Subcortical functions

Subcortical functions in the formation mechanisms of behavioral reactions of humans and animals function subcortical formations appear always in close cooperation with the bark of the big hemispheres. To subcortical formations include patterns, which lies between the crust and the oblong brain, the thalamus (see brain), hypothalamus (see), basal nodes (see), complex entities be merged in the limbic system of the brain, and reticular formation (see) in the brain stem and the thalamus. Last leading role in the formation of the ascending activating fluxes of excitation, generalizovannom covering the cerebral cortex. Any afferent excitement caused by irritation of the receptors in the periphery, on the level of the brainstem transformed into two streams of excitations. One thread on specific routes reaches a specific irritation projection area of a bark; the other from specific ways to collaterals gets in the reticular formation and from her in the form of high-rising excitement goes to the bark of the big hemispheres, activating it (Fig.). Devoid of relations with the reticular formation of the brain cortex comes in active state, characteristic for the sleep state.


The scheme of the rising activating retikuliarna formations (Magonu): 1 and 2 - specific (lemniscomys) pathway; 3 - collaterals, the exhaust from a specific path retikuliarna formations barrel brain; 4 - ascending activating system reticular formation; 5 - a generalized effect of the reticular formation in the cerebral cortex.

The reticular formation has close functional and anatomical connection with hypothalamus, thalamus, oblong brain limbic system, the cerebellum, so all the most common body functions (regulation of the constancy of the internal environment, the breath, the food and painful reaction) are under its supervision. The reticular formation is a wide area of interaction of flows excitations of different nature, as to its neurons converge as afferent excitation from peripheral receptors (sound, light, tactile, temperature and others)and excitation coming from other parts of the brain.
Afferent flow excitations from peripheral receptors on the way to the bark of the big hemispheres have numerous synaptic switch to the thalamus. From lateral group of nuclei of the thalamus (specific kernel) excitation sent in two ways: by subcortical ganglia and specific projection areas of the cortex of the brain. The medial group of nuclei of the thalamus (non-kernel) serves as a venue switch ascending activating influences that go from the stem reticular formation in the brain. Close functional relationship between specific and non-specific nuclei of the thalamus provide an initial analysis and synthesis of all the afferent excitations coming into the brain. In animals at the lowest levels of phylogenetic development, the thalamus and the limbic education play a role is the highest point of integration of conduct, providing all necessary reflex animal acts aimed at preserving his life. The higher animals and man the highest point of integration is the bark of the big hemispheres.
From a functional point of view to subcortical formations include the complex structures of the brain that plays a leading role in the formation of the basic innate reflexes of human and animal: food, sex and defensive. This area received the name of the limbic system and includes cingulate gyrus, the hippocampus, pear-shaped area, olfactory tubercle, almond-shaped complex and the area partitions. The Central place among entities of the limbic system plays a hippocampus. Anatomically installed hippocampal circle (hippocampus → code → mamillaria body → front thalamic nuclei → cingulate gyrus → cingulum → hippocampus), which together with the hypothalamus plays a leading role in the formation of emotions. Regulatory impact limbic system is widely spread on the vegetative functions (maintenance of the constancy of the internal environment of the body, regulation of blood pressure, respiration, tone of blood vessels, motor function of the gastrointestinal tract, sexual function).
The cerebral cortex has a permanent downward (brake and relieving) effect on subcortical structures. There are various forms of cyclic interactions between the cortex and subcortex, expressed in circulation excitations between them. The most pronounced closed circular relationship exists between the thalamus and somatosensory area of the brain functional components in relation to the whole. Cortical-subcortical circulation excitations is determined not only thalamocortical bonds, but more extensive system of subcortical formations. This is based on all the conditioned-reflex activity of an organism. The specificity of cyclic interactions of the cortex and subcortical structures in the process of formation of behavioral reactions of the organism is determined by its biological conditions (hunger, pain, fear, approximately research reaction).

