A tether system for cardiovascular studies with the behaving micropig

A tether system has been developed for continuous monitoring of blood pressure in the micropig. The micropig is a suitable model for blood-pressure research because of the similarity of its cardiovascular system to that of humans and because of its sensitivity to high sodium intake. The system consists of a metal boom, attached via a universal joint to a wall 6 ft above floor level, that extends horizontally to the center of the enclosure. A fluid and electronic swivel affixed to the boom is connected to a flexible, hollow, metal tether that descends to a vest worn by the micropig. The vest contains a pressure transducer to which an indwelling arterial catheter is connected via a stopcock. The transducer cable and an infusion line ascend through the interior of the tether to the swivel. The system remains in equilibrium through a system of pulleys and counterweights. Continuous, 24-h recording shows a diurnal variation characterized by higher heart rate but lower blood pressure during the day than at night. The system has been found to be effective for continuous studies over intervals of a month or more.     

Response-key input via the IBM PC/XT/AT’s parallel printer port

A simple and inexpensive way to connect response keys to the IBM PC/XT/AT’s parallel printer port is presented.     

Shaw’s stored information as a quantitative measure of sequential structure

In this paper, we describe a method to study the sequential structure in interevent times. The technique uses the stored information of an iterative map developed by-Shaw (1984). The stored information is a quantitative measure of the sequential organization or predictability in data. This paper discusses the concept of stored information and provides a FORTRAN routineto compute the stored information of interevent time data. Several synthetic data sets with known sequential structures are examined. Finally, we present some initial results from computing the stored information of experimental interresponse time data.     

GRADER: A computer program that recommends student letter grades

GRADER, a computer program that makes student test and/or course letter grade recommendations to instructors, is described. The program uses an algorithm to combine the content mastery (percentage correct) and peer comparison (“curve”) approaches to set grade cutoffs. In addition to standardizing the procedures with which letter grade cutoffs are made, GRADER may help to reduce instructor grading subjectivity and obviate tendencies toward grade inflation or deflation.     

Reflections on human pavlovian decelerative heart-rate conditioning with negative tilt as US: Alternative approaches

The negative-tilt preparation that has been reported since the late seventies is a specific form of Pavlovian conditioning that is of scientific interest and has potential applications. In this paper I reflect on the usefulness, to the development of this preparation, of two approaches to Pavlovian conditioning. One approach is the older S-R learning, stimulus-substitution paradigm exemplified by learning texts of the sixties. The other is the modern, Tolman-like view, according to which the phenomenon of Pavlovian conditioning is “now described as the learning of relations among events so as to allow the organism to represent its environment.” The three assumptions encapsulated by this approach are: (a) that only CS-US contingency relations are learned; (b) that teleological modes of explanations are adequate; (c) that the representational theory of knowledge is sound. Concerning Pavlovian conditioning in general, questions been raised in the literature for all three assumptions; they have not been adequately answered. Regarding the specific problem of developing the human Pavlovian heart-ratedecelerative conditioning with negative tilt as the US, I suggest that the cognitive approach has been much less helpful than the older, S-R, stimulus-substitution paradigm. Nevertheless, other literature clearly indicates that the cognitive, S-S approach has generated considerable interest and research, especially in preparations like the conditioned emotional response (CER), which are CS-IR ones in the sense that the effects on the CR are assessed indirectly through measuring an indicator or instrumental response (IR). Finally, even in CS-CR preparations like human GSR conditioning, it is important to study the cognitive, S-S learning process through using such dependent variables as continuously assessed subjective CS-US contingency.     

Application of chaos theory to biology and medicine

The application of “chaos theory” to the physical and chemical sciences has resolved some long-standing problems, such as how to calculate a turbulent event in fluid dynamics or how to quantify the pathway of a molecule during Brownian motion. Biology and medicine also have unresolved problems, such as how to predict the occurrence of lethal arrhythmias or epileptic seizures. The quantification of a chaotic system, such as the nervous system, can occur by calculating the correlation dimension (D2) of a sample of the data that the system generates. For biological systems, the point correlation dimension (PD2) has an advantage in that it does not presume stationarity of the data, as the D2 algorithm must, and thus can track the transient non-stationarities that occur when the systems changes state. Such non-stationarities arise during normal functioning (e.g., during an event-related potential) or in pathology (e.g., in epilepsy or cardiac arrhythmogenesis). When stochastic analyses, such as the standard deviation or power spectrum, are performed on the same data they often have a reduced sensitivity and specifity compared to the dimensional measures. For example, a reduced standard deviation of heartbeat intervals can predict increased mortality in a group of cardiac subjects, each of which has a reduced standard deviation, but it cannot specify which individuals will or will not manifest lethal arrhythmogenesis; in contrast, the PD2 of the very same data can specify which patients will manifest sudden death. The explanation for the greater sensitivity and specificity of the dimensional measures is that they aredeterministic, and thus are moreaccurate in quantifying the time-series. This accuracy appears to be significant in detecting pathology in biological systems, and thus the use of deterministic measures may lead to breakthroughs in the diagnosis and treatment of some medical disorders.     

