Lecture 31
CEREBRAL HEMISPHERES
The hemispheres form most of the outer surface of the brain. The hemispheres have four lobes: frontal, parietal, temporal, occipital. The cerebral cortex is also subdivided into the "new" cortex - neocortex , and "old" cortex - archicortex and palaeocortex . The neocortex has six distinct layers of cells, and the "old" cortex has usually three layers.
Cortical areas are further divided into primary areas with a direct input from the sensory pathways, secondary areas supplied from the primary areas, and association areas obtaining input both from the primary ans secondary areas. All areas of the cortex are further divided into cellular columns passing through all six layers of the cortex and containing neurons performing one common function.
HEMISPHERIC CONTROL OF MOVEMENT
There are two areas within the hemispheres involved in the control of motility, the cerebral cortex and the basal ganglia.
Motor Area
The primary motor cortex, M1, is area 4 of Brodmann . It is located in the anterior wall of the central sulcus, in adjacent parts of the precentral gyrus and in the paracentral lobule on the medial surface of the hemisphere. The map of the motor area, the motor homunculus , resembles the somatosensory homunculus.
The somatosensory and motor areas lay side by side and cooperate closely. They form the sensorimotor cortex . The motor area has somatotopic organization, with the feet near the midline and face near the lateral fissure. The projection of various parts of the body is proportional and depends on the involvement of the area in the control of fine and specialized movements.
Input to the motor cortex comes from other areas of the cerebral cortex; from the somatic sensory fibers; from the ventromedial, ventrolateral and anterior ventral nuclei of the thalamus; from fibers from the intralaminar nuclei of thalamus.
Pyramidal cells , 10 - 100 microns in diameter, are numerous in the motor area. They have a single apical dendrite that sends branches toward the outer

surface of the cerebral cortex. The basal dendrites run tangentially to the surface of the cortex. They are classified into small, medium, large and giant neurons. The last ones are called Betz pyramids . The pyramidal neurons are found mainly in cortical layers III and V., and the Betz pyramids prevail in layer V. of the motor cortex.
The cortical cell columns operate as an integrative information processing system. They also function as an amplifying system stimulating a number of corticospinal fibers.
Some pyramidal cells produce a dynamic response.
They are excessively activated for a short time at the beginning of a muscle contraction. They are responsible for the initial development of the contraction force. Other pyramidal neurons produce a static response . They fire at a much slower rate and maintain the force of contraction.
CORTICOSPINAL PATHWAYS
The pyramidal cells are the origin of the corticospinal pathways. About 30% of the fibers originate in the primary motor cortex in the Betz pyramids, 30% in the premotor cortex and 40% in the surrounding areas. The corticospinal pathways control the voluntary movements. The pathways have two components: dorsolateral and ventromedial. The difference between them is that the dorsolateral pathway is crossed at the level of lower medulla and runs in the lateral columns whereas the ventromedial pathway runs in the ventral columns and is crossed at various levels of the spinal cord.
Some fibers of the dorsolateral pathway reach the spinal cord directly . They cross to the other side of the CNS and terminate on small interneurons of the spinal gray matter in the areas controlling rapid voluntary movements of the wrists, hands, fingers and toes. Some fibers end directly on the motoneurons. The other fibers pass through the nucleus ruber forming the dorsolateral corticorubrospinal tract . The corticorubrospinal pathway synapses on the interneurons that activate the motoneurons innervating the distal muscles of the arms and legs.
The ventromedial pathway has a direct branch as well as a branch going through the brainstem ( ventromedial cortico-brainstem-spinal tract) . The direct ventromedial tracts are more diffuse. They innervate interneurons in several spinal segments, and the projection is bilateral. The ventromedial pathways innervate proximal muscles of the arms, shoulders, hips and legs. They are involved in the control of posture and whole-body movements such as walking and climbing. In the brainstem, the tectum, the vestibular nuclei, the reticular formation and the motor nuclei of the cranial nerves, the ventromedial cortico-brainstem-spinal tract controls the motility.
The motor cortex also sends collaterals back to the Betz pyramids, fibers to

