Roman R. Poznanski is a leading authority on modeling in the neurosciences. He has written papers in prestigious high impact ISI-indexed neuroscience journals, including the Journal of Integrative Neuroscience: an interdisciplinary journal that combines theories of information handling in the brain with experimental brain research.
In computational neuroscience, reductionist approaches span multiple levels of neural organization; however in integrative neuroscience, each level is seamlessly sculptured as part of a continuum of levels. Reductionism assumes a direct causal relationship between a molecular/cellular mechanism and a behavioral phenomenon, ignoring the constraints that higher-level properties exert on the possible functions of that mechanism. One of these constraints is dynamic continuity which is intrinsically difficult to harness computationally because compartmentalization and/or discretization is subject to dynamical misalignment, producing a false sense of biological reality. Integration depends on dynamic continuity, which is selected by the electric field inside neurons and across synapses that results in a field of influence for augmenting unconscious processes in the assemblies of networks.
Current approximations to neural dynamics rely on multi-scale models through the doctrine of biological computation. An alternative approach is through relational biology where functional relations between neurobiological processes depend on hierarchical and functional integration in the brain. From this perspective, hierarchical integration is structural involving dynamic continuity in spatiotemporal patterns, bringing about functional organization, while functional integration is relational enabling a relational organization to be mapped from the functional organization.
The brain represents and processes information is a central dogma of computational cognitive neuroscience for 60 years. There are no representations in the neural circuitry of the brain, but physical interactions influenced by the electric field enable dynamic continuity to be entrained inside neurons and across synapses. No neural information processing, but rather selectionism maneuvering dynamic continuity as an adaptive pressure from which semantics spontaneously emerge. Consequently, one begins to move beyond principles of information theory to explore how the result of unpredictable, nonlinear interactions among billions of neurons depends on selectionism, integration, and dynamic continuity.
Computational neuroscience defines loosely 'computations' as the mantra associated with functioning of the brain. What these 'computations' signify and portray are often mysterious mechanisms that are yet to be elucidated with precision. The central dogma of computational neuroscience is that it assumes information processing and information theory to be modus operandi. Consequently, the field is often entwined with how a computer operates. Conversely, 'selectionism', 'integration', and 'dynamic continuity' define the essence of operations that are needed to elucidate brain function. Neuroelectrodynamics as a computational theory attempts to understand brain function on a systems level through molecular physical interactions. However, it is now evident that 'computations' based on concepts from information theory are irrelevant to how the brain integrates and selects dynamic continuity across scale.
His main contribution to research began on the modeling of retinal neurons in visual perception with W.R.Levick, FRS from the John Curtin School of Medicine, Australian National University in Canberra. His modeling work was first to predict the locus of retinal direction selectivity in individual dendritic branches of starburst amacrine cells in the retina in 1990 (and published in 1992). He subsequently developed a more accurate model of a starburst amacrine cell in order to show how direction-selectivity is produced by a network of these cells. The unification of the yet unknown subcellular model of retinal direction selectivity with starburst network topology remains one of his current research themes together with Amane Koizumi of the National Institute for Physiological Sciences, Okazaki, Japan. In particular, on establishing the topology underlying a presynaptic scheme of directional selectivity, he proposed an acetylcholine (ACh) model of directionally selective starburst amacrine cells (Poznanski, R.R. Cellular Inhibitory Behavior Underlying the Formation of Retinal Direction Selectivity, J. Integr. Neurosci. 9, 299-335, 2010). Although experimental studies have shown that during retinal development (prior to vision) the assembly of retinal cholinergic network connections are 'eliminated' in which the glutamatergic networks are formed, such studies categorically do not rule out the possibility of the 'eliminated' ACh connections reconnecting after vision takes place in the mature retina. A model of the inner plexiform layer is currently missing from any prototype bionic eye giving only rudimentary vision to the blind.
His other research direction has been on the establishment of a new generation of neural networks, in particular, the biophysical foundations of neural network theory (as embodied in his book, Biophysical Neural Networks, Mary Ann Liebert, 2001). He was the first to reveal how microscopic-level biophysical properties (e.g., endogenous structures, ion channels; neuronal geometries) may be explicitly incorporated into an analytical formalism that predicts mesoscopic-level functionality. This approach has two major advantages: (1) avoids entirely the mathematical errors and uncertainties inevitable in iterative computational models that necessarily discretize time and space; (2) provides a framework for generating complete and exact solutions for network output enabling dynamical continuity to be reflected through spatiotemporal patterns as a field of influence for dynamic cognitive processes. This led him to consider more sophisticated artificial systems, like the 'cognitive' brain-computer interface (embodied in the book, Modeling in the Neurosciences: From Biological Systems to Neuromimetic Robotics, CRC Press, 2005) .
