To see the other types of publications on this topic, follow the link: Synchrony.
Dissertations / Theses on the topic 'Synchrony'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Synchrony.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Hasan, Rasha. "Hybrid synchrony virtual networks." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2017. http://tede2.pucrs.br/tede2/handle/tede/7344.
Full textAbstract:
Submitted by Caroline Xavier (caroline.xavier@pucrs.br) on 2017-06-08T18:15:48Z
No. of bitstreams: 1
TES_RASHA_HASAN_COMPLETO.pdf: 5197991 bytes, checksum: bfd855e20678be1fe11d1731c4cbc317 (MD5)Made available in DSpace on 2017-06-08T18:15:48Z (GMT). No. of bitstreams: 1 TES_RASHA_HASAN_COMPLETO.pdf: 5197991 bytes, checksum: bfd855e20678be1fe11d1731c4cbc317 (MD5) Previous issue date: 2017-01-16
Nas ?ltimas tr?s d?cadas de pesquisa em Sistemas Distribu?dos (SDs), um aspecto central discutido ? o de sincronia. Com um sistema ass?ncrono, n?o fazemos suposi??es sobre velocidades de execu??o de processos e / ou atrasos de entrega de mensagens; Com um sistema s?ncrono, fazemos suposi??es sobre esses par?metros [Sch93b]. Sincronismo em SDs impacta diretamente a complexidade e funcionalidade de algoritmos tolerantes a falhas. Uma infra-estrutura s?ncrona contribui para o desenvolvimento de sistemas mais simples e fi?veis, mas tal infra-estrutura ? muito cara e ?s vezes nem sequer vi?vel de implementar. Uma infra-estrutura totalmente ass?ncrona ? mais realista, mas alguns problemas foram mostrados como insol?veis em tal ambiente atrav?s do resultado de impossibilidade por Fischer, Lynch e Paterson [FLP85]. As limita?es tanto em ambientes totalmente s?ncronos como totalmente ass?ncronos levaram ao desenvolvimento de sistemas distribu?dos como s?ncronia parcial [CF99, Ver06]. Em um estudo de funcionalidade de sistemas distribu?dos s?ncronos parciais e de propriedades de Redes Virtuais (RVs), descobrimos que existem v?rios desafios para este tipo de sistemas que podem ser resolvidos com RVs devido ?s propriedades que a virtualiza??o traz. Por exemplo a) partilha de recursos fornecida por RVs permite diminuir o custo ao partilhar a parte s?ncrona da infra-estrutura f?sica, b) isolamento fornecido por a natureza da RVs, isso pode beneficiar os SDs coexistentes na mesma infra-estrutura f?sica que exigem certo n?vel de isolamento,c) resili?ncia garantido atrav?s do processo de aloca??o de recursos de Redes Virtuais, isso permite alocar recursos de reposi??o ao lado dos prim?rios para redes virtuais que exigem garantias de disponibilidade, por exemplo, SDs tolerantes a falhas. Em nosso trabalho, argumentamos que as RVs e um adequado processo de aloca??o de recursos das RVs oferecem um ambiente adequado para executar aplicativos distribu?dos com sincronia parcial. Isto levou ? abstra??o de um novo tipo de RVs: As Redes Virtuais com sincronia h?brida (RVSHs). Nesta tese, apresentamos a id?ia geral das Redes Virtuais com sincronia h?brida motivado pelos SDs com s?ncronia h?brida, e dividimos nosso trabalho em duas partes: a) Espa?oRVSHs propostos pelo SDs com sincronia h?brida em espa?o, e b) Tempo-RVSHs propostos pelo SDs com sincronia h?brida em tempo. No SDs com s?ncronia h?brida em espa?o, a infraestrutura ? composta de subconjuntos de componentes s?ncronos e ass?ncronos, e cada um desses subconjuntos mant?m seu status de sincronia atrav?s do tempo (i.e., os subconjuntos s?ncronos permanecem s?ncronos e os ass?ncronos permanecem ass?ncronos). No SDs com s?ncronia h?brida em tempo, a infra-estrutura ? composta de subconjuntos de n?s e la?os que podem alternar seu status de sincronia atrav?s do tempo (i.e., os componentes se comportam de forma s?ncrona durante os intervalos de tempo e de forma ass?ncrona durante outros intervalos de tempo). As principais contribui??es desta tese s?o: a) caracterizam os RVSHs em seus dois tipos Espa?o-RVSHs e Tempo-RVSHs para refletir tanto a natureza de sincronia em espa?o e em tempo; b) propor uma estrutura adequada para o processo de aloca??o de recursos para ambos Espa?o-RVSHs e Tempo-RVSHs, e c) fornecer uma avalia??o dos modelos propostos para RVSHs.
In the last three decades of research in Distributed Systems (DSs), one core aspect discussed is the one of synchrony. \Vith an asynchronous system, we make no assumptions about process execution speeds andj or message delivery delays; with a synchronous system, we do make assumptions about these parameters [Sch93b]. Synchrony in DSs impacts directly the complexity and functionality of fault-tolerant algorithms. Although a synchronous infrastructure contributes towards the development of simpler and reliable systems, yet such an infrastructure is too expensive and sometimes even not feasible to implemento On the other hand, a fully asynchronous infrastructure is more realistic, but some problems were shown to be unsolvable in such an environment through the impossibility result by Fischer, Lynch and Paterson [FLP85]. The limitations in both fully synchronous or fully asynchronous environments have led to the development of partial synchronous distributed systems [CF99, Ver06]. In a study of partial synchronous distributed systems functionality, and of Virtual Networks (VNs) properties, we found that there are several challenges for this kind of systems that can be solved with VNs due to the properties that virtualization brings. For example a) resources sharing provided by VNs allows decreasing the cost when sharing the synchronous portion of the physical infrastructure, b) isolation provided by the VNs nature can benefit the coexistent DSs on same physical infrastructure that demand certain leveI of isolation, c) resilience guaranteed through the Virtual Networks Embedding (VNE) process that allows allocating spare resources beside the primary ones for virtual networks that require availability guarantees, for example fault tolerant DSs. In our work, we argue that VNs and a suitable VN embedding process offer suitable environment for running distributed applications with partial synchrony. This has led to the abstraction of new type of VNs: The Hybrid Synchrony Virtual Networks (HSVNs). In this thesis, we introduce the general idea of Hybrid Synchrony Virtual Networks (HSVNs) motivated by the hybrid synchronous DSs, and we branch our work into two branches: a) Space-HSVNs addressed to spatial hybrid synchronous DSs, and b) TimeHSVNs addressed to the time hybrid synchronous DSs. In spatial hybrid synchronous DSs, the hybrid synchronous physical infrastructure is composed of subsets of synchronous and asynchronous components, and each of these subsets maintains its synchrony status through time (i.e., synchronous subsets remain synchronous and asynchronous ones remain asynchronous). In time hybrid synchronous DSs, the hybrid synchronous physical infrastructure is composed of subsets of nodes and links that can alternate their synchrony status through time (i.e., the components behave synchronously during time intervals, and asynchronously during other time intervals). The main contributions of this thesis are: a) characterize the HSVNs in its two types Space-HSVNs and Time-HSVNs to reflect both the synchrony space-variant and time-variant nature ofDSs; b) propose a suitable embedding framework for both Space-HSVNs and TimeHSVNs, and c) provide an evaluation of the embedding mo deIs addressed to the HSVNs.
2
Chen, Y. "Formal methods for global synchrony." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365295.
Full text
3
al, Azad Abul Kalam. "Nonlinear synchrony dynamics of neuronal bursters." Thesis, University of Exeter, 2009. http://hdl.handle.net/10036/96226.
