What Is the Cerebral Cortex?

It is gray matter covering the surface of the cerebral hemisphere. The deep part is the medulla, which contains the basal ganglia.

The sulcus on the surface of the brain enlarges the surface area of the cortex. The volume of the cerebral cortex is about 300 cm3, and its surface area is 2200-2850 cm2, of which about 2/3 is buried in the groove. The thickest part of the central cortex is about 4.5mm, and the thinnest part of the occipital cortex is about 1.5mm.

Chinese name: Cerebral cortex
Foreign name: cerebral cortex
Constitute: Gray matter

Thickness: About 1 to 4mm
Definition: The surface of the brain
Features: Neural conduction between the two hemispheres

Histological characteristics of the cerebral cortex

Histologically, the cerebral cortex is generally divided into 6 layers, which are molecular layer, outer granular layer, pyramidal cell layer, inner granular layer, nodal cell layer, and polymorphic layer in order from outside to inside. The types of neurons in the cerebral cortex are divided into two categories, pyramidal cells and non-pyramidal cells. There are two main types of afferent fibers entering the cerebral cortex:

1. Non-specific afferent fibers, which generally originate from the thalamic midline nucleus group, lamina nucleus group, thalamic reticular nucleus, etc., can branch out when entering the cortex through each layer, but mainly in layers 2 and 5;

2. Specific afferent fibers from the posterior ventral nucleus of the thalamus (to the sensory cortex) and the ventrolateral nucleus (to the motor cortex). According to the cell type and arrangement of the various parts of the cerebral cortex, the thickness of each layer and the density of the fibers, the cerebral cortex can be divided into several regions. There are many division methods, but the widely used in basic and clinical is the Brodmann partition method divided into 47 areas.

Anatomy of the cerebral cortex

With the evolution of human beings, the two hemispheres of the brain and each leaf have very complicated development and differentiation, and the cerebral hemispheres on both sides are not exactly the same. Generally, the right-handed person takes the left side as the dominant hemisphere.

Frontal cortex

The frontal lobe is located before the central sulcus and above the lateral fissure. The symptoms of frontal lobe damage are mainly voluntary movement, language expression and mental activity disorders.

The frontal surface includes: exercise area, pre-exercise area

Destructive lesions in the frontal lobe that damage the motor area: contralateral paralysis of the limbs, often paralysis of the upper limbs, facial paralysis, upper limb paralysis, hand involvement is more serious than the proximal muscles of the upper limbs, and muscle tension does not increase. If the lesion involves the pre-exercise area, the muscle tension of the paralyzed limb increases. Stimulative lesions produce focal motor epilepsy. If the convulsions persist in a certain part of the muscle, it is called persistent partial epilepsy. If the convulsions develop in the order of the representative area of the cortex, it is called Chaxon epilepsy. When the exercise suppression area is excited, the active limb can stop moving. Pre-exercise lesions produce spastic muscle tension increase on the sides and limbs, which may be accompanied by mild paralysis, released by strong grip, groping, and sucking reflexes, and motor apraxia may occur. Such as left-sided lesions can cause bilateral motor dysfunction. Impairment of the eyeballs in the same-direction oblique motion zone results in joint dyskinesia of the opposite side of the eyes. Destructive lesions cause the eyeball to stare at the lesion side; irritant lesions stare at the contralateral side. Due to the damage of the frontal bridge cerebellar tract, ataxia of contralateral limbs may still occur. Lesions in the posterior inferior frontal gyrus in the main hemisphere produce motor aphasia, often accompanied by aphasia, with or without facial, lip and tongue apraxia, and left-hand apraxia. Mental symptoms can occur when the prefrontal lobe is damaged on either side, showing mildly elevated emotions, euphoria, multilingualism, jokes, lack of wit, difficulty in adapting, and loss of initiative. The symptoms of bilateral prefrontal lesions are more obvious, showing indifferent emotions, memory loss, mental retardation, slow action, lack of will, and the formation of a typical indifferent-inability to exercise-loss of will sign. In severe cases, even silence, stiffness State, and there are various types of strong grip, sucking reflexes, gait disorders, urinary incontinence and so on.