He has spent years in research at the interface of neuroscience and mathematical modeling with particular emphasis on developing neuronal models across scale. His recent collaboration with Dorian Aur (Stanford University, CA) focuses on the development of a new cable theory for understanding the precise effect of protein polarization on membrane potential and on the excitability process. The new theory finds its true foundations in Maxwell's theory of the electromagnetic field. In classical Nernst-Planck theory, the membrane has no structure and therefore, any attempt at combining the dynamics described by time-dependent Nernst-Planck equation for the spatial distribution of ionic concentration with cable theory is fortuitous. Ionic current flow based on Maxwellian approach is not physico-chemical and currents caused by concentration gradients are neglected. However, this new cable theory of protein polarization approximates electrodiffusion in physico-chemical systems, and is comparable with, yet resilient to the epistemological limitations inherent in the classical Hodgkin-Huxley system. It was Hodgkin who said: “electrodiffusion is like a flea hopping in the storm” meaning that ionic current flow in the presence of an electric field has no coherency compared with an action potential, but Hodgkin never envisaged ionic current flow as a propagating 'shock wave'. It was Huxley who in 1959 suggested that a subthreshold disturbance can be initiated by numerically solving Hodgkin-Huxley equations, but these subthreshold oscillations as envisaged by Andrew F. Huxley in the 1950s are not the only subthreshold responses. Subthreshold oscillations do not have a rapid leading-edge reminiscent of a 'shock wave' for memory selection.
Dr. Poznanski has embarked on the physics of memory and how it depends on: (i) changes in protein metabolism accompanying learning; (ii) memory trace formation and storage (consolidation) in assemblies at the subcellular level through phosphorylation; and (iii) memory selection through dendritic protein polarization by subthreshold membrane potentials at the subcellular level. The prevalent hypothesis is that memory is sub-served by modulation in gene expression.
First book on the development of a nonlinear functional analysis to better understand the intricate fallacies of methodological reductionism in neuroscience
He has also embarked on a research collaboration with Stanislaw Brzychczy (AGH University of Science and Technology) on the development of a nonlinear analysis methods to better understand the intricate fallacies of methodological reductionism in neuroscience. One recent example of this research is the application of nonlinear functional analysis to the cable equation proving that discrete models of neurons like 'multicompartmental models and spiking model neurons' are both dynamically implausible representations of real neurons. This research has implications to 'multi-scale' modeling that are supposed to be ultra 'realistic' attempts at modeling the brain. One limitation is that such 'multi-scale' models are incapable of harnessing 'bridges' across scale without producing a false sense of biological reality. This is because compartmentalization and/or discretization is subject to dynamical misalignment. All research based on compartmental methods should be treated with skepticism. The results of compartmental modeling to explain complex dynamical phenomena must be taken with a grain of salt. Infinite systems represent hierarchical levels in a way that will not delude the continuous dynamics of neuronal systems across spatiotemporal scales.
L-R: Drs. Masumi Ishikawa, Roman Poznanski, and Chee Peng Lim. At far right,
Dr. Jonathan Chan. Discussion on higher brain function at a meeting in Kuala Lumpur.
He has advised several graduate students: (1) Hiroshi Yamamoto 1996 M.Sc. “Computer Simulation of Bipolar Cell Coupling in the Teleost Retina,” Faculty of Information Sciences, Toho University, Japan; (2) Tirad Almalahmeh 2009 Ph.D. "Directional Selectivity by Network of Starburst Amacrine Cells in Retina", Faculty of Computer Science and Information Technology, University of Malaya, Malaysia; (3) Seyed Maysam Torabi 2010 M.Sc. "Noisy Cables", Faculty of Computer Science and Information Technology, University of Malaya, Malaysia; (4) Chan Siow Cheng 2013 Ph.D "Neural Activity in a Morris-Lecar Population Density Model", Faculty of Engineering and Science, UTAR, Malaysia.
His most significant achievements include:
(i) First to pinpoint the locus underlying retinal direction selectivity in mammals, circa 1992. Through modeling starburst amacrine cells he was first to predict that direction selectivity is linked to their individual dendritic branches in a way that is still unknown with precision [5,6,13, 32].
(ii) First to show that conduction velocities in dendrites are nonconstant . This theoretical result showed that sparse distribution of ionic channels will determine how information is processed differently in the dendrites of neurons as opposed to those in axons [21, 22].
(iii) First to find approximate analytical solutions to the Frankenhaeuser-Huxely equations [14, 38].
(iv) First to construct synaptically and gap-junctionally connected neural networks with ionic channels in dendritic cable structures. Such models have been applied to brain function through the development of large-scale brain cell assemblies [17, 23, 24, 27, 39, 40].
(v) First to introduce the conceptual idea that cognition is determined by how the distribution of endogenous proteins (e.g., ion channels) and synaptic inputs along the dendrites of neurons is integrated with the collective behavior of a large population of neurons grouped together as assemblies .
(vi) First to propose and develop nested neural network models for fMRI .
(vii) First to debunk the assumption of isopotentiality of small compartments (under 0.2λ) as a result of significant thermal noise .
(viii) First to propose a model-based framework for the development of a cognitive brain-computer interface .
(ix) Together with Brzycyhczy first to use functional analysis to prove how neural responses differ when continuous space is discretized in computational models [2,9].
(x) New theories of long-term memory away from synapses and dependent on ionic charge configurations [3,4].
(xi) First to elucidate the precise effect of protein polarization on membrane potential and on the excitability process through propagating subthreshold threshold shock waves that are conducive of rich-logic requirements in dendrites underlying memory selection .
(xii) First book in mathematical neuroscience that goes beyond unrealistic dynamics of physical abstractions into the realm of integrative modeling and dynamic continuity in spatiotemporal patterns [ Published].