Biology subjects

Tozzi, A.

Publications and source records attributed to Tozzi, A..

28 records · Page 2Linked to original sources

bioRxiv2020

QUATERNIONIC ASSESSMENT OF EEG TRACES ON NERVOUS MULTIDIMENSIONAL HYPERSPHERES

The nervous activity of the brain takes place in higher-dimensional functional spaces. Indeed, recent claims advocate that the brain might be equipped with a phase space displaying four spatial dimensions plus time, instead of the classical three plus time. This suggests the possibility to investigate global visualization methods for exploiting four-dimensional maps of real experimental data sets. Here we asked whether, starting from the conventional neuro-data available in three dimensions plus time, it is feasible to find an operational procedure to describe the corresponding four-dimensional trajectories. In particular, we used quaternion orthographic projections for the assessment of electroencephalographic traces (EEG) from scalp locations. This approach makes it possible to map three-dimensional EEG traces to the surface of a four-dimensional hypersphere, which has an important advantage, since quaternionic networks make it feasible to enlighten temporally far apart nervous trajectories equipped with the same features, such as the same frequency or amplitude of electric oscillations. This leads to an incisive operational assessment of symmetries, dualities and matching descriptions hidden in the very structure of complex neuro-data signals.

neuroscience↗

bioRxiv2020

The Mathematics Underlying Eeg Oscillations Propagation

Whenever one attempts to comb a hairy ball flat, there will always be at least one tuft of hair at one point on the ball. This seemingly worthless sentence is an informal description of the hairy ball theorem, an invaluable mathematical weapon that has been proven useful to describe a variety of physical/biological processes/phenomena in terms of topology, rather than classical cause/effect relationships. In this paper we will focus on the electrical brain field - electroencephalogram (EEG). As a starting point we consider the recently-raised observation that, when electromagnetic oscillations propagate with a spherical wave front, there must be at least one point where the electromagnetic field vanishes. We show how this description holds also for the electric waves produced by the brain and detectable by EEG. Once located these zero-points in EEG traces, we confirm that they are able to modify the electric wave fronts detectable in the brain. This sheds new light on the functional features of a nonlinear, metastable nervous system at the edge of chaos, based on the neuroscientific model of Operational Architectonics of brain-mind functioning. As an example of practical application of this theorem, we provide testable previsions, suggesting the proper location of transcranial magnetic stimulations coils to improve the clinical outcomes of drug-resistant epilepsy.

neuroscience↗

bioRxiv2019

NON-EQUILIBRIUM BELOUSOV-ZHABOTINSKY REACTION DESCRIBES THE SPONTANEOUS ACTIVITY OF THE BRAIN

Belousov-Zhabotinsky (BZ) reactions describe chemical patterns in terms of non-equilibrium thermodynamics, chaotic evolution of nonlinear oscillators, excitability under the influence of peculiar chemical stimulations. In touch with this chemical model, we hypothesized that the nonlinear brain electric activity at the edge of the chaos could be triggered by neural oscillation equipped with BZ dynamics, and that changes in neural activity might be correlated with the transient occurrence of (either short and long-range) BZ-like reactions in cortical subareas. To prove our hypothesis of neuronal waves driven by BZ-like processes, we evaluated fMRI movies that assess in vivo BOLD resting state activity of the human brain. We found that the spontaneous activity of the brain display features fully overlapping the recently-introduced local circuits based on BZ chemical reaction. Therefore, neuronal paths during spontaneous activity of the brain match BZ dynamics previsions. Our results point towards the brain as crossed by diffusive nonlinear neural oscillations patterns that are predictable. Furthermore, our results suggest that chaotic dynamics arise from nothing else than the network arrangements subtending physical and biological systems.

neuroscience↗

bioRxiv2019

Topological inference from spontaneous activity structures in FMRI videos with peristence barcodes.

