Transcript Higher nervous activity of a human

Physiological bases of
behavior: attention,
memory, thinking,
consciousness
Type of nervous system
 Type of nervous system determines rate
of creation of new conditioned reflexes,
strength and stability of these reflexes,
intensity of external and internal
inhibition, rate of irradiation and
concentration of nervous processes, the
capacity for induction and less or grater
possibility for development of
abnormalities of higher nervous activity.
Type of nervous system
after I.P. Pavlov
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I.P. Pavlov classifies types of higher nervous activity according to
several attributes that considered as most reliable indices of higher
nervous activity. These were intensity of the excitation and inhibition,
the ratio of these processes in central nervous system and their
mobility, that is rate at which excitation was replaced by inhibition
and wise versa. In experimental practice the following four principle
types of higher nervous activity are met:
1) strong unbalanced type, characterized by predominance of
excitation over inhibition;
2) strong well-balanced active type, characterized by high mobility of
nerve processes;
3) strong well-balanced passive type, characterized by low mobility
of nerve processes;
4) weak type, characterized by extremely weak development of both
excitation and inhibition, which cause fatigue and low workability.
The first and second
signaling system
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The analysis and synthesis of the direct stimuli from surroundings first
signal system performs. This includes impressions, sensations. This
functional mechanism is common in human and animals. In the course of
his social development and labor activity second signal system, which
based on using verbal signals, develop. This system includes perception
of words, reading and speech.
The development of the second signaling system was incredibly
broadened and changed quality of higher nervous activity of cerebral
hemispheres. Words are signals of other signals. Man uses verbal signals
for everything he perceives through the receptors. Words are abstraction
of reality and allow generalization, processing of surrounding primary
information. This gives the first general human empiricism and finally
science, the instrument of man's higher orientation in the environment
and its own self.
So, second signaling system is socially determined. Outside the society,
without association with other people second signaling system is not
developed.
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Nerve
substrate
of
speech
There are two aspects of communication: sensory, involving reading, hearing of
speech, and second, the motor aspect, involving vocalization and its control. It is
known, that lesion of posterior portion of the superior temporal gyrus, which is
called Wernicke's area, and is part of auditory associative cortex, make
impossible to the person to interpret the meanings of words. This Wernicke's
area is located in dominant hemisphere, which is usually the left. The process of
speech includes two principle stages of mentation: formation of thoughts to be
expressed and motor control of vocalization. The formation of thoughts is the
function of associative areas in the brain. Wernicke's area in the posterior part of
the superior temporal gyrus is most important for this ability. Broca's speech
area lies in prefrontal and premotor facial region in the left hemisphere. The
skilled motor patterns for control of the larynx, lips, mouth, respiratory system
and other accessory muscles of speech are all initiated from this area.
Articulation means movements of mouth, tongue, larynx, vocal cords, and so
forth that are responsible for the intonations, timing, and rapid changes in
intensities of the sequential sounds. The facial and laryngeal regions of the
motor cortex activate these muscles, and the cerebellum, basal ganglia, and
sensory cortex all help control the sequences and intensities of muscle
contractions. Transmitters such as dopamine, noradrenaline, serotonin and
certain neuropeptides transmit their signals by what is referred to as slow
synaptic transmission. The resulting change in the function of the nerve cell may
last from seconds to hours. This type of signal transmission is responsible for a
number of basal functions in the nervous system and is of importance for e.g.
alertness and mood. Slow synaptic transmission can also control fast synaptic
transmission, which in turn enables e.g. speech, movements and sensory
perception.
Development of signaling
systems in children
 The ability of a full-term baby to develop temporary
connections of the first signaling system arises in a few
days after the birth.. In the first six months of life
speech sounds mean little to a child. They are simply
stimuli to the auditory analyzer like any other sounds.
 The first signs of development of the second signaling
system appear during the second half of the first year
of life. If a person or an object is named and shown to
a child many times, reaction to this name develops.