Full textAbstract:
We study the appearance of a novel phenomenon for coupled identical bursters: synchronized bursts where there are changes of spike synchrony within each burst. The examples we study are for normal form elliptic bursters where there is a periodic slow passage through a Bautin (codimension two degenerate Andronov-Hopf) bifurcation. This burster has a subcritical Andronov-Hopf bifurcation at the onset of repetitive spiking while the end of burst occurs via a fold limit cycle bifurcation. We study synchronization behavior of two Bautin-type elliptic bursters for a linear direct coupling scheme as well as demonstrating its presence in an approximation of gap-junction and synaptic coupling. We also find similar behaviour in system consisted of three and four Bautin-type elliptic bursters. We note that higher order terms in the normal form that do not affect the behavior of a single burster can be responsible for changes in synchrony pattern; more precisely, we find within-burst synchrony changes associated with a turning point in the spontaneous spiking frequency (frequency transition). We also find multiple synchrony changes in similar system by incorporating multiple frequency transitions. To explain the phenomenon we considered a burst-synchronized constrained model and a bifurcation analysis of the this reduced model shows the existence of the observed within-burst synchrony states. Within-burst synchrony change is also found in the system of mutually delaycoupled two Bautin-type elliptic bursters with a constant delay. The similar phenomenon is shown to exist in the mutually-coupled conductance-based Morris-Lecar neuronal system with an additional slow variable generating elliptic bursting. We also find within-burst synchrony change in linearly coupled FitzHugh-Rinzel 2 3 elliptic bursting system where the synchrony change occurs via a period doubling bifurcation. A bifurcation analysis of a burst-synchronized constrained system identifies the periodic doubling bifurcation in this case. We show emergence of spontaneous burst synchrony cluster in the system of three Hindmarsh-Rose square-wave bursters with nonlinear coupling. The system is found to change between the available cluster states depending on the stimulus. Lyapunov exponents of the burst synchrony states are computed from the corresponding variational system to probe the stability of the states. Numerical simulation also shows existence of burst synchrony cluster in the larger network of such system.
4
Jackson, Andrew. "Synchrony in the primate motor system." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404940.
Full text
5
Nalon, ClaÌudia. "Resolution for synchrony and no learning." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402269.
Full text
6
Hayward, Guy Daniel. "Singing as one : community in synchrony." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708494.
Full text
7
Campbell, Shannon R. "Synchrony and desynchrony in neural oscillators /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487945744574556.
Full text
8
Reyna, Barbara. "Mother-Infant Synchrony during Infant Feeding." VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/157.
Full textAbstract:
MOTHER-INFANT SYNCHRONY DURING INFANT FEEDING By Barbara A. Reyna, PhD A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University. Virginia Commonwealth University, 2010. Major Director: Rita H. Pickler, PhD Endowed Nursing Alumni Professor Department of Family and Community Health Nursing, School of Nursing Synchrony between a mother and her infant is fundamental to their developing relationship. Feeding is an essential activity that provides an opportunity for interaction between a mother and her infant and may lead to synchronous interaction. The purpose this study was to develop and test a coding system, the Maternal-Infant Synchrony Scale (MISS), for assessing synchrony of feeding interaction between a mother and her preterm infant. The secondary aims were to: (1) describe mother and preterm infant synchrony during feeding; (2) examine mother-infant synchrony during feeding over time; (3) examine the mediating effects of infant severity of illness, behavior state, birth gestation, and birth weight, and maternal depression, and maternal responsiveness and sensitivity on mother-infant synchrony; and (4) test the criterion-related validity of the synchrony scale. A descriptive, longitudinal design using data collected during an earlier study was employed; a sample dataset from 10 mother-infant dyads that completed three data collection points (30 observations total) was used. Data were also collected on maternal depression and responsiveness and sensitivity and dyadic tension and reciprocity. For this analysis, scores for infant severity illness and behavior state were computed. The Noldus Observer XT 8.0 (Noldus Information Technology b.v., 2006) was used for data review and coding. The MISS was created by determining the frequency of select behaviors and the percentage of time behaviors occurred during the feeding; changes in behaviors over the three observations periods were calculated. Mothers were attentive and focused during feedings. The influence of infant maturation on feeding behaviors was evident across observations; infant attempts at interaction (gazing at mother) were greater than the mother attempts to engage her infant. MISS scores were not significantly different over the observations, the selected mediators had no significant effect on synchrony, and the criterion validity for the MISS was not established. This study revealed behaviors that are descriptive of the interaction and can be used to develop interventions that would support the developing relationship. Use of the MISS with a larger sample size and a cohort of healthy, term newborns is needed to establish the MISS as a valid and reliable measure of synchrony.
9
Funk, Gregory Douglas. "Locomotor-respiratory synchrony in the Canada goose." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/41446.
Full textAbstract:
Using a variety of preparations, (intact birds during treadmill and overground
walking/running and free-flight; decerebrate birds during electrically induced
walking/running, passive wing flapping, and electrically induced wing flapping and
"Active" flight), this thesis examines some of the mechanisms involved in the
production and control of locomotor-respiratory coordination (entrainment) during
alternating hindlimb locomotion (walking/running) and synchronous forelimb
locomotion ("flight") in the Canada goose.
Significant coordination of locomotor and respiratory rhythms was observed
during both modes of locomotion in intact as well as decerebrate birds. While
coordination of forelimb motion and respiration was virtually complete, coordination
of hindlimb motion and respiration was sporadic. The level of entrainment during
hindlimb locomotion, however, increased with increased stride frequency, rather than
increased work rate, suggesting that proprioceptive feedback from the limbs is
involved in the production of locomotor-respiratory entrainment. Further evidence for
a role of proprioceptive feedback in the production of entrainment was provided by
the entrainment of respiration by passive wing motion in decerebrate geese.
Although feedback from the periphery was sufficient for the entrainment of wing
motion and respiration, motor nerve outputs to the wing and respiratory musculature
were also synchronized in paralyzed, decerebrate birds during electrically induced
activity, in the complete absence of phasic afferent feedback. Thus, both feedback
and feedforward mechanisms appear sufficient for the coordination of wing beat and
respiration.Science, Faculty of
Zoology, Department of
Graduate
10
Zukoff, Sam 1987. "Indo-European reduplication : synchrony, diachrony, and theory." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/113772.
Full textAbstract:
Thesis: Ph. D. in Linguistics, Massachusetts Institute of Technology, Department of Linguistics and Philosophy, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 311-323).
The reduplicative systems of the ancient Indo-European languages are characterized by an unusual alternation in the shape of the reduplicant. The related languages Ancient Greek, Gothic, and Sanskrit share the property that root-initial consonant clusters exhibit different reduplicant shapes, depending on their featural composition. Moreover, even though the core featural distinction largely overlaps across the languages, the actual patterns which instantiate that distinction are themselves distinct across the languages. For roots beginning in stop-sonorant clusters (TRVX- roots), each of these languages agrees in displaying a prefixal CV reduplicant, where the consonant corresponds to the root-initial stop: TV-TRVX-. These three languages likewise agree that roots beginning in sibilant-stop clusters (STVX- roots) show some pattern other than the one exhibited by TRVXroots. However, each of the three languages exhibits a distinct alternative pattern: V-STVX- in the case of Ancient Greek, STV-STVX- in the case of Gothic, TV-STVX- in the case of Sanskrit. This dissertation provides an integrated synchronic and diachronic theoretical account of the morphophonological properties of verbal reduplication in the ancient Indo-European languages, with its central focus being to explain this core alternation between TRVX- roots and STVX- roots. Set within Base-Reduplicant Correspondence Theory, a framework for analyzing reduplication in Optimality Theory, the comprehensive synchronic analyses constructed in service of understanding this distinction and other interrelated distinctions allow us to probe complex theoretical questions regarding the constraints and constraint interactions involved in the determination of reduplicant shape. This dissertation seeks not only to develop in depth, consistent accounts of both the productive and marginal/archaic morphophonological aspects of reduplication in the Indo-European languages, it aims to understand the origins of these patterns - from a historical and comparative perspective, and from the perspective of morphophonological learning and grammar change - and attempts to motivate the conditions for the onset, development, and retention of the changes that result in the systems observed in the attested languages. As such, these analyses constitute a valuable set of case studies on complex systemic change in phonological grammars.
by Sam Zukoff.
Ph. D. in Linguistics
11
Tarashansky, Igor 1976. "Virtual synchrony semantics : a client-server implementation." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86828.
Full textAbstract:
Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (p. 43-45).
by Igor Tarashchanskiy.
M.Eng.
12
Tcheslavski, Gleb V. "Coherence and Phase Synchrony Analysis of Electroencephalogram." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/30186.
Full textAbstract:
Phase Synchrony (PS) and coherence analyses of stochastic time series - tools to discover brain tissue pathways traveled by electrical signals - are considered for the specific purpose of processing of the electroencephalogram (EEG).
