Old Chinese the alternation of initials in voicing was a conventional means of creating new words from one basic form. The rules of vocalic correpondences among Indo-European dialects are quite complex. Vowels permanently change their qualities from one language to another, and from time to time within one language also, as is well known from the history of English pronunciations. Generally, the vocalism of Old Greek is taken as the standard for Proto-Indo-European. Old Chinese vowels corresponds nearly (cf. p. 30), but the details about the reconstruction of Middle and Old Chinese vocalism will be treated later (pp. 26-30). For the moment, it is necessary to notice in advance that the stem of ablauting Germanic verbs is the form of preterite or noun, rather than that of infinitive as assumed hitherto. Therefore, in some cases I must slightly modify the basic vowel of verbal stems given in Pokorny, in order to get better basis for comparison. As Old Chinese verbs were non-flexional, they might probably have preserved the original vowel the best
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