 Later after leaning a few words, a child begins to name
objects itself. Finally, at a later time he uses a stock of
words to communicate with other people.
Functions of speech
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Main functions of speech are communicative, regulatory, programming
and gives general notion about surroundings. Communicative function
permits exchange of information between people. Such a function is also
present in animals, which use for this aim vocalization of different intensity
to warn about danger or express positive and negative emotions. People
use verbal signals for everything he perceives through the receptors.
Words are abstraction of reality and allow generalization, processing of
surrounding primary information.
Verbal instructions may direct human activity, give suggestion about
proper mode of behavior. This is programming function of speech.
Programming function of speech involves emotional component also,
which may influence to emotional status of a person. As limbic system,
which controls emotions, has direct connection with autonomic nervous
system.
So speech through emotions may influence to functions of visceral
organs. Physician may use this effect for psychotherapy. It is necessary
remember about jatrogenic disorders also.
Attention as psychical
function
 Attention is selectiveness of psychical
processes or any kind of mental activity, which
helps in getting and processing the information.
There are sensory, motor, intellectual and
emotional forms of attention, depending to kind
of activity of a person.
 There are voluntary and involuntary levels of
attention. Involuntary attention is present from
the birth of man. Voluntary attention develops
in life course, due to mental activity, formation
of speech function and studying languages.
Physiological mechanisms
of attention
 Involuntary attention is controlled by lower portion of
brain stem and midbrain, where centers of roof reflexes
are locates. Voluntary attention appears as a result of
higher cortical activity in visual, auditory, motor areas
and so on.
 Lesion of these cortical areas leads to such
disturbances in processing special sensory information
as ignore of stimuli of different modality. Intellectual
attention appears because of function of prefrontal
associative cortical area. The limbic system of the brain
is responsible for emotional attention.
Memory as psychical
function
 Memory function helps fixing of perceived information,
keeping it in verbal form or as traces of percept stimuli
and recognizing of this information in proper time.
Genetic memory keeps information about body
structure and forms of its behavior. Biological memory
is presented in both philogenetic and ontogenetic
forms. The immune memory and psychical memory for
instance, belong to ontogenetic memory.
 General characteristics of memory are duration,
strength of keeping the information and exactness of its
recognizing. In man mechanisms of perception and
keeping the information are developed better,
comparing to other mammalians.
 According to duration is concerned short-time and
long-time memory; in relation to kind of information –
sensory and logic.
Thinking process as
psychical function
 The prefrontal association area is essential to carrying out thought
processes in the mind. This presumably results from some of the
same capabilities of the prefrontal cortex that allow it to plan motor
activities.
 The prefrontal association area is frequently described as
important for elaboration of thoughts to store on a short-term basis
“working memories” that are used to analyze each new thought
while it is entering the braine. The somatic, visual, and auditory
association areas all meet one another in the posterior part of the
superior temporal lobe. This area is especially highly developed in
the dominant side of the brain – the left side in almost all righthanded people.
 It plays the greatest single role of any part of cerebral cortex in the
higher comprehensive levels of brain function that we call
intelligence. This zone is also called general interpretative area,
the gnostic area, the knowing area, tertiary association area. It is
best known as Wernike’s area in honor of the neurologist who first
describes it.
Nerve substrate of
memory
 It’s discovered the nervous substrate of longterm memory is mostly cerebral cortex. The
most important regions are temporal lobes,
prefrontal area and hippocampus.
Experimental researches revealed that some
thalamic nuclei and reticular formation take
part in memory function.
 Reticular formation gives ascending stimulatory
influences to cerebral cortex, which help in
keeping awake condition of cortex and
provides voluntary attention.
Physiological mechanisms
of memory
 At the molecular level, the habitation effect in the sensory terminal
results from progressive closure of calcium channels through the
presynaptic terminal membrane.