We propose the Phase Synchrony Processor (PSP), as a tool for implementing phase synchrony analysis, and examine its properties on the basis of known signals. Long observation times and wide filter bandwidths can decrease bias in PS estimates. The value of PS is affected by the difference in frequency of the sequences being analyzed and can be related to that frequency difference by the periodic sinc function.
PS analysis of the EEG shows that the average PS is higher - for a number of electrode pairs - for non-ADHD than for ADHD participants. The difference is more pronounced in the δ rhythm (0-3 Hz) and in the γ rhythm (30-50 Hz) PS. The Euclidean classifier with electrode masking yields 66 % correct classification on average for ADHD and non-ADHD subjects using the δ and γ1 rhythms.
We observed that the average γ1 rhythm PS is higher for the eyes closed condition than for the eyes open condition. The latter may potentially be used for vigilance monitoring. The Euclidean discriminator with electrode masking shows an average percentage of correct classification of 78 % between the eyes open and eyes closed subject conditions.
We develop a model for a pair of EEG electrodes and a model-based MS coherence estimator aimed at processing short (i.e. 20 samples) EEG frames. We verify that EEG sequences can be modeled as AR(3) processes degraded by additive white noise with an average SNR of approximately 11-12 dB.
Application of the MS coherence estimator to the EEG suggests that MS coherence is generally higher for non-ADHD individuals than for ADHD participants when evaluated for the θ rhythm of EEG. Also, MS coherence is consistently higher for ADHD subjects than for the majority of non-ADHD individuals when computed for the low end of the δ rhythm (i.e. below 1 Hz).
ADHD produces more measurable effects in the frontal lobe EEG and for participants performing attention intensive tasks.Ph. D.
13
Trujillo, Logan. "Does neural synchrony reflect conscious visual perception?" Thesis, The University of Arizona, 2002. http://hdl.handle.net/10150/278786.
Full textAbstract:
This study investigated the relationship between synchronous neural activity and conscious visual perception by directly measuring neural synchrony in human EEG data collected during a perceptual task that controlled for the influence of attention. Improving a recently developed experimental paradigm and synchrony detection method (Rodriguez et al., 1999), participants viewed upright and scrambled Mooney face stimuli (fragmented black and white shapes that are perceived as faces upon visual closure) over 1000 ms exposures while performing a secondary attention task. During both presentation conditions, gamma-band synchrony increased to a maximum and then decreased to an above-baseline stationary level. Synchrony for the upright condition was significantly greater than synchrony for the scrambled condition during early and late portions of the exposure period. This result supports the hypothesis that neural synchrony mediates conscious visual organization and feature binding, although the possibility for a role in perception-related attention processes cannot be excluded.
14
Goings, Sydney Pia. "Neural Synchrony in the Zebra Finch Brain." Scholarship @ Claremont, 2012. https://scholarship.claremont.edu/scripps_theses/41.
Full textAbstract:
I am interested in discovering the role of field potential oscillations in producing synchrony within the song system of the male zebra finch brain. An important function attributed to neural synchrony is sensorimotor integration. In the production of birdsong, sensorimotor integration is crucial, as auditory feedback is necessary for the maintenance of the song. A cortical-thalamic-cortical feedback loop is thought to play a role in the integration of auditory and motor information for the purpose of producing song. Synchronous activity has been observed between at least two nuclei in this feedback loop, MMAN and HVC. Since low frequency field potential oscillations have been shown to play a role in the synchronization of nuclei within the brain of other model animals, I hypothesized that this may be the case in the zebra finch song system. In order to investigate whether oscillatory activity is a mechanism behind the synchronous activity observed between HVC and MMAN, I performed dual extracellular recordings of neural activity within the zebra finch song system. Results suggest that oscillations are likely not involved in the synchrony observed in these nuclei. Future study may reveal that the structure of the feedback loop is necessary, and possibly even sufficient, for the synchronous activity in the zebra finch song system.
15
Torre, Emiliano [Verfasser], Sonja [Verfasser] Grün, Björn [Akademischer Betreuer] Kampa, and Laura [Akademischer Betreuer] Sacerdote. "Statistical analysis of synchrony and synchrony propagation in massively parallel spike trains / Emiliano Torre, Sonja Grün ; Björn Kampa, Laura Sacerdote." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1125911522/34.
Full text
16
Esnaola, Acebes Jose M. "Patterns of spike synchrony in neural field models." Doctoral thesis, Universitat Pompeu Fabra, 2018. http://hdl.handle.net/10803/663871.
Full textAbstract:
Els models neuronals de camp mig són descripcions fenomenològiques de
l'activitat de xarxes de neurones espacialment organitzades. Gràcies a
la seva simplicitat, aquests models són unes eines extremadament útils
per a l'anàlisi dels patrons espai-temporals que apareixen a les
xarxes neuronals, i s'utilitzen àmpliament en neurociència
computacional. És ben sabut que els models de camp mig tradicionals no
descriuen adequadament la dinàmica de les xarxes de neurones si
aquestes actuen de manera síncrona. No obstant això, les simulacions
computacionals de xarxes neuronals demostren que, fins i tot en estats
d'alta asincronia, fluctuacions ràpides dels inputs comuns que arriben a
les neurones poden provocar períodes transitoris en els quals les
neurones de la xarxa es comporten de manera síncrona. A més a més, la
sincronització també pot ser generada per la mateixa xarxa, donant
lloc a oscil·lacions auto-sostingudes.
En aquesta tesi investiguem la presència de patrons espai-temporals deguts a la
sincronització en xarxes de neurones heterogènies i espacialment distribuïdes.
Aquests patrons no s'observen en els models tradicionals de camp mig,
i per aquest motiu han estat àmpliament ignorats en la literatura.
Per poder investigar la dinàmica induïda per l'activitat sincronitzada de les neurones,
fem servir un nou model de camp mig que es deriva exactament d'una població de
neurones de tipus quadratic integrate-and-fire. La
simplicitat del model ens permet analitzar l'estabilitat de la xarxa
en termes del perfil espacial de la connectivitat sinàptica, i obtenir
fórmules exactes per les fronteres d'estabilitat que caracteritzen la
dinàmica de la xarxa neuronal original. Aquest mateix anàlisi també
revela l'existència d'un conjunt de modes d'oscil·lació que es deuen
exclusivament a l'activitat sincronitzada de les neurones. Creiem que
els resultats presentats en aquesta tesi inspiraran nous avenços
teòrics relacionats amb la dinàmica col·lectiva de les xarxes neuronals,
contribuïnt així en el desenvolupament de la neurociència computacional.Neural field models are phenomenological descriptions of the activity of spatially organized, recurrently coupled neuronal networks. Due to their mathematical simplicity, such models are extremely useful for the analysis of spatiotemporal phenomena in networks of spiking neurons, and are largely used in computational neuroscience. Nevertheless, it is well known that traditional neural field descriptions fail to describe the collective dynamics of networks of synchronously spiking neurons. Yet, numerical simulations of networks of spiking neurons show that, even in the case of highly asynchronous activity, fast fluctuations in the common external inputs drive transient episodes of spike synchrony. Moreover, synchronization may also be generated by the network itself, resulting in the appearance of robust large-scale, self-sustained oscillations. In this thesis, we investigate the emergence of synchrony-induced spatiotemporal patterns in spatially distributed networks of heterogeneous spiking neurons. These patterns are not observed in traditional neural field theories and have been largely overlooked in the literature. To investigate synchrony-induced phenomena in neuronal networks, we use a novel neural field model which is exactly derived from a large population of quadratic integrate-and-fire model neurons. The simplicity of the neural field model allows us to analyze the stability of the network in terms of the spatial profile of the synaptic connectivity, and to obtain exact formulas for the stability boundaries characterizing the dynamics of the original spiking neuronal network. Remarkably, the analysis also reveals the existence of a collection of oscillation modes, which are exclusively due to spike-synchronization. We believe that the results presented in this thesis will foster theoretical advances on the collective dynamics of neuronal networks, upgrading the mathematical basis of computational neuroscience.
17
Cieniak, Jakub. "Stimulus Coding and Synchrony in Stochastic Neuron Models." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20004.