Spatio-temporal brain activities with variable delay detectable in resting-state functional magnetic resonance imaging (rs-fMRI) give rise to highly reproducible structures, termed cortical lag threads, that can propagate from one brain region to another. Using a computational topology of data approach, we found that Betti numbers that are cycle counts and the areas of vortex cycles covering brain activation regions in triangulated rs-fMRI video frames make it possible to track persistent, recurring blood oxygen level dependent (BOLD) signals. Our findings have been codified and visualized in what are known as persistent barcodes. Importantly, a topology of data offers a practical approach in coping with and sidestepping massive noise in neuro data, such as unwanted dark (low intensity) regions in the neighbourhood of non-zero BOLD signals. A natural outcome of a topology of data approach is the tracking of persistent, non-trivial BOLD signals that appear intermittently in a sequence of rs-fMRI video frames. The end result of this tracking of changing lag structures is a persistent barcode, which is a pictograph that offers a convenient visual means of exhibiting, comparing and classifying brain activation patterns.

neuroscience↗

bioRxiv2018

Reaction-Diffusion Mechanisms Underlying Hirschprung’s Disease and their Practical Impications

The erratic extent of aganglionic and hypoganglionic segments in Hirschsprungs disease (HD) makes it difficult to predict the amount of the intestine to remove in order to restore the proper functional motility. Our aim was to assess whether the embryonic rostro-caudal intestinal colonization by neuroblasts from the neural crest follows a predictable pattern in HD. In touch with Turings reaction diffusion model (RD), which describes biological patterns (such as leopard spots and lung branching morphogenesis) in terms of interactions/competitions between activating and inhibiting factors, we hypothesized that intestinal neural density could be triggered by local gut factors that counteract the proximal-distal embryonic progression of neural progenitors. While the neuronal number is approximately the same throughout the whole intestine in healthy subjects, in HD neural density decreases rostro-caudally towards the rectal region, due to an augmented activity and concentration of distal local inhibitors. In order to prove our hypothesis of HDs nervous rostro-caudal adjustments driven by Turing-like processes, we compared the neuronal density patterns achieved through RD models simulations with the neuronal numbers detected in different colonic regions from affected children. We showed that the virtual and the real plots display fully overlapping and matching features. The fact that neuronal decreases in impaired colons match Turing equationss previsions points towards the human intestine (both healthy and sick) as colonized through a diffusive proximal-distal neural pattern that is predictable, allowing us to straightforwardly calculate the length of the gut to resect during surgical procedures for HD.

pathology↗

bioRxiv2017

Cortical Entropy Values Correlate With Brain Scale-Free Dynamics

A two-dimensional shadow may encompass more information than its corresponding three-dimensional object. If we rotate the object, we achieve a pool of observed shadows from different angulations, gradients, shapes and variable length contours that make it possible for us to increase our available information. Starting from this simple observation, we show how informational entropies might turn out to be useful in the evaluation of scale-free dynamics in the brain. Indeed, brain activity exhibits a scale-free distribution, which appears as a straight line when plotted in a log power versus log frequency plot. A variation in the scale-free exponent and in the line scaling slope may occur during different functional neurophysiological states. Here we show that modifications in scaling slope are associated with variations in Renyi entropy, a generalization of Shannon informational entropy. From a three-dimensional objects perspective, by changing its orientation (standing for the cortical scale-free exponent), we detect different two-dimensional shadows from different perception angles (standing for Renyi entropy in different brain areas). We perform simulations showing how, starting from known values of Renyi entropy (easily detectable in brain fMRIs or EEG traces), it is feasible to calculate the scaling slope in a given moment and a given brain area. Because changes in scale-free cortical dynamics modify brain activity, suggests the possibility of novel insights in mind reading and description of the forces required for transcranial stimulation.

