Schizophrenia limbic system

On this evidence one can confidently equate EPS with neuroleptic DA receptor (D2) antagonism in the striatum and possibly a reduction in the positive symptoms of schizophrenia through similar action in the limbic system (nucleus accumbens). 

The net effect is to push the brain in a very REM dream-like direction. PET studies of schizophrenic patients brains show deficient frontal cortical activation and limbic overactivation. The working hypothesis of schizophrenia investigators is that psychosis results when the overactive mesolimbic pathway is released from deficient cortical control. This is formally identical to our hypothesis of dream psychosis the dorsolateral prefrontal cortex is deactivated and the limbic system is hyperactivated. 

Schizophrenia appears to be caused by an overactivity of dopamine pathways in certain parts of the brain such as the limbic system.2,23 This idea is based primarily on the fact that most antipsychotics block dopamine receptors, thereby reducing dopaminergic hyperactivity in mesolimbic pathways and other limbic structures (see the next section of this chapter). The increased dopamine influence underlying psychosis could be caused by excessive dopamine synthesis and release by the presynaptic neuron, decreased dopamine breakdown at the synapse, increased postsy-naptic dopamine receptor sensitivity, or a combination of these and other factors. 

Bogerts B, Meertz E, Schonfeldt-Bausch R. 1985. Basal ganglia and limbic system pathology in schizophrenia. A morphometric study of brain volume and shrinkage. Arch Gen Psychiatry 42 784-791. 

Tamminga CA, Thaker GK, Buchanan R, Kirkpatrick B, Alphs LD, et al. 1992. Limbic system abnormalities identified in schizophrenia using positron emission tomography with fluorodeoxyglucose and neocortical alterations with deficit syndrome. Arch Gen Psychiatry 49 522-530. 

Antipsychotic medications, also known as neuroleptics or major tranquilizers, are used to treat schizophrenia and other disorders, such as mania, agitated depression, toxic psychoses, emotionally unstable personalities, and psychoses associated with old age. These medications affect primarily the reticular activating system, the limbic system, and the hypothalamus. 

The nigrostriatal pathway and the limbic system also seem to be involved in behavioural effects, and there is evidence that schizophrenia in humans is associated with dopaminergic hyperactivity, and dopamine receptor antagonists are used as antipsychotic agents see dopamine... 

Bachevaher J (1991) An animal model for childhood autism memory loss and sodoemotional disturbances following neonatal damage to the limbic system in monkeys. In Advances in neuropsychiatry and psychopharmacology, volume 1 Schizophrenia research (Tamminga CA, Schulz SC, eds), pp. 129-140. New York Raven Press. 

Around the central core of the brain are a number of structures that collectively make up the deep brain nuclei, which are organized into the limbic system, and the basal nuclei. These systems are closely connected to the thalamus, the hypothalamus and the sensory and motor areas of the cerebral cortex. The limbic system is concerned with emotions, behaviour and memory and the basal nuclei are concerned with control of movement, although there is overlap between the two. Malfunction of these areas is implicated in disorders such as Parkinson s disease and schizophrenia. 

PET scanning makes it possible to measure the availability of dopamine receptors in the patients with schizophrenia compared with nonschizophrenics. The striatum, limbic system, and the cortex are the principal locations of dopamine neurons. Studies of young, drug-naive schizophrenic patients failed to demonstrate abnormalities in the densities... 

C. A. Tamminga. Limbic system abnormalities identified in schizophrenia using positron emission tomography... 

Becker T, Becker G, Seufert J, Hofmann E, Lange KW, Naumann M (1997) Parkinson s disease and depression evidence for an alteration of the basal limbic system detected by tianscranial sonography. J Neurol Neurosurg Psych 63 590-596 Becker EB, Bonni A (2005) Beyond pioUferation-cell cycle control of neuronal survival and differentiation in the developing mammalian brain. Semin Cell Dev Biol 16 439-448 Benes FM (2000) Emerging principles of altered neural circuitry in schizophrenia. Brain Res Brain Res Rev 31 251-269... 

Tamminga CA, Thaker GK, Buchanan R et al (1992) Limbic system abnormalities identified in schizophrenia using positron emission tomography with fluorodeoxyglucose and neocortical alterations with deficit syndrome. Arch Gen Psychiatry 49 522-530 Tamminga CA (1997) Neuropsychiatric aspects of schizophrenia. In Yudofsky SC, Hales RE (eds) The American psychatric press textbook of neuropsychiatry, 3rd edn. American Psychiatric Press, Washington DC, London Taylor JL, McCloskey DI (1996) Selection of motor responses on the basis of unperceived stimuli. Exp Brain Res 110(1) 62-66... 

Dopamine receptor blocking agents. Many of the neuroleptics used in the treatment of schizophrenia frequently produce parkinsonian symptoms as unwanted effects. Neuroleptics block dopamine receptors and their therapeutic effect seems to be related to this action. Although these drugs act on DA systems without distinction, some are more selective. Thioridazine, clozapine and molindone, for example, have electrophysiological effects in the limbic region of the brain but little action in the nigro-striatal area. This selectivity may be related to receptor subtype specificity (see Chs 12 and 54). 

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