Subcortical functions. The cerebral cortex is the highest place of the analysis and synthesis of all the afferent excitations, the area of formation of all complex adaptive acts of a living organism. However, the full analytical-synthetic activity of the cerebral cortex is possible only under condition of coming to it from subcortical structures powerful generalized flows excitations, energy-rich and capable to ensure the systemic nature of cortical lesions excitations. From this point of view and consider options subcortical formations, which, in the words of I. P. Pavlov, "energy source for bark".
In anatomical plan to subcortical formations include the neuronal structure, located between the cerebral cortex (see) and oblong brain (see), and from a functional point of view - subcortical structures in close cooperation with the bark of the big hemispheres form an integrated response of the body. These are the thalamus (see), hypothalamus (see), basal nodes (see), so-called the limbic system of the brain. From a functional point of view to subcortical formations include the reticular formation (see) in the brain stem and the thalamus, which have a leading role in the formation of the ascending activating flow to the cerebral cortex. Ascending activating retikuliarna formations opened Moruzzi, Megan (G. Moruzzi, N. W. Magoun). Irritating electrical shock, reticular formation, these authors observed the slow transition the electrical activity of the cortex in high-frequency, low-amplitude. The same changes in the electrical activity of the cortex ("the reaction of revival", "the reaction of de") was observed in the transition from a sleepy state of the animal to awake. On the basis of this arose the assumption that evoke the influence of the reticular formation (Fig. 1).

Fig. 1. "The reaction of de" cortical bioelectric activity during stimulation of the cat sciatic nerve (marked by arrows): CM - sensorimotor area of the cerebral cortex; TK - parietal-occipital region of the brain (l - left, C - right).

It is now known that the response of de-cortical electrical activity (cortical activation of the brain) may occur if any of afferent impact. This is due to the fact that at the level of the brain stem afferent excitement arising at any irritation of receptors, transformed into two excitation current. One stream is sent to a classical letniskowa way and reaches a specific cortical stimulation projection area; the other one gets from letniskowa system for collaterals in the reticular formation and from her in the form of a powerful upward flow is routed to the brain generalizovannom activating it (Fig. 2).

Fig. 2. The scheme of the rising activating retikuliarna formations (Magonu): 1-3 - specific (lemniscomys) pathway; 4 - collaterals, the exhaust from a specific path retikuliarna formations barrel brain; 5 - ascending activating system reticular formation; generalized influence of the reticular formation in the cerebral cortex.