Full textAbstract:
A stochastic leaky integrate-and-fire neuron model was implemented in this study to simulate the spiking activity of the electrosensory "P-unit" receptor neurons of the weakly electric fish Apteronotus leptorhynchus. In the context of sensory coding, these cells have been previously shown to respond in experiment to natural random narrowband signals with either a linear or nonlinear coding scheme, depending on the intrinsic firing rate of the cell in the absence of external stimulation. It was hypothesised in this study that this duality is due to the relation of the stimulus to the neuron's excitation threshold. This hypothesis was validated with the model by lowering the threshold of the neuron or increasing its intrinsic noise, or randomness, either of which made the relation between firing rate and input strength more linear.
Furthermore, synchronous P-unit firing to a common input also plays a role in decoding the stimulus at deeper levels of the neural pathways. Synchronisation and desynchronisation between multiple model responses for different types of natural communication signals were shown to agree with experimental observations. A novel result of resonance-induced synchrony enhancement of P-units to certain communication frequencies was also found.
18
Lee, Catherine. "Perception of synchrony between auditory and visual stimuli." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6375.
Full textAbstract:
The literature has fairly consistently reported a difference in how well humans perceive synchrony depending on the order of auditory and visual stimuli. When the auditory stimulus occurs first and the visual stimulus follows, subjects are more sensitive and so perceive asynchrony with smaller time delay between the stimuli. On the other hand, when the auditory follows the visual stimulus, the subjects are more tolerant and perceive stimuli with larger time delays as synchronous. Thresholds of synchrony perception in these two conditions are thus asymmetrical. The present study attempts to test the Lewkowicz Model, by which the asymmetrical thresholds are explained as a result of arrival-time differences between auditory and visual stimuli to the brain, such that visual stimulus takes longer in processing to be perceived versus auditory one. Reaction-times to these stimuli were measured to determine the arrival-time difference and plotted with synchrony perception. On the basis of Lewkowicz Model we predicted that reaction-time difference between the two stimuli correlate with subjective synchrony. The results did not support the Lewkowicz Model. The expected tendency of 30--40ms of subjective synchrony was not shown. The subjects took, in average, only 7.7ms to detect asynchrony when the auditory stimulus followed the visual stimulus. That the subjects did not tolerate greater temporal gap when the auditory followed versus when it preceded the visual stimulus was a very different result from majority of previous studies. Different factors in perceiving synchrony are discussed in this paper, as well as the application of the research in telecommunications.
19
Alexander, David B. "The Spanish postnominal demonstrative in synchrony and diachrony." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1189813638.
Full text
20
Androulidakis, Alexandros Georgios. "The role of oscillatory synchrony in motor control." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444096/.
Full textAbstract:
Synchronized oscillations are manifest in various regions in the motor system. Their variable nature has increased the interest in the functional significance. Subcortical and cortical activity in the beta band is pathologically increased in Parkinson's disease (PD) - a state dominated by bradykinesia and rigidity. After the administration of the drug levodopa, beta activity and motor impairment are substantially decreased, while activity in the gamma band is increased. The function of beta bursts within the healthy motor system remains unknown. Recent evidence suggests that beta activity may promote the existing motor set and posture. In this thesis, with the use of positional hold tasks the role of beta activity on performance will be examined. It will be demonstrated that during bursts of beta synchrony in the corticomuscular system of healthy subjects there is an improvement, in the performance of these tasks. The findings will argue that physiological fluctuations in the beta band in the motor system may be of behavioural advantage during fine postural tasks involving the hand. The present work will also examine the role of population oscillations in the parkinsonian basal ganglia. It will demonstrate that under levodopa treatment the pattern of movement-related reactivity in the subthalamic nucleus (STN) and the pedunculopontine nucleus (PPN) as well as the background activity in the PPN change significantly. It will be shown that levodopa suppresses movement-related beta activity around the time of self-paced movements and promotes the increase of movement-related gamma activity contralateral to the movement side, following the same pattern as in the non dopamine-depleted brain. This suggests that dopaminergic therapy restores a more physiological pattern of reactivity in the STN. In the untreated state, beta activity in the STN will be shown to be modulated during repetitive self-paced movements, reflecting a role in ongoing performance, but only when motor performance is maximal and not when bradykinesia occurs. Finally, it will be demonstrated that levodopa promotes alpha band activity in the PPN at rest and before movement suggesting a possible physiological role of this activity in this nucleus. These observations provide further insight in the function of neuronal synchronization in the motor system in health and disease.
21
Lumsden, Joanne. "Moving in time with others : exploring interpersonal synchrony." Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=192191.
Full textAbstract:
The temporal coordination of interpersonal behaviour is a foundation for effective joint action, and research reveals that it occurs spontaneously during social interactions. Moreover, synchronous movement has been evidenced to be associated with core aspects of social exchange and person perception (reviewed in Chapter 1). However, synchronisation is not unique to humans, and the emergence of coordination across a variety of domains (e.g., in nature, mechanics, intrapersonal coordination) has been demonstrated to follow similar patterns. The aim of the current work was to explore potential influences on the degree of rhythmic movement synchrony between interaction partners by incorporating methods and theory from both the social psychological and coordination dynamics literatures. Over the course of six studies, several social influences on the emergence and perception of interpersonal synchrony were identified. The degree to which individuals coordinate with the movement rhythms of an interaction partner was found to be shaped by their partner’s social identity (Chapter 2), the individual’s own social motives (Chapter 3), and also their sex (Chapter 4). Therefore, the coordination dynamics governing synchrony were shown to be affected by social factors. In a separate but related thread of research, it was revealed that third-party perceptions of physically synchronous interactions are also influenced by socially relevant information (Chapter 5). Thus, it appears that social forces modulate the degree of synchronisation between interaction partners, and also outsider perceptions of rhythmic movements. The results are discussed in terms of their theoretical and methodological implications, as well as the overall contribution they make to the extant literature (Chapter 6). From an overarching theoretical standpoint, it is suggested that the findings should be viewed from a dynamical systems perspective as, in contrast to alternative theories (e.g., the mirror-neurons theory), this account can more fully explain the phenomena of synchrony and the patterns which emerge.
22
Toftegaard, Tenna. "Temperature and the synchrony of plant-insect interactions." Doctoral thesis, Stockholms universitet, Institutionen för ekologi, miljö och botanik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-131313.
Full textAbstract:
Increasing temperatures resulting from climate change have within recent years been shown to advance phenological events in a large number of species worldwide. Species can differ in their response to increasing temperatures, and understanding the mechanisms that determine the response is therefore of great importance in order to understand and predict how a warming climate can influence both individual species, but also their interactions with each other and the environment. Understanding the mechanisms behind responses to increasing temperatures are however largely unexplored. The selected study system consisting of host plant species of the Brassicaceae family and their herbivore Anthocharis cardamines, is assumed to be especially vulnerable to climatic variations. Through the use of this study system, the aim of this thesis is to study differences in the effect of temperature on development to start of flowering within host plant species from different latitudinal regions (study I), and among host plant species (study II). We also investigate whether different developmental phases leading up to flowering differ in sensitivity to temperature (study II), and if small-scale climatic variation in spring temperature influence flowering phenology and interactions with A. cardamines (study III). Finally, we investigate if differences in the timing of A. cardamines relative to its host plants influence host species use and the selection of host individuals differing in phenology within populations (study IV). Our results showed that thermal reaction norms differ among regions along a latitudinal gradient, with the host plant species showing a mixture of co-, counter- and mixed gradient patterns (study I). We also showed that observed differences in the host plant species order of flowering among regions and years might be caused by both differences in the distribution of warm days during development and differences in the sensitivity to temperature in different phases of development (study II). In addition, we showed that small-scale variations in temperature led to variation in flowering phenology among and within populations of C. pratensis, impacting the interactions with the butterfly herbivore A. cardamines. Another result was that the less the mean plant development stage of a given plant species in the field deviated from the stage preferred by the butterfly for oviposition, the more used was the species as a host by the butterfly (study IV). Finally, we showed that the later seasonal appearance of the butterflies relative to their host plants, the higher butterfly preference for host plant individuals with a later phenology, corresponding to a preference for host plants in earlier development stages (study IV). For our study system, this thesis suggest that climate change will lead to changes in the interactions between host plants and herbivore, but that differences in phenology among host plants combined with changes in host species use of the herbivore might buffer the herbivore against negative effects of climate change. Our work highlights the need to understand the mechanisms behind differences in the responses of developmental rates to temperature between interacting species, as well as the need to account for differences in temperature response for interacting organisms from different latitudinal origins and during different developmental phases in order to understand and predict the consequences of climate change.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.
