Application of chaos theory to a model biological system: Evidence of self-organization in the intrinsic cardiac nervous system

The neural organization that determines the specific beat-to-beat pattern of cardiac behavior is expected to be demonstrated in the independent regulation of the RR intervals (chronotropy) and the corresponding QT subintervals (inotropy), as the former defines the rate of contraction and the latter has a linear negative correlation with the peak pressure inside the contracting ventricular muscles. The neurons of the isolated cardiac nervous system, many of which are located in the fat-pads of the heart, exhibit the same types of mechanical and chemical receptors and the same types of cholinergic and noradrenergic effectors as those found in the neural superstructure. In the surgically isolated and perfused rabbit heart we studied the responses of the QT and RR intervals evoked by block of coronary blood flow. We found that if we separated each RR cycle into QT and RR-QT components, then the dynamics of variation for each subinterval series often had the same fractional number of degrees of freedom (i.e., chaotic dimensions), a finding which suggests they are both regulated by the same underlying system. The ischemia/anoxia evoked transient dimensional increases and separations between the two subinterval series that, after the temporary divergence, reconverged to having the same lower value. The dimensional fluctuations occurred repeatedly and preceded or coincided with alterations in the magnitude and sign of the slope of QT vs RR-QT. We interpret the dimensional fluctuations of the two subinterval series as correlates of adaptation-dependent self-organization and reorganization in the underlying intrinsic cardiac nervous system during accumulating ischemia/anoxia. Such attempts at functional reorganization in this simple neurocardiac system may explain the transient dimensional changes in the RR intervals that precedes by 24 hrs the occurrences of fatal ventricular fibrillation in high-risk cardiac patients.     

Lexical creativity during instances of word-finding difficulty: Broca's vs. Wernicke's aphasia

Lexical innovation--the creation of a word by combining existing morphemes in a novel way (e.g. "map ball" for "globe")--was evaluated as a method for circumventing word-finding difficulty in Broca's and Wernicke's aphasia. Aphasic groups were matched for naming performance and compared to a control group of normal adults matched for age and education. Lexical innovations were collected during the administration of a confrontation naming test, and were then analyzed in terms of the correctness of morpheme combination, semantic accuracy, novelty, and communicative effectiveness. An innovation was considered to be communicatively effective when its intended referent was understood by a naive judge. The lexical innovations of the two aphasic groups were diametrically opposed: as compared to both Broca's aphasics and normal adults, Wernicke's aphasics innovated significantly less often, and their innovations were significantly inferior in terms of: semantic precision, the proper construction of morpheme combination, and communicative effectiveness. This pattern suggests that lack of verbal fluency may be compatible with lexical creativity, while empty logorrheic speech may be an impediment to lexical creativity. Similarly, we conclude that the agrammatism of Broca's asphasia does not interfere with lexical innovation, while the paragrammatism of Wernicke's aphasia does interfere with lexical innovation, thus suggesting that paragrammatism affects morpheme combination at the word level as well as the sentence level.     

The effect of alcohol and barbiturate on the frequency of atrial and ventricular premature beats during sleep

Integrative Psychological and Behavioral Science - Repeated EEG and ECG monitoring during sleep was carried out in two subjects with ischemic heart disease and one presumably healthy control. All...     

SUPERVISING PARAPROFESSIONAL TUTORS IN A REMEDIAL READING PROGRAM1

Applied researchers increasingly report the use of paraprofessionals to implement key program components. However, despite such apparent advantages as increased availability and lower salaries, problems in maintaining acceptable levels of on-the-job performance in these workers have been reported. This study assessed the effects of a supervisory package on the work behavior of five paraprofessional tutors in a remedial reading program. The package consisted of written handouts and instructions, tests of tutor understanding, a video tape, mention of tutor performance by supervisors, and publicly posted feedback on work performance. One randomly chosen tutor received feedback each day on (1) his degree of completeness in tutoring one student's answers to comprehension-check questions, (2) his accuracy in tabulating that student's data sheet, and (3) his promptness in beginning the first student's tutorial session. The supervisory package produced marked improvement in completeness, some improvement in accuracy, but no improvement in promptness. Application of the supervisory package seemed practical, as an average of nine daily tutorial sessions (approximately 270 min of tutoring) required a total daily average of only 28 min of supervision. It was concluded that completeness performance by nondegreed, paraprofessional tutors was closely related to the extent to which they were supervised. Despite the fact that no improvement was observed in tutor promptness, and only partial improvement was observed in tutor accuracy, the improvement to near-perfect levels in tutor completeness suggests that further research is warranted to develop supervisory packages that might ensure the reliable and efficient use of paraprofessional workers.     

A cognitive model of musical sight-reading

The author, a professional flutist and psychologist, interviewed four pianists noted for their sight-reading abilities. The results of the interviews are considered from several points of view. Sight-reading is analyzed as a problem in pattern recognition: a movement from a sonata by Handel is used to illustrate the principle of scanning for familiar patterns. The close relationship between musical sight-reading and the reading of conventional texts is also suggested. Finally, drawing on the findings of other studies, a cognitive model of musical sight-reading is proposed. The schematic model of interlocking information-processing systems explains the differences between skilled and unskilled sight-readers; it also explains why some experienced, professional musicians are poor sight-readers. Verification of the model is provided in an additional section in which conversations with unskilled sight-readers are reported.     

Generating complex waveforms

A wide variety of complex waveforms can be generated by approximating the desired analog waveform from an array of digital values. Some basic properties of these digital approximations are discussed in terms of pulse amplitude modulation and sampling theory. The waveforms are generated by transferring the digital values to a digital-to-analog converter followed by a low-pass filter. This usually requires the dedicated use of a computer. We have built a device, incorporating solid state memory, that can store, time, and transfer previously computed digital values, so that a computer is no longer necessary to generate the waveforms. Specifications of the digital-to-analog converter and appropriate settings of the filter are discussed, along with a simplified procedure for calculating waveforms that have line spectra. An adaptation of this procedure enables the device to be used as a high-speed programmable pure-tone source.