Harrison et al. (1) analyzed samples of cardiac and skeletal muscle obtained from patients who had died of congestive heart failure and found them to be abnormally poor in potassium.It is their belief (2, 3) that this diminution in the potassium content is related to overwork and the attendant fatigue.The heart in experimental thyrotoxicosis seemed to offer a possible opportunity of examining the hypothesis in question under controlled conditions.In addition, the effect of thyroid intoxication on the potassium content of the greatly enlarged heart has an interest of its own.Thirty-six male albino rats 140 days old and 14 rats 100 days old were divided into two groups on the basis of body weight.For two weeks they all received a special diet described elsewhere (4).In
Parallel recordings of spike trains of several single cortical neurons in behaving monkeys were analyzed as a hidden Markov process. The parallel spike trains were considered as a multivariate Poisson process whose vector firing rates change with time. As a consequence of this approach, the complete recording can be segmented into a sequence of a few statistically discriminated hidden states, whose dynamics are modeled as a first-order Markov chain. The biological validity and benefits of this approach were examined in several independent ways: (i) the statistical consistency of the segmentation and its correspondence to the behavior of the animals; (ii) direct measurement of the collective flips of activity, obtained by the model; and (iii) the relation between the segmentation and the pair-wise short-term cross-correlations between the recorded spike trains. Comparison with surrogate data was also carried out for each of the above examinations to assure their significance. Our results indicated the existence of well-separated states of activity, within which the firing rates were approximately stationary. With our present data we could reliably discriminate six to eight such states. The transitions between states were fast and were associated with concomitant changes of firing rates of several neurons. Different behavioral modes and stimuli were consistently reflected by different states of neural activity. Moreover, the pair-wise correlations between neurons varied considerably between the different states, supporting the hypothesis that these distinct states were brought about by the cooperative action of many neurons.
A number of experimental observations on the effect of environmental temperature on shock have recently been made.1It was observed that extremes of heat and cold have deleterious effects on the survival time of animals in shock.1a,bThere have been wide differences of opinion as to the optimal environmental temperatures for shocked persons. Thus, Elman and his co-workers1crecommended a temperature of 75 F., Cleghornld72 F. and Wakim and Gatchle85 F. Examination of the data presented by the various authors shows that these variations may be due to study of an insufficient number of temperatures in the region of 65 to 95 F. Likewise, the number of animals employed may not always have been adequate for demonstrating significant responses with small differences in temperature.2It is the purpose of this report to determine in a more complete manner the optimal temperature for
