My
research interests are in nonlinear dynamics, stochastic dynamics, theoretical
and computational neuroscience, complexity theory, biological physics,
mathematical biology and nonequilibrium thermodynamics. The main
focus of my research is on theoretical and computational studies of the
nervous system. I develop mathematical models of neural activity at different
levels in the nervous system. The levels range from that of the single cell,
where I study e.g. the biophysics of sensory transduction, neural plasticity
and information processing, to that of systems of cells, where I work on e.g.
memory and the role of feedback within and between populations of cells. My
interest also extends to other physiological systems where I investigate the
origins of variability in organ activity, the role played by multiple feedback
control loops, and the production and dissipation of entropy by non-equilibrium
systems such as the human body. My work is generally strongly tied into
experimental data, and I collaborate with various experimental groups in the
University of Ottawa's Center for
Neural Dynamics (see below) and elsewhere. This research is highly
interdisciplinary, and involves studies in one or more of the following areas,
depending on the projects:
My work in nonlinear dynamics is often inspired by problems in neural modeling and, more generally, in physiology and biology. I am particularly interested in the response properties of models of cells or systems of cells to deterministic and/or stochastic inputs, and on the role of feedback. My current research activity involves work on delay-differential equations, chaos, noise-induced transitions, noise shaping, neural field equations, stochastic resonance, multistability, dynamical memory, and nonlinear time series and point process analysis aimed at guiding and testing modelling studies. I also am interested in emergent computation, i.e. in the new properties that arise through the interaction of simpler nonlinear elements.
Recently I have begun investigating the learning properties of small neural networks in mouse and zebrafish (collaboration at uOttawa and the Kavli institute in Trondheim). We are figuring out the circuitry that underlies the detection of a "novel" stimulus, time representation and sequence memory.
A third of my past computational and theoretical neuroscience work concerns weakly electric fish, due to close interactions with two experimental groups at the University of Ottawa (Maler and Lewis). These animals have a sufficiently simple brain (compared e.g. to monkeys), yet exhibit sufficiently interesting behaviors, to enable us to figure out how information is processed and stored in their brains - thus revealing the building blocks of processing in more complex brains. Thus, apart from generating a wealth of knowledge on the neural functioning of weak electric fish (wave but also pulse type), this work leads to general principles of neural organization that applies in many cases to higher mammals.
Further, I have projects in visual neuroscience and psychophysics. For example, I work on the problem of the dynamics of eye saccade programming, on the dynamics of attention shifts, and on the link between the two. I have worked on motor control and internal models, e.g. in the context of posture control.
I also study how the nervous system can disambiguate mixtures of signals (as in the cocktail party effect), and in particular, why certain mixtures are significant and lead to specific behaviors. This is relevant to musical consonance and to social communication in a variety of animal species. It is also particularly relevant to the design of novel prosthetic devices such as cochlear implants.
I am also working on modeling how abnormal firing (including ectopic firing) occurs after traumatic impacts on nerve fibers, on the associated onset of pain responses, and on the alteration of propagation delays between different parts of the nervous system in MS, epilepsy and other conditions and their functional consequences.
I collaborate with a clinician (Seely) and an exercise physiologist (Kenny) on projects on heat and entropy management in humans, and its dysregulation with aging, lack of fitness and certain diseases. Entropy production and dissipation are explored as correlates of health.
The long-term goals of my research are to understand how neurons and other biological units self-organize and perform computations, and what links cellular biophysics and biological complexity. At the core of this work is the physical understanding of how deterministic dynamics and stochasticity (i.e. noise sources) interact in nonlinear systems, producing complex, and often unpredictable behaviors.
My research also aims to understand how nature solved signal processing
problems. This knowledge is useful for the design of new signal processing
strategies for e.g. bionic, prosthetic, clinical and
machine learning applications (e.g. for brain-machine interfaces), and to better
understand the ethical implications of AI in these fields. The goal of my
research on physiological regulation and energetics from the point of view of
nonlinear stochastic dynamics is the design of novel therapies for treatment of
certain diseases or of novel criteria for intervention in the intensive care
unit.