the putamen and caudate nucleus, fibers to the reticular substance and vestibular nuclei, fibers to the pontine nuclei and to the inferior olivary nucleus.
INITIATION OF MOVEMENTS
Several theories have been proposed regarding the brain sites where movements are planned and initiated. The posterior parietal cortex , which is an association area, has been considered. It receives input from the visual, auditory and sensorimotor systems. This information is integrated and sent to the motor cortex. The central pattern generators are networks of interconnected neurons that collectively control a set of muscles needed to produce a movement or sequence of movements. They have been studied in relation to cyclic and rhythmic behavior such as swimming, walking and scratching.
SUPPLEMENTARY MOTOR AREA (M2)
The second motor area is located in front of the motor cortex near the midline. It is mostly hidden inside the longitudinal fissure on the medial surface of the hemisphere. It is somatotopically organized. The leg area is posterior and the face is most anterior. Movements elicited by the stimulation of this area are usually bilateral. It is probably involved in the planning of voluntary movements.
Sequencing of movements is also planned here. The sensory input is mostly somatosensory.
Before the initiation of movement, an electrical " vertex readiness potentia l" may be detected in this area. It is an EEG wave present right over the
M2 areas of both hemispheres. It projects to M1, and M1 projects back to M2. The stimulation here also elicits synergistic movements. Supplementary motor lesions cause the inability to perform movements in the proper sequence.
Besides the supplementary motor areas, there is also Broca's area for motor expression of speech, the frontal eye field in area 8 above Broca's area controlling voluntary eye movements, the head rotation area in the motor association cortex and the area for hand skills anterior to the primary motor cortex in the premotor area.
PREMOTOR CORTEX (area 6, PM)
The third motor area, the premotor cortex, is functionally related to the supplementary motor area (M2), which is localized more centrally. It is somatotopically organized. The face is localized most laterally and the arm, trunk and leg areas are represented in a more medial direction. The sensory input is mostly visual. It is also involved in the planning of movements, presumably in connection with visual and auditory input. Its neurons fire in response to sensory input, and also before the movement is initiated.

The PM is bilaterally connected to M1. Giant pyramidal cells are absent.
The representation of the peripheral muscles in this area is bilateral and thus, motor responses persist after the unilateral removal of this area. Also, there is output into the reticular formation, corticoreticulospinal tract . Following the lesion of the
PM, the grasp reflex (normally present after birth, but not later) may be elicited.
APRAXIA is the inability to properly execute a learned skilled movement:
* limb apraxia characterized by the problems with the movements of arms, fingers and hands;
* oral apraxia characterized by the problems with movements of muscles used in speech;
* apraxic agraphia that is a writing deficit.
* constructional apraxia characterized by difficulties in drawing or constructing objects. Lesions of the motor cortex cause different types of apraxias, adjacent parts of the parietal lobe or even of the corpus callosum. They may result from the stroke or from trauma. Apraxia must be distinguished from aphasia that is an inability to comprehend language.
Most parts of the central nervous system are paired. The corresponding sections of the brain are connected by cerebral commissures. The corpus callosum is the largest of them, and connects most of the cerebral cortex of both sides. One side of the CNS is usually not a simple replication of the other side. The two sides differ markedly in structure and function. In the previous chapter, we have shown that the language functions are almost completely limited to the left hemisphere.
This difference is described by the term "lateralization of function" .
ANATOMICAL DIFFERENCES BETWEEN THE HEMISPHERES
One example of this interhemispheric difference is the presence of a larger temporal plane in the left temporal lobe in 65% of people. The temporal planes of both sides are about equal in 25%. The left one is smaller in 11%. This difference is present in infants even before language develops. Also, the Sylvian fissure is longer on the left side.
FUNCTIONAL DIFFERENCES BETWEEN THE HEMISPHERES
The asymmetry of the hemispheres is associated with handedness and with the localization of language in the left hemisphere. Unilateral brain damage to the left hemisphere is often expressed as aphasia , a brain-produced deficit of speech