Frontal lobe damage: Incontinence can occur when the posterior frontal gyrus and anterior sacral gyrus are damaged. Frequent urination and urgency occur early, and patients can perceive it; however, if the lesion expands and invades the frontal lobe, No sense of urinary incontinence. The paralobular lesions of the paracentral area produce paralysis of the contralateral lower limbs, with the foot as the weight, the muscle strength above the knee joint is not damaged, and seizures usually start from toe convulsions. When the area is damaged, urination and defecation disorders also occur. In front of the lateral central leaflet is the auxiliary sports area (Figure 5), which is the extension of the outer side of the pre-motion area on the inner side, and produces symptoms similar to the pre-motion area. Changes in blood pressure and heart rate can also occur when the lesions are brought back.

Frontal surface of cerebral cortex

Including orbital gyrus, straight gyrus, mainly autonomic and mental functions. Lesions in this area can produce overeating, excessive gastrointestinal motility, polydipsia and polyuria, high fever, sweating, vasodilation, changes in blood pressure and breathing. Mental aspects may include euphoria, or excitement, anger, compulsive crying, recent memory forgetting or silence, stiffness, waxy curvature, tension and other symptoms.

Cerebral cortex temporal lobe

The front end of the temporal lobe is the temporal pole, and the lateral flanks are clearly separated from the upper frontal lobe, and the upper and rear posterior and parietal lobe and occipital lobe are unknown. The superior temporal gyrus forms the temporal part of the island cover, and the posterior part is called the transverse temporal gyrus is the auditory area, and its periphery is the perceptual speech area where auditory impulses are converted into auditory imagery (areas 41, 42). The vestibular functional cortex is behind the auditory sensory area. There is still a cortex that perceives music in the medial temporal gyrus, and the medial temporal gyrus and posterior inferior temporal gyrus are related to memory. The hook gyrus and hippocampus on the medial side of the temporal lobe are the olfactory regions. The taste cortex has not been identified.

The clinical manifestations of temporal lobe damage include the following:

1. Cortical deafness. Cortical deafness results from the central temporal auditory sensation of bilateral deafness. Patients with cortical deafness may not know that they are deaf, which is called apathy.

2. There are three types of auditory insufficiency: auditory aphasia (sensory aphasia), loss of music ability, and non-speech sound. Non-verbal sounds fail to recognize animal calls, bells, sirens, raindrops, etc. He is often accompanied by aphasia and loss of music ability.

3, the word deaf means sensory aphasia, can not understand the listening, often accompanied by loss of music and aphasia.

4. Named aphasia can not say the name of the object, or can not remember, the lesions may be in the medial temporal gyrus of the main hemisphere and the posterior part of the inferior temporal gyrus.

5. Lost music can include obstacles to the perception and use of music. Recent studies have shown that the site for identifying music is in the temporal gyrus, not the temporal pole. The ability to feel notes and tunes is in the right temporal, and the ability to name music scores and the meaning of music is in the left temporal.

6. Hearing loss or hearing loss. Temporal lobe damage can occur when hearing is preserved. The sound can become larger or smaller than normal. The tone and timbre can also change. The sound or words can become strange, strange or unpleasant . There may also be repetitions of the strange characteristics of words (that is, hard of hearing). Misunderstandings can persist and can affect the feeling of music. There are simple hallucinations (murmurs, wind sounds, running sounds, water sounds, motor sounds, flutes, snoring sounds, etc.), which can be caused by lesions on any side of the temporal lobe; , Chorus, talking, etc.) are mostly caused by lesions in the main hemisphere. Hearing can be persistent or paroxysmal. Patients can recognize wrong hearing or auditory hallucinations as abnormal hearing, can also be sure, and have an emotional response to it. Hearing may decrease before and during auditory auditory events. Whether auditory hallucinations occur as damage to the lateral gyrus is unclear, but can only be said to be related to lateral lesions of the temporal lobe.

