Biomedical subjects
P Lansky
Publications and source records attributed to P Lansky.
Computational model of the effects of stochastic conditioning on the induction of long-term potentiation and depression.
The long-term potentiation (LTP) or long-term depression (LTD) of synaptic strength are currently considered to be the first microscopic steps leading to learning and memory. The great majority of experiments (both in vitro and in vivo) studying the basic mechanisms of LTP and LTD induction use conditioning protocols in which the presynaptic stimuli are delivered at constant frequencies. This is not, however, what is commonly found in vivo, where a highly irregular spiking activity seems to drive most of the neuronal functions. Thus, some important aspects of the induction characteristics of LTP and LTD expressed in vivo might have been overlooked by the experiments. Using a simple schematic model for a synapse we show here that, in fact, the statistical properties of a presynaptic conditioning signal could change the probability to induce LTP and/or LTD, suggesting a new and faster operating mode for a synapse.
Long-term potentiation and depression induced by a stochastic conditioning of a model synapse.
Protracted presynaptic activity can induce long-term potentiation (LTP) or long-term depression (LTD) of the synaptic strength. However, virtually all the experiments testing how LTP and LTD depend on the conditioning input are carried out with trains of stimuli at constant frequencies, whereas neurons in vivo most likely experience a stochastic variation of interstimulus intervals. We used a computational model of synaptic transmission to test if and to what extent the stochastic fluctuations of an input signal could alter the probability to change the state of a synapse. We found that, even if the mean stimulation frequency was maintained constant, the probability to induce LTD and LTP could be a function of the temporal variation of the input activity. This mechanism, which depends only on the statistical properties of the input and not on the onset of additional biochemical mechanisms, is not usually considered in the experiments, but it could have an important role to determine the amount of LTP/LTD induction in vivo. In response to a change in the distribution of the interstimulus intervals, as measured by the coefficient of variation, a synapse could be easily adapted to inputs that might require immediate attention, with a shift of the input thresholds required to elicit LTD or LTP, which are restored to their initial conditions as soon as the input pattern returns to the original temporal distribution.
Possibility of hypnosis as an aid in cancer therapy.
Explore the source record for details and available documents.
Alpha detection: some comments on Hardt and Kamiya, "Conflicting results in EEG alpha feedback studies".
The problem of defining EEG alpha activity, and of detecting and measuring it, is outlined. Some advantages of a threshold method are presented and compared with an amplitude-integration method. Characteristics of percent-time scoring, based upon observable alpha spindles in the waking EEG, are discussed. A probability distribution of percent-time alpha as a function of detection threshold is derived and compared with empirical data.
Some kinetic and inhibition properties of human brain mitochondrial monoamine oxidase (EC 1.4.3.4).
Explore the source record for details and available documents.
On population aspects of group disasters: an evolutionary view.
Simple mathematical models were constructed (using a DEC PDP 11/40 computer) to evaluate the probable significance of differences between individuals in adaptive reserve--survival time (modelled as "failure rate")--for group survival and of basic population parameters (fertility and mortality) for the gradual compensation of group size/age distribution of a population after an acute group disaster. The results indicate that reversion to prehuman biological regulative mechanisms probably occurs, and that after short-lasting group disasters the time-course for compensation (normalization) of population size and age distribution (when probable values of fertility and mortality were considered) is prolonged.