Lecture
The problem of consciousness has a pronounced interdisciplinary character. Nevertheless, numerous data allow us to single out a particular psycho-physiological aspect of the problem of consciousness. Its content is the objective phenomenology of states of consciousness, their dynamics under the influence of various external and internal factors and a reflection of this dynamics in indicators of bodily functioning.
There is no doubt that the individual human consciousness is inextricably linked with the material processes occurring in the human body, primarily in the central nervous system and the brain. The problem is to establish exactly what material processes, mechanisms and states of the brain underlie consciousness. The solution of this problem is fraught with great theoretical, methodological and methodical difficulties. And the main reason is that in the study of the brain mechanisms of the human psyche, there are still a number of fundamental problems that do not have even an approximate explanation.
One of the most significant questions is the following: why doesn’t reflect in the consciousness the “work of the brain itself”? It is known, for example, that receptors in human sensory systems have a very high sensitivity, which makes it possible to react to immeasurably small stimuli. It is argued, for example, that a sound tone with a frequency of 2000 Hz can be perceived when the amplitude of movements of air particles at the eardrum does not exceed the diameter of the hydrogen molecule. Why, with such amazing possibilities of the auditory analyzer, we do not “hear” how the brain works? There is one more unsolvable question at the moment. Thanks to which hypothetical mechanism, the brain, perceiving information, transmitting it along conductive paths, analyzing this information, represents not its activity in consciousness (transmission of excitement from one department to another), but only its productive side in the form of a picture of objective reality and subjective experiences of a person?
Comprehension of the neurophysiological basis of consciousness is impossible until answers to these and many other questions are found. Nevertheless, empirical studies and clinical observations allow us to formulate some ideas about the physiological bases of consciousness.
There is no single generally accepted definition of consciousness in psychology and psychophysiology. In most cases, consciousness is defined through the functions it performs. For example, H. Delgado, a neurophysiologist, author of the well-known book Brain and Consciousness, represented consciousness as an organized group of processes in the nervous tissue that occur immediately on prior intrapsychic (caused by internal causes) or extrapsychic (caused by external causes) processes. This group of nerve processes, i.e. consciousness, perceives, classifies, transforms and coordinates the processes that caused it in order to start an action based on the prediction of its consequences and depending on the available information.
Other definitions emphasize the systematic nature of consciousness, the complexity of its functions, its connection with memory (the past and the future of man), attachment to the brain substrate. P.V. Simonov (1987), for example, emphasizes the communicative aspect of consciousness, defining it as the manipulation of knowledge, the ability to direct the transfer of information from one person to another.
However, to understand the physiological nature of consciousness, existing ideas about the mechanisms underlying functional states, and first of all the concept of levels of wakefulness, are of greater importance (see Topic 3).
Consciousness and levels of wakefulness. When analyzing consciousness as a psychophysiological phenomenon, it is necessary to clearly distinguish its two aspects. First, consciousness corresponds to a certain range in the existing "sleep-wakeful" continuum . It is known that with a strong decrease in the level of wakefulness a state develops, which is defined as coma (“unconscious”). It is also obvious that with relatively low levels of wakefulness, for example in a dream, the consciousness in its full range of functions is not detected. That is why the dream is proposed to qualify as an altered state of consciousness. The physiological condition for the manifestation of consciousness is the state of passive and active wakefulness.
Secondly, it is proposed to single out the content of consciousness as an independent characteristic. The latter is directly related to mental reflection and performs all the functions listed in the definition given above.
Obviously, both sides of consciousness are closely related. Thus, upon waking from sleep, as the level of wakefulness increases, the content of consciousness becomes more and more saturated. At the same time, with a very strong emotional stress, when the level of wakefulness reaches its highest values, the content of consciousness begins to suffer, its peculiar "narrowing" occurs. Finally, there is the phrase "clear consciousness", i.e. such a state when a person freely implements all the functions of consciousness listed above, and the decisions made by him are most conscious. There is every reason to believe that this corresponds to a special level of excitation of the cerebral cortex, which is called optimal.
So, in psychophysiology, consciousness is understood, first of all, as a special state of the brain, in which only the realization of higher mental functions is possible. In other words, consciousness is a specific state of the brain that allows certain cognitive operations to be performed. Exit from this state leads to the shutdown of higher mental functions while maintaining life-support mechanisms.
Consciousness and attention. The classic of experimental psychology e.B. Titchener defined attention as "the ability and ability to concentrate the mind." He singled out two levels of consciousness, from which the "upper layer" referred to the zone of clear vision, and the "lower" to the zone of vague. Similarly determined the attention of S.L. Rubinstein: "the field of our consciousness is not plane. A part of the conscious is coming to the fore in the form of a" figure "on a receding and receding background." And in cognitive psychology, attention is defined as the focus of information processing activities on a limited part of the “input”, while there is a premonition representing “activities outside the main flow of information” (Nayser). Thus, selective attention in psychology has always been associated with a restriction of consciousness.
