Research

Brief information about my research projects. For detailed information about some of these projects you can visit the Theoretical Neuroscience Group ( TNG ) website or email me at

Structured Flows on Manifolds

We propose a general theoretical architecture, entitled Structured Flows on Manifolds (SFM), to help us understand and situate within a mathematical framework, human behavioral,perceptual and cognitive processes. Here we suggest phase flows, described by dynamical systems as unbiased general representations of these complex dynamical processes. Such flows for the control of movement processes have been postulated earlier [1] within the domain of Human Movement Sciences.The framework we present derives from such work and is based on the principles of non-linear dynamical systems and synergetics [2] and is informed by the current state of neuroscience and human movement science.

Biological systems when performing functionally meaningful dynamics often do not utilize all the degrees of freedom available to them. The dynamics of this behavior is most often constrained onto a lower dimensional space. Such behavior implies that the system itself is living in a high-dimensional space and depending on parameters or initial conditions the lower dimensional flows a generated accordingly. Such mechanisms that give rise to lower dimensional flows from higher dimensional systems will allow for features such as flexibility and robustness in the system.

The relevance of such a framework becomes clear when one considers high dimensional neural networks that produce functionally meaningful low dimensional dynamics, is also flexible enough to exhibit different types of flows and robust enough to reliably generate the flows despite perturbations. But how such high dimensional networks with complex connectivity gives rise to functionally meaningful dynamics is poorly understood. How does a neural network give rise to function? How can such functional dynamics be systematically obtained from networks? We propose structured flows on manifolds as a framework within which to address these questions.

SFN 2007 Poster of this project ...

More info at the TNG website...

1. Viktor K Jirsa and J. A Scott Kelso. The excitator as a minimal model for the coordination dynamics of discrete and rhythmic movement generation. J Mot Behav, 37(1):35–51, Jan 2005.

2. H. Haken. Synergetics. an introduction. Springer Series in Synergetics, 1983

Team Dynamics Evolves Along Low-Dimensional Manifolds

What is specific about team interaction and how can it be measured? Such question addresses the essential nature of human social interactions, but despite being a presence in daily life, it has not been answered satisfactorily. A team consisting of one excellent and several poor members may score reasonably well by conventional standards, but may not in terms of team interaction.

Our aim is to develop a metric by which the quality of team interaction can be assessed without the knowledge of an outcome (such as a score in a basketball match). This requires a quantitative analysis of team interaction for which we use a dynamical systems approach. In this approach at every point in time each team can be described by a set of variables (location of the team members, head orientations, etc.) and their temporal derivatives. Taken together, these variables form a team vector, that, across time, passes through a trajectory in a high-dimensional phase space. Multiple trajectories from the team performing the same task over and over again, lie in some manifold in phase space. The conceptual idea is that the properties of the manifold inform us about the quality of team interaction. For instance we expect the manifold to be low-dimensional due constraints imposed by team interaction.

Poster on team dynamics from Cooridnation Dynamics 2007 conference

More info at the TNG website...

Rate Dependent BOLD Activity in the Auditory Cortex

In this study we systematically investigate the effect of stimulation rate on location of neural activity within the human auditory cortex using fMRI. Human subjects were presented with simple tones at rates ranging from 0.5Hz to 5.0Hz. We found that with increase in the stimulation rate the center of mass of the activity moves posterior along the superior temporal plane (STP). Previous studies have systematically investigated the neural correlates of rhythmic auditory stimulation using imaging modalities such as EEG and MEG. Using the BOLD activity observed in our experiment as an anatomical constraint we calculate the theoretical EEG and MEG forward solutions and its changes according to the conditions.

SFN 2005 Poster of this project ...

More info at the TNG website...

Neural Basis of Auditory Streaming Percepts using fMRI

Auditory streaming is an auditory perceptual phenomenon exhibiting monostable and bistable perceptual properties analogous to foreground-background perceptual phenomena. The phenomenon can be elicited by listening to stimuli consisting of alternating pure tone sequences of fixed tone durations with amplitude, frequency, and inter-onset interval (IOI) as the primary control parameters.

Our fMRI study was motivated by dynamical perceptual models consisting of interacting neural networks with and without tonotopic architectures. Using set theoretical operations on fMRI data we show that the percept of auditory streaming involves regions other than just the primary auditory areas. Networks specific and common to both amplitude and frequency streaming were identified. This lends support to models of perception conceived as interacting neural subnetworks acting as information convergence zones for the classification of the perceptual world.

More info at the TNG website...

Theoretical Analysis Platform: TAP

Theoretical Analysis Platform (TAP) is a GUI written in Matlab, which provides an interface for the modelling of brain-behavior dynamics. The interface defines two levels, a behavioral level and a brain level. The behavioral level provides two excitator models which capture the intrinsic dynamics of human limbs. These may be coupled so that their behavior is not independent, contributing to extrinsic dynamics components. External stimuli, visual, auditory or tactile, may be read in and provide external information for the excitator system. These elements together define a platform, which allows the modelling of human bimanual or unimanual dynamics, discrete or rhythmic, under the impact of environmental information.

The TAP home page