Bio Mechanism of Schizophrenia

*** What is schizophrenia *****
Schizophrenia is one of neurobiological brain disorder apears mainly in adlescence or young adult generation (15 - early 30s) and has the next symptoms.

a.Basic symptoms.
1.Cognitive defects(blocking thought process, attension defect).
*Disturbunce of smooth thinking, association or recall.
*Defect of cash memory (called "Working Memory" in brain science).
*Disability to keep attension and concentration.

2.Negative symptoms.
* Behavioral disturbance concert with environment or people.
* Apathy (lack of volotion, lack of vividness)
* Blunted emotion (lack of speach and expression)

b.Secondary symptom.
3.Positive symptom.
*Delusional mood (horror mood)
*Hallucinations (mainly auditory hallucination; hearing angry voces)
*Incoherent speach
*others

***The neuro system of schizophrenia. *****
Scientists beleave that dysfunction of parts in brain called frontal cortex(cognition and motor action field) and limbic system(emotion and memory field) produces symptoms of schizophrenia.

A: Dysfunction of frontal cortex.
Frontal cortex(area in frontal side of brain) is divided two areas, 1)prefrontal cortex (cognitive association field) and 2) motor association field.

Scientists beleave that cognitive defect or thought disorder is based on dysfunction of prefrontal cortex. Prefrontal cortex has a area called WORKING MEMORY which accumurates second order memory.
(for example; When you memorize a telephone number to call someone, your WORKING MEMORY can be active enough.)
Some scientists have confirmed that working memory dosen't work correctly in brain of schizophrenic patients. And neurons with dopamin D1 receptors which coordinate activities of frontal cortex are not active enough in brains of schizophrenic patients.

And scientists also know that neurons with dopamin D2 receptor in the brain part called frontal cingulate gyru are not active enough.
Scientist assume that in the part, D2 type dopamin neurons, inhibiting muting neuron connected with pyramidal neurons which transmit perceptive messages, activate frontal cingulate gyru. And activation of frontal cingulate gyru makes prefrontal cortex active and this activitation produces volitional (or willing) action in brain. So it suggests that low level activity of frontal cingulate gyru derived from lack of dopamine function produces various frontal cortex dysfunction, that is cognitive and motor( or behavior) disorders such like apathy, blunted expression and other negative symptoms.

A part in prefrontal cortex called orbital part is related with active level of consciousness. Some brain scientists call the part "considering brain part" or "doubting brain part". So if activity of the part is down, we can't consider or doubt anything enough. Or we can be thoughtful with the function of the part.
We can assume that the dysfunctioning of the orbital part may lead to delusion or erroneous beliefs coupling with overdriving of emosion and memory area in a brain.
Frontal cortex have a motion programing part. Programings for volitional or willing speach, expression and/or motion are produced in the area. So inactivity of frontalcortex leads to disability to concert with environment, diminishing ability of ordering or organizing of speach or other behavior.

B: Overactivity of emotion circuit in brain.
A brain area called thalamus and limbic system including hippocampus and amygdala is emotion circuit or subsystem. In detail, hippocampus is related with memory especialy long-term memory, recall or experience, and amygdala is related with emotion or mood.

Overactivity in Hippocampus and Amygdala produces overflow of association or recall and horror or delusional mood. It is like trafic jam of brain circuit. That is confusional or "hot and bothered" condition of brain.

Hippocampus in limbic system recalls long-term memory from temporal lobe(side part of brain) and sends the message to frontal cortex(front side of brain). Overactivity of hippocampus leads to "flood of association" and under the condition, under the condition, we can't have coherent thought.
Amygdala in limbic system is a part of emotion and value judgement. Sientists know overload of the part produces morbid anxiety and fear or horror mood.

It is possible that the interference between auditory sense area in temporal lobe and limbic system which is placed inner side of temporal lobe, under overflow association or overheat condition causes auditory hallucination. In fact, Scientists have comfirmed that limbic system and thalamus, which is emotion circuit, was overactive, meanwhile cortex especially frontal cortex was depressive in brains of schizophrenic persons who have auditory hallucination.

Limbic system has neurons which have dopamine receptors. Scientists assume that projecting of dopamine into the neurons makes the limbic system active. Scientists have found some evidences of that D2 type receptors in limbic system of schizophrenic persons increased, compared with normal persons. It suggests that limbic system of schizophrenic persons has over sensibility for dopamine.

Emotion circuit consists of limbic system, thalamus and some other parts. Thalamus is gate of senses from environment and it determines volume of the senses or perceptive inputs. It means that if thalamus is overactive we can get over-sensibility.

Thalamus is usually muted by inhibital neuron in a brain part called basal-gangalia. And basalgangalia has D2 type dopamine neurons and it inhibits activity of thalamus. So overactivity of dopamine in the area causes over acutivity of thalamus, turning off mute system of basal gangalia to thalamus. It means that overactivity of dopamine neurons in the area leads to over-sensibility.

* Low activity of frontal cortex and over activity of limbic system.
Neurons of frontal cortex under busy condition recieving stresses send dopamine launcher, which is in stem part of brain, a message to release dopmine into neurons of frontal cortex and limbic system.

If procedure of frontal cortex can run smoothly and finish it's own job, it means that if frontal cortex can be released from busy condition performing it's own tasks smoothly, neurons of frontal cortex sends dopamine launcher a message to turn down dopamin release.

But if the neurons of frontal cortex have dysfunction or dopamine projection into frontal cortex is not enough, procedure of frontal cortex doesn't progress smoothly, it means that frontal cortex is in busy state continuously and so dopamine launcher keeps on releasing dopamine.

So we can assume that brain of schizophrenic patient is low activity in frontal cortex which includes cognitive or thinking part, and limbic system�@which is emotion and memory part of brain is in over active under strong or continuous stress conditions or environment. The condition of brain can produces confusion, anxiety and/or other abnormal states.

Scientists have some evidences of defect glutamate neuron and dopamine neuron in brains of schizophrenic patients. The neurons control and coordinate activities of neurons assembly in frontal cortex and limbic system.

Some scientists suggest that low activities of glutamate neurons and low activities dopamine neurons mainly in frontal cortex produce basic and cronic symptom of schizophrenia , that is cognitive impairments(thinking and concentration defect) and negative symptoms(lack of volotion and expression), and the disorders of frontal cortex lead to over activities of dopamine neurons projecting into limbic system, it means over activity of limbic system, it may generate positive symptoms like auditory hallucination, delusional mood and/or incoherent thoughts.

Frontal cortex is cognitive behavior module of brain. And limbic system is moods, memories and sensibility module, as described above. Freezed cognitive behavior module and bursted mood-sensibility module derived from dopmine imbalance is one of assumptional schema of schizophrenic brain.
Frontal cortex is central procedure unit of brain which integrate idea and other senses or perception from limbic system and other area in brain (we call this process "thinking or cognition"). So state of low activity of frontal cortex and over activity of limbic system causes traffinc jam or accident of neuro network in brain, that is confusing or disorganized state of mind function.