This generalized ascending activating influence of the reticular formation is essential stay awake brain. Devoid of excitation source, which serves as the reticular formation of the brain cortex comes in active state, followed by a slow-amplitude electrical activity that is typical of the sleep state. The following picture can be observed with decerebrati, i.e. the animal with a severed brain stem (see below). In these circumstances, nor any afferent irritation, no direct irritation of the reticular formation does not cause diffuse, generalized reaction in timing. Thus, the presence in the brain of at least two main channels of receipt of the relevant impacts on the bark of the big hemispheres: classic letniskowa path and collaterals through the reticular formation of the brain stem.
As any afferent irritation generalized activation of the cortex of the brain, as measured by EEG indicator (see Electroencephalography), always accompanied by a reaction in timing, many researchers have concluded that any ascending activating retikuliarna formations in the cerebral cortex are nonspecific. The main arguments in favor of this conclusion was the following: a) lack of sensory modality, i.e. uniformity changes bioelectric activity when exposed to various sensory stimuli; b) permanent activation and generalized distribution of excitation on the bark measured again on electroencephalographic indicator (reaction in timing). On this basis, all kinds of generalized de cortical electrical activity was recognized also one that is not differ on any physiological qualities. However, the holistic formation of adaptive reactions of the organism ascending activating retikuliarna formations in the cerebral cortex are specific, appropriate biological activity of the animal - food, sex, defensive (P. K. Anokhin). This means that in the formation of various biological reactions involving different areas of the reticular formation, conducting the activation of a bark of the big hemispheres (A. I. Shumilina, V., Agafonov, Century havlíček).
Along with the rising influence on the bark of the big hemispheres reticular formation, may also have a downward impact on the reflex action of the spinal cord (see). In the reticular formation there are areas that have the inhibiting and facilitating effect on the motor activity of the spinal cord. By their nature, these effects diffuse and affect all groups of muscles. They are on a downward spinal paths that are different for inhibiting and facilitating influences. On the mechanism reticulospinal effects there are two points of view: 1) the reticular formation has a braking and facilitate impact directly on motoneurone spinal cord; 2) these impacts on motoneurone passed through the cells of Rancho. Especially clearly descending retikuliarna formations expressed in decerebration animal. Decerebrate by transection brain front line of cetverokatnice. While developing the so-called decerebration rigidity with a sharp increase of a tone of all muscles extensor. Consider that this phenomenon is caused by the break paths leading from the overlying formations of the brain by inhibiting the Department reticular formation, resulting in a reduction of the tone of this Department. In the ease of retikuliarna formations begin to dominate, leading to increased muscle tone.
An important feature of the reticular formation is its high sensitivity to various chemical substances circulating in the blood (WITH2, adrenaline and other). This enables the reticular formation in the regulation of some of vegetative functions. The reticular formation is also the scene of the electoral action of many drugs and medication, which is used in the treatment of some diseases of the Central nervous system. High sensitivity of the reticular formation to barbiturates, and some neurologically funds allowed to reimagine the mechanism of narcotic sleep. Acting inhibitory effect on neurons reticular formation, drug thereby deprives the brain cortex source of energizing influences and determines the development of the sleep state. Hypothermic effect of chlorpromazine and similar drugs explain the influence of these substances on the reticular formation.
The reticular formation has close functional and anatomical connection with hypothalamus, thalamus, oblong brain and other parts of the brain, so all the most common functions of the organism (thermoregulation, food and painful reaction, regulation of the constancy of the internal environment of the body) are in one or another functional dependence on it. A number of studies, accompanied by registration with the microelectrode equipment electrical activity of individual neurons reticular formation, has shown that this area is a place of interaction of the afferent flow of different nature. To the same neuron reticular formation can converge much excitement that occur not only at the irritation of various peripheral receptors (sound, light, tactile, temperature and others), but also coming from the bark of the big hemispheres, cerebellum and other subcortical structures. On the basis of this mechanism of convergence in the reticular formation is a redistribution of afferent excitations, after which they are in the form of ascending activating flows going to the neurons of the cerebral cortex.
Before you reach the crust, these flows excitation have numerous synaptic switch to the thalamus, which serves as if the interim, the link between the lower formations barrel brain and cerebral cortex. Impulses from the peripheral end of all external and internal analyzers (see) are switched in lateral group of nuclei of the thalamus (specific kernel) and go from here in two ways: by subcortical ganglia and specific projection areas of the cortex of the brain. The medial group of nuclei of the thalamus (non-kernel) serves as a venue switch ascending activating influences that go from the stem reticular formation in the brain.
Specific and nonspecific thalamic nuclei are in close functional relationship that provides an initial analysis and synthesis of all the afferent excitations coming into the brain. In the thalamus has a clear localization offices afferent nerves from different receptors. These afferent nerves end in certain specific nuclei of the thalamus, and from each core fibres go in the cerebral cortex to the specific projection zones of representation of one or the other afferent function (visual, auditory, tactile, and so on). Especially closely thalamus associated with somatosensory area of a bark of the big hemispheres. This relationship is due to the presence of closed circular relationships, directed from the bark of the thalamus, and the thalamus to the cortex. So somatosensory area of the cortex and thalamus in terms of functionality can be considered as a whole.
In animals at the lower levels of phylogenetic development, thalamus plays the role of higher center of integration of conduct, providing all necessary reflex animal acts aimed at preserving his life. In animals, standing on the higher stages of phylogenesis stairs, and a person of the highest point of integration is becoming a bark of the big hemispheres. The functions of the thalamus are in regulation and implementation of a number of complex reflex acts, which is a basis upon which to create adequate purposeful behavior of the animal and man. These limited options thalamus clearly manifested in the so-called thalamic animal, i.e., the animal with remote cerebral cortex and subcortical knots. The animal can move independently maintains the basic posture-tonic reflexes, providing normal position of head and body in space, saves the regulation of body temperature and all vegetative functions. But it cannot adequately respond to different stimuli external environment due to a sharp violation of conditioned-reflex activity. Thus, the thalamus in functional relationship with reticular formation, providing local and generalized effects on the bark of the big hemispheres, organizes and regulates somatic the function of the brain as a whole.
Among the structures of the brain related to subcortex from the functional point of view, highlight the complex formations, which plays a leading role in the formation of major congenital activities of the animal: food, sex and defensive. This complex has been called the limbic system of the brain and includes the hippocampus, pear-shaped area, olfactory tubercle, almond-shaped complex and the area of walls (Fig. 3). All these formations are combined on a functional basis, as they take part in ensuring the maintenance of a constancy of the internal environment, regulation of vegetative functions, in the formation of emotions (see) and motivations (see). Many researchers attribute to the limbic system and hypothalamus. The limbic system is directly involved in the formation of emotive, primitive innate behaviour. This particularly applies to the formation of the sexual function. When lesions (tumors, trauma and other) of some structures of the limbic system (the temporal area, cingulate gyrus) the person often there are sexual disorders.