Physiologically selective attention is manifested in the local activation (increased excitability) of certain areas of the cortex in combination with a more or less pronounced inhibition of the remaining areas of the cortex of the big hemispheres. Depending on the nature of the activity, the zone of increased activation can move along the cortex of the big hemispheres. According to some data, the highest level of consciousness and selective attention corresponds to the localization of the center of increased activation in the left frontal area, and the lowest level in the right occipital area. Thus, the local activation of the cerebral cortex during the implementation of conscious activity has a dynamic nature, determined by the signal significance of the acting stimuli and the nature of the activity performed ( Kostandov , 1983).
Neurophysiological basis of consciousness. I.P. Pavlov figuratively presented consciousness as a zone of increased excitability moving along the cortex - a “bright spot of consciousness” against a dark background of the rest of the cortex. Currently, according to the data obtained using the PET tomography method, the local activation zone does look like a bright spot on a dark background.
The modern analogue of Pavlov’s ideas can be considered the “searchlight” theory (Crick). The crucial role in it is assigned to the thalamus, it is he who directs the flow of excitation into the cerebral cortex. Moreover, the process is carried out in such a way that at any given moment in time only one of the thalamic centers is in a state of excitement sufficient to create a zone of increased excitability in the cortex. The period of such high excitability lasts about 100 ms, and then the influx of impulses amplified by non-specific thalamic excitation goes to another section of the cortex. The region of the most powerful impulses creates the center of attention, and thanks to the constant movements of the excitation flow in other areas of the cortex, it becomes possible to combine them into a single system.
As the supposed mechanism linking neurons into a single system, Crick considers the appearance of synchronized discharges with a frequency in the gamma range of 35-70 Hz. Synchronization of neural activity is a mechanism for uniting cells into an ensemble . Thus, according to Crick's theory, the neural processes that are in the center of a hypothetical “searchlight beam” determine the content of our consciousness at the current time, and the thalamus performs the control function of the searchlight beam, creating a nonspecific excitation (local activation ).
According to the concepts described above, the emergence of consciousness becomes possible only when a certain level of arousal of the cerebral cortex is reached. The idea of a threshold of excitation as a condition for the emergence of consciousness cannot, however, explain many aspects of the functioning of consciousness. For this reason, back in the 80s. another neurophysiological mechanism of consciousness emergence was proposed, called the theory of re-entry (Edelmen). In this theory, the mechanism of re-entry of excitation is considered as a central mechanism for the emergence of consciousness. This means that the excitation that has arisen in the group of neurons of the primary cortex returns to the same neural group after additional processing of information in other nerve centers or the receipt of new information from the external environment, as well as from long-term memory. This re-entry allows you to compare previously available information with changes that occurred during one information processing cycle. The combination of two streams of information (primary and secondary) constitutes one cycle or a repeating phase of the activity of consciousness. The passage of one cycle of excitation is carried out in 100-150 ms. Repeated cycles create a neurophysiological "fabric" of consciousness.
The representations of J. Edelman were further developed, in particular, in the concept of A.M. Ivanitsky (1997). The central place in this concept is occupied by the concept of information synthesis (see Topic 5, Section 5.3), which provides for the integration of information about the physical and semantic features of a stimulus. Information about the physical properties of the stimulus comes in sensory-specific ways, and information about the significance of the stimulus is extracted from memory. The synthesis of these two types of information (current and retrieved from memory) ensures the emergence of sensation. This process is carried out with a quantization period of approximately 100-180 ms. Identification of the stimulus occurs with the participation of the frontal areas of the brain, approximately 300 ms from the moment of presentation. Sequential flow of information from the receptors leads to a repeated movement of the excitation along the indicated ring, providing a constant comparison of signals coming from the external and internal environment (see Chrestomat. 11.1).
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The scheme of the annular motion of excitation in the event of sensations (according to A.M. Ivanitsky). The central link is the synthesis of information about the physical and signaling properties of the stimulus on the neurons of the projection cortex. |
Recently, when discussing the neurophysiological basis of consciousness, much attention has been paid to the high-frequency bioelectric activity of the brain ( Danilova , 1998). The leading role in the emergence of consciousness is attributed to the high-frequency components of the EEG spectrum in the range from 35 Hz to 120 Hz. Consciousness is defined as the product of synchronization of neural activity in the specified frequency range. It is assumed that the coherent electrical activity of a sufficiently large number of neurons creates a necessary and sufficient condition for the phenomenon of consciousness, even in the absence of sensory stimulation, such as, for example, in a dream.
In this context, the temporal sequence, which combines the activity of multiple neurons into a single space-time pattern, is of great importance. The principle of "temporal binding" of elementary symbols (neurons) into more complex structures based on the correlation of their signals in time is considered as fundamental. Moreover, particular importance is attached to the frequency of 40 Hz, which optimally ensures the synchronization of the pulsed activity of the neurons involved in the formation of images and the maintenance of consciousness.
In conclusion, it should be noted that the above ideas about the neurophysiological mechanisms of consciousness by no means exhaust all the diversity in studying this problem (see Danilova , 1998). Nevertheless, they are very illustrative in their diversity, highlighting the different neurophysiological mechanisms: moving the focus of increased excitability around the cortex, returning the excitation and synchronizing the high-frequency activity of neurons.