functions. Another sign of damage to the left hemisphere is apraxia , difficulty in performing skilled movements. The deficit is usually bilateral and does not appear when the patients are not thinking about what they are doing. These symptoms appear more often if the left hemisphere is damaged in right-handed people
( dextrals , in about 60% cases), but less in left-handed people ( sinistrals , in 30% cases). The brains of males are more lateralized than the brains of females.
These studies lead to the concept of hemispheric dominance. One hemisphere controls the activities of the other one.
SPLIT-BRAIN STUDIES
Myers and Sperry (1953) demonstrated that in cats, when the corpus callosum and optic chiasma were cut, each hemisphere functions independently of the other one. Sperry (1968) described the consequences of the transection of the corpus callosum ( commissurotomy ) in patients with intractable epilepsy (the splitbrain operation). This situation is similar, but not identical, to the spontaneous development of the brain without a corpus callosum. These people behave almost normally although their motor coordination is awkward. They suffer little impairment of intellectual abilities, language, motivation or emotion.
But, their two hemispheres process information and answer questions independently. One hemisphere then does not know what the other is doing. Due to the crossing of visual or tactile pathways, it is possible to direct visual or tactile input to one or the other hemisphere. Of course, the input into one half of both retinae have to be blocked. This is best done by Z contact lenses (Z after Zaidel who in 1975 proposed a contact lens, half of which is opaque).
Input into the right hemisphere has no conscious content. The consciousness does not know what the right hemisphere is doing, and therefore, the consciousness is located in the left hemisphere.
The left (major) hemisphere has access to language, all memories past, knowledge of self. Within the left hemisphere, the localization of consciousness may be related to the association cortex , areas of the cortex not committed to the primary analysis of sensory input. Here, the memories may be stored, and input from various senses integrated. That helps us to form an accurate sense of self and environment. The frontal cortex is the largest association area. It is involved in judgment and planning. Language is located in the vicinity of the temporal lobe.
The verbal memory span in the left hemisphere is seven words. The average memory span for words in the right hemisphere is only three words. The right
(minor) hemisphere has a crude knowledge of language; it can recognize some nouns, but not verbs, is not connected with the self-awareness, cannot express itself in language and is an unconscious part of the brain. The minor hemisphere is always unconscious, but has spatial abilities, pictorial recognition and construction

of complex visual pattern, geometrical and perspective understanding. It is also musical. The right hemisphere is also superior to the left hemisphere in the recognition of faces. The right hemisphere is better in recognizing the pattern by touch (blind people read the Braille script better with their left hands). The right hemisphere is involved in the emotional content of speech, humor and irony in speech. In general, the right hemisphere is more involved in emotional expression.
Understanding of music depends on specific brain circuitry, it can be dissociated from other sounds, speech etc. Right hemisphere is more activated by music. Frontal and temporal lobes.
HANDEDNESS AND LATERALITY
About 10% of people are left-handed or ambidextrous. Handedness is probably not inherited by simple Mendelian laws. Lefthanders are more likely than right-handers to be prone to dyslexia , migraine headaches and disorders of the immune system.
Explanation of laterality
There are at least two theories:

It is advantageous for the brain to locate areas performing the same function in one hemisphere. Sperry (1974) claims that there are two modes of thinking, analytical and synthetic. Analytical mechanisms are in the left hemisphere, synthetic mechanisms are in the right hemisphere.

Sensorimotor theory of cerebral lateralization (Kimura, 1979) proposes that the left hemisphere specializes in the control of fine movements, including speech, whereas the right hemisphere controls extensive body movements.
Geschwind and Galaburda (1985) propose that a high level of testosterone delays the maturation of the left hemisphere and therefore, left-handedness.
PHYSIOLOGY OF LANGUAGE
Communication through various visual, auditory and olfactory stimuli is common to all the animal species, including humans, that live in groups or at least interact with other members of the same species.
Language mechanisms
The human language results from a specific biological capacity of our species. Each human child exposed even in limited ways to the triggering experience of linguistic data develops a full capacity to speak. Efforts to teach human language to other species failed.
A prominent feature of the language-related functions in the humans is their lateralization in the cerebral cortex.

The model explaining the control of speech by the cerebral cortex centers on the existence of the motor center for speech that controls the speech production in the inferior portion of the left prefrontal cortex ( Broca's center ), and on the existence of a center for language comprehension in the left temporal lobe
( Wernicke area ). Both centers were discovered through the analysis of patients with auditory agnosias .
The study of the biological mechanisms of language in humans began with the observations of patients with brain damage. Damage to the auditory cortex does not mean deafness. Rather, the patients are unable to understand the meaning of sounds. Auditory agnosia is a pathological state characterized by the impaired ability to recognize nonverbal sounds without hearing loss. This is categorized as either amusia , or agnosia for nonverbal sounds. It usually results from damage to the right hemisphere.
Wernicke's Aphasia, Receptive Aphasia
Aphasia is speech disorder. The Wernicke's aphasia is also called fluent aphasia because the person can still speak smoothly. It is " word deafness " in that the patients do not understand the meaning of words. This defect is usually caused by damage to the Wernicke area. Wernicke's area is in the posterior portion of the superior transversal gyrus. It stores memories of sounds that constitute words.

