Biomedical subjects

P Erdi

Publications and source records attributed to P Erdi.

25 records · Page 2Linked to original sources

PubMed1991

On the dynamic organization of memory. A mathematical model of associative free recall.

The interaction of memory structures and retrieval dynamics is discussed. A mathematical model for associative free recall is presented to support the view that the organization of simple processing units plays an important role in the retrieval of memory traces. Computer simulations show that "flexibility" and "fidelity" of the dynamics strongly depend on the network structure, the amplification and decay parameters, and the noise term.

Association Learning↗

PubMed1988

Neurobiological approach to computing devices.

According to the old metaphor of classical cybernetics the brain can be considered as a computer. Newer theoretical endeavours reverse the question and ask: what could neurobiology offer to engineers of near-future generation computer systems? Three not completely disjoint abstract functions of the nervous system, namely pattern formation, pattern recognition and action, can be treated in a unified conceptual framework. Storage and retrieval mechanisms of information are connected to fault-tolerant, adaptive parallel structures. "Learning" and "plastic behaviour" are interpreted in terms of the theory of non-linear dynamic systems. As neural development and plasticity can be approached by deterministic models superimposed by random influence, noise might also have a positive role to play during the operation of technical computing devices. Molecular computation is discussed in relation to eventual hardware realization of "neurobiology-based" computers.

Cybernetics↗

PubMed1984

Self-organizing mechanism for the formation of ordered neural mappings.

A model for the formation of ordered neural mappings in general, and of retinotectal connections, in particular is given. The main point came from the theory of "noise induced transitions", i.e. order may be the result of the interplay between deterministic and random interactions. An activity-dependent self-organizing mechanism is presented in terms of modifiable synapses. Simulation experiments were done not only for the normal ontogenetic development but also for the plastic behaviour of the retinotopic connections.

Animals↗

PubMed1983

Hierarchial thermodynamic approach to the brain.

A thermodynamic approach to understanding the brain is presented. Thermodynamics may be extended to "higher than molecule" levels. The role of the concept of entropy in thermodynamic-based nonthermodynamic systems has been discussed. Static and dynamic structures, cooperative and competitive mechanisms and some of their neurobiological applications are discussed. Postsynaptic membrane noises, dynamic synaptic activity, synaptogenesis, plasticity, retinotopy and perception have been considered as self-organizing neural structures appearing at different hierarchical levels.

Animals↗

PubMed1979

Investigation of transmitter-receptor interactions by analyzing postsynaptic membrane noise using stochastic kinetics.

The stoichiometric and kinetic details of transmitter-receptor interaction (the number of conformations and the rate constants of conformation changes( in synaptic transmission have been investigated analyzing postsynaptic membrane noises by the aid of the fluctuation-dissipation theorem of stochastic chemical kinetics. The main assumptions are the following: (i) the transmitter-receptor interactions is modelled by a closed compartment system (a special complex chemical reaction) of unknown length,--(ii) the quantity of transmitter is maintained at a constant level,--(iii) the conductance is a linear function of the conformation quantity vector.--The main conclusion is: the conductance spectral density function is determined by three qualitatively different factors: (i) the length of the compartment system,--(ii) the precise form of the conductance-conformation quantity vector--(iii) the matrix of the reaction rate constants.

Acetylcholine↗

PubMedDate not supplied

On the role of self-excitation in the development of topographic order in the visual system of the frog.

A two-level model is presented for explaining the development of the topographically ordered retinotectal connections of the visual system of the frog. The columnar structure of the tectum were taken into account explicitly. Simulations suggest that the self-excitatory intracolumnar connections play an important role in the formation of the topography. In the case of self-excitation the system is able to recognize the topology of the visual field by the continuity of the object's movement.

Animals↗

PubMedDate not supplied

Dynamic phenomena in the olfactory bulb.

A mathematical model of the olfactory bulb is presented to study the dynamics of the bulbar information processing. A two level model is adopted to describe both neural activity and synaptic modifiability. The model takes explicitly into account the existence of lateral interactions in the mitral layer, and the synaptic modifiability of these connections. A series of bifurcation phenomena among fix points, limit cycle and strange attractors have been demonstrated. Chaos occurred only in the case of excitatory lateral connections. Coexistence between oscillation and chaos, and synaptic modification induced transition have also been found. The model attempts to demonstrate the associative memory character of the olfactory bulb. Odour qualities are coded in distributed spatial amplitude patterns. Differential equations for the mitral and granule cell activities have been supplemented by a continuous-time local learning rule. A nonlinear forgetting term and a selective decreasing term is added to the Hebbian learning rule. A learned odour can be recalled by a subset of the pattern. There is a strict restriction on the parameters: only those values can be admitted which generate physiologically justified activity signals.

Humans↗