23
Preyer, Amanda Jervis. "Coupling and synchrony in neuronal networks electrophysiological experiments /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/24799.
Full textAbstract:
Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Butera, Robert; Committee Member: Canavier, Carmen; Committee Member: DeWeerth, Stephen; Committee Member: Hasler, Paul; Committee Member: Lanterman, Aaron; Committee Member: Prinz, Astrid.
24
Sterratt, David C. "Spikes, synchrony, sequences and Schistocerca's sense of smell." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/23207.
Full textAbstract:
This thesis starts from the assumption that individual neuronal action potentials (spikes) have computational and dynamical significance. Two of the types of activity that networks of spiking neurons can engage in are sequences and synchrony. The first part of the work reviews the role spikes, sequences and synchrony play in coding, dynamics and learning in the nervous system and models of the nervous system. Models of spiking neurons, especially the spike response model (SRM), feature strongly, as do synfire chains, a form of spatiotemporal sequence. A methodology chapter deals with the problem of efficient simulation of networks of threshold-fire neurons such as integrate-and-fire (IF) neurons and SRM neurons. I show that networks of SRM neurons can be simulated with larger time steps than are required for numerical integration of equivalent networks of IF neurons. I extend an introduction method for more accurate simulation of IF neurons to noiseless and stochastically-firing SRM neurons, and show that a network of noiseless, interpolated SRM neurons can be simulated with larger time step than the equivalent network of interpolated IF neurons. Synfire chains can be learned with a temporal learning rule and a supervised training protocol. I extend previous analyses of the speed of recall of a synfire chain by (a) explicitly including the speed at which the synfire chain was trained and (b) performing an analysis on a synfire chain comprising discrete neurons rather than starting from a continuum approximation. I conclude that synfire chains can be recalled much faster than the speed at which they were trained.
25
Peterson, Sandra L. "Causal synchrony in the design of distributed programs." W&M ScholarWorks, 1994. https://scholarworks.wm.edu/etd/1539623855.
Full textAbstract:
The outcome of any computation is determined by the order of the events in the computation and the state of the component variables of the computation at those events. The level of knowledge that can be obtained about event order and process state influences protocol design and operation. In a centralized system, the presence of a physical clock makes it easy to determine event order. It is a more difficult task in a distributed system because there is normally no global time. Hence, there is no common time reference to be used for ordering events. as a consequence, distributed protocols are often designed without explicit reference to event order. Instead they are based on some approximation of global state. Because global state is also difficult to identify in a distributed system, the resulting protocols are not as efficient or clear as they could be.;We subscribe to Lamport's proposition that the relevant temporal ordering of any two events is determined by their causal relationship and that knowledge of the causal order can be a powerful tool in protocol design. Mattern's vector time can be used to identify the causal order, thereby providing the common frame of reference needed to order events in a distributed computation. In this dissertation we present a consistent methodology for analysis and design of distributed protocols that is based on the causal order and vector time. Using it we can specify conditions which must be met for a protocol to be correct, we can define the axiomatic protocol specifications, and we can structure reasoning about the correctness of the specified protocol. Employing causality as a unifying concept clarifies protocol specifications and correctness arguments because it enables them to be defined purely in terms of local states and local events.;We have successfully applied this methodology to the problems of distributed termination detection, distributed deadlock detection and resolution, and optimistic recovery. In all cases, the causally synchronous protocols we have presented are efficient and demonstrably correct.
26
Rogoff, Jana. "Audiovisual (a)synchrony in early Soviet sound film." Doctoral thesis, Humboldt-Universität zu Berlin, Philosophische Fakultät II, 2016. http://dx.doi.org/10.18452/17533.
Full textAbstract:
Die Dissertation ist eine medienhistorische Studie über die Einführung des Tons im sowjetischen Kino, die ästhetische und technologische Veränderungen in einem weiter gefassten politischen und kulturellen Kontext interpretiert. In historischen Untersuchungen des frühen Tonfilms der letzten zehn Jahre wurde der sowjetischen Methode des asynchronen Tons häufig die verbreitetere Methode der möglichst genauen Synchronisation gegenübergestellt, wie sie von der Filmindustrie in Hollywood in den späten 1920er und frühen 1930er Jahren entwickelt wurde. Die Arbeit geht über diese zum Standard gewordene Erzählung hinaus. In einer Reihe von Fallstudien wird die Arbeit sowjetischer Filmemacher, Drehbuchautoren, Filmtheoretiker und Toningenieure analysiert, um zu demonstrieren, dass in der Sowjetunion in der Frühphase des Filmtons sehr unterschiedliche Haltungen zum Ton existierten. Die Dissertation konzentriert sich sowohl auf die Theorien des Filmtons als auch auf die Praktiken, wobei es sich unter anderem auf Dziga Vertov, Nikolai Ekk, Michail Cechanovskij und Pavel Tager bezieht. Die Begriffe „Asynchronizität“ und „Synchronizität“ haben in den Debatten über die Einführung des Tonfilms in der Sowjetunion eine zentrale Rolle gespielt. Die vorliegende Dissertation bietet die erste grundlegende Untersuchung dieser Begriffe innerhalb des Kontextes der komplexen Ursprünge des frühen sowjetischen Tonfilms.The dissertation is a media-historical study of the emergence of sound in Soviet cinema, which links aesthetic and technological changes to the broader political and cultural context. Over the last decade, histories of early sound film have usually contrasted the Soviet method of asynchronous sound to the prevalent method of tight synchronization as it was popularized by the Hollywood film industry in the late 1920s and early 1930s. The dissertation looks beyond this standardized narrative. In a series of case studies, it analyzes the work of Soviet filmmakers, screenwriters, film theoreticians and acoustical engineers to demonstrate that many diverse approaches to sound were actually in play at the onset of film sound in the Soviet Union. The dissertation focuses on both film sound theory and practice mainly in the works of Dziga Vertov, Nikolai Ekk, Pavel Tager and Mikhail Tsekhanovsky. The terms “asynchronicity” and “synchronicity” were central in the debates about the emergence of sound film in the Soviet Union. This study provides the first thorough examination of these terms within the context of the complex origins of early Soviet sound cinema.
27
Suzuki, Daisuke. "English Modal Adverbs: Their Functions in Synchrony and Diachrony." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199006.
Full text
28
Tuncgenc, Bahar. "Movement synchrony, social bonding and pro-sociality in ontogeny." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:b766e5a0-9cbe-4af2-b545-3e87c3d6d573.
Full textAbstract:
Human sociality, with its wide scope, early ontogeny and pervasiveness across cultures, is remarkable from an evolutionary perspective. We form bonds with other individuals and live in large social groups. We help, empathise with and share our resources with others, who are unfamiliar and genetically unrelated to us. It has been suggested that interpersonal coordination and rhythmic synchronisation of movements may be one proximate mechanism that enables such widespread human sociality and facilitates cooperation. In the last decade, considerable research has examined the effect of movement synchrony on social bonding and cooperation. However, when this thesis started, there was virtually no experimental study investigating the ontogeny of the movement synchrony-social bonding link, which is proposed to have deep evolutionary roots and important, long-lasting consequences in social life. This thesis aims to investigate the effects of movement synchrony on social bonding and cooperative behaviour across different time points in ontogeny. Three experimental studies were conducted examining infancy, early childhood and middle childhood. Each study explored a different aspect of social bonding and cooperation based on the motor, social and cognitive developments that mark that age group. Study 1a found that at 12 months of age, infants prefer individuals who move in synchrony with them, when the individuals are social entities, but not when they are non-social. Study 1b showed no preferences for synchrony at 9 months in either social or non-social contexts, however. Study 2 revealed that in early childhood, performing synchronous movements actively with a peer facilitates helping behaviour among the children, as well as eye contact and mutual smiling during the interaction. Finally, Study 3 showed that the social bonding effects of movement synchrony applied to inter- group settings and that performing synchronous movements with out-groups increased bonding towards the out-group in middle childhood. This thesis followed an interdisciplinary, integrative and naturalistic approach, where (i) literature from a wide range of disciplines motivated and guided the present research; (ii) links between motor, social and cognitive aspects of development, which are often investigated separately, are formed; and (iii) the experiments were designed in ways that represent the real-life occurrences of the investigated phenomena. The current findings provide the first substantial evidence that movement synchrony facilitates social bonding and cooperation in childhood and thereby provides a foundation for future research.
