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Integrative and Intellectual Functions of the Brain. Higher nervous activity Lecture is prepared by EKATERINA ELISEEVA Ass. Prof. of the Normal Physiology Department Stavropol state medical university, 2015. Learning. is the most characteristic ability of humans and higher animals.
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Integrative and Intellectual Functions of the Brain Higher nervous activity Lecture is prepared by EKATERINA ELISEEVA Ass. Prof. of the Normal Physiology Department Stavropol state medical university, 2015
Learning • is the most characteristic ability of humans and higher animals. • This process make an individual possible to change his behavior according current needs and environment changes. • Learning and memory are the functions of nervous system based on conditioned and unconditioned reflexes.
Conditioned reflex • Is a reflex response to a stimulus which does not elicit the response itself but acquires after repeated application with another specific stimulation that normally evokes such a response. • Conditioning = training
Unconditioned vs. conditioned • Inborn, inherited • Stable, constant • Activity of low nerve centers • Adequate stimulation only • Specific (for species) • Based on the certain reflex arch • Give certain adaptation • Acquired during life • May be established or abolished • Activity of cortical (higher) centers • Any stimulus may be conditioned • Individual • Based on temporary connection of neurons • Give better adaptation
Characteristics • Variability, which is the most characteristic feature of a conditioned reflex, ensures the body’s adjustment to the external environment. A conditioned signal that gives incorrect information on the external environment ceases to be a stimulus for responsive behaviour, and the reaction to such a signal disappears. This phenomenon is based on internal inhibition, which causes a sensitive discrimination among stimuli according to their physiological and biological properties and which helps the body dispense with conditioned reflexes that are no longer biologically useful.
Characteristics • The conditioned reflex warns person about approach of the subsequent kinds of activity and prepares them for future kinds of activity (eating, avoidance of danger and another). • With the help of the conditioned-reflex mechanism such function of nervous system as purposeful behaviour of the person in an environment and society, the adaptation to varied conditions of an environment are carried out. Such activity of nervous system concerns to the higher nervous activity.
Classification • I. According to biological importance • Nutritional • Defensive • Sexual • Homeostatic, etc. • II. According to reflex reactions • Motor • Visceral • Cardiac • Secretary, etc.
Classification • III. According to base reflexes • First order reflex • Second order reflex • High order reflex • IV. According to time periods • Classic • Traced • Reflex for time
Classification • V. According to receptors • Exteroreceptive • Interoreceptive • Proprioreceptive • VI. According to basal methodic • Natural • Instrumental (Artificial)
Characteristics & Features • Depending on the stimulus causing the reflex, conditioned reflexes are classified as either natural or artificial. • Natural conditioned reflexes are evoked by the inherent properties of an unconditional reinforcement that have biological significance for an animal, for example, the sight and smell of food. • Artificial conditioned reflexes are evoked by stimuli that are initially unconnected to a reinforcement, for example, a bell, a light, or the sound of a metronome.
Rules for conditioned reflexes • Combination of two stimuli: conditioned stimulus must be the first in order and unconditioned stimulus must follow it. • Conditional stimulus is at first relatively neutral(indifferent) and evokes orientation reflex. Thegoal is to suppress this reaction by applying the conditioned stimulation several times.
The orientation reflex has a special place among unconditioned reflexes. It is a reflex response to novelty, elicited by any sufficiently quick change in the external environment, and is outwardly expressed in alertness, listening for new sounds, sniffing, turning the eyes and head, and sometimes the whole body toward a stimulus, etc. This reflex facilitates best perception of an acting agent and has great adaptive significance. As Pavlov figuratively described it, the orientation reaction is a "What is it?" reflex.
Rules for conditioned reflexes • Both stimulimust be more intensive than threshold.Intensity of unconditioned stimulus must be more than intensity of conditioned one. • For example: Conditional nutritional reflex may be established if the dog is hungry. Ringing (at first neutral signal, which then becomes conditional one) is followed by some food in a few second (strong unconditional reinforce). Repetitive combination of both signals provokes formation of conditional nutritional reflex: secretion of saliva. This means that now ringing provokes secretion of saliva without any food.
Rules for conditioned reflexes • Combination of conditioned and unconditioned stimuli must be repetitive. • Formation of temporary connections requires normal active state of central nervous system.