The effect of unilateral stellectomy on the regulation of heart rate during behavioral stress

Changes in heart rate were examined during classical aversive conditioning before and after either left (n=10) or right stellectomy (n=8). Heart rate (HR) significantly (p<0.01) increased in response to the conditional stimulus with a further increase noted during the unconditional stimulus. After right stellectomy (RSGx) the aversive stress elicited a significantly (p<0.01) smaller increase in heart rate (peak HR change: control 66.8 +/- 6.0; RSGx 36.1 +/- 6.8 beats/min). In contrast left stellectomy did not significantly alter the heart rate conditional response. Cardioselective beta-adrenergic receptor blockade, metoprolol HCl (BB, 1.0 mg/kg, n=8), significantly (p<0.01) reduced the heart-rate conditional response (peak HR change: control 66.8 +/- 6; BB 25.1 +/- 3.8 beats/min) to the same extent as noted during RSGx. These data suggest that the heart-rate increases elicited by aversive stress are mediated in part by sympathetic nerves that originate or pass through the right stellate ganglion. The residual HR increase noted after RSGx or BB probably results from the withdrawal of cardiac parasympathetic activity.     

Amplitude rise time and the perception of the voiceless affricate/fricative distinction

Variation of amplitude envelope at stimulus onset has been considered to be of primary importance for distinguishing voiceless affricates from fricatives (e.g., |t∫| and |∫|). In earlier perceptual experiments, however, variation in amplitude rise time was confounded with variation in frication duration. In two experiments, these variables were independently manipulated, and their individual and combined effects for perception of |t∫| and |∫| were examined. Variation in amplitude rise time alone was not sufficient to signal the voiceless affricate/fricative contrast in these experiments, but variation in frication duration alone was sufficient.     

Low-dimensional chaos maps learning in a model neuropil (olfactory bulb)

Quantification of a chaotic system can be made by calculating the correlation dimension (D2) of the data that the system generates (Packard et al., 1980). The D2 algorithm, however, requires stationarity of the generator, a feature that biological data rarely reflect (Mayer-Kress et al., 1988). So we developed the “point correlation dimension” (PD2), an algorithm that accurately tracks D2 in linked data of different dimensions (Carpeggiani et al., 1991). We now present a mathematical argument that, for stationary data, individual PD2s converge to D2 and we demonstrate that the algorithm rejects contributions made by bursts of noise. Data were obtained from the surface of the olfactory bulb of the conscious rabbit (64 electrodes, 640 Hz each, 1.3 sec epochs) before and after presentation of a novel or habituated odor. D2 could be calculated in only 1 of 10 novel-odor trials, whereas PD2 could be calculated in all. Both algorithms indicated that a novel odor evokes a spatially uniform dimensional increase. The PD2 uniquely exhibited the dimensional decreases that occur during inspiration and the gradients of mean dimension present during the nonstimulated control state. These control gradients remained unchanged without odor experience, but showed spatially specific PD2 increases following odor habituation. It is interpreted that, 1) the PD2 issensitive, accurate, and appropriate for dimensional assessment of biological data, 2) that during analysis of unfamiliar information a singleglobal process is transiently evoked in the neuropil, and 3) after experience multiplespatially specific processes tonically map the sites of learning. Grant Support: National Institutes of Health, HL 31164 and NS27745     

The putative role of free radicals in the loss of neuronal functioning in senescence

One of the hallmarks of the aging process is a loss of sensitivity in central neuronal receptors to agonist stimulation. This appears to be especially true in central (hippocampal, striatal) muscarinic cholinergic systems and in the striatal dopamine systems. For these two systems, any decline in their sensitivity can be of extreme importance in determining the behavioral capabilities of the organism. Decrements in the striatal dopamine system may be reflected as motor behavioral deficits, while the central cholinergic systems play a major role in the processing of memory through the activation of muscarinic receptors (mAChR). Declines in the function of these receptors appear to be at least partially responsible for the marked deterioration of cognitive function in normal aging and, more notably, in Alzheimer’s disease (AD). Previous work has indicated only minimal success in improving performance in tasks that assess memory in senescent animals or humans with pharmacological agents which enhance cholinergic functioning. The present review describes research that indicates that two of the factors involved in this decline in receptor sensitivity include: (a) decreased receptor concentrations and (b) age-related decrements in signal transduction pathways. Studies are reviewed that indicate that the oxidative neural damage that occurs via kainic acid or ionizing radiation parallel those seen in aging. It is suggested that the common mechanism that may exist among all of the age-, disease-, excitatory amino acid- or radiation-induced deficits in neuronal transmission may involve free-radical-mediated alterations in membrane integrity through lipid peroxidation.