29
Emme, Kathryn A. "Synchrony in recruitment of fishes in Ohio River tributaries /." Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1594490541&sid=2&Fmt=2&clientId=1509&RQT=309&VName=PQD.
Full text
30
Greendyk, Jesse. "Redeeming the time diachrony and synchrony in biblical hermeneutics /." Online full text .pdf document, available to Fuller patrons only, 2002. http://www.tren.com.
Full text
31
Olderbak, Sally. "Attachment Style and Nonverbal Behavioral Synchrony in Romantic Couples." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202511.
Full textAbstract:
Eshkol-Wachmann Movement Notation was applied to describe and quantify nonverbal behavioral synchrony between romantic partners. The interaction of 30 couples was observed across three study conditions, Pre-Stressor, and two Post-Stressor conditions when the female partner had been targeted with a stress manipulation. Participant-level behavior, and forms of dyadic synchrony were predicted with the male and females' self-reported attachment style. Results support theories from the attachment literature.
32
Ikumi, Montserrat Nara 1986. "The effect of cognitive factors on cross-modal synchrony perception." Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/398008.
Full textAbstract:
Perception in our everyday life takes place in multisensory environments, and hence involves the processing of a multitude of signals captured by various sensory modalities. Given the different nature of the signals, understanding how all the information is combined in the brain to form an integrated percept is not straightforward. One of the paramount questions is how the considerable timing differences between sensory information processing are managed. For example, in the last years there has been a tremendous surge in interest to understand how the perceptual system elicits the subjective impression of synchrony for stimuli coming from different sensory modalities. Yet, most evidence so far concerns stimulus-related properties in simple contexts. The present dissertation addresses the influence of cognitive factors and participants’ inner state (such as attention, action task demands, and ongoing brain rhythms) on synchrony perception between audio-visual events. In the first two studies of the dissertation, we have addressed the role of selective attention and action during cross-modal temporal recalibration. The results of these studies provide evidence that subjective simultaneity can be strongly modulated as a function of the focus of the observer’s endogenous attention, in otherwise identical stimulation conditions. In the third study, we have recorded electroencephalographic activity while participants performed an audio-visual simultaneity judgment task for stimuli presented at different asynchronies. Our results show that the phase of low frequency neural oscillations, reflecting brain states prior to the occurrence of an audio-visual event, can predict perceptual variability in synchrony judgments. Overall, our results shed new light on how cognitive factors can modulate multisensory perception.La percepció del nostre entorn és multisensorial, és a dir, involucra el processament de senyals a través de diverses modalitats sensorials. Combinar aquesta informació en el cervell per tal de formar una percepció coherent i integrada és un procés complex, degut a la diferent naturalesa de les senyals. A més, això farà que el cervell hagi de resoldre diferències temporals durant el processament de la informació. En els últims anys, ha sorgit un profund interès per entendre com el sistema perceptiu genera la impressió de sincronia d’estímuls provinents de diferents modalitats sensorials. La major part dels estudis han examinat propietats de la percepció de sincronia relacionades directament amb els estímuls físics, en contexts molt simplificats. En aquesta tesi investigo la influència de factors cognitius i de l’estat intern de l’individu (com per exemple l’atenció, demandes en tasques motores, i els ritmes interns cerebrals) en la percepció de sincronia entre estímuls audiovisuals. En els primers dos estudis de la tesi, hem examinat la funció de l’atenció i les accions durant la recalibració temporal d’estímuls audiovisuals. Els resultats dels estudis mostren com la sincronia subjectiva pot ser fortament modulada en funció d’on es dirigeixi el focus atencional del participant, en condicions on l’estimulació física és idèntica. En el tercer estudi, hem enregistrat l’activitat electroencefalogràfica dels participants, mentres realitzaven una tasca de simultaneïtat. Durant aquesta tasca presentàvem diferentes asincronies entre estímuls audiovisuals per tal d’estudiar la percepció de sincronia (vs. asincronia). Els resultats indiquen que la fase de les oscil•lacions neuronals, que reflecteixen estats cerebrals abans de la presència d’un estímul audiovisual, poden predir la resposta en quan a percepció de sincronia. En resum, els nostres resultats aporten coneixement sobre com alguns factors cognitius poden modular la percepció multisensorial.
33
Pazienti, Antonio. "Manipulations of spike trains and their impact on synchrony analysis." Phd thesis, Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1744/.
Full textAbstract:
The interaction between neuronal cells can be identified as the computing mechanism of the brain. Neurons are complex cells that do not operate in isolation, but they are organized in a highly connected network structure. There is experimental evidence that groups of neurons dynamically synchronize their activity and process brain functions at all levels of complexity. A fundamental step to prove this hypothesis is to analyze large sets of single neurons recorded in parallel. Techniques to obtain these data are meanwhile available, but advancements are needed in the pre-processing of the large volumes of acquired data and in data analysis techniques. Major issues include extracting the signal of single neurons from the noisy recordings (referred to as spike sorting) and assessing the significance of the synchrony.
This dissertation addresses these issues with two complementary strategies, both founded on the manipulation of point processes under rigorous analytical control. On the one hand I modeled the effect of spike sorting errors on correlated spike trains by corrupting them with realistic failures, and studied the corresponding impact on correlation analysis. The results show that correlations between multiple parallel spike trains are severely affected by spike sorting, especially by erroneously missing spikes. When this happens sorting strategies characterized by classifying only good'' spikes (conservative strategies) lead to less accurate results than tolerant'' strategies. On the other hand, I investigated the effectiveness of methods for assessing significance that create surrogate data by displacing spikes around their original position (referred to as dithering). I provide analytical expressions of the probability of coincidence detection after dithering. The effectiveness of spike dithering in creating surrogate data strongly depends on the dithering method and on the method of counting coincidences. Closed-form expressions and bounds are derived for the case where the dither equals the allowed coincidence interval.