Fig. 3. Schematic representation of the main relations of the limbic system (on Mac lane): N - nucleus interpeduncularis; MS and LS - medial and lateral olfactory strips; S - partition; MF - medial forebrain bundle; T - olfactory tubercle; AT - front nucleus of the thalamus, M - mamillaria body; SM - stria medialis (arrows indicate the distribution of excitation on the limbic system).

The Central place among entities of the limbic system plays a hippocampus. Anatomically installed hippocampal circle (hippocampus → code → mamillaria body → front thalamic nuclei → cingulate gyrus → cingulum → hippocampus), which together with, the hypothalamus (SR.) plays a leading role in the formation of emotions. Continuous circulation of excitation on hippocampal circle determines mainly the tonic activation of the cerebral cortex, and the intensity of emotions.
Often in patients with severe psychosis and other mental illnesses after death found pathological changes in the structures of the hippocampus. Assume that the circulation of excitation on hippocampal ring is one of the mechanisms of memory. A distinctive feature of the limbic system is the close functional relationship between its structures. Thanks to this, the excitement caused in the structure of the limbic system, immediately covers the remaining education and for a long time does not exceed the limits of the whole system. Such long, "stagnant" excitation of limbic structures probably also underlies the formation of emotional and motivational States of organism. Some of education of the limbic system (the amygdala complex) have generalized ascending activating effect on the cerebral cortex.
Given the regulatory impact of the limbic system on the vegetative functions (blood pressure, breathing, vascular tone, motility of the gastrointestinal tract), you can understand the vegetative reactions that accompany any conditioned reflex act of the body. This act as a holistic response is always with the direct participation of the cerebral cortex, which is the highest instance of analysis and synthesis of afferent excitations. In animals after removal of cortex (decorticating) greatly disturbed conditioned-reflex activity, and the higher is the animal in the evolutionary respect, the brighter expressed these violations. Behavioral reactions of animal subjected decortication, get very upset; most of the time these animals sleep, waking up only by strong stimuli and to make simple reflex acts (urination, defecation). Such animals can develop a conditioned reflex reaction, however, is too primitive and insufficient to ensure adequate adaptive functioning of the body.
The question, at what level of the brain (in the bark or the child) is the closure of the conditioned reflex, currently not regarded as fundamental. The brain is involved in the formation of adaptive behaviour of the animal, which is based on the principle of conditioned reflex, as a single integrated system. Any stimuli - both conditional and unconditional - converge to the same neuron different subcortical structures, as well as to one neuron different areas of the cerebral cortex. Study of mechanisms of interaction of the cortex and subcortical structures in the process of formation of behavioral reactions of the organism is one of the main tasks of modern physiology of the brain. The bark of the big hemispheres, being the highest authority of the afferent synthesis excitations, organizes internal neural link to commit sympathetic reflex act. The reticular formation and other subcortical structures, providing multiple ascending impact on the cerebral cortex, only create the necessary conditions for the organization of more sophisticated temporary cortical connections, and in a result - and the development of appropriate behavioural responses of the organism. The bark of the big hemispheres, in turn, has a permanent downward (brake and relieving) effect on subcortical structures. In this close functional interaction between the bark and the underlying entities brain lies the heart of integrative brain activity as a whole. From this point of view, the division of functions of the brain on a purely pure cortical and subcortical to some extent artificial and it is only necessary to understand the role of different entities of the brain in the formation of integrated adaptive reactions of the organism.