The patients can produce language, but they have problems comprehending the verbal and written communications of others.

Also, meaningless speech is produced. Speech is fluent, not difficult, grammatical, but does not make too much sense. There are paraphasic errors in which words are replaced with similar words. The patient is often unaware of the defect.
Broca's Aphasia, Expressive Aphasia
It is also called nonfluent aphasia because the patient cannot speak fluently.
Broca's area is located anterior to the face region of the motor cortex. It presumably contains memories of muscle movements needed to articulate words.
Damage to the Broca's area produces only a temporary defect in speech. Extensive damage to the left motor cortex, some areas posterior to the motor cortex, thalamus or basal ganglia produce the full syndrome. Broca's aphasia is characterized by:

Better language comprehension than language production. The patients can understand much of what is said to them, but still, comprehension in Broca's aphasias is not totally normal. Word order is not always recognized. Thus, the sequencing of words may also be a function of the Broca's area.

Difficulty in language production: slow, laborious, nonfluent speech, the patient cannot find words (anomia ). Some patients cannot speak at all.


Telegraphic speech : the function words (the, some, in, about) are absent. There is agramatism , a difficulty using grammatical constructions, function words, grammatical markers (-ed, have).

Apraxia that is a difficulty with phonetics, inability to make specific oral movements. But, they are able to sing a song.
Wernicke-Geschwind model
Based on these findings, Geschwind in 1965 formulated a theory incorporating the function of:
 the primary visual or auditory cortex

Wernicke's area
 the arcuate fasciculus
 the angular gyrus
 the primary motor cortex

Broca's area where speech is comprehended.
In a response, the Wernicke area generates the thought, activates Broca's area via the arcuate fasciculus. From Broca's area, the program of articulation activates the orofacial muscles through the primary motor cortex, and speech is produced.
During reading aloud, the visual input into the primary visual cortex is transmitted to the angular gyrus that translates the visual form of the word into the auditory code comprehended by the Wernicke area. The Wernicke area then triggers Broca's area through the arcuate fasciculus. Broca's area sends the message to the primary motor cortex and speech sounds are generated.
Objections to the model:

The model is based on clinical cases of traumatic lesions, strokes and tumors that are seldom strictly localized.

The model requires a very precise localization of functions that does not exist in the association areas of the brain;

Broca and Wernicke's aphasias do not exist in pure forms and are usually not localized in the Broca and Wernicke areas.
 lesions of these areas do not have permanent effect on comprehension and articulation;
 some lesions quite remote from the speech-controlling areas, such as the cingulate cortex and the supplementary motor area, may also cause aphasia.
Aphasia may even result from damage to the subcortical structures.
Mapping of the speech-controlling areas by electrical stimulation is necessary to avoid these areas during brain surgery. These areas extend far beyond the Wernicke and Broca fields. These observations showed that the language areas

are probably organized individually in different subjects. There are phonological
(sound-related) areas around the lateral fissure that are associated with grammatical (structure of language) and semantic (pertaining to meaning) areas elsewhere.
PET studies
Positron-emission tomography (PET) scanning measures the amount of blood flow to various brain areas during various language-related activities.
Petersen et al. (1989 - 1990) showed that:
 reading a printed word elicited metabolic activity in the secondary (18) visual area bilaterally;
 hearing a word activates the primary and secondary auditory areas bilaterally;
 repeating them aloud activated the area around the central fissures of both hemispheres and near the lateral fissure of the right hemisphere;
 verb-association added activity in the prefrontal cortex of the left hemisphere in front of Broca's area and in the medial cortex above the front portion of the corpus callosum.
Wernicke's area and the angular gyrus were not activated at all, and the semantic processing occurred in the frontal and medial cortex.
Findings come from the nuclear magnetic resonance studies,
Conduction Aphasia
The conduction aphasia is caused by damage to the arcuate fasciculus connecting the Broca and Wernicke areas. Speech is fluent, but nonsensical, and language comprehension is good. However, they have problems repeating what other people say and carrying on a conversation. It is rare.
Reading and Writing Disorders
These skills, alexia and agraphia , are absent in patients with aphasias. In
Broca's aphasia the writing is agrammatical. Some reading and writing difficulties are not accompanied by aphasia. A lesion of the left angular gyrus supposedly causes pure alexia (inability to read) and pure agraphia (inability to write). They may exist independently. A lesion of the visual cortex may also cause alexia.
Parts of the palaeocortex and the archicortex along with structures located deep in the hemispheres form the limbic system, a phylogenetically old area involved in the control of drives and emotions.