This work provides new insights into the methodologies of identifying synchrony in large-scale neuronal recordings, and of assessing its significance.Die Informationsverarbeitung im Gehirn erfolgt maßgeblich durch interaktive Prozesse von Nervenzellen, sogenannten Neuronen. Diese zeigen eine komplexe Dynamik ihrer chemischen und elektrischen Eigenschaften. Es gibt deutliche Hinweise darauf, dass Gruppen synchronisierter Neurone letztlich die Funktionsweise des Gehirns auf allen Ebenen erklären können. Um die schwierige Frage nach der genauen Funktionsweise des Gehirns zu beantworten, ist es daher notwendig, die Aktivität vieler Neuronen gleichzeitig zu messen. Die technischen Voraussetzungen hierfür sind in den letzten Jahrzehnten durch Multielektrodensyteme geschaffen worden, die heute eine breite Anwendung finden. Sie ermöglichen die simultane extrazelluläre Ableitung von bis zu mehreren hunderten Kanälen. Die Voraussetzung für die Korrelationsanalyse von vielen parallelen Messungen ist zunächst die korrekte Erkennung und Zuordnung der Aktionspotentiale einzelner Neurone, ein Verfahren, das als Spikesortierung bezeichnet wird. Eine weitere Herausforderung ist die statistisch korrekte Bewertung von empirisch beobachteten Korrelationen. Mit dieser Dissertationsschrift lege ich eine theoretische Arbeit vor, die sich der Vorverarbeitung der Daten durch Spikesortierung und ihrem Einfluss auf die Genauigkeit der statistischen Auswertungsverfahren, sowie der Effektivität zur Erstellung von Surrogatdaten für die statistische Signifikanzabschätzung auf Korrelationen widmet. Ich verwende zwei komplementäre Strategien, die beide auf der analytischen Berechnung von Punktprozessmanipulationen basieren. In einer ausführlichen Studie habe ich den Effekt von Spikesortierung in mit realistischen Fehlern behafteten korrelierten Spikefolgen modeliert. Zum Vergleich der Ergebnisse zweier unterschiedlicher Methoden zur Korrelationsanalyse auf den gestörten, sowie auf den ungestörten Prozessen, leite ich die entsprechenden analytischen Formeln her. Meine Ergebnisse zeigen, dass koinzidente Aktivitätsmuster multipler Spikefolgen durch Spikeklassifikation erheblich beeinflusst werden. Das ist der Fall, wenn Neuronen nur fälschlicherweise Spikes zugeordnet werden, obwohl diese anderen Neuronen zugehörig sind oder Rauschartefakte sind (falsch positive Fehler). Jedoch haben falsch-negative Fehler (fälschlicherweise nicht-klassifizierte oder missklassifizierte Spikes) einen weitaus grösseren Einfluss auf die Signifikanz der Korrelationen. In einer weiteren Studie untersuche ich die Effektivität einer Klasse von Surrogatmethoden, sogenannte Ditheringverfahren, welche paarweise Korrelationen zerstören, in dem sie koinzidente Spikes von ihrer ursprünglichen Position in einem kleinen Zeitfenster verrücken. Es zeigt sich, dass die Effektivität von Spike-Dithering zur Erzeugung von Surrogatdaten sowohl von der Dithermethode als auch von der Methode zur Koinzidenzzählung abhängt. Für die Wahrscheinlichkeit der Koinzidenzerkennung nach dem Dithern stelle ich analytische Formeln zur Verfügung. Die vorliegende Arbeit bietet neue Einblicke in die Methoden zur Korrelationsanalyse auf multi-variaten Punktprozessen mit einer genauen Untersuchung von unterschiedlichen statistischen Einflüssen auf die Signifikanzabschätzung. Für die praktische Anwendung ergeben sich Leitlinien für den Umgang mit Daten zur Synchronizitätsanalyse.
34
Capstick, Gary. "Audiovisual Prior Entry: Evidence from the Synchrony Comparison Judgment Task." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23100.
Full textAbstract:
Prior entry refers to the notion that attended stimuli are perceived sooner than unattended stimuli due to a speed up in sensory processing. The century long debate regarding the prior entry phenomenon’s existence has always been grounded in the degree to which the methods applied to the problem allow for cognitive response bias. This thesis continues that trend by applying the synchrony comparison judgment method to the problem of audiovisual prior entry. Experiment 1 put this method into context with two other common psychophysical methods – the temporal order judgment and the synchrony judgment – that have been applied to the prior entry problem. The results of this experiment indicated that the temporal order judgment method was out of step with the other two methods in terms of the parameter estimates typically used to evaluate prior entry. Experiment 2 evaluated and confirmed that a specific response bias helps explain the difference in parameter estimates between the temporal order judgment method and the other two. Experiment 3 evaluated the precision of the synchrony comparison judgment method. The results indicated that the method was precise enough to detect potentially small prior entry effect sizes, and that it afforded the ability to detect those participants with points of subjective synchrony that deviate substantially from zero. Finally, Experiment 4 applied the synchrony comparison judgment method to a prior entry scenario. A prior entry effect was not realized. Overall, this thesis highlights the drawbacks of all previous methods used to evaluate audiovisual perception, including prior entry, and validates the use of the synchrony comparison judgment. Further, due to the resistance of this method to response bias, this result now stands as the most convincing evidence yet against the prior entry phenomenon.
35
Vatakis, Argiro. "Assessing the factors modulating synchrony perception for complex audiovisual stimuli." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443004.
Full text
36
Sitaridou, Ioanna. "The synchrony and diachrony of Romancce infinitives with nominative subjects." Thesis, University of Manchester, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507971.
Full textAbstract:
Infinitives are trivially considered to license PRO, a covert null-Case pronoun, which represents the understood subject of an infinitive complement. However, two Romance infinitive constructions deviate from this canonical pattern and have their subject position filled by a phonetically realised lexical noun (or pronoun), which has nominative Case. In other words they license pro, which normally represents the understood subject of a finite clause. It follows that these infinitive constructions pose a problem for current theories of Control. The present thesis investigates inflected and personal infinitives in Romance languages from a synchronic and a diachronic perspective. The main goal is to offer a unified treatment of inflected and personal infinitives with regard to subject realisation, Case-licensing, Tense and non-obligatory control properties. Synchronically, on an empirical level, the generalisation is that infinitives with nominative subjects cannot surface as complements unless they bear agreement or are introduced by a complementiser. First, it is argued that agreement is not crucial to the licensing of nominative Case because other non-finite constructions, for example gerunds, license nominative subjects despite its absence. However, the latter is shown to correlate with postverbal subjects. Second, a minimalist analysis of inflected and personal infinitives is presented. It argues that both constructions are similar in that Tense licenses nominative Case . on the subjects but vary with respect to distribution: personal infinitives -unless they are introduced by a complementiser- cannot surface as complements whereas inflected infinitives can. Third, the non-obligatory control properties of inflected and personal infinitives are argued to derive from Agree not applying at CO (cf. Landau 2000), thus blocking the matching of features between the matrix and the infinitive subject, i.e. a controlled interpretation. Diachronically also, inflected and personal infinitives are intriguing since they have no direct lineage from Latin. It is proposed that there is no unique source and that inflected and personal infinitives have distinct sources. First, it is argued that the Accusativus cum Infinitivo construction cannot be proven to be the predecessor of these constructions. Second, the Spanish personal infinitive is shown to have two sources: for the personal infinitives as complements there is a learned source which has ceased to be productive and for personal infinitives as adjuncts a learnability-based account is put forward. The latter, based on a theory of acquisition and change, provides a model for the emergence of personal infinitives as adjuncts in Old Castilian that is consistent with the synchronic analysis.
37
Hu, Xiaoling. "Topics in Chinese syntax : word order in synchrony and diachrony." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/1196/.
Full text
38
Eby, Christine A. "Pediatric Cochlear Implant Outcomes in Auditory Neuropathy/Auditory Dys-Synchrony." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1085691784.
Full text
39
Wilson, Troy E. "Spatial Synchrony in Terrestrial Breeding Birds: Implications for Metapopulation Processes." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1400857466.
Full text
40
Rodriguez, Vanessa. "Exploring Social-Emotional Cognition and Psychophysiologic Synchrony During Teaching Interactions." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:27112694.
Full textAbstract:
Conceptions of learning have evolved from behaviorist and mechanistic models to models that are dynamic, complex, and process-oriented. Educators’ and researchers’ understanding of teaching can benefit from a similar evolution, one that embodies teaching as a dynamic, cognitive skill. Because teaching is an inherently interactive phenomenon, it can be characterized as a social-emotional cognitive skill.
Using a dynamic systems and social-emotional cognitive lens, in this dissertation, I describe two studies that explored teaching from these perspectives. The first, presented in Chapter 2, used structured cognitive interviews to elicit expert teachers’ reflections on their teaching processes, as well as to illuminate the interactive nature of these processes and the factors that influence the teachers’ capabilities. In the second study, presented in Chapter 3, I borrowed methods from interactive social-emotional cognitive studies to identify periods of psychophysiologic synchrony between the teachers and students to determine if these correlated with their relational experiences.
Five themes, or awarenesses, emerged from the interview data: (a) awareness of learner (AoL), (b) awareness of teaching practice (AoTP), (c) awareness of context (AoC), (d) awareness of self as a teacher (AoST), and (e) awareness of interaction (AoI). Within each theme, I identified several categories that characterized the teachers’ reflections on the individual social-emotional cognitive processes employed during teaching. These data show that expert teaching leverages a complex, social-emotional cognitive framework to achieve learning goals.
In the second study, I observed significant increases of psychophysiologic synchrony in the teacher–student dyads that were engaged in a supported teaching task. This elevated synchrony was correlated with multiple domains of two established measures of individual social-emotional cognition. Moreover, after dividing the data by the median of achieved synchrony into an upper and lower group, strong but unique correlation patterns were observed between the teacher–student synchrony and the social-emotional cognitive survey measures. In particular, several student measures of the teachers’ perspective taking demonstrated inverse associations between the lower and upper 50th percentiles of synchrony. These data indicated that the ability to create synchrony during supported interactions was connected to the teacher’s distinct social-emotional cognitive capacity. These results also support the potential neurobiologic and psychophysiologic bases of teachers’ social-emotional cognitive processing.