7. Temporal dysfunction. Temporal lobe lesions on either side can produce time-memory related mental disorders. You can feel that time is stagnant, or it passes quickly, or the time cannot be accurately estimated, which is common in temporal lobe seizures. Such as the state of dreams that occurred during the hook-up episode, past situations in consciousness (also known as experiential hallucinations), or a familiar feeling (unlike acquaintance) with a strange environment, or a strange environment (like acquaintance) ), A "dual experience" state can appear, that is, you feel that you are in two different environments at the same time. It can also be seen in Korsakov's syndrome, which cannot be identified and linked to things in different tenses.

8. Hookback attacks are a typical manifestation of temporal lobe dysfunction, which usually starts with the precursors of hallucinations and smells (often unpleasant odors such as stinky eggs), often accompanied by nasal inhalation, tongue-taste, appreciation and chewing , Followed by a dream-like state, which can also be accompanied by visual illusions, auditory hallucinations, or emotional disorders (fear-like), and transient lesions of the left-side lesions can also appear, thinking that the thought suddenly stops like "brain empty" ", Or vice versa.

9. As the visual line passes through the temporal lobe, temporal lobe lesions can produce upper 1/4 visual field defects. Vertigo and cortical areas can occur when the cortical area is stimulated.

When stimulated by the anterior medial amygdaloid nucleus, it can cause olfactory and emotional experiences, as well as obvious autonomic nerve reactions: such as increased blood pressure, faster pulses, faster and deeper breathing, and panic and sexual desire. Exception, etc. Damage to the hippocampus in bilateral anterior temporal lobe can cause severe memory impairment. Such as Kosakoff's memory loss, apparent recent forgetting. Extensive damage to the anterior part of the temporal lobe can lead to changes in mood and behavior, such as indifference, loss of normal emotional response, increased libido, and increased appetite. It is called Kluver-Bucy syndrome, which is caused by damage to the limbic system such as the hook gyrus and hippocampus.

Parietal cortex

The anterior border of the parietal lobe is the central sulcus, and the posterior border is the border between the parietal sulcus and anterior occipital notch and the occipital lobe. Clinically, the damage of the parietal-temporal-occipital structure is closely related, so it is difficult to classify it into a certain leaf. Parietal lobes are divided into central posterior gyrus, superior parietal gyrus, and superior parietal gyrus.

Clinical manifestations of parietal lobe damage

1. Damage to the central posterior gyrus and parietal gyrus mainly results in cortical sensory disturbances (see "Sensory Disorders"), and special paresthesia lesions may occur on the right parietal lobe. Lesions on either side of the parietal lobe can appear on the opposite side of the lesion with hemiplegia and decreased muscle tone, and withdrawal and withdrawal responses of the limbs can also be seen, as opposed to frontal lobe damage with a strong grip reflex. Juvenile patients with limb dystrophy may develop unilateral small hand muscle atrophy and underhand development on the contralateral side of the lesion, with autonomic symptoms.

2. The top and bottom gyrus damage causes apraxia, miscalculation, reading, writing, body image disorder and visual spatial orientation disorder.

3. Body image obstacle Body image is the reflection of the positional relationship between your body and various parts of the body in the consciousness field. It is derived from the continuous integration and development of vision, touch, body movement, balance, and spatial orientation through the parietal lobe. . Body image disorder is auto-spatial confession, which is common in parietal lobe lesions, and can show both positive and negative. The phantom limb phenomenon after amputation and the third phantom limb in left hemiplegia are positive bodies. Negative body image disorder is that the patient cannot perceive or think that he is ill at least half of his own body, so he feels comfortable, indifferent, indifferent, and unresponsive to himself. Often combined with other abnormalities, such as cognitive impairment of various sensations: sensory neglect, sensory fading, visual neglect, heterolateral sensation, unilateral apraxia. It can also be combined with hemianopia, head and eyeballs deviating to the lesion side, and strong gripping groping reactions in non-paralyzed limbs.

