Biomedical subjects

Botond Roska

Publications and source records attributed to Botond Roska.

4 recordsLinked to original sources

PubMed2006

Parallel processing in retinal ganglion cells: how integration of space-time patterns of excitation and inhibition form the spiking output.

Our goal was to understand how patterns of excitation and inhibition, interacting across arrays of ganglion cells in space and time, generate the spiking output pattern for each ganglion cell type. We presented the retina with a 1-s flashed square, 600 microm on a side, and measured patterns of excitation and inhibition over an 1,800-microm-wide region encompassing many ganglion cells. Excitatory patterns of on ganglion cells resembled rectified versions of the voltage patterns of on bipolar cells. Inhibitory patterns in on ganglion cells resembled the rectified versions of voltage patterns of off bipolar cells. off ganglion cells received off excitation and on inhibition. Many ganglion cells also received an additional wide field transient inhibition derived from the activity of both on and off bipolar cells. Ganglion cell spiking was suppressed in those space-time regions dominated by inhibition. We classified each ganglion cell type by correlating its space-time patterns with its dendritic morphology. These studies suggest the bipolar and amacrine cell circuitry underlying the interplay between on and off signals that generate spiking patterns in ganglion cells. They reveal a surprising synergistic interaction between excitation and inhibition in most ganglion cells.

Action Potentials↗

PubMed2004

Bio-inspired nano-sensor-enhanced CNN visual computer.

Nanotechnology opens new ways to utilize recent discoveries in biological image processing by translating the underlying functional concepts into the design of CNN (cellular neural/nonlinear network)-based systems incorporating nanoelectronic devices. There is a natural intersection joining studies of retinal processing, spatio-temporal nonlinear dynamics embodied in CNN, and the possibility of miniaturizing the technology through nanotechnology. This intersection serves as the springboard for our multidisciplinary project. Biological feature and motion detectors map directly into the spatio-temporal dynamics of CNN for target recognition, image stabilization, and tracking. The neural interactions underlying color processing will drive the development of nanoscale multispectral sensor arrays for image fusion. Implementing such nanoscale sensors on a CNN platform will allow the implementation of device feedback control, a hallmark of biological sensory systems. These biologically inspired CNN subroutines are incorporated into the new world of analog-and-logic algorithms and software, containing also many other active-wave computing mechanisms, including nature-inspired (physics and chemistry) as well as PDE-based sophisticated spatio-temporal algorithms. Our goal is to design and develop several miniature prototype devices for target detection, navigation, tracking, and robotics. This paper presents an example illustrating the synergies emerging from the convergence of nanotechnology, biotechnology, and information and cognitive science.

Animals↗

PubMed2003

Rapid global shifts in natural scenes block spiking in specific ganglion cell types.

The mammalian retina contains more than a dozen different ganglion cell types, each with dendrites ramifying at different strata within the inner plexiform layer (IPL) and each carrying a unique representation of the visual world. We studied the inhibitory and excitatory inputs, as well as the spiking output, of each of the rabbit retinal ganglion cell type during rapid global shifts in 'natural' videos designed to mimic saccadic eye movements. These shifts generated stratum-specific transient inhibitory activity, affecting only those ganglion cells whose dendrites ramify within the central strata of the IPL. The inhibition was GABA-mediated, acted both pre- and postsynaptically and was fast enough to either prevent or delay spiking. These findings indicate that the fast, transient elevation of visual threshold during rapid shifts in scene has a significant retinal component.

Action Potentials↗

PubMed2002

Tuning FlaSh: redesign of the dynamics, voltage range, and color of the genetically encoded optical sensor of membrane potential.

The optical voltage sensor FlaSh, made from a fusion of a GFP "reporter domain" and a voltage-gated Shaker K(+) channel "detector domain," has been mutagenically tuned in both the GFP reporter and channel detector domains. This has produced sensors with improved folding at 37 degrees C, enabling use in mammalian preparations, and yielded variants with distinct spectra, kinetics, and voltage dependence, thus expanding the types of electrical signals that can be detected. The optical readout of FlaSh has also been expanded from single wavelength fluorescence intensity changes to dual wavelength measurements based on both voltage-dependent spectral shifts and changes in FRET. Different versions of FlaSh can now be chosen to optimize the detection of either action potentials or synaptic potentials, to follow high versus low rates of activity, and to best reflect electrical activity in cell types with distinct voltages of operation.

Biosensing Techniques↗