Together, these two studies represent an initial step along a larger trajectory of future research that could advance the conception of teaching as a social-emotional cognitive skill that develops as a complex system.
41
Afghan, Muhammad K. N. "Computational Study of Stimulus-Induced Synchrony in the Cat Retina." Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1107274001.
Full text
42
Lögdberg, Frida. "Population dynamics in variable environments – impacts of noise colour and synchrony." Doctoral thesis, Linköpings universitet, Teoretisk Biologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-72951.
Full textAbstract:
Environmental variation is an essential part of population dynamics, and two characteristics of such variation—variance and the temporal autocorrelation termed ‘noise colour’—are essential for determining the persistence of a population. In addition, the spatial correlation of local environmental variation between habitat patches (i.e., synchrony) is equally important in subdivided populations connected via dispersal. The research underlying this thesis explored the effects of noise colour and synchrony on population dynamics. The dynamics were studied primarily in single-species models with fast or slow population responses to environmental changes, and several-species systems (i.e., food webs) with different stability properties were also considered. Populations were spatially subdivided with local dynamics in discrete patches, and patch positions were modelled either implicitly or explicitly, with different landscape configurations in the latter case. It has previously been shown that the effect of increased environmental redness on extinction risk in nonspatial models depends on population responsiveness, seen as increased and decreased risks for fast and slow responding populations, respectively. Here, increased redness of noise decreased the extinction risk for fast-responding populations (in accordance with non-spatial studies) in a simple implicit landscape model (Papers I and II). Slow-responding populations in some cases showed a raised extinction risk for intermediate noise colour values (Paper I), which does not agree with earlier results. However, increasing the spatial complexity evened out the differences that were caused by responsiveness (Papers III and IV). Thus, in general, the explicit landscape models displayed a decrease in extinction risk with increasing environmental redness regardless of whether the populations were fast or slow in responding to environmental variation. Still, fast and slow responsiveness of populations differed in relation to the following: overall levels of extinction risk (Papers I, III, and IV), synchrony of population variations (Paper II), colour of population variations (Paper II), and response to landscape structure (Papers III and IV). For fast-responding populations, the degree of synchrony of population variations was similar to the synchrony of environmental noise (Paper II). Local populations of a model organism that responded slowly to environmental variation were more synchronized than the environmental variation itself, and the largest shift between the environment and the populations was seen for intermediate red noise colours (Paper II). This indicated that dispersal-induced population synchrony could be enhanced by reddened noise. Landscape configuration proved to be important for the general levels of extinction risk. This effect was most pronounced for fast-responding populations (Papers III and IV) and became even more distinct when distance-dependent synchrony was added between the environmental variations (Paper IV). Adding explicit landscapes led to an decrease in the differences between fast- and slow-responding populations, when considering the influence of noise colour on extinction risk. Also, landscape configuration affected the importance of degree of synchrony through its impact on distances between patches, which resulted in configurations where extinction risk depended solely on noise colour. The effects on stability exerted by populations embedded in food webs were investigated in an implicit landscape model (Paper V). Three types of food webs with different properties of inherent stability all showed a decrease in stability at increased environmental variance and increased redness of environmental variation. In conclusion, the single-species models showed that the survival conditions of populations that were near extinction were improved by all of the following: decreased synchrony, reddening of noise, and aggregation of patches. The results of the web simulations indicate that we need better understanding of how findings obtained using single-species models can be used to reveal the effects of noise colour on species communities. From a management perspective, altering landscape structure may compensate for increased extinction risks caused by changed noise colour of environmental variation, which is a predicted outcome of climate change.
43
Gómez, Pamela Brigitte. "Audio-visual synchrony in the intermodal perception of children with autism." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq22853.pdf.
Full text
44
Shlens, Jonathon. "Synchrony and concerted activity in the neural code of the retina." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3258325.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed May 22, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 136-156).
45
Smith, Jennifer. "Synchrony and diachrony in the evolution of English : evidence from Scotland." Thesis, University of York, 2000. http://etheses.whiterose.ac.uk/10887/.
Full text
46
Kaye, Steven James. "Conjugation class from Latin to Romance : heteroclisis in diachrony and synchrony." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:c856559e-bd2b-475d-b4b5-afe1e164056a.
Full textAbstract:
This thesis investigates the origins and behaviour of the non-canonical morphological phenomenon of heteroclisis in the verb paradigms of Latin and the Romance languages. Heteroclisis is the coexistence, within a single paradigm, of forms which pattern according to different inflectional classes existing otherwise in the language: a heteroclite lexeme can thus be seen as 'mixed' or 'undecided' as to its inflectional identity. I begin by examining the development of the theoretical concept of heteroclisis and approaches to the idea of inflectional class in general, before situating heteroclisis in typological space in comparison with better-known instances of non-canonical morphology such as deponency and suppletion; heteroclisis exists at a different level of generalization from these, because its identification presupposes the existence of inflectional classes, themselves generalizations over the behaviour of individual lexemes. I also consider two recent theoretical treatments of the phenomenon and survey recent linguistic studies making use of the notion. I then look at the synchronic and diachronic behaviour of heteroclisis in Latin and Romance verbs: the great time depth of our attestations of these languages gives us the chance to witness the development of successive examples of heteroclisis, and their subsequent treatment within the morphological system, in the history of a single family. Focusing chiefly on data from Latin, Romanian and Romansh, I find that the principal (though not the only) source for new instances of heteroclisis in Latin/Romance lies in regular sound change, and find that speakers can treat these synchronically anomalous patterns as robust models of inflectional behaviour to be extended over the lexicon or brought into line with pre-existing types of paradigm-internal alternation. These findings concur with previous demonstrations that speakers make use of non-canonical phenomena as markers of the internal structure of inflectional paradigms.
47
Trinh, Michael Bao. "Achieving global synchrony in a distributed system with free-running local clocks." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/4175.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Computer Science. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
48
Posledovich, Diana. "Effects of climate on phenological synchrony between butterflies and their host plants." Doctoral thesis, Stockholms universitet, Zoologiska institutionen, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-116664.
Full textAbstract:
Shifts in species’ phenologies and phenological asynchronies between the interacting organisms have received a lot of attention in the context of climate change. Changes in temporal overlap between species, caused by phenological asynchrony, make species depending on one another become so separated in time that they can no longer interact. This may have important consequences both for single species, like fluctuations in abundances, and for the functioning of whole communities by creating mismatches between trophic levels and rearrangements of community structure. This thesis focuses on the impact of temperatures on spring timing and phenological synchrony in a herbivorous insect – host plant system, consisting of the orange tipbutterfly Anthocharis cardamines and five of its Brassicaceae host plant species. Paper I demonstrates that diapause duration and winter thermal conditions can determine the timing of spring emergence in the herbivore, and these traits may differ between species with different feeding strategies. In paper II we show that thermal reaction norms of post-winterdevelopment of A. cardamines display cogradient latitudinal variation.Paper III shows that temperature-mediated phenological plasticity of A. cardamines butterflies and a majority of the most used host plant species is similar within populations originating from different latitudes. Thus, the species’ timing appeared well conserved in response to thermal variation. In paper IV we explored the importance of the butterfly’s adult emergence and thermal conditions on the succeeding part of the butterfly’s life-cycle – larval development. The outcome from the interaction was examined for both the insect and the plant side. The degree in phenological overlap between the female butterflies and host plants as well as temperatures during larval development were found to influence larval development but had no effect on plant reproductive fitness. The four papers of the presented thesis demonstrate that developmental preadaptations, evolvedin a herbivore to maintain phenological synchrony with host plants across yearly variation of spring conditions, can prevent disruption of the interaction under a wide range of temperatures. This indicates that temporary constrained interactions are not always vulnerable to decoupling, particularly if they involve generalist strategy.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Submitted.
Ekoklim
49
Holder, Philip. "Urea recycling to the rumen of sheep : the influence of diet synchrony." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286242.
Full text
50
Golledge, Huw D. R. "Does inter-columnar neuronal synchrony play a role in visual feature binding?" Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323355.
Full text