INTEGRATIVE ROLE OF THE BRAIN CORTEX LECTURE 5

Questions 1. General characteristic of the cortex. 2. 3. 4. 5. Limbic system. Structural and functional organization of the neocortex Cortical localization of the functions in the brain cortex Functional asymmetry of the cortex Methods of investigation of the brain

The brain cortex is divided into: üarcheocortex üpaleocortex üneocortex

The archeocortex includes: olfactory bulb üolfactory tract üolfactory tubercle üolfactory centre ü They form the rhiencephalon - cortical centre of the olfactory analyser.

Paleocortex consists from ü cingulate gyrus ü hippocamp ü amygdala

Paleocortex consists from

Functions of archeo- and paleocortex (“visceral brain”): ü regulation of the visceral functions ü providing of homeostasis ü formation of instinctive forms of a behaviour

The archeo- and paleocortex are: ü the parts of the limbic system ü participate in a formation of the emotions

Limbic system Hypothalamus Cyngulate gyrus Hippocampus Amygdala Epithalamus Anterior nucleus of the thalamus Paraolfactory area

Hypothalamus As centre of motivations includes: Centers of pleasant (satisfaction) and unpleasant (aversion) “reward” and punishment

Hippocampus Emotional memory, learning

Amigdala The “window” through which the limbic system “sees” the place of the person in the world (social status)

Papetz’s circle

Neocortex consists from gyres and fissures

Neocortex is the youngest functional part of the brain cortex.

2. Neocortex Ø it is composed mainly of 6 thin layers of neurons Ø 2 to 5 millimetres Ø covering all surface of the brain Ø has different types of cells

Typical Histological structure (6 layers): ü molecular ü external granular ü layer of pyramidal cells ü internal granular layer ü large pyramidal cell layer ü layer of fusiform or polimorphic cells

Histological structure

The granular cells have short axons and therefore function mainly as intracortical interneurons.

The upper layers (2 -4) are principally the afferent (sensory) layers.

Most of the output signals leave the cortex from neurons located in layers 5 and 6. The very large fibbers to the brain stem and cord arise generally in layer 5, and to the thalamus arise in layer 6.

6 layer’s structure is a typical organization of the brain cortex.

53 fields by Brodman. Each such area has the concrete histological structure and functions.

But the structural and functional unit of brain cortex is vertical column.

Vertical column It is an association of neurons of all cortex layers that regulates one function

Motor column formation of efferent command for definite position of the joint (not for the separate muscles).

Columns of visual and motor cortex

Function of vertical column provides an analyse of many sensory signals in upper layers of the cortex and the formation of complex strategy efferent commanding in inner layers.

3. Dynamic localization of the cortical functions three functional areas (zones): sensory ümotor üassociative ü

Sensory and motor areas are called the specific areas, because they are responsible for the definite functions.

Areas Motor Sensory Association Localization Pre-central gyrus Postcentral gyrus Temporal area (hear) Occipital area(vision) Prefrontal area Parieto-occipitotemporal Limbic

Sensory areas are represented by visual, acoustic, vestibular, somato-sensory cortex.

The function receipt and analysis of sensory information that come from different receptors.

Sensory areas are divided into: Øprimary Øsecondary

The primary areas have direct connections with specific sensory receptors

The secondary areas make sense out of the functions of the primary areas.

Example Supplemental and premotor areas function along with the primary motor cortex and basal ganglia to provide highly specific patterns of motor activity.

Function of secondary visual areas interpreting the shape or texture of an object in one’s hand; the color, the light intensity, the directions of lines and angles, and other aspects of vision

Function of secondary acoustic areas combination of tones, sequence of tones, and beginning interpretation of the meaning of auditory signals

Primary visual cortex is located on occipital area (17, 18 and 19 fields).

The auditory and vestibular areas is located in temporal lobe.

The primary somatic area is located in the postcentral gyrus.

Somatic and motor areas have the detail topography of our body (homunculus) areas.

Different organs are represented by different neurons

Associative zones large areas of the cerebral cortex that do not fit into the rigid categories of primary or secondary motor and sensory areas

Function receipt and analysis signals from multiple regions of the cortex and even subcortical structures.

The most important associative areas in neocortex 1. the parieto-occipito- temporal association area; 2. the prefrontal association area

The parieto-occipito-temporal assosiative area provides a high level of interpretive meaning for signals from all the surrounding sensory areas.

important area for language comprehension is Wernike’s area

Damage of this speech center causes the sensory afasia when human can speak but its speech has no sense.

The prefrontal association area takes participation with the motor cortex in a planning of complex movements. But the most important function of this area is the higher psychic functions such as mental activity, personal characteristics etc.

A special region in the frontal cortex called Broca’s area, provides of word formation.

damage of this center causes a motor afasia. It means inability to speak, although the person can understand speech.

The limbic association area is responsible for behavior, emotions and motivation. It is a part of a much more extensive system – the limbic system, that includes a complex set of neuronal structures in the midbasal regions of the brain and that provides most of the drives for setting the other areas of the brain into action

Functional asymmetry of brain There is a significant difference between a functioning of the left and right hemisphere.

Left hemisphere provides ü all intellectual functions associated with language or verbal symbolism such as Ø ability to read, Ø ability to perform mathematical operations, Ø even the ability to decide a logical problems.

Right hemisphere ü understanding and interpreting music, ü nonverbal visual experiences, ü spatial relationships between the person and surroundings, ü the significance of “body language” and intonations of person’s voices

All persons can have more capable of abstract-logical operations or sensory reception, i. e. to be a “thinker” or an “artist”.

Correlation of activity between 2 hemispheres realizes by corpus callosum and anterior commissure to transfer thoughts, memories, training and other information

Damage in early childhood of one hemispere, the opposite one can develop these abilities dynamic localization of function.

Control of brain activity By excitatory signals from the Brain Stem – bulboreticular facilitory area (the reticular substance of the midbrain and pons) By Excitatory and inhibitory neurotransmitter agents – aminergic systems: a) Norepinephrinergic (adrenergic) system – excitation b) Serotonin- and dopamineergic system – excitation and inhibition

Dopaninergic system

Adrenergic system

Cholinergic system

Serotoninergic system

Antidepressants increase the effect of aminergic systems

psychoactive substance similar to monoamines

Methods of brain research include: 1. a damage of concrete structure and centers by different chemical agents and electrical stimuli and observation 2. clinical observation 3. EEG and microelectrode technique

EEG

EEG – is recording of summary bioelectrical brain activity.

Source of the EEG Sum of postsynaptic potentials It has different characteristics in depends on functional state of human body.

There are 4 main types of electrical brain activity or 4 types of EEGrhythms a) alpha-rhythms frequency is 8 -13 cycles/sec amplitude till 50 mkv is recording during relaxed states while the eyes are closed but patient not sleep.

Beta-waves Frequency more then 14 cycles/sec Amplitude 25 mk. V during periods of mental activity.

Theta- waves frequency 4 -7 cycles/sec. Amplitude more 50 mk. V not deep sleep, easy anesthesia These rhythm occur emotional stress mainly during

Delta-waves Frequency - below 4 cycles per second. Amplitude – 150 mk. V Very deep sleep, anesthesia and in serious organic brain diseases.

Death of a brain (1 -th old year child, no fenomens with amplitude more 1. 5 μV)

Epilepsy (single spike and triplets)

In result of EEG- analysis by the probable tomography the focus of organic lesion of brain is revealed

Comparison with anatomical tomography

Evoked potentials

Be careful! Brain is working!