The human brain is constantly exposed to a variety of influences. However, only a small part of them is recognized, and an even smaller part is in the focus of attention. It is assumed that a specific nerve mechanism responsible for the conscious perception of significant irritants for the subject is responsible for the integration and coordination of the neural activity of various parts of the cerebral cortex and subcortical structures. At the same time, such a mechanism does not allow a multitude of stimuli to the level of consciousness, which cause only short-term activation of the cortex, which is not enough for their awareness.
The question arises, under what neurophysiological conditions is the awareness of sensory effects.
Stimulus parameters. One of the main conditions for awareness of the stimulus is its intensity. A short-term, but strong stimulus always penetrates the consciousness (for example, a thunderclap). Weak stimuli for short-term exposure remain unconscious. The condition of their awareness is the duration of presentation. At the same time, a peculiar accumulation or summation effect is observed: the longer a weak stimulus acts, the more likely it becomes the possibility of its awareness. Thus, weak and very short-term stimuli are not recognized if there are no additional conditions for their amplification.
Activation "support". It is assumed that the physiological basis of awareness of the stimulus is the level of activation resulting from the impact of this stimulus. With weak intensities of the stimulus, it is insufficient for awareness. However, it is possible to enhance the background on which perception is carried out at the expense of other conditions. If the level of activation of brain structures is increased, then the perception of even a weak stimulus becomes more likely. In other words, an additional opportunity to realize even weak stimuli is to enhance the activating effect of information with the help of additional factors that are peculiar catalysts for the process of awareness.
These factors play the role of "support". There are two of the most significant types of "support": motivational-affective and associative. It is implied that when they are included, in addition to sensory activation, activation caused by the activity of emotional and associative centers associated with memory is added. In other words, weak stimuli are more likely to be recognized if they are emotionally significant to a person or associated with some prior experience.
Thus, translation of unconscious information into the sphere of consciousness is provided by the interaction of at least three links: specific sensory, motivational - affective and associative. The possibilities of awareness of the stimulus in a particular case depend on the degree of actualization of each link and their ratio.
Neural mechanisms of conscious perception. The factors listed above give an idea of the conditions conducive to the awareness of weak stimuli acting at the level of the brain as a whole. For understanding the neural mechanisms underlying conscious perception, the models of E.N. Sokolova (1996) and R. Naatanen (1998).
In the model E.N. Соколова механизм возникновения субъективного образа связан с активацией гностических нейронов, которые расположены на вершине пирамиды, образуемой нейронами-детекторами, осуществляющими выделение отдельных признаков объекта (см. тему 5 п. 5.2). Возбуждения, поступающие из таламуса, сначала достигают нейронов-детекторов отдельных признаков, образуя своеобразные карты, или экраны, возбуждения. При этом элементарный признак вызывает максимум возбуждения в отдельной точке этого гипотетического экрана. На другом уровне пирамиды находятся комплексные признаки, которые образованы комбинациями элементарных признаков, они представлены в виде максимумов возбуждения на картах сложных детекторов. Как полагает Е.Н. Соколов, необходимым условием каждого осознанного восприятия является активация пирамиды гештальта, которая возникает при поступлении активирующих влияний из модулирующих систем мозга . Такая активированная гештальт-пирамида иерархически организованных нейронов представляет базисный механизм актов сознания.
В соответствии с моделью Р. Наатанена, сенсорные процессы как таковые не обеспечивают осознанного восприятия, они образуют только его сенсорно-информационный базис, или содержание. Возникнет "осознанный образ восприятия" или нет, зависит от сенсорных свойств стимула, вызывающих внимание. Предполагается, что помимо системы детекторов признаков, сенсорный вход одновременно активизирует также другую функциональную систему — систему сенсорного анализа, избирательно чувствительную только к появлению или исчезновению энергии стимула.
Речь идет о системе так называемых детекторов переходных процессов, определяющих наличие сенсорных событий, независимо от их качественных особенностей. Именно эта система будет превращать субъективно неощущаемые сенсорные события в факт осознанного восприятия, но только в тех случаях, когда реакция, вызванная стимулом в системе детекторов переходных процессов, превысит некоторый порог. Таким образом, согласно модели, осознанное восприятие возникает только в том случае, когда уровень возбуждения системы детекторов переходных процессов достаточен, чтобы активизировать исполнительский механизм, задача которого анализировать информацию, поступающую от детекторов существенных признаков.
Из этого следует, что паттерн активации системы детекторов признаков, закодированный в механизме сенсорной памяти, вступает в контакт с семантической информацией, хранящейся в долговременной памяти, и может, следовательно, обеспечить условия для осознанного восприятия в виде, например, акустического образа хорошо знакомого звукового сигнала.
