512 research outputs found
Detection of time reversibility in time series by ordinal patterns analysis
Time irreversibility is a common signature of nonlinear processes, and a
fundamental property of non-equilibrium systems driven by non-conservative
forces. A time series is said to be reversible if its statistical properties
are invariant regardless of the direction of time. Here we propose the Time
Reversibility from Ordinal Patterns method (TiROP) to assess time-reversibility
from an observed finite time series. TiROP captures the information of scalar
observations in time forward, as well as its time-reversed counterpart by means
of ordinal patterns. The method compares both underlying information contents
by quantifying its (dis)-similarity via Jensen-Shannon divergence. The
statistic is contrasted with a population of divergences coming from a set of
surrogates to unveil the temporal nature and its involved time scales. We
tested TiROP in different synthetic and real, linear and non linear time
series, juxtaposed with results from the classical Ramsey's time reversibility
test. Our results depict a novel, fast-computation, and fully data-driven
methodology to assess time-reversibility at different time scales with no
further assumptions over data. This approach adds new insights about the
current non-linear analysis techniques, and also could shed light on
determining new physiological biomarkers of high reliability and computational
efficiency.Comment: 8 pages, 5 figures, 1 tabl
Beware of the Small-World neuroscientist!
The SW has undeniably been one of the most popular network descriptors in the
neuroscience literature. Two main reasons for its lasting popularity are its
apparent ease of computation and the intuitions it is thought to provide on how
networked systems operate. Over the last few years, some pitfalls of the SW
construct and, more generally, of network summary measures, have widely been
acknowledged
Hacia una crítica del positivismo en la historia de las organizaciones
El comportamiento humano actual es un reflejo de su experiencia y evolución
frente a nuevos retos, en donde la prioridad se ha basado en satisfacer
sus principales necesidades, las cuales se han complejizado a medida que
la vida ha demandado nuevas prácticas, a costa de cualquier sacrificio, sea
éste de carácter humano, material o ambiental. A través de este documento
de investigación se evidencia un corto recuento de los hechos históricos más
relevantes asociados con las organizaciones, en donde la práctica crematística
y la obtención de poder han sido la principal causa en los conflictos más
caóticos de nuestra humanidad debido a que estamos inmersos aún en el
paradigma del positivismo.The current human behavior is a reflection of the human own experience
and evolution in front of new challenges, in which the central point has been
based in satisfying our main needs. These needs have been more complex at
the same time as life demands new practices at the expenses of any human,
material or environmental sacrifice. Throughout this research document a
short report of the most relevant historical events related with organizations
is evidenced, where the chrematistic practices and the power struggle have
been the main cause of the most chaotic human conflicts, because we continue
to be immersed in the positivism paradigm
Evaluating the effect of aging on interference resolution with time-varying complex networks analysis
In this study we used graph theory analysis to investigate age-related reorganization of functional networks during the active maintenance of information that is interrupted by external interference. Additionally, we sought to investigate network differences before and after averaging network parameters between both maintenance and interference windows. We compared young and older adults by measuring their magnetoencephalographic recordings during an interference-based working memory task restricted to successful recognitions. Data analysis focused on the topology/temporal evolution of functional networks during both the maintenance and interference windows. We observed that: (a) Older adults require higher synchronization between cortical brain sites in order to achieve a successful recognition, (b) The main differences between age groups arise during the interference window, (c) Older adults show reduced ability to reorganize network topology when interference is introduced, and (d) Averaging network parameters leads to a loss of sensitivity to detect age differencesThis work has been supported by the Spanish MINECO under project [FIS2013-41057], as well as Fundación Carolina Doctoral Scholarship Program and Colciencias Doctoral Program 56
Evaluating the effect of aging on interference resolution with time-varying complex networks analysis
In this study we used graph theory analysis to investigate age-related reorganization of functional networks during the active maintenance of information that is interrupted by external interference. Additionally, we sought to investigate network differences before and after averaging network parameters between both maintenance and interference windows. We compared young and older adults by measuring their magnetoencephalographic recordings during an interference-based working memory task restricted to successful recognitions. Data analysis focused on the topology/temporal evolution of functional networks during both the maintenance and interference windows. We observed that: (a) Older adults require higher synchronization between cortical brain sites in order to achieve a successful recognition, (b) The main differences between age groups arise during the interference window, (c) Older adults show reduced ability to reorganize network topology when interference is introduced, and (d) Averaging network parameters leads to a loss of sensitivity to detect age differencesThis work has been supported by the Spanish MINECO under project [FIS2013-41057], as well as Fundación Carolina Doctoral Scholarship Program and Colciencias Doctoral Program 56
Functional brain networks reveal the existence of cognitive reserve and the interplay between network topology and dynamics
We investigated how the organization of functional brain networks was related
to cognitive reserve (CR) during a memory task in healthy aging. We obtained
the magnetoencephalographic functional networks of 20 elders with a high or low
CR level to analyse the differences at network features. We reported a negative
correlation between synchronization of the whole network and CR, and observed
differences both at the node and at the network level in: the average shortest
path and the network outreach. Individuals with high CR required functional
networks with lower links to successfully carry out the memory task. These
results may indicate that those individuals with low CR level exhibited a dual
pattern of compensation and network impairment, since their functioning was
more energetically costly to perform the task as the high CR group.
Additionally, we evaluated how the dynamical properties of the different brain
regions were correlated to the network parameters obtaining that entropy was
positively correlated with the strength and clustering coefficient, while
complexity behaved conversely. Consequently, highly connected nodes of the
functional networks showed a more stochastic and less complex signal. We
consider that network approach may be a relevant tool to better understand
brain functioning in aging.Comment: Main manuscript: 23 pages including references, 20 pages text, 8
figures and supplementary information include
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