Bang-bang control of feeding: role of hypothalamic and satiety signals.

Rats, people, and many other omnivores eat in meals rather than continuously. We show by experimental test that eating in meals is regulated by a simple bang-bang control system, an idea foreshadowed by Le Magnen and many others, shown by us to account for a wide range of behavioral data, but never explicitly tested or tied to neurophysiological facts. The hypothesis is simply that the tendency to eat rises with time at a rate determined by satiety signals. When these signals fall below a set point, eating begins, in on-off fashion. The delayed sequelae of eating increment the satiety signals, which eventually turn eating off. Thus, under free conditions, the organism eats in bouts separated by noneating activities. We report an experiment with rats to test novel predictions about meal patterns that are not explained by existing homeostatic approaches. Access to food was systematically but unpredictably interrupted just as the animal tried to start a new meal. A simple bang-bang model fits the resulting meal-pattern data well, and its elements can be identified with neurophysiological processes. Hypothalamic inputs can provide the set point for longer-term regulation carried out by a comparator in the hindbrain. Delayed gustatory and gastrointestinal aftereffects of eating act via the nucleus of the solitary tract and other hindbrain regions as neural feedback governing short-term regulation. In this way, the model forges real links between a functioning feedback mechanism, neuro-hormonal data, and both short-term (meals) and long-term (eating-rate regulation) behavioral data.

3D statistical parametric mapping of EEG source spectra by means of variable resolution electromagnetic tomography (VARETA).

This article describes a new method for 3D QEEG tomography in the frequency domain. A variant of Statistical Parametric Mapping is presented for source log spectra. Sources are estimated by means of a Discrete Spline EEG inverse solution known as Variable Resolution Electromagnetic Tomography (VARETA). Anatomical constraints are incorporated by the use of the Montreal Neurological Institute (MNI) probabilistic brain atlas. Efficient methods are developed for frequency domain VARETA in order to estimate the source spectra for the set of 10(3)-10(5) voxels that comprise an EEG/MEG inverse solution. High resolution source Z spectra are then defined with respect to the age dependent mean and standard deviations of each voxel, which are summarized as regression equations calculated from the Cuban EEG normative database. The statistical issues involved are addressed by the use of extreme value statistics. Examples are shown that illustrate the potential clinical utility of the methods herein developed.

Computer-analysed EEG for monitoring cerebrovascular insufficiency - abstract

This report aims to show that computer analysis of the electroencephalogram (EEG) can greatly enhance and accelerate its diagnostic capability, permitting rapid, on-line detection of changes in cerebral cortical activity. We describe the use of the computer-analysed EEG to detect critical cerebral under-perfusion due to lowered systemic blood flow during cardiac bypass surgery. Such hypo-perfusion frequently results in post-operative neurological deficits. We demonstrate that computer-generated maps of the scalp distribution of percent power in the frequency band can indicate areas of critical cerebral cortical ischaemia sufficiently rapidly to allow raising of perfusion rate and reversal of functional deterioration before the onset of permanent damage. We show that computer-analysed EEG can detect abnormal levels of band activity within seconds after a drastic fall in systemic perfusion, indicating the "probability of abnormality" by performing a z-transform of the measured levels, against age-adjusted norms stored in the computer. We then introduce data indicating that the computer-analysed EEG, by combining several z-transformed EEG measures, can detect both symptomatic and asymptomatic cerebrovascular disease more effectively than the 133 Xe regional cerebral blood flow technique. Since cerebrovascular disease is a major cause of adult mortality and morbidity in the West Indies, this technique should be of great interest in the present context (AU)

Long term behavioural consequences of severe protein-calorie malnutrition - abstract

A study of the long term behavioural consequences of severe nutritional marasmus was undertaken in Barbados, West Indies. The index cases were boys (n=60) and girls (n=36) who had been hospitalized with malnutrition in the first year of life and followed longitudinally by the National Nutrition Centre. At the time of the current study, their ages ranged from four to eleven years. Each index child was matched by age, gender and handedness with a control child from the same school or parish as the index child. Descriptions of the child's behaviour were obtained by interviewing the primary caretaker of each child. Information concerning the social, physical and biological ecology was also gathered since these factors may independently influence behavioural development. Index children had more behavioural problems than their matched controls. Multiple regression analyses were performed to partial out the contribution of nutritional history of the child and economic conditions of the family, which differed in the two groups. These analyses confirmed that the behavioural deficits present among the index children were a consequence of malnutrition and not economic factors. Behavioural deficits persisted even in the older children as compared with their controls. In contrast with the behavioural results, anthropometric measures failed to distinguish between the two groups by ten years of age (AU)