Turtle cortex Micro Circuits in Turtle Visual Cortex
Zoran Nenadic, Bijoy K. Ghosh

The goal of this project is to model the visual cortex of the freshwater turtles. It contains three cellular layers. The intermediate layer contains pyramidal cells with dendrites extending to layers 1 and 3. The outer layer1 and inner layer 3 contain mainly inhibitory interneurons. Excitatory synapses are connected to the dendrites of pyramidal cells and the layer 1 neurons. Our model captures the basic geometry and temporal structure of the visual cortex and generates propagating waves of activity for a moving stimulus. more ...
Movie 1 - Simulation using a light flash
Movie 2 - Simulation of a Stationary Stimulus
Movie 3 - Simulation of a Moving Stimulus
Related publications

Pyramidal cells Decoding the position of a Visual Stimulus from the Cortical Waves of Turtles
Xiuxia Du, Bijoy K. Ghosh

This project addresses the question of obtaining the position of a visual stimulus from the cortical waves of the fresh water turtles. Gaussian-noise-disturbed stimulus was applied to the left, center and to the right of the turtles' visual field and the corresponding cortical waves are generated using the model of the turtle visual cortex developed in our lab . Principle Component Analysis and Moving Time Window techniques are applied to analyze the features of the waves locally in time. We propose the idea of Alpha and Beta spaces to represent the waves quantitatively. more ....

Eye movement control Modelling 3D Eye Movements and Visual Attention
Ashoka D. Polpitiya, Bijoy K. Ghosh

Modelling and Control of eye movements has been the topic among neurologists and engineers for a long time. Each eye is attached to its orbital layer via six extraocular muscles. We try to model the eye with the effect of recently discovered rectus muscle pulleys, to generate 3D eye movements. The extraocular musculotendons are modelled using the Hill-type approach. Listing's Law is discussed with a Differential Geometric view point. We call List the submanifold of SO(3) on which the movements obey the Listing's Law. Geomtry of List (Geodesics, Riemannian connection, Curvature tensor etc.) as well as various Optimal Control stratergies on List are also discussed. Visual Attention i.e. "withdrawal from some things in order to deal effectively with others", connected to saccadic eye movements is another topic of interest. Attention is allocated to the chosen target shortly before the saccade is made to look at it.
Related publications

Spiky neurons Computations with a Population of Neurons
Zoran Nenadic, Bijoy K. Ghosh

We try to understand how a pool of biological neurons would encode an analog signal and ways to decode the spike trains to extract the information carried over. We use the idea of an "activity curve" of a nuron, and for a pool of neurons, the weighted sum of these activities approximate a given function. In effect, we investigate how to solve an ordinary differential equation by dynamically updating the activities of the neuron pool. Algorithms for finding optimal synaptic weights are developed and various filtering schemes are introduced in order to decode spike signals from neurons. GENESIS neural simulator is used as the testbed. more...
Related publications

Mobile robotics Mobile Robotics, Machine Vision and Multisensor Fusion
Ping Liu, Bijoy K. Ghosh

An important problem in machine vision, particularly in problems related to parameter estimation by fusing the noisy data from multiple sensors, is to characterize to what extent the motion and shape parameters be identified. With our XR4000 mobile robot, we investigate these issues using the Charged Coupled Device (CCD) cameras, a laser range finder and a set of ultrasonic and tactile sensors. The goal is to move around and observe stationary or moving objects in the environment and estimate the shape of the object and the asociated motion parameters. Related to this problem is also the 2D/3D map building and localization. more ...
Related publications page 1, page 2

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