neuroscience↗

bioRxiv2017

Just One Brain Activity

The term brain activity refers to a wide range of mental faculties that can be assessed either on anatomical/functional micro-, meso- and macro-spatiotemporal scales of observation, or on intertwined levels with mutual interactions. Here we show, based on novel topological findings, how every brain activity encompassed in a given anatomical or functional level necessarily displays a counterpart in others. Different brain activities are able to scatter, collide and combine, merging, condensing and stitching together in a testable and quantifiable way. We point out how, despite their local cortical functional differences, all the mental processes, from perception to emotions, from cognition to mind wandering, may be reduced to a single, general brain activity that takes place in dimensions higher than the classical 3D plus time. In physics, the term duality refers to the case where two seemingly different systems turn out to be equivalent. Our framework permits a topological duality among different brain activities and neuro-techniques, because it holds for all the types of spatio-temporal nervous functions, independent of their cortical location, inter- and intra-level relationships, strength, magnitude and boundaries.

neuroscience↗

bioRxiv2016

A LOGICAL INQUIRY OF EMOTIONS AND COGNITION

Experimental procedures in neuroscience rely on the standpoints that the mind is a functional state of the brain and a clear subdivision among different mental faculties does exist in the cortex. According to cognitive neuroscientists, the term \"mind\" encompasses just the \"cognitive\" faculties, such as consciousness, perception, thinking, judgement, memory, leaving apart the \"emotional\" states. Here, taking into account the powerful tools of the first-order predicate logic, we evaluated whether: a) the mind is a function on the physical brain activity; b) different mental faculties can be reduced to a more general one; c) the division of mental faculties in cognition and emotion holds true. We demonstrated that nervous activity is equivalent to mental faculties and that emotions and cognition do not stand for two separated functions of the mind. This means that, counter to our common-sense belief, cognition and emotions are splitted and every faculty of the mind necessarily displays a counterpart in other ones. We point out how it is possible for condensed mind faculties to be unglued in order to become apparently different functions. Therefore, seemingly different mind faculties turn out to be equivalent, because the same logical framework holds for all the types of brain activities, independent of their boundaries and magnitude.

neuroscience↗

bioRxiv2016

A TOPOLOGICAL/ECOLOGICAL APPROACH TO PERCEPTION

During the exploration of the surrounding environment, the brain links together external inputs, giving rise to perception of a persisting object. During imaginative processes, the same object can be recalled in mind even if it is out of sight. In this proof of concept study, Borsuks theory of shape and the Borsuk-Ulam theorem provide a mathematical foundation for Gibsons notion of persistence perception. Gibsons ecological theory of perception accounts for our knowledge of world objects by borrowing a concept of invariance in topology. A series of transformations can be gradually applied to a pattern, in particular to the shape of an object, without affecting its invariant properties, such as boundedness of parts of a visual scene. High-level representations of objects in our environment are mapped to simplified views (our interpretations) of the objects, in order to construct a symbolic representation of the environment. The representations can be projected continuously to an ecological object that we have seen and continue to see, thanks to the mapping from shapes in our memory to shapes in Euclidean space.

neuroscience↗

bioRxiv2016

CRACKING THE BARCODES OF FULLERENE-LIKE CORTICAL MICROCOLUMNS

Artificial neural systems and nervous graph theoretical analysis rely upon the stance that the neural code is endowed in logic circuits, e.g., spatio-temporal sequences of ON/OFF spiking neurons. Nevertheless, this assumption does not fully explain complex brain functions. Here we show how nervous activity, other than logic circuits, could instead depend on topological transformations and symmetry constraints occurring at the micro-level of the cortical microcolumn, i.e., the embryological, anatomical and functional basic unit of the brain. Tubular microcolumns can be flattened in guise of a fullerene-like two-dimensional lattices, equipped with about 80 nodes, standing for pyramidal neurons, where neural computations take place. We show how the countless possible combinations of activated neurons embedded in the lattice resemble a barcode. Different assemblies of firing neurons might stand for diverse codes, each one responsible for a single mental activity. A two-dimensional fullerene-like lattice not just simulates the real microcolumns microcircuitry, but also allows us to build artificial networks equipped with robustness, plasticity and fastness, because they are grounded on simple topological changes corresponding to pyramidal neurons activation.

neuroscience↗