4. Unilateral spatial recognition cannot include judgment of body image and environment. That is, the relationship between itself and the location of objects in the environment in space cannot be correctly identified (obstruction obstacles in the recognition of external space or environmental orientation are called comprehensive obstacles in amorpho-synthesis space). This disorder is limited to the spatial orientation of the opposite side of the lesion, and is only seen at the right temporal-parietal-occipital junction. The patient felt that the positional relationship between the objects in the left half of the field of vision could not be identified. Although the eyeball looked at the objects in the field of vision, they could not take it in the correct direction, and even everything did not exist. Patients do not intentionally compensate with eye movements, so they are not blind, and have nothing to do with eye gaze disorders. One side of spatial recognition must not be limited to vision, but may involve hearing or other sensations. It is the basis of application-cognition dysfunction.

5. Bilateral spatial recognition cannot be common in the left parietal posterior lesions. Patients cannot distinguish left and right, cannot identify and name their own and others' individual fingers, often accompanied by miscalculation and miswriting (Gersterman syndrome). . This miscalculation and miswriting is based on spatial recognition, and patients cannot confirm the correct order of words or words, so they cannot calculate and write correctly.

6. Apraxia or use cannot be achieved without motor paralysis, loss of sensation, and ataxia, and the patient cannot complete the purposeful technical actions that can be completed before. Normal and purposeful skills and movements need to recognize the process of one idea and one application. The left top parietal gyrus and marginal gyrus are the ideation center of the action. The impulses from this point are connected with the pre-motor cortex and the motor cortex through the arch fibers, resulting in Various skill movements of the side limbs. The connection between the left premotor area and the right premotor area and the motor area cortex is through the corpus callosum. Each skill movement can be divided into several stages, so apraxia can be divided into sports, mind exercise and ideation. When the left parietal lobe is damaged, bilateral delusional apraxia occurs; when the parietal locus of the central lobe and the pre-motor cortex are damaged, the common mental motility is clinically lost due to the loss of connection between mental memory and motor memory. Apraxia; motor apraxia in the prefrontal lobe or motor cortical lesions. Apraxia can involve a variety of actions such as washing the face, brushing teeth, combing hair, dressing, taking off socks, rowing firewood, pouring tea, opening the door with a key, greeting others, etc. Clinically encountered tongue muscle apraxia, the patient only Can open mouth but not tongue. Structural apraxia is not based on spatial knowledge. Patients cannot draw or assemble simple graphics, and they can often be accompanied by half-sided spatial neglect. The graphics only draw the right half, and damage to the parietal lobe on either side is acceptable. Structural apraxia occurs, but it is obvious when the right parietal lobe is damaged. The apraxia of wearing clothes is also based on the obstacles of visual space recognition. The parts of the clothes are unrecognizable, and they cannot be dressed. They are often neglected on one side, and most of them are lesions on the right parietal lobe.

7. Pain signals are not recognized and do not recognize pain or fearful stimuli. They can perceive painful nociceptive stimuli, but do not cause corresponding emotional reactions and defense or protective reflexes. For example, when the burning cigarette butt of a finger burns, the cigarette butt is not discarded. The lesions are on the marginal gyrus and involve part of the angular gyrus and parietal gyrus.

The center of optokinetic nystagmus is in the marginal gyrus and angular gyrus. When it is damaged, optokinetic nystagmus cannot move to the opposite side of the lesion.

Cerebral cortex occipital lobe

Clinical manifestations of occipital lobe damage: mainly cortical blindness, blindness, illusions and visual hallucinations, and visual inconsistency (object inconsistency, comprehensive inconsistency, facial inconsistency, geographic memory loss, and color vision inconsistency). Destructive lesions in the unilateral visual area produce the corresponding visual field defect on the contralateral side, with directional hemianopia or quadrant blindness, full-blind or horizontal upper or lower hemianopia on both sides, and cortical hemianopia does not involve the central macular area (macular avoidance). The photoreaction does not disappear. Lesions of the left visual cortex and posterior corpus callosum may appear simple aphasia.