Семантическая активация, однако, далеко не всегда сопровождается возникновением осознаваемого образа. Другими словами, сенсорные и семантические процессы имеют собственные пороги активации, отличные от порога активации системы детекторов переходных процессов, обеспечивающей осознанное восприятие. Существованием собственных порогов сенсорной и семантической активации, которые ниже порогов осознанного восприятия, можно объяснить данные о наличии своеобразного "подпорогового" возбуждения, вызываемого стимулами, которые не обнаруживаются на поведенческом уровне.
Сходным образом существование таких дифференциальных порогов может объяснять те факты, что пациенты с определенным поражением мозга способны руководствоваться сенсорной информацией, но не осознавать ее. Этот феномен получил название "слепого взора", поскольку фиксирует возможность зрительного различения без осознания.
Согласно вышеизложенному, "путь" сенсорных сигналов из области неосознаваемых ощущений к осознанию образа восприятия включает этап подключения внимания к сенсорной памяти. Более того, сигнал активации внимания, генерируемый механизмом детекторов переходных процессов, варьирует во времени и вызывает переключение внимания только в том случае, когда его величина превысит некоторый порог. По-видимому, этот порог оказывается достаточно низким в ситуации предвосхищения, когда внимание заранее антиципирующим образом направлено на стимул.
Unconscious perception. Along with the conscious mental processes, there is a large area of unconscious mental phenomena, in particular, unconscious perception. In the 50's and 60's In foreign psychology, many experimental studies have been conducted on the problem of unconscious perception and perceptual protection.
В этих исследованиях изучали, влияет ли эмоциональное содержание слов на эффективность их восприятия, опознания и запоминания. Типичный эксперимент включал определение "порогов опознания" для различных слов — нейтральных и эмоционально окрашенных. В целом было установлено, что для правильного опознания слов, вызывающих негативные ассоциации (например: проститутка, насилие, смерть), испытуемым требуется больше времени, чем для опознания нейтральных слов (например: дерево, ручка). Это дало основания предполагать, что некоторый психологический механизм контролирует эмоциональное содержание слов в процессе их восприятия и может каким-то образом влиять на опознание слов, удерживая "угрожающие" слова вне осознанного восприятия. Хотя эти эксперименты по перцептивной защите были несовершенны, (в них, например, не контролировали длину слов, частоту их встречаемости и т.д.), обнаруженные в них эффекты нашли подтверждение и в некоторых более поздних и более тщательных экспериментах (Купер).
В отечественной науке экспериментальное изучение неосознаваемого или подпорогового восприятия было осуществлено Г.В. Гершуни (1977) путем сопоставления объективных показателей ориентировочной реакции ( КГР , расширение зрачка, блокада альфа-ритма ) и субъективных отчетов испытуемых при предъявлении очень слабых звуковых или электрокожных раздражителей. В этих исследованиях было показано, что ориентировочная реакция на слабый стимул может возникать, независимо от субъективных отчетов испытуемых.
В психофизиологии для изучения описанных выше явлений неосознаваемого восприятия и перцептивной защиты использовали метод регистрации вызванных потенциалов (см. тему 2). В ряде экспериментов с предъявлением эмоционально значимых и нейтральных слов было показано, что ответы мозга на эти стимулы и субъективные отчеты испытуемых о виденном не всегда совпадают. Было установлено, что информация о внешнем раздражителе по специфическим сенсорным путям поступает в соответствующие проекционные зоны коры и перерабатывается там независимо от того, находится человек в сознании или без сознания. Наиболее существенным оказался тот факт, что наличие ВП (ответа на стимул) в проекционных зонах коры не означает, что человек осознает, какой именно стимул ему предъявили ( Костандов , 1983).
Следовательно, для осознания сигнала недостаточно переработки информации в проекционных зонах коры, должен существовать нервный механизм, обеспечивающий дополнительные условия осознания сигнала. Этот механизм, по мнению Э.А. Костандова, осуществляет интеграцию нейронной активности различных участков коры больших полушарий и подкорковых структур с целью наилучшего восприятия значимого сигнала. Очевидно, пишет Э.А. Костандов, следует признать существование в мозге чувствительного механизма, реагирующего на физически очень слабые, но психологически значимые для данной личности, раздражители. Этот механизм не обеспечивает осознание эмоционально значимого раздражителя, но активизация этого механизма может приводить к целому ряду биоэлектрических и вегетативных реакций, а также к изменению некоторых психологических функций и состояний ( Костандов , 1983).
Клиницистами давно замечено, что сознание сохраняется после удаления или поражения относительно небольшого участка коры больших полушарий, но оно неизбежно исчезает, теряется, если в результате патологического воздействия нарушаются некоторые подкорковые структуры, в первую очередь в диэнцефальной области.
Значение глубоких структур мозга. Открытие в 50-е гг. ретикулярной формации, и в частности неспецифического таламуса, и установление их роли в активации коры больших полушарий позволило ряду исследователей отождествить сознание с активностью этих систем. Эксперименты известных нейрофизиологов У. Пенфилда, Х. Джаспера и ряда других, подтвердившие важнейшую роль подкорковых структур, и прежде всего ретикулярной формации, для проявления сознания, дали основание предположить существование гипотетической центрэнцефалической системы, отвечающей за сознание.
