Biomedical subjects

T Hervé

Publications and source records attributed to T Hervé.

6 recordsLinked to original sources

PubMed2001

An experimental health smart home and its distributed internet-based information and communication system: first steps of a research project.

We present a study and whole experimental tele-monitoring and medical tele-surveillance system for maintaining patients at home. The project features networked sensors, in a fully equipped apartment, operated by an advanced information and communication system based on Internet, Java, and object oriented modeling. The sensors are connected, mainly wirelessly, with a in-home software module devoted to signals analysis and detection of critical situation such as falls, sickness, sudden palsy, stroke, hypothermia, etc. This module communicates, either via modem or ethernet network, with a remote medical control station in charge of appropriate response to received information and alarms. The system is designed to be a powerful information and communication tools for medical and social workers. It offers a series of functions such as medical file management, user profiles and rights management, drafting and management of ordinances and visit notes, confidentiality of medical information, and management of scenarios of detectable events. The access to the system is allowed to authorized users only (physicians, emergentists, social workers, etc.), and is available on as much authorized computers as needed, by means of a Java applet invoked from any traditional web browsers.

Computer Communication Networks↗

PubMed2000

Statistical procedures for spatiotemporal neuronal data with applications to optical recording of the auditory cortex.

This article presents new procedures for multisite spatiotemporal neuronal data analysis. A new statistical model - the diffusion model - is considered, whose parameters can be estimated from experimental data thanks to mean-field approximations. This work has been applied to optical recording of the guinea pig's auditory cortex (layers II-III). The rates of innovation and internal diffusion inside the stimulated area have been estimated. The results suggest that the activity of the layer balances between the alternate predominance of its innovation process and its internal process.

Animals↗

PubMed2000

Diffusion and innovation rates for multidimensional neuronal data with large spatial covariances.

The diffusion model has been introduced as a statistical model for processing multidimensional neuronal data. This paper extends estimation procedures for the parameters of this model when spatial covariances are large. The new method is based upon linear regression techniques. It is applied to an optical recording of the auditory cortex of a guinea pig stimulated with pure tone bursts (frequency 14 kHz).

Algorithms↗

PubMed1997

Evidence for synchronised responses in the piriform cortex by using Gibbs potential analysis.

The piriform cortex is a large paleocortical area which receives direct projections from the olfactory bulb. In order to study the spatiotemporal distribution of the piriform cortex activity, we chose optical recording of the responses evoked by olfactory bulb electrical stimulation. Such a stimulation elicited a large signal corresponding to cortical reactivation (disynaptic activity) via intrinsic association fibres. As the disynaptic activity was observed over the entire piriform area, we wondered whether or not this redistribution contributes to a synchronisation of the activity in the piriform cortex. In order to answer this question, we developed a statistical approach which allows us to take the temporal dimension into account. The analysis was performed by using the Gibbs potential analysis. The neural response of the diode is represented by a stochastic point process (occurrence of latency peak), and the response of the diode array is given as successive realisations of a binary random field defined on a finite set. The Gibbs measure associated with this field is then estimated through the interaction potentials of the field's configurations, which provide a quantitative evaluation of the interaction and the synchronisation between the neural sites. The analysis was performed on the latency of the peak of disynaptic activity, which was determined from signals from 60 different acquisitions realised with the same stimulus parameters. From these 60 files of latency values, we estimated the Gibbs interaction potential of singletons and pairs. The former gave an image of the spatiotemporal distribution of the disynaptic activity, which appears to propagate from the anterior to the posterior part of the area recorded. The estimation of the interaction potential of pairs allows us to characterise the degree of synchronisation between two neighbouring recording sites. It appeared that, in the anterior half of the area recorded, the disynaptic activity was statistically desynchronised whereas, in the posterior part the disynaptic activity appeared strongly synchronised. The functional implications of such a spatiotemporal distribution of the activity are discussed.

Models, Biological↗

PubMed1996

A new stimulation strategy for recording electrical auditory evoked potentials in cochlear implant patients.

Recording electrical auditory brainstem responses (EABR) provides clinical insight about responses of the residual post-cochlear neural system to electrical stimulation in profoundly deaf patients. A new strategy is presented for stimulating patients already implanted with a 15-electrode cochlear implant. Since the device is fully re-programmable via a RS-232 PC interface, it was possible to load a specific stimulating strategy designed to improve the spatial locus and the temporal structure of the impulse stimulation. Waves III to V emerge more clearly when this method is applied.

Adult↗

PubMed1990

Random field and neural information.

A representation--the Ear-Th representation--of the activity of an assembly of neurons is proposed that allows us to describe simultaneous recorded spike trains through the concept of the random field. This representation intrinsically takes into account the fundamental properties of the neuronal signal: its temporal, stochastic, and spatial nature. As a consequence, a neural network, considered as a kind of parallel random automata, delivers an output random field in response to the excitation provided by a random field that represents the activity of some input fibers. Each random field is represented by its associated Gibbs measure, whose potential is plotted in our representation. This approach is applied to the modeling of an intermediary neural network, which receives its input excitation from the auditory nerve fibers and delivers its response to the next auditory neuronal layer.

Auditory Perception↗