Mechanism of conditioned reflex Conditioned reflexes, as a rule, reproduce the structure of an unconditioned reflex, since the conditioned stimulus excites the same nerve centers as the unconditioned one. Therefore the components of the conditioned reflex are similar to those of the unconditioned reaction. They include primary components specific for the type of reflex and secondary, unspecific components. In the defensive reflex the leading role is played by I he motor component, in the nutritional reflex by the motor and secretory components.
Conditioned stimulus center Unconditioned reflex center
PAVLOV'S CONCEPT: Conditional reflexes are built on the basis of unconditional ones. The building of a conditional reflex is based on the formation of temporary connections between two cortical centers: (a) perceiving the conditional stimulus and (b) perceiving the unconditional one. Important role in the mechanism of interaction between different cortical regions play (a) cortico-subcortico-cortical pathways and (b) the dominant phenomenon. When conditioned and unconditioned stimuli are combined, the excitation is summated. Nervous cells of both cortical regions are involved in a rhythmic activity. Circulation of impulses along the same neuronal chains ensures the formation of temporary connections. Functional changes are important only for brief impression of traces of stimuli on the cortex ("short-term memory"). Long retention of temporary connections ("long-term memory") is based on some molecular plastic changes taking place in the synapses and neurons.
Biologicalimportanceofconditionedreflexes: reflex reactions appear a certain time before actual unconditioned stimulation thus preparing the organism. Conditioned reflexes help to find food, to avoid danger in proper time, to eliminate harmful influences, etc, they are base for habits. Reflexes may be applied in clinical and psychological practice.
Inhibition of higher nervous activity • External inhibition – conditioned reflex is weakened or suppressed by simultaneous excitatory process • Temporary • Permanent • Internal inhibition – inhibitory effects in the cortical center of conditioned reflex • Extinction • Differential inhibition • Conditioned inhibition • Inhibition of delay
Temporary inhibition • Inhibitory effect arises in a new cortical center, not in centers involved into conditioned reflex. • E.g., orientation reflex – any new stimulation suppresses current conditioned activity. • Importance – readiness to give response to a stimulus
Extinction • If the conditioned stimulus is repeated without unconditioned base for several times, reflex becomes extinct, suppressed. • Importance – brain does not keep reflexes and habits which are not necessary.
Extinction Example of extinction: a dog has been previously conditioned to come when he hears a bell because he knows he will get food. But the previous handful of times the dog did not receive food so no longer comes when he hears the bell. The figure is another example, applied on mouse.
Differential inhibition • Firstly conditioned response may be given to different stimuli rather similar to conditioned stimulus (generalization period in reflex activity). • After several repetitions response in given accurately to certain stimulus only, other are inhibited in differential manner. • Importance – the base for learning.
Inhibition of delay • If unconditioned base is delayed the established conditioned reflex is inhibited. • Importance - organism gives response only to stimulus applied in proper time.
Type of nervous system • determines the rate at which conditioned reflexes are built, the strength and stability of these reflexes, the rate of irradiation and concentration of nerve process, greater or lesser susceptibility to various influences causing pathology in higher nervous activity.
Human’s types of nervous system (1) Thinking type - with dominant left hemisphere (2) Art type - with dominant right hemisphere (3)Mixed type - with equallydeveloped functions of left and right hemispheres (4)Genius type – with equally overdeveloped functions of left and right hemispheres
Emotions • Emotion is a kind of psyco-physiological phenomenon, it is a multifaceted form of behavior, involving: • Different somatic reactions (smiling, laughing, running, etc.); • Variety of autonomic responses (heart rate changes, paleness, fainting, etc.)
Aspects of emotions • Cognition determines the emotion that in its type and degree is appropriate to given situation • Expression in form of somatic and autonomic activity during emotional state • Experience is the subjective aspect, basis for pleasant and unpleasant emotions • Excitement may be delight or distress
Nerve control of emotions • Hypothalamus is often considered as the seat of emotions. It is the principle center where various components of emotional reactions are organized into definite pattern. • Stimulation of different parts of hypothalamus shows different emotional reactions.
Nerve control of emotions • Thalamus – anterior nuclei, dorsomedial nucleolus, posteroventral nucleous are part of limbic system. • Cerebral cortex and limbic system – amygdaloid nucleous complex, hyppocampus, hypothalamus, thalamus, ancient cortex – form “circles” making possible prolonged analyzes of information, base for behavior and emotions.
