68 research outputs found
Design of the Artificial: lessons from the biological roots of general intelligence
Our desire and fascination with intelligent machines dates back to the
antiquity's mythical automaton Talos, Aristotle's mode of mechanical thought
(syllogism) and Heron of Alexandria's mechanical machines and automata.
However, the quest for Artificial General Intelligence (AGI) is troubled with
repeated failures of strategies and approaches throughout the history. This
decade has seen a shift in interest towards bio-inspired software and hardware,
with the assumption that such mimicry entails intelligence. Though these steps
are fruitful in certain directions and have advanced automation, their singular
design focus renders them highly inefficient in achieving AGI. Which set of
requirements have to be met in the design of AGI? What are the limits in the
design of the artificial? Here, a careful examination of computation in
biological systems hints that evolutionary tinkering of contextual processing
of information enabled by a hierarchical architecture is the key to build AGI.Comment: Theoretical perspective on AGI (Artificial General Intelligence
Considering Hilbert's Approach: Problems from a Cell's Perspective
Reducing the events in cellular systems and examining disconnected components
has proven to be successful in uncovering molecular reactions and interactions.
However, Ad-hoc and subsequent theory-less composition of the discrete bits has
failed to create a system-scale map due to the missing links: unknown variables
and the ensuing nonlinearities in the complex high-dimensional parameter space,
not taking into account the natural noisiness and stochasticity of the cellular
events, ignoring causal influence and disregarding the temporal dynamics.
Composite static and phenomenological descriptions, as complicated as they may
look, lack the essence of what makes the biological systems ``complex''.
Formalization of system-level problems is key in the path towards constructing
a metatheory of biology. As a template for such formalization, this wotk aims
to tease apart a few problems that cells need to resolve. This approach may
serve as a model in the path towards axiomatizing biological investigations
Ensemble Inhibition and Excitation in the Human Cortex: an Ising Model Analysis with Uncertainties
The pairwise maximum entropy model, also known as the Ising model, has been
widely used to analyze the collective activity of neurons. However, controversy
persists in the literature about seemingly inconsistent findings, whose
significance is unclear due to lack of reliable error estimates. We therefore
develop a method for accurately estimating parameter uncertainty based on
random walks in parameter space using adaptive Markov Chain Monte Carlo after
the convergence of the main optimization algorithm. We apply our method to the
spiking patterns of excitatory and inhibitory neurons recorded with
multielectrode arrays in the human temporal cortex during the wake-sleep cycle.
Our analysis shows that the Ising model captures neuronal collective behavior
much better than the independent model during wakefulness, light sleep, and
deep sleep when both excitatory (E) and inhibitory (I) neurons are modeled;
ignoring the inhibitory effects of I-neurons dramatically overestimates
synchrony among E-neurons. Furthermore, information-theoretic measures reveal
that the Ising model explains about 80%-95% of the correlations, depending on
sleep state and neuron type. Thermodynamic measures show signatures of
criticality, although we take this with a grain of salt as it may be merely a
reflection of long-range neural correlations.Comment: 17 pages, 8 figure
Theoretical Principles of Multiscale Spatiotemporal Control of Neuronal Networks: A Complex Systems Perspective
Success in the fine control of the nervous system depends on a deeper understanding of how neural circuits control behavior. There is, however, a wide gap between the components of neural circuits and behavior. We advance the idea that a suitable approach for narrowing this gap has to be based on a multiscale information-theoretic description of the system. We evaluate the possibility that brain-wide complex neural computations can be dissected into a hierarchy of computational motifs that rely on smaller circuit modules interacting at multiple scales. In doing so, we draw attention to the importance of formalizing the goals of stimulation in terms of neural computations so that the possible implementations are matched in scale to the underlying circuit modules
Physical computation and compositionality
Developments in quantum computing and, more in general, non-standard
computing systems, represent a clear indication that the very notion of what a
physical computing device is and does should be recast in a rigorous and sound
framework. Physical computing has opened a whole stream of new research aimed
to understand and control how information is processed by several types of
physical devices. Therefore, classical definitions and entire frameworks need
to be adapted in order to fit a broader notion of what physical computing
systems really are. Recent studies have proposed a formalism that can be used
to carve out a more proper notion of physical computing. In this paper we
present a framework which capture such results in a very natural way via some
basic constructions in Category Theory. Furthermore, we show that, within our
framework, the compositional nature of physical computing systems is naturally
formalized, and that it can be organized in coherent structures by the means of
their relational nature
Causal Unit of Rotors in a Cardiac System
The heart exhibits complex systems behaviors during atrial fibrillation (AF),
where the macroscopic collective behavior of the heart causes the microscopic
behavior. However, the relationship between the downward causation and scale is
nonlinear. We describe rotors in multiple spatiotemporal scales by generating a
renormalization group from a numerical model of cardiac excitation, and
evaluate the causal architecture of the system by quantifying causal emergence.