 In case of facilitation, the molecular mechanism is believed to be
following. Facilitated synapse releases serotonin that activates
adenylyl cyclase in postsynaptic cell. Then cyclic AMP activates
proteinkinase that then causes phosphorylation of proteins. This
blocks potassium channels for minutes or even weeks. Lack of
potassium causes prolonged action potential in the presynaptic
terminal that leads to activation of calcium pores, allowing
tremendous quantities of calcium ions to enter the sensory
terminal. This causes greatly increased transmitter release,
thereby markedly facilitating synaptic transmission.
 Thus in a very indirect way, the associative effect of stimulation the
facilitator neuron at the same time that the sensory neuron is
stimulated causes prolonged increase in excitatory sensitivity of
the sensory terminal, and this establishes the memory trace.
Short and long term
memory
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Eric Kandel showed initially that weaker stimuli give rise to a form of short
term memory, which lasts from minutes to hours. The mechanism for this
"short term memory" is that particular ion channels are affected in such a
manner that more calcium ions will enter the nerve terminal. This leads to
an increased amount of transmitter release at the synapse, and thereby to
an amplification of the reflex. This change is due to a phosphorylation of
certain ion channel proteins, that is utilizing the molecular mechanism
described by Paul Greengard.
A more powerful and long lasting stimulus will result in a form of long term
memory that can remain for weeks. The stronger stimulus will give rise to
increased levels of the messenger molecule cAMP and thereby protein
kinase A. These signals will reach the cell nucleus and cause a change in
a number of proteins in the synapse. The formation of certain proteins will
increase, while others will decrease. The final result is that the shape of
the synapse can increase and thereby create a long lasting increase of
synaptic function.
In contrast to short term memory, long term memory requires that new
proteins are formed. If this synthesis of new proteins is prevented, the
long term memory will be blocked but not the short term memory.
Consciousness and its
mechanisms
 Consciousness is special form of perceiving
surroundings and goal-orientated activity of person with
interrelation to surroundings. Only social life forms
consciousness. It involves life experience of entire
society.
 This ability of prefrontal areas to keep track of many
bits of information could well explain abilities to
prognosticate, do plan for the future, delay action in
response to incoming sensory signals, consider the
consequences of motor actions even before they are
performed, solve complicated mathematical, legal, or
philosophical problems, correlate all avenues of
information in diagnosing rare diseases and control our
activities in accord with moral laws.
Notion “emotions”
 Emotions are aspect of higher nervous
activity that characterize subjective
attitude of person to various stimuli
arousal in surroundings.
 Emotional status reflects actual needs of
man and helps in its realization.
Classification of emotions
 According to subjective status there are positive and
negative emotions. Negative emotions are sthenic
(aggression, affect) that stimulate human activity and
asthenia (horror, sadness, depression) that inhibit
behaviour. Lower or elementary emotions are caused
by organic needs of man or animal as hanger, thirst
and survival, so on).
 In humans even lover emotions undergo to cortical
control and are brining up. Social, historical and
cultural customs cause also formation of higher
emotions that regulates public and private relations in
society. Higher emotions appear due to consciousness
and may inhibit lower emotions.
Appearance of emotions
in ontogenesis
 In newborns emotions of horror, anger,
pleasure, are revealed just after birth. Hunger,
pain, getting cool, wet bedclothes cause in
newborn child negative emotions with grimace
of suffering and crying. Sudden new sound or
loss equilibrium causes horror and loss of free
movement causes anger.
 Final formation of human emotions develops
gradually with maturation of nervous and
endocrine regulatory systems and needs up
brining.
Biological importance of
emotions
 Emotions are important element of human
behaviour, creation of conditioned reflexes and
mentation.
 Negative emotions give fusty evaluation of
current situation does it useful or not.
Mobilizing of efforts helps then to satisfy
current needs of person.
 Positive emotions help to put in memory
scheme of behaviour, which was useful and
have lead to success.
