Study On Mechanisms Of Prefrontal Executive Control In Macaca Mulatas And Rats

Adjusting behavioural responses to internal needs and environmental changes is a fundamental property of adaptive and flexible intentional behaviours. This ability to control behavior and impulse belongs to an important higher cognitive function of prefrontal cortex that develops gradually from children to adults. It has been reported that damage of prefrontal cortex produce poor cognitive function, poor judgment, planning and decision-making, reduce ability to learn and complete complex tasks and time order. Patients with damaged prefrontal cortex can't make planning for future (including social activity), can't manage common everyday life situations like buying food. Recently the theory of executive control of PFC was emphasized, and also different behavior was adjusted by different executive function: the anterior cingulated cortex is thought to play a role in monitoring competition between two conflicting processes during task performance; the dorsolateral prefrontal cortex participates in active suppression of inappropriate movement and behavior. There exists deficit of executive control in schizophrenia, attention deficit hyperactivity disorder, obsessive-compulsive disorder; Tourette syndrome, conduct disorder, anti-social personality disorder and so on. In a word, the PFC is very important when behavior must be guided by internal states or intentions.Many researches supports that the dysfunction of PFC is crucial in schizophrenia and maybe it is related to GABAergic system: the reduced amount of GABA and GABAergic interneurons in PFC. Theelectrophysiological results shows 70% neurons have increased activity but nosignificant increase in basic activity, half of silent neurons become activated in movement period after microinjection of BMI (bicuculline methiodite) into PFC. These suggest that the inhibition of GABA is a key point in executive control of behavior. The non-competitive antagonist of NMDA/glutamate receptors has recently been shown to induce schizophrenia-like symptoms in healthy volunteers and in schizophrenic patients. This is in line with experimental research in rodents where central or peripheral administration of NMDA-antagonists has been shown to produce effects that resemble some symptoms of schizophrenia. Bilateral injections of competitive and non-competitive antagonists in the medial PFC (mPFC) induced hyperactivity. All these suggest that Glutamate and NMDA-R also play a role in executive function. Recently neuroimaging technique was used extensively and found that there is close relationship between brain energy metabolism and psychological process. PET research shows there are increase of regional cerebral blood flow in prefrontal, occipital and parietal cortices during go/ no go discrimination tasks in the monkeys. But it is not clear about the neurochemistry mechanism of executive control. Our research were divided into four parts: (1)Behavioral and electrophysiological study on executive control of PFC in the Macaca Mulatas; (2) The PET study on executive control of PFC in the Macaca Mulatas; (3) The effects of amino acid neurotransmitters and their receptors on executive control of PFC in the Macaca Mulatas and rats; (4)Ultrastructural study on executive control of PFC in rats. Our main results and conclusions are as follows:l.The behavioral and electrophysiological characters of executive control in Macaca MulatasThe response time are 419 18ms,376 26ms and 540 21ms in three monkeys when they perform go/no go tasks. A total of 41 tetrodes penetrations were made in the PFC of two monkeys. A total of 92 task-relatedneurons were sampled and categorized as 5 types: visual signal related neurons, decision-making related neurons, go-movement related neurons, reward related neurons and multi-events related neurons. These results indicate that the neurons are complex and diverse in PFC. Maybe this is the base of executive control of PFC.The discharge rate of a neuron to a go si...