Review of the limbic system
The word "limbic" is derived from the Latin word "limbus" which means
" border ". The limbic system is located around the diencephalon and the corpus callosum on the medial surface of the hemisphere. The limbic system is prominent in amphibians, reptiles and in primitive mammals. The phylogenetically oldest input into the limbic system comes from the olfactory system. The principal executive of the system is the hypothalamus. In humans, it is divided into the cortical and subcortical portion.
Primary olfactory input to the limbic system
From the olfactory nerve, bulb and tract, the nerve fibers go to
* the anterior portion of the parahippocampal gyrus and further to
* the amygdala
Cortical parts of the limbic system
* parahippocampal gyrus;
* hippocampus;
* cingulate cortex;
* entorhinal cortex;
* parts of the orbital cortex;
Subcortical structures
* septal area with nucleus accumbens septi
* amygdala,
* anterior thalamic nuclei
* and a majority of the hypothalamic nuclei.
The main fiber tracts connecting the limbic system:
* fornix,
* mamillothalamic tract
Papez circuit
Individual components of the limbic system are connected into the Papez circuit. From the hippocampal formation, the fibers of the fornix pass to the mamillary body. The mamillothalamic tract projects to the anterior thalamus, then to the cingulate cortex, entorhinal area of the cortex and back again to the hippocampal formation.
EMOTION AND MOTIVATION
There is no clear definition of emotion. Perhaps, it may be defined as
" subjectively felt affect ". Feelings such as fear, apprehension, joy or passion is obvious, but there are hundreds of emotions, some even do not have a name.

Emotional behavior, based on the internal state of emotion, is a means to communicate the motivational state to another individual.
Emotions are associated with the inner state of physiological arousal , expressive changes of the muscle function , and alterations of behavior. Emotions are mostly associated with the activity of the sympathetic division of the autonomic nervous system: changes of heart rate, changes in blood pressure, dilation or constriction of the eye pupils, electrodermal response and sweating.
Cognition and emotion
Other parts of the cerebral cortex are connected to the limbic system.
Thinking and experience located in the cerebral cortex interact with its function.
The experience gives meaning to the events. This is also important in the experience of stress and pain.
AGGRESSION is one of the emotions difficult to define. It is important in the development of many species, including ours.
Types of aggression are:
* predatory;
* competitive;
* defensive = dependent on fear;
* irritable = rage;
* territorial;
* maternal protective;
* sex-related (male-to-male aggression).
Different neural circuits control different types of aggression . Aggression may eventually be turned into freezing or flight . The animals must protect their backs, gather information about the attacker, assess the risk and make a decision whether to hide, attack or escape.
Brain areas controlling aggression are:
- lateral septum
- medial nucleus accumbens septi
- medial hypothalamus
- lateral hypothalamus
- amygdala
- raphe nuclei in medulla and pons.
Aggressive behavior may be elicited by the electrical stimulation of the hypothalamus or the amygdala . The electrical stimulation of the septal region inhibits aggression.
Hormones ( testosterone , adrenal cortical hormones ) may influence

emotional state and aggressivity, more in animals than in people. But, high level of testosterone does not lead to increased aggression. The neurotransmitters involved in aggression are serotonin , epinephrine , and norepinephrine.
Also some brain peptides are involved, such as endorphins .
ANXIETY AND FEAR
Fear is defined as a response to a perceived immediate threat. Anxiety is an emotional state produced by the anticipation of some undesired event. Major categories of anxiety disorders include panic attacks , phobias and generalized anxiety . Anxiety disorders are associated with autonomic symptoms, tachycardia, hypertension, nausea and difficulty breathing.
Fear and anxiety depend on the aversion system in the brain , which begins in the orbitofrontal cortex (on the basal surface of the frontal lobe) and continues through the amygdala into the anterior and ventromedial hypothalamus . The thin zone of the periventricular nucleus adjacent to the third ventricle controls fear.
From here the system continues down to the periaqueductal gray and other midbrain areas.
The most important area in the generation of fear is the amygdala . It probably connects the relevant memories to the appropriate emotional responses.
The orbitofrontal cortex is considered to be the " limbic frontal lobe ", its removal reduces averse reactions to danger (e.g., in monkeys). The response circuit itself is localized in the brain stem and the spinal cord. The amygdala is connected to these areas through the hypothalamus. Smith and DeVito (1984) called this area the
HACER ( hypothalamic area for conditioned emotional responses ). It is a small zone surrounding the descending fibers of a fiber tract originating in hippocampus, the fornix, on its way to the mamillary bodies. This area organizes the cardiovascular and other sympathetic responses to fear. Area just medial to
HACER organizes escape responses and flight.
The neurotransmitter GABA may be involved in the pathogenesis of anxiety. The experimental test for anxiety in the experimental animals is the
"elevated-plus-maze", a four-arm cross-shaped maze. Two arms have sides, two do not, and the maze is elevated 50 cm from the floor. The time spent in the arms with sides is a measure of anxiety.
REWARD AND PUNISHMENT SYSTEM
James Olds (1953) stimulated electrically the hypothalamus and parts of the brain stem in the vicinity of the medial forebrain bundle in rats. Rats were easily trained to activate electrically the neural circuits by pressing a lever and thus connecting the stimulating current. The presumably pleasant positive feelings were elicited in particular in the lateral and ventromedial area of the hypothalamus .

