Part 3. Cognitive processes
Chapter 6. Feelings
There is nothing in the mind, which would not have been in the senses before.
Philosophers-sensualists of the XVIII century.
The concept and functions of sensations
The simplest mental process by which we receive information from the outside world is sensation. However, it is called the simplest only in comparison with more complex cognitive processes. In reality, sensation is an important and complex process of knowing the world.
Sensation is a reflection of a separate sensory quality or an undifferentiated impression of the environment when the stimulus is directly influenced by the senses.
The mechanism of sensations can be described without exaggeration as ancient. In order to respond to changes in the surrounding world in time, in the course of evolution, groups of specialized receptor cells (from Latin - to receive), sensitive to various influences from the internal and external environment, developed in living organisms.
The individual properties of objects and phenomena affecting our senses are called stimuli, the process of action is an irritation, and the nervous process resulting from stimulation is excitation.
Each sense organ (eye, ear, sensitive skin cells, taste buds of the tongue) specializes in receiving and processing various specific external influences. The main part of each sense organ - the end of the sensory nerve - is the receptors. They convert the energy of the external stimulus into a nerve impulse. An effect that can excite a receptor is called a stimulus.
The nerve impulse generated by the receptor in the centripetal, afferent (from Latin - bringing) nerve pathways enters the corresponding parts of the brain. Receptors, ascending (afferent) neural pathways and corresponding areas in the cerebral cortex are three components of the analyzer.
For the sensation to appear, the analyzer's work as a whole is necessary. Therefore, it can not be said that visual sensations arise in the eye. Only an analysis of the nerve impulse coming from the eye in the corresponding parts of the cerebral cortex (occipital part) leads to the appearance of a visual sensation. On the way from the receptors to the cerebral cortex, impulses pass through various brain structures, where they receive primary processing.
The activity of analyzers is conditionally-reflex: the brain, receiving a feedback signal about the activity of the receptor, continuously regulates its work. Formed in the cerebral cortex, the nerve impulse, spreading through the centrifugal, efferent (from Latin - enduring) nerve pathways, affects the motor mechanisms of the sensory organ and causes an appropriate adjustment of the sensitivity of the receptor.
Thus, sensation is not a one-pass passive reflection of a property, but an active process, the most complex activity of analyzers, having a certain structure. Each type of sensation has its own neurophysiological mechanism, its analyzer. The sensory organs are connected with the organs of motion. So, in the process of visual sensations the eye makes continuous movements, as if feeling the object. The motionless eye is almost blind. The activity of various analyzers is interrelated. The aggregate activity of all analyzers is called the sensory sphere of the human psyche.
If the signal is caused by a stimulus that threatens to cause damage to the body, or is addressed to the autonomic nervous system, it is very likely that it will immediately trigger a reflex response from the spinal cord or other lower center, and this will happen earlier than we realize this impact. Our hand is pulled from the cigarette when the burn is burned, the pupil contracts in bright light, the salivary glands begin to salivate if the candy is put into the mouth, and all this occurs before our brain deciphers the signal and gives the appropriate order (Figure 1). The survival of the body often depends on the short nerve chains that make up the reflex arc.
Fig. 1 . Consequences of a mosquito bite The signal from the receptor (1) is sent to the spinal cord (2), and the reflex pulmonary that is triggered can trigger the withdrawal of the hand (3). The signal in the meantime goes further to the brain (4), heading along the straight path to the thalamus and cortex (5) and along the indirect path to the reticular formation (6). The latter activates the bark (7) and prompts it to pay attention to the signal, about the presence of which she has just learned. Attention to the signal is manifested in the movements of the head and eyes (8), which leads to the recognition of the stimulus (9), and then to programming the reaction of the other hand in order to drive away the guest (10).
The signal continues its way through the spinal cord and then follows two different paths: one path leads to the cerebral cortex through the thalamus, and the other, more diffuse, passes through the filter of the reticular formation, which supports the cortex in the waking state and decides, is the signal transmitted in a direct way sufficient to make it decipher the core? If the stimulus is considered important, a complex process will begin that will lead to its perception by consciousness. This will entail a change in the activity of many thousands of cortical neurons that will need to structure and organize a sensory signal in order to give meaning to it.
First of all, the attention of the cerebral cortex to the stimulus will entail a series of movements of the eyes, head or trunk. This will allow you to get a deeper and more detailed knowledge of the information coming from the primary source of this signal, and, possibly, connect other senses.
Sensations not only carry information about individual properties of phenomena and objects (information function), but also perform a brain-activating function.
The well-known United States physician S.I. Botkin (1832-1889) described a rare case when the patient lost all kinds of sensitivity, except vision with one eye and a touch on a small part of the arm. When the patient closed her eyes and no one touched her hand, she fell asleep, as communication with the outside world was lost.
This case and experiments on sensory isolation convincingly prove the tremendous importance of the process of sensation in the organization of the work of our consciousness.
As observations show, a lack of influx of stimuli leads to a peculiar experience, called the sensory hunger. Sensory hunger arises from the lack of impressions from reality. THEM. Sechenov noted that one of the necessary conditions for normal human mental activity is the known minimum of stimuli entering the brain from the senses.Requests for practice (aviation, scuba diving, astronautics) have led to numerous studies on animals and humans in order to comprehensively study the effect of limiting stimuli on the mental state of a person.
Experimental research in this area began to be carried out in public by D.O. Hebb in the 1940s, and on animals - I.P. Pavlov even earlier, at the beginning of the century, in the famous "tower of silence". A systematic study of sensory deficiency in the interests of aviation and cosmonautics began in the 1950s. In the course of experiments, the researchers have no doubt that the absence of sensations from the external environment inhibits or distorts the work of consciousness.
Very interesting experiments on sensory isolation, which were conducted in simulators of spacecraft. In the ordinary conditions of life on Earth, hundreds and thousands of different pictures of nature and the creations of his own hands are replaced before the eyes of man. All sorts of sounds constantly act on the hearing organs, creating a discordant acoustic background. Skin receptors perceive changes in temperature.
In an interplanetary flight, astronauts for months will see in the portholes only bright unblinking stars in a black, bottomless sky and a dazzling disk of the sun. There will be no day, no night, no winter, no summer, which people are so used to on this planet.
Starting from the first flights to the moon, the crew members of the spacecraft Apollo complained about the monotony of impressions on the "overtake" Earth-Moon. When the ship's marching engines are switched off, the astronauts enter the realm of silence.
Due to the fact that sensory isolation is not an experimentally created, but a real phenomenon for cosmonauts, for pilots, polar explorers, it was necessary to carefully study the effect of sensory hunger on the psyche.
During experiments on sensory isolation, unusual mental states were observed in humans. One of the pilots during a 30-hour space flight simulator "saw" TV, floating in a state of weightlessness, and among the instruments of the control panel - some unfamiliar faces. However, he tried to cope with these impairments of perception, trying to deflect the view away from the TV and devices.
Such experiments clearly demonstrate the role of sensations in the functioning of our consciousness.
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