Papers by Maurizio Mattia
Rapporti ISTISAN, 2006
Mattia M, Caccia B, Amati G, Andenna C, Benassi M, D'Angelo A, Frustagli G, Iaccarino G, Mar... more Mattia M, Caccia B, Amati G, Andenna C, Benassi M, D'Angelo A, Frustagli G, Iaccarino G, Marzi S, Occhigrossi A, Valentini S, Zicari C. Trattamento radioterapeutico: calcolo avanzato per l'ottimizzazione del piano di cura. In: Caccia B, Mattia M, Grisanti F, ed. Convegno nazionale Sistemi di ...
Annali dell'Istituto superiore di sanità, 2001
We review a series of implementations of electronic devices aiming at imitating to some extent st... more We review a series of implementations of electronic devices aiming at imitating to some extent structure and function of simple neural systems, with particular emphasis on communication issues. We first provide a short overview of general features of such "neuromorphic" devices and the implications of setting up "tests" for them. We then review the developments directly related to our work at the Istituto Superiore di Sanità (ISS): a pilot electronic neural network implementing a simple classifier, autonomously developing internal representations of incoming stimuli; an output network, collecting information from the previous classifier and extracting the relevant part to be forwarded to the observer; an analog, VLSI (very large scale integration) neural chip implementing a recurrent network of spiking neurons and plastic synapses, and the test setup for it; a board designed to interface the standard PCI (peripheral component interconnect) bus of a PC with a spec...
Annali dell'Istituto superiore di sanità, 2001
Intensity modulated radiation therapy (IMRT) is one of the most innovative techniques in oncologi... more Intensity modulated radiation therapy (IMRT) is one of the most innovative techniques in oncological radiotherapy, allowing to conform the dose delivery to the tumoral target, preserving the normal tissue. The high number of parameters involved in the IMRT treatment planning requires an automated approach to the beam modulation. Such optimization process consists in the search of the global minimum of a cost function representing a quality index for the treatment. The complexity of this task, has been analyzed with a statistical approach for three clinical cases of particular interest in IMRT. Our main result is that a cost function based on dose-volume constraints entails lower complexity of the optimization process, in terms of the choice of the parameters defining the cost function and in a smaller sensitivity to the initial conditions for the optimization algorithm.
Lecture Notes in Computer Science, 2002
Lecture Notes in Computer Science, 1997
We analyse in detail all the statistical properties of a \canonical" integrate-and-re VLSI neuron... more We analyse in detail all the statistical properties of a \canonical" integrate-and-re VLSI neuron with a linear integrator 1]. We show that a network of such elements can maintain both stable spontaneous activity and selective delay activity, contrary to current opinion. The spike statistics appears to be qualitatively the same as in networks of conventional (exponential) integrate-and-re neurons that in turn, exhibit a wide variety of characteristics observed in cortical recordings 2].
Physical review letters, Jan 29, 2014
The timing of certain mental events is thought to reflect random walks performed by underlying ne... more The timing of certain mental events is thought to reflect random walks performed by underlying neural dynamics. One class of such events--stochastic reversals of multistable perceptions--exhibits a unique scalar property: even though timing densities vary widely, higher moments stay in particular proportions to the mean. We show that stochastic accumulation of activity in a finite number of idealized cortical columns--realizing a generalized Ehrenfest urn model--may explain these observations. Modeling stochastic reversals as the first-passage time of a threshold number of active columns, we obtain higher moments of the first-passage time density. We derive analytical expressions for noninteracting columns and generalize the results to interacting columns in simulations. The scalar property of multistable perception is reproduced by a dynamic regime with a fixed, low threshold, in which the activation of a few additional columns suffices for a reversal.
• Alternation between various perceptual states • Distribution of dominance periods Mean T , coef... more • Alternation between various perceptual states • Distribution of dominance periods Mean T , coefficient of variability C v and Skewness γ 1 • T varies widely between observers and displays • Distribution are well approximated by Gamma distributions (γ 1 /C v ≈ 2) Input strength dependence
Synapses in neuron networks filter incoming spikes with a wide variety of time constants, affecti... more Synapses in neuron networks filter incoming spikes with a wide variety of time constants, affecting the stability of various collective dynamics , the selectivity in transmitting information and the reactivity to suddenly appearing exogenous stimuli . Even for extremely simplified models of spiking neurons and network connectivities, theoretical approaches including non-instantaneous transmission rely on approximations valid for relatively small time scales or on the assumption of a quasi-adiabatic dynamical regime .
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Papers by Maurizio Mattia