Хотя в дальнейших исследованиях идея центрэнцефалической системы была отвергнута, но значение ствола мозга и подкорки в обеспечении функций сознания не вызывает сомнения. Модулирующие системы мозга ( ретикулярная формация и лимбическая система ) имеют решающее значение не только для поддержания уровня бодрствования, но и для обеспечения энергетического аспекта сознания. Кроме того, по-видимому, структуры подкорки могут определять не только энергетическую, но и информационную составляющую сознания.
Видная роль здесь отводится такой структуре как гиппокамп. Значение гиппокампа в обеспечении содержания сознания объясняется той ролью, которую тот играет в процессах памяти (см. тему 7 п. 7.2). Однако, несмотря на несомненный вклад гиппокампа и лимбической системы в целом в обеспечение содержания сознания, информационный аспект сознания формируется в основном за счет деятельности коры больших полушарий.
Функции коры больших полушарий. Для понимания роли коры в обеспечении сознания важны представления, сформулированные американским физиологом Ф. Маунткаслом (1981) об ансамблевой организации коры (см. тему 1 п. 1.4).
Модуль фактически представляет собой морфофункциональную единицу переработки информации в коре. Модули группируются в более крупные объединения, образующие зоны коры. Описанный способ строения коры образует так называемые "распределенные" системы, которые обеспечивают условия для реализации самых сложных психических функций, в том числе и сознания. Описанные выше нейрофизиологические феномены такого типа, как повторный вход возбуждения или синхронизация электрической активности нейронов, естественным образом реализуются в распределенных системах.
The latter also have another feature: since the products of these systems cannot be the result of the activity of only one module, the loss of one or more modules cannot prevent its functioning. Due to this, the distributed systems of the cerebral cortex possess a holographic principle of functioning. Distributing the properties of a hologram to the function of the cerebral cortex means that information in the cortex is distributed, and turning off some part of the system (within acceptable limits) leads to a weakening of the function, not to its loss ( Pribram , 1975).
Consciousness and hemispheric asymmetry. Back in the middle of the XIX century. an eminent scientist G. Fehner considered consciousness as an attribute of the cerebral hemispheres and believed that the integrity of the brain is an essential condition for the unity of consciousness. If it were possible to divide the brain along the middle line, he reasoned, then this would lead to something like a doubling of the personality. A similar operation to dissect the corpus callosum was performed almost a century later by R. Sperry and others. Its results indicate a separate specific localization in both hemispheres of different brain functions related to consciousness (see Video).
The fundamental importance of the position that the brain as a whole is a carrier of consciousness is clearly traced in clinical studies (Bragin, Dobrokhotov) aimed at studying the specifics of a consciousness disorder due to selective lesions of the right or left hemisphere in right-handed and left-handed people, which turn out to be very different.
Right-handed people with the defeat of the right hemisphere are the most frequent violations of consciousness with the phenomena of loss of a sense of reality and self. The world around it may lose its objective value for them. In some cases, the patient perceives only half of the external world, and the left half of the perceived world located to the right of him is replaced by past memories.
With the defeat of the left hemisphere, other states of consciousness arise with “thought failures” or, on the contrary, experiencing a multitude of thoughts that interfere with each other. There are frequent cases of short-term cessation of consciousness or the so-called twilight states of consciousness in which the patient can maintain psychomotor activity.
A different picture of the change in consciousness is given by lesions of the hemispheres in left-handers. Their features of impaired consciousness do not depend so much on the side of brain damage. Hallucinatory phenomena predominate, with hallucinations vague, blurred and polymodal (visual, auditory, tactile, etc.). The intensity of the experience of hallucinations in left-handers is almost equal to the strength of real events, in addition, they are repeated many times. Sometimes these patients have special extrasensory abilities, for example: skin vision, perception of what is beyond the reach of visual space, and others.
N.N. Bragina and T.A. Dobrokhotov hypothesizes that consciousness is a property of the spatial and temporal organization of the brain, in which the coordinated activity of the hemispheres is achieved through a special temporary organization of their dual work, when the right hemisphere is addressed to the present and past human experience, and the left to the present and future. Although this hypothesis is more like a metaphor, it is interesting because it draws attention to the need to include the time factor in the study of the psycho-physiological mechanisms of consciousness.
Parapsychological phenomena. Another mystery of the human psyche and consciousness may be related to the peculiarities of the right hemisphere processing of information. We are talking about phenomena called parapsychological, such as clairvoyance, telepathy, etc. There is no doubt that the solution of this problem requires the accumulation and thorough verification of empirical material that would confirm the existence of such phenomena. Nevertheless, it is significant that modern brain science does not impose a fundamental ban on the existence of such phenomena. The latter is connected, first of all, with the special possibilities of the right hemisphere in information processing.
Numerous data suggest that the right hemispheric components of information processing mechanisms do not obey the rules of formal logic, are not bound by the laws of cause-effect relationships and are not limited by the probabilistic forecast framework, therefore their participation in the so-called "supersensible" perception cannot be a priori rejected. The first and so far single studies conducted in this direction (telepathic sessions during REM sleep and when the left hemisphere of the brain is turned off) indicate the special role of the right hemisphere in providing the supersensible phenomena of the mind and consciousness.