1. Optical illusion, also known as visual object deformation, is the lesion of the striated peripheral area (area 18, 19) and the angular gyrus (received by visual impulses into perception). The size, shape, color, orientation or distance of the object seen Distortion or distortion. Such as getting bigger (megalophobia), getting smaller (microopia), getting closer, getting farther, the color disappears or the color is wrong, there is more vision, monocular diplopia or triple vision, the illusion of movement or staticness of the object, etc .; Complex optical illusions include small and far sighted objects, too large or too close, continuous or repeated appearance of vision, and a sense of distance from vision. In addition to visual illusions found in lesions of the occipital lobe, lesions at the apical, occipital, and temporal junctions can also occur. It can be seen in drug poisoning (lysergic acid, prickly toxin, prickly pear, atropine, etc.), fever delirium, migraine, neurosis, psychosis, etc.

2. Illusions are simple, such as flashes, white spots, colors, etc., or various geometric figures (round, square, or polygonal), static or moving (vibration, beating); complex illusions, such as seeing The shape and size of objects, people or crowds, animals, and people or animals can also be changed, including delusional illusions about the surrounding scenes, such as distortion, familiarity, and dreams. Phantom vision can occur in the occipital lobe, parietal lobe, and posterior temporal lobe (such as epilepsy). Occipital lobe lesions are mostly simple hallucinations and appear in the visual field on the opposite side of the lesion, while those caused by lesions in the posterior temporal lobe are more complex and appear in the entire visual field.

3, visual misidentification of the object, color, picture can not recognize its name and role, called visual misidentification, but once you touch or hear the sound, or smell the taste can speak. Mostly caused by lesions in the bilateral striated peripheral area or the gyrus.

4. Visual comprehensive misunderstanding can recognize people and objects in scenes or pictures, but cannot understand the meaning of the panorama or the whole picture, which can be seen in bilateral occipital lobe lesions.

5. Face-failure When you see the face of an acquaintance or even your own face in the mirror, you need to identify it by other people's pronunciation, special signs of the face such as moles, hair color, beard, etc. It can be accompanied by other failures, such as Color failure, visual comprehensive failure. Some attributable facial confession to one of visual comprehensive confession. This sign can be seen in bilateral occipital lobe lesions.

6. Visual orientation and spatial orientation of geographic memory disorders require vision, touch, and kinesthetic. Visual disorientation manifests itself as the patient cannot point out the city on which he lives. If you can't tell the way from his home to the factory, it is a geographic memory disorder. The lesions are more common in the posterior part of the right occipital lobe than in the parietal lobe.

7. Balint syndrome includes cortical gaze palsy, eye movement disorders, and visual impairment. However, spontaneous and reflexive eye movements are preserved in bilateral occipital lobe lesions.

8. Bonnet syndrome is ocular hallucination. Patients with total or partial blindness may develop simple or complex types of hallucinations, appearing in the full field of vision of the blind eye or on the side of the blind. The vision can disappear after moving or closing the affected eye, and the lesions are on the bilateral occipital lobe.

Cerebral cortex island leaf

The island leaves are hidden in the lateral fissure, covered by the frontal, apical, and temporal lobe island covers, and have a representative area of visceral autonomic function. There is a representative area of taste, second sensation, and pain in the island leaf area.

Cerebral cortex marginal lobe

Marginal lobes include cingulate gyrus, fornix gorge, hippocampal gyrus, and hippocampal hook. The limbic system is composed of limbic lobe and related subcortical structures. The limbic system has a wide range of regulating effects on visceral activity and autonomic nerves, and it also has a great impact on human emotional behavior. For example, when the heartbeat speeds up, breathing increases, skin blood vessels contract, cold sweats, pupil dilatation, dry mouth and other changes in plant functions, sadness often shed tears, runny nose, and pale. Decreased muscle tone and sluggishness are related to the regulation of the limbic system.