Pribram / Luria Psychophysiology of the Frontal Lobes

1. Auflage 2013
ISBN: 978-1-4832-1935-6
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 344 Seiten

Psychophysiology of the Frontal Lobes covers the frontal lobe function. The book discusses the modern concepts relating to the problem of the frontal lobes; the effect of frontal lesions on the electrical activity of the brain of human; and the nature of the electrical activity of the frontal cortex in human. The text then describes the nature of electrical activity in the frontal cortex of nonhuman primates; the relationship between frontal cortex and subcortical brain function; as well as experimentally based models of frontal lobe function. Psychologists, psychiatrists, and neurologists will find the book invaluable.

Autoren/Hrsg.

Pribram, K. H.

Luria, A. R.

Leseproben

Chapter 1

THE FRONTAL LOBES AND THE REGULATION OF BEHAVIOR

A.R. LURIA,     University of Moscow, Moscow, U.S.S.R

Publisher Summary

The frontal lobes play a most important role in human mental activity. Frontal lobe lesions lead to disturbances of conscious behavior. The formal intellect of those patients may remain relatively intact, but they are unable to properly interact with their cultural environment. The delicate components of their mental activity are lost, their critical faculties are violated, and they become spontaneous. Their ability to work out programs of proper behavior, as it were, becomes lost. Specific features of activity of the human frontal lobes may best be investigated under conditions where the patient must fulfill some special task. It is important to study the changes that develop in the frontal lobes of the brain during mental exercise. Electrophysiological methods have been used, along with other methods, to determine the exact nature of that difficulty in mental activity. This chapter discusses the comparison of records of normal subjects and of patients with a delusional form of schizophrenia subjected to special tasks. Mental strain is of particular importance there. When the frontal lobes become nonfunctional, mental activity markedly slows down. The functional state of the cortical frontal lobes and their participation in mental activity are to a considerable degree determined by the corticosubcortical correlations and, above all, by influences exerted by the reticular formation of the midbrain.

New attainments in the field of neuropsychology in the last decades have resulted in a radical revision of our views concerning one of the most intricate problems of natural science–the localization of functions in the brain cortex.

Classical concepts advocating of complex psychological functions within limited parts of the cortex, which once played essential roles in the development of neurology, have now become serious obstacles to further research in this branch of knowledge and have been discarded. Similarly, the naïve concept of , in which the brain was regarded as a single unit and in which the character of functional disturbances was determined by the mass action of the affected brain, have now become things of the past. In their place, concepts of “system” localization of functions have become established; according to these concepts, each mode of psychological activity is a functional system based upon a complex interaction of jointly functioning parts of the brain, each of which contributes to the mode’s expression (Luria, 1966a, b).

Radical changes have also taken place in the basic physiological concepts concerning the main principles governing nervous system activity; the classical concept of a reflex arc has given way to the concept of a servomechanism, a view that allows an approach to the analysis of the brain as a self-regulating system. A new theory of complex interaction between the specific and nonspecific systems in the neural process has come into being, and interaction between the activating apparatuses of the brain stem and the differentiated parts of the brain cortex appears now in a new light. A theory of the principal modes of activity of single neurons has been developed in which one part of the neuron is considered to show a highly specific character, whereas the other part is now regarded as being composed of extremely complex units that react sensitively to any changes in the incoming signal, compare the actual influences with past experience, and regulate the state of general brain activity.

These recent hypotheses have made possible a number of new approaches to the analysis of the functions of one of the most complex neural structures—the frontal lobes of the human brain.

I shall try to present herein a review of modern concepts relating to this problem, perhaps the most difficult problem confronting neural science today.