It is extremely important to identify the psycho-physiological patterns of the functioning of the psyche is the study of altered states of consciousness. This concept covers a fairly wide range of phenomena. Changes in the state of consciousness occur in a person under normal conditions of life, for example, during the transition from wakefulness to sleep. Changes in the states of consciousness are possible in conditions of complicated labor activity: for example, in conditions of high mountains with low oxygen content in the air and other difficult ecologically inadequate conditions. Along with this, there are artificially induced altered states of consciousness, such as meditation and hypnosis.
Meditation. There are various types of meditation, but psycho-physiological studies have been conducted only for some of them. One of the most common methods of meditation is the so-called transcendental meditation (TM). An analysis of the biocurrents of the brain before meditation, in the TM state and after meditation, shows that the frequency spectrum of brain biopotentials during meditation resembles an intermediate state between the frequency spectra characteristic of wakefulness and drowsiness. According to other data, during the TM of meditation a more regular and high-amplitude alpha rhythm is recorded compared with wakefulness and drowsiness, without pronounced hemispheric asymmetry. With TM, the coherence of the alpha rhythm increases, especially in the frontal regions, and in the later stages of meditation, the alpha rhythm turns into a theta rhythm . The latter is related to the duration of meditation practice.
Based on a polygraphic recording of physiological parameters, a number of researchers argue that meditation is characterized by a lower level of wakefulness compared to the state of relaxation. At the same time, according to the concepts accepted in psychophysiology, a high-amplitude alpha rhythm with a tendency to decrease should reflect a state of relaxation, a reduced level of vigilance, but this is not true for a state of meditation.
Another common type of meditation is Zen meditation, characterized by calm and intense concentration. Objects that are addressed during meditation are perceived without any emotional reactions or cognitive assessments. Perhaps independence from past experience and the impossibility of disagreement between the actual impression and the expected event causes a lack of emotional reaction. There is no mismatch, because there is no forecast based on past experience, and all events are equal to expected or equally unexpected.
It must be emphasized that during Zen meditation, active contact with the outside world is maintained, at least at the perceptual level. Proof of this is the peculiarities of EEG changes. In the usual state of consciousness with eyes closed, any unexpected signal causes a desynchronization reaction — blocking the alpha rhythm for a few seconds, followed by recovery. It is known that the approximate reaction has the ability to fade: with repeated repetition of the same signal at equal intervals of time, the desynchronization reaction becomes shorter and eventually fades. Each subsequent signal is perceived as completely identical to the previous one.
In the state of Zen meditation, no matter how often the signal of the extinction of the reaction repeats, the activation does not occur: the blockade of the alpha rhythm lasts for two seconds each time. Consequently, the signal every time is perceived as new and causes an active orientation reaction, which indicates the relative constancy of the level of wakefulness.
According to some assumptions, the alpha rhythm, most often recorded during meditation, is not similar in its functional meaning to the alpha rhythm of calm wakefulness. This rhythm, according to VS Rothenberg, reflects the high variability and disorder of the figurative thinking that dominates during meditation. Due to this, after a session of meditation, there is a feeling of relaxation, a decrease in physical and mental tension and fatigue, increased mental activity and general vitality.
Hemispheric asymmetry and meditation. Of great interest are the data accumulated as a result of studies of meditation and hemispheric asymmetry using the EEG method. According to the so-called "right hemisphere theory of meditation," the process of meditation changes the states of consciousness by inhibiting the cognitive functions associated with the dominant (left) hemisphere, opening up great opportunities for right-hemisphere functions. Thus, it was shown that the initial stage of meditation is associated with greater deactivation of the left hemisphere than the right, which is presumably due to the fact that meditation "turns off" the verbal, logical mental functions and the sense of time inherent in the left hemisphere, and the right hemisphere begins to dominate, responsible for the holistic perception of the environment, outside of language and logic.
The most important and bright EEG characteristic of meditation is the tendency to intra-and hemispheric synchronization of the EEG. Moreover, a high degree of consistency of bilateral activity was observed in meditators not only during the meditation itself, but also as a meditational after-effect. Moreover, the EEG synchronization in meditation is significantly higher than in the state of sleep or drowsiness, but in the BDG stage, the EEG synchronization is as high as during meditation. The latter suggests the existence of a psychophysiological similarity between BDG sleep and meditation. Moreover, a number of researchers argue that meditation can significantly reduce the time of sleep BDG in meditators and can even serve as a substitute for it, but it is nonetheless not identical to sleep.
It is important to emphasize that in the process of meditation a kind of "emptiness" of consciousness is reached - a condition that is not amenable to verbalized description. Before the formation of modern ideas about different types of thinking, meditation practice seemed to be mystical. Progress in science requires the study of special states of consciousness and a detailed analysis of the complex data obtained in these states.