Causal emergence is an information-theoretic metric that quantifies emergence
or reduction between microscopic and macroscopic behaviors of a system by
evaluating effective information at each spatiotemporal scale. We find that
there is a spatiotemporal scale at which effective information peaks in the
cardiac system with rotors. There is a positive correlation between the number
of rotors and causal emergence up to the scale of peak causation. In
conclusion, one can coarse-grain the cardiac system with rotors to identify a
macroscopic scale at which the causal power reaches the maximum. This scale of
peak causation should correspond to that of the AF driver, where networks of
cardiomyocytes serve as the causal units. Those causal units, if identified,
can be reasonable therapeutic targets of clinical intervention to cure AF.Comment: 19 pages, 9 figures. arXiv admin note: text overlap with
arXiv:1711.1012
Comparative power spectral analysis of simultaneous elecroencephalographic and magnetoencephalographic recordings in humans suggests non-resistive extracellular media
The resistive or non-resistive nature of the extracellular space in the brain
is still debated, and is an important issue for correctly modeling
extracellular potentials. Here, we first show theoretically that if the medium
is resistive, the frequency scaling should be the same for electroencephalogram
(EEG) and magnetoencephalogram (MEG) signals at low frequencies (<10 Hz). To
test this prediction, we analyzed the spectrum of simultaneous EEG and MEG
measurements in four human subjects. The frequency scaling of EEG displays
coherent variations across the brain, in general between 1/f and 1/f^2, and
tends to be smaller in parietal/temporal regions. In a given region, although
the variability of the frequency scaling exponent was higher for MEG compared
to EEG, both signals consistently scale with a different exponent. In some
cases, the scaling was similar, but only when the signal-to-noise ratio of the
MEG was low. Several methods of noise correction for environmental and
instrumental noise were tested, and they all increased the difference between
EEG and MEG scaling. In conclusion, there is a significant difference in
frequency scaling between EEG and MEG, which can be explained if the
extracellular medium (including other layers such as dura matter and skull) is
globally non-resistive.Comment: Submitted to Journal of Computational Neuroscienc
Florid Cemento-Osseous Dysplasia at the Site of Previous Teeth Extraction: Report of a Case
Objective: Florid cemento-osseous dysplasia (FCOD) is a rare bone lesion that predominantly involves the women’s jaws in middle age. This condition is usually asymptomatic and has a benign course.Case: This paper presents a rare case of FCOD in a white middle aged woman, which had affected mandible bilaterally and was diagnosed after tooth extraction and treated conservatively.We believed tooth extraction was a contributing factor for outbreak of such a lesion in this susceptible patient.Conclusion: For the asymptomatic patients, the best management consists of regular recall examinations with prophylaxis and reinforcement of oral hygiene to prevent periodontal diseases and tooth loss, but with accession of clinical signs and symptoms, surgical intervention is inevitable
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