External manifestations of
emotions
 Motor manifestations of emotions are mimic,
gesticulation, body posture and walk.
 Emotional excitation usually is followed by autonomic
reactions as blush, dilation of pupils; increase of
arterial pressure, rate of heartbeat and breathing. Level
of catecholamines in blood and 17-oxycetosteroides in
urine rises also.
 Positive emotion may activate parasympathetic division
of autonomic nervous system. Severe emotional
excitation may result in visceral disorders because of
circulatory disturbances and excess hormones in
blood.
Nerve substrate of
emotions
 Several limbic structures are particularly concerned with the
affective nature of sensory sensations – that is whether the
sensations are pleasant or unpleasant. The major rew3ard centres
have been found to be located along the course of the medial
forebrain bundle, especially in the lateral and ventromedial nuclei
of the hypothalamus.
 Less potent reward centres are found in the septum, amygdala,
certain areas of the thalamus, basal ganglia, and extending
downward into the basal tegmentum of the mesencephalon. The
most potent areas for punishment and escape tendencies have
been found in the central grey area surrounding the aqueduct of
Sylvius in the mesencephalon and extending upward into the
periventricular zones of the hypothalamus and thalamus.
 Less potent punishment areas are found in some locations in the
amygdala and the hippocampus. Electrical recording from the
brain show that newly experienced types of sensory stimuli almost
excite areas in the cerebral cortex.
Theories of emotions
 Biological theory of emotions (P.K. Anochkin) considers that life
course includes two main stages of behavioural act: 1) formation
of needs and motivations that results from negative emotions and
2) satisfaction of needs that leads to positive emotions it case of
complete accordance of image and result of action. Incomplete
compliance of suspected and real result of action cause negative
emotions and continues behavioural act.
 Information theory of emotions (P.V. Simonov)considers that
emotions reflect strength human of need and possibility of its
satisfaction in current moment. In absence of needs emotions
can’t arise. There is also not emotional excitation, if getting excess
information about mode of satisfaction this need. Lac of
information already causes negative emotions that help to recall to
mind life experience and to gather information about current
situation.
Neurotransmission of
emotional excitation
 Emotional excitation is spread in the brain due to
variety of neurotransmitters (noradrenalin,
acetylcholine, serotonin, dopamine and neuropeptides
including opioides.
 Positive emotions may be explained by revealing
catecholamines and negative emotions, aggression
result from production acetylcholine in the brain.
Serotonin inhibits both kinds of emotions.
 Decrease of serotonin in blood is followed by
groundless anxiety and inhibition of noradrenergic
transmission results in sadness.
Structure
of behavioural act
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According to theory of functional systems (Anochking)
there are such stages of behavioural act:
1) afferent synthesis; 2) taking of decision;
3) acceptor of result of action;
4) efferent synthesis (or programming of action);
5) performing of action;
6) evaluation of final result of action.
Due to converging and processing of both sensory
information and memory traces afferent synthesis in
the brain is performed. Taking of decision is based on
afferent synthesis by choosing optimal variant of
action.
Neuronal mechanisms of
behaviour
 In the very lowest animals olfactory cortex plays essential roles in
determining whether the animal eats a particular food, whether the
smell of a particular object suggest danger, and whether the odour
is sexually inviting, thus making decisions that are of life-or-death
importance. The hippocampus originated as part of olfactory
cortex.
 Very early in the evolutionary development of the brain, the
hippocampus presumably becomes a critical decision-making
neuronal mechanism, determining the importance of the incoming
sensory signals. Once this critical decision-making capability had
been established, presumably the remainder of the brain began to
call on it for the same decision making. Therefore, if the
hippocampus says that a neuronal signal is important, the
information is likely to be committed to memory.
 Thus, a person rapidly become habituated to indifferent stimuli but
learns assiduously any sensory experience that causes either
pleasure or pain. It has been suggested that hippocampus
provides the drive that causes translation of short-term memory
into long-term memory.