Hypnosis. This is a special state of consciousness that arises under the influence of suggestion, including self-suggestion. It can be assumed that hypnotic changes in consciousness can also be explained by the relative dominance of the imaginative components of thinking.
All these manifestations may be due to a combination of the limitation of verbal-logical components of thinking with the emancipation of its figurative components, as evidenced by a significant shift in the EEG of activation in the right-hemisphere direction when highly hypoviable subjects enter a state of hypnosis. In general, for hypnotic states, two variants of changes are described: first, the alpha rhythm hypersynchronization , the presence of short flashes of the theta rhythm and the preservation of the alpha rhythm with open eyes, and secondly, the same EEG pattern as in the waking state. Since the hypnotic state itself can be of different depths, the EEG picture of these states can be quite polymodal - from exaltation of the alpha rhythm to its suppression.
There is a very large similarity between decision making in the state of hypnosis and in pathology associated with brain splitting. The latter gives grounds to assume that hypnosis is an analogue of the functional cleavage of the brain, in which the mechanisms of the right hemispheric forms of activity are responsible for the results of the subject's action.
Coma. Coma is defined as a state of deep impairment of consciousness, characterized by the depression of the functions of the central nervous system, a violation of the regulation of vital centers in the brain. A person in a coma has no reaction to external stimuli, all reflexes are inhibited, there is no motility.
According to severity, there are three stages of coma. For a light coma, some reflexes (for example, tendon) and reactions are preserved. With a slight disorder of respiratory function and cardiac activity, swallowing is difficult. The activity of the cortical-subcortical departments is impaired.
In severe coma, there are no reactions to external stimuli, habitual reflexes are not caused. However, the presence of pathological reflexes, in particular, disrupted the excretory systems. The breathing process takes on pathological forms, which is accompanied by cardiac arrhythmia, a weak pulse and a decrease in blood pressure. To a decrease in the activity of the cortical and subcortical functions, stem depression and a decrease in spinal functions are added.
Deep coma is characterized by symptoms indicating a lesion of the cortical-subcortical, bulbar and spinal functions. There are gross violations of the process of respiration and cardiac activity. As a special condition, the exorbitant coma is distinguished, it is an artificial extension of the vegetative functions of the body after the onset of "brain" death. This extension is achieved by artificial ventilation of the lungs, drug stimulation of blood circulation. At the same time, all mental functions are completely disturbed, and the electroencephalogram is represented by an even line.
Fundamentally new opportunities in the development of the problem of consciousness opened in connection with the introduction of the information approach.
The phenomenon of consciousness and information. Since the phenomenon of consciousness requires a substantive, philosophical description, and the brain processes of consciousness involve description in natural science terms, it is extremely difficult to unite them in interpreting the essence of consciousness. However, according to the philosopher D.I. Dubrovsky, the concept of information makes it possible to combine both types of description in a single theoretical key, and thus serve as the basis for a conceptual explanation of the connection between phenomena of consciousness and brain processes. The reason is that, taken in a broad sense, the concept of information has a dual essence, since it includes both the content of the information and its code form. In other words, the concept of information makes it possible to display in a single conceptual plan both the properties of the “content” (semantic and pragmatic aspects) and the properties of the material carrier in which this information is necessary, i.e. its spatial characteristics and physical properties.
The main provisions. Every phenomenon of consciousness (as a phenomenon of subjective reality) is certain information inherent in a particular social individual. As information, every phenomenon of consciousness must be embodied in its material carrier. This carrier is the corresponding cerebral neurodynamic system of a given individual, which encodes the relevant information presented to this individual as a phenomenon of subjective reality. It should be emphasized that the informational approach makes it possible to analyze brain processes and mental phenomena, i.e. phenomena of two levels, in a single conceptual system, which can be defined as neuroinformatics.
The Homunculus Paradox. Homunculus is a hypothetical "little man" supposedly inside the brain that integrates the sensations of "I". He observes, guides actions, experiences needs and emotions, etc. In other words, the homunculus is identical with the human "I". At the psychological level, its existence is not in doubt. Однако в физиологии до сих пор не обнаружено каких-либо мозговых образований, на которые можно было бы возложить данную функцию.
Наиболее вероятный кандидат на эту роль — мозговая система памяти. Действительно, во многом человеческое "Я" — это воспоминания о прошлых событиях, отношении к ним и своих действиях. Метафорически эту мысль выразил писатель Д. Гранин: "...человеческое "Я" не может существовать без памяти. Из кирпичиков памяти складывается индивидуальность".
Однако все чаще высказывается мнение, что поиски гомункулуса как определенной, интегрирующей ощущения своего "Я" мозговой структуры, не имеют смысла. Предполагается, что "Я" — это динамическая информационная система, включающая разные отделы мозга. Этот "информационный гомункулус", одновременно оперирующий как памятью, так и текущим опытом, и есть наиболее вероятная мозговая "эго-система".