I THE PROBLEM OF THE FRONTAL LOBES

Theories about the functions of the frontal lobes have always been contradictory. Neurologists who had observed patients with lesions of the frontal lobes but who did not detect any disturbances either in sensitivity or within the motor and reflex spheres often concluded that patients with such lesions remained symptomless and that this “youngest and least differentiated” part of the brain, in the words of Hughlings Jackson, had no strictly defined functions. However, psychiatrists who studied the distinctive features of behavior of patients with massive frontal lobe lesions and who described the “disturbances of motives () and the absence of criticism” observed in such patients were inclined to regard the frontal lobes as one of the most important apparatuses of the human brain. Unfortunately, they too were unable to characterize the essence of the disorders observed in distinct physiological and psychological terms.

It is noteworthy that even leading physiologists experienced similar difficulties. I. P. Pavlov, for example, who observed dogs deprived of their frontal lobes, stated that the system of conditioned (salivary) reflexes did not undergo any substantial change, whereas general expedient behavior proved to be affected to such a degree that a lobectomized dog could be regarded as a “completely mutilated animal with few manifestations of expedient behavior left … a profound invalid and helpless idiot …” (Pavlov, 1949). Bekhterev also pointed out the great changes that take place in the behavior of such animals. He considered the frontal lobes of the dogs’ brain to insure the “evaluation of the results of their actions and direct the movements to conform with this evaluation”: thus, they perform a “psychoregulating function” Bekhterev, 1907, pp. 1964-1968). However, even in these cases the observers failed to analyze more thoroughly the mechanisms responsible for the disturbances of these higher forms of behavior, and science is still faced with the task of explaining frontal lobe function in clear terms accessible to further analysis. One is left with the impression that this is due to the fact that the concepts of classical physiology, especially the reflex arc scheme, are not adequate for disclosing the nature of frontal lobe activity and that explanation will come from considering the brain as a highly organized self-regulating system.

Some more successful attempts to elucidate frontal lobe function in such terms have recently been made by a number of scientists, who have investigated the behavior of (e.g., Pribram and his co-workers such as Rosvold and Mishkin, and by Konorsky and his group) and an analysis based on these principles of frontal lobe function has been made in my laboratory over the last three decades.

The rest of this chapter presents a summary of the basic data obtained from these investigations.

II THE FRONTAL LOBES AND REGULATION OF THE ACTIVATION PROCESSES

Each human activity starts from definite intention, directed at a definite goal, and is regulated by a definite program which demands that a constant cortical tone be maintained. It is known that when this tone declines, for example, when the cortex is in an inhibitory phasic state, selective responses of the higher neural processes tend to disappear: the normal finding that strong stimuli (or their traces) cause pronounced reactions and weak stimuli (or their traces) provoke less pronounced reactions, cease, and the mutilated cortex either begins to respond to strong and weak stimuli with more or less equal reactions (equalization phase) or the weak stimuli (or their traces) begin to provoke even more intense reactions than the strong ones did (paradoxical phase). The laws governing these phasic states have been thoroughly studied by the Pavlovian school. Their manifestations can readily be observed in a human when he is asleep or half awake. Such observations suggest that no organized thought is possible in these states and that selective connections are replaced by nonselective associations deprived of their purposeful character. It is possible that much of the peculiar logic of dreams can be explained by these physiological facts.

Anatomical, psychological, and clinical data obtained over the past years lead to the assumption that an essential role is played by the interrelations of the brain stem apparatuses and the frontal (especially mediofrontal) cortex in the maintenance of the latter’s active state.

As is known, the nonspecific activating system of the brain stem is closely bound to the cerebral cortex, especially the cortex of the limbic region and medial parts of the frontal lobe. It is likewise known that descending impulses, which regulate the activating formation by modifying the state of cortical activity to conform to the subject’s arising intentions, come predominantly from formations in the frontal parts of the brain.

These morphological and morphophysiological facts, the fundamentals of which were discovered by a brilliant group of researchers (Magoun, Moruzzi, Jasper, and others), have been more clearly elucidated in research by Grey Walter and M. N. Livanov, as well as in a number of investigations carried out over the past years by Homskaya and her...