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J T Hackett

Publications and source records attributed to J T Hackett.

44 records · Page 3Linked to original sources
PubMed1969

Steady potential correlates of positive reinforcement: reward contingent positive variation.

A positive reinforcement with food produced high-voltage bursts of alpha activity over the posterior marginal gyrus in a cat deprived of food and water. This synchronization was always associated with a large (180 to 300 microvolt), positive steady potential shift comparable to that occurring during the onset of sleep. Since this shift was contingent upon the relative appropriateness and desirability of food reward, it was termed reward contingent positive variation.

Animals↗
PubMedDate not supplied

Stochastic modeling of facilitated neurosecretion.

Two models of neurosecretion were evaluated in terms of their ability to predict the dependency of quantal content (m) on the frequency of repetitive stimulation of a lobster motoneuron. First, the hypothesis that neurosecretion is limited by a fixed number of release sites was tested by the fit of the distribution of m by uniform and nonuniform binomial statistics. The obtained release probabilities suggest that frequency facilitation can be due to activation of a group of sites with high release probabilities. However, the fit obtained using this model is not statistically significant due to a large number of fitting parameters. Second, the hypothesis that neurosecretion is limited by the rates of exchange between the releasable pool and the total store of quanta and that each stimulus enhances quantal mobilization was tested. Monte Carlo simulation was carried out in accordance with this model and reproduced the observed distribution of m with very few fitting parameters and therefore with a high level of significance (>0.1). This result demonstrates that mobilization of extra vesicles with each stimulus is a mechanism that allows a very accurate and parsimonious quantitative description of frequency facilitation.

Action Potentials↗