Сознание как эмерджентное свойство мозга. Системный подход утверждает, что любая функционирующая система приобретает свойства, не присущие ее компонентам, так называемые системные, или эмерджентные, свойства, исчезающие при разложении системы на элементы. С позиций нового философского учения, именуемого эмерджентным материализмом (Дж. Марголис), сознание рассматривается как эмерджентное свойство мозговых процессов, находящееся в сложной взаимосвязи с этими процессами.
Возникая как эмерджентное свойство мозговых систем, начиная с некоторого, пока неизвестного уровня их консолидации, сознание (в силу явления эмерджентного детерминизма) приобретает уникальную способность выполнять функцию нисходящего контроля над нейронными процессами более низкого уровня, подчиняя их работу задачам психической деятельности и поведения.
Эмерджентный детерминизм. Детерминизм предполагает установление причинной обусловленности изучаемых явлений. Эмерджентный детерминизм базируется на представлении о существовании у центральной нервной системы особого типа свойств — системных, или эмерджентных, свойств. Главным отличием свойств такого рода является их несводимость к сумме свойств элементов, из которых образована система. Развитие этих идей позволяет рассматривать психическое как системное (эмерджентное) свойство мозговой "сверхсистемы" или мозга как целого (см. тему 1).
В соответствии с этими представлениями, психическая деятельность мозга не может получить исчерпывающего объяснения в физико-химических, молекулярно-биологических или электрофизиологических категориях. Как пишет один из наиболее выдающихся физиологов ХХ в. лауреат Нобелевской премии Р. Сперри:"физические, химические и электрические силы в мозге, несмотря на то, что они также наличествуют и действуют, как и раньше, оказываются (образно говоря) "вставленными" или "упакованными" вовнутрь и следовательно контролируются и программируются... законами и динамикой более высокого порядка сознательных и подсознательных психических процессов. Более высоко развитые "макро" процессы или холистические психические свойства мозговой деятельности определяют то, когда и как будут происходить элементарные молекулярные процессы, не вмешиваясь, однако, в деятельность физико-химических законов на молекулярном уровне".
По этой логике, особое значение для выявления физиологических основ психической деятельности и поведения приобретают не отдельные клеточные элементы, в частности нейроны, а свойства новых форм и моделей, в которых акцент делается на нисходящий контроль над низшим со стороны высших. Сказанное означает, что психические процессы и функции, будучи эмерджентными свойствами мозговых систем разного уровня организации, в силу эмерджентного детерминизма способны подчинять своим задачам функции отдельных компонентов мозговых микро- и макросистем.
Test_Data [0] = new Array ( "Верно ли, что физиологическим условием проявления сознания служит состояние пассивного и активного бодрствования?", "..\11.html#p1", "Yes", "not", 1.0, 0.0 ); Test_Data [1] = new Array ( "Верно ли, что в состоянии медитации снижается способность к направленной регуляции вегетативных функций?", "..\11.html#p10", "Yes", "not", 1.0, 0.0 ); Test_Data [2] = new Array ( "Верно ли, что в состоянии гипноза и в постгипнотическом состоянии происходит повышение творческой активности?", "..\11.html#p11", "Yes", "not", 1.0, 0.0 ); Test_Data [3] = new Array ( "Верно ли, что информация о внешнем раздражителе по специфическим сенсорным путям поступает в соответствующие проекционные зоны коры и перерабатывается там независимо от того, находится человек в сознании или без сознания?", "..\11.html#p4", "Yes", "not", 1.0, 0.0 ); Test_Data [4] = new Array ( "Верно ли, что наличие вызванного потенциала в проекционных зонах коры означает, что человек осознает, какой именно стимул ему предъявили?", "..\11.html#p5", "not", "Yes", 1.0, 0.0 ); Test_Data [5] = new Array ( "Выберите четыре правильных варианта ответа. Главными условиями осознания стимула являются его:", "..\11.html#p3", "модальность", "включенность в ассоциативные связи", "длительность предъявления", "значение", "интенсивность", 0,1,1,1,1, 0,0,0,0,0 ); Test_Data [6] = new Array ( "Выберите два правильных варианта ответа. Гипотеза о существовании центрэнцефалической системы, локализованной в подкорковых структурах, и прежде всего в ретикулярной формации, отвечающей за сознание, развивалась:", "..\11.html#p6", "А.Р. Лурия", "Х. Джаспером", "У. Кенноном", "У. Пенфилдом", "Г. Мэгуном", 0,1,0,1,0, 0,0,0,0,0 ); Test_Data [7] = new Array ( "Выберите правильный вариант ответа. Н.Н. Брагина и Т.А. Доброхотова выдвигают гипотезу, согласно которой сознание обеспечивается особой временной организацией работы полушарий, когда:", "..\11.html#p8", "правое левое адресуется к настоящему и прошлому опыту человека, а правое - к настоящему и будущему", "правое полушарие адресуется к настоящему и прошлому опыту человека, а левое - к настоящему и будущему", "правое полушарие адресуется к пространственному опыту человека, а левое - к вербальному", "правое полушарие адресуется к вербальному опыту человека, а левое - к пространственному", 0.1.0.0, 0,0,0,0 );
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Psychophysiology
Terms: Psychophysiology