Less potent reward centers are located in the septum , the amygdala , some areas of the thalamus , the basal ganglia and the basal tegmentum of the midbrain. Some of these areas are not related to the medial forebrain bundle. Stimulation of the dopamine - producing neurons of the substantia nigra and the ventral tegmental area , called the mesotelencephalic dopamine system also produces rewarding brain self-stimulation. These fibers terminate in a variety of sites, neocortex, limbic system, amygdala, nucleus accumbens septi and many others.
Norepinephrine-transmitting neurons of the locus coeruleus have the same effect. These neurons innervate the basal ganglia, prefrontal neocortex, limbic cortex, nucleus accumbens septi, amygdala and septum.
According to the Olds and Milner theory the intracranial self-stimulation activates the natural reward circuits of the brain. Specific characteristics of the selfstimulation are:
* brain self-stimulation may elicit specific behaviors such as maternal behavior, eating, drinking, and copulation;
* increased or decreased levels of natural motivation (hunger, water deprivation, and castration) alter the rate of self-stimulation.
Addictive drugs may also activate the reward system. The rewarding effects of opiates are mediated by the mesotelencephalic dopamine system. The rewarding effects of cocaine and amphetamine are also attributed to their effects on the dopaminergic systems. In the case of amphetamine, the ventral tegmental area and the n.accumbens septi are involved.
On the contrary, the periventricular system (located medially of the medial forebrain bundle) can label stimuli as aversive . One part of the periventricular aversive system is the ventromedial hypothalamus . The animal shows signs of displeasure, fear and terror. Long-term stimulation (over 24 hours) may lead to death. Also stimulation of other structures may elicit emotional states: septum, prefrontal cortex, amygdala, cingulate cortex, hippocampus.
RAGE
The generation of rage involves the hypothalamus and other limbic structures . Strong stimulation of the punishment (aversive) centers causes the animal to develop a defensive posture, extend the claws, hiss, spit, growl, develop piloerection, wide-open eyes, dilated pupils.
Normally, the rage phenomenon is controlled by the ventromedial nucleus of the hypothalamus . The hippocampus, amygdala and parts of the cingulate gyrus help suppress rage.
The sham rage has been observed in completely decorticated rats , which respond to the slightest provocation with a severe aggressive response not directed against any particular target.

LOSS-OF-CONTROL SYNDROME
Uncontrollable emotional outbursts are accompanied by abnormal electrical discharges in the temporal lobe and the amygdala . They resemble the epileptic aura. These outbursts represent a real pathological state, and in some cases, only surgery may help.
Removal of the whole temporal lobe causes Kluever-Bucy syndrome , characterized by psychic blindness (inability to recognize objects), abnormal oral tendencies (the objects examined by mouth), hypermetamorphosis (repeated examination of objects), tameness (lack of fear or avoidance of objects), and changes in sexuality.
PSYCHIATRIC DISORDERS INVOLVING THE LIMBIC SYSTEM
The major psychiatric disorders are disabling diseases with a genetic predisposition and no known cure.
He affective disorders include:
 major depression, including suicide
 bipolar disorder (manio-depressive disorder)
Both involve norepinephrinergic changes in the brain including limbic system.
Schizophrenia is a collective name for a group of psychotic disorders that vary greatly in symptoms among individuals.