Functions of the thalamus in psychiatry: the relationship between the thalamus and schizophrenia

The thalamus involves two electrophysiological systems of the specific projection system and the non-specific projection system. The electrical stimulation of the former induces the augmenting response in the cerebral cortex and the same of the latter induces the recruiting response in the cortex. The non-specific projection system is also known as the diffuse thalamo- cortical projection system and it is concerned with the maintenance mechanism of consciousness such as sleep and wakefulness. The thalamus is concerned in the higher nervous functions such as language, cognition, memory and intelligence. Severe nerve cell loss with proliferation of hypertrophic astroglia was found in the association nuclei and sensory relay nuclei in the thalami of patients suffering from Creutzfeldt-Jakob disease. In the brain imaging study, volume reduction of the thalamus, especially of dorsomedial nuclei, degradation of glucose metabolism were observed in the thalami of patients with schizophrenia. Carlsson considered schizophrenia as a subcortical neurotransmitter imbalance syndrome based on the hypothesis of a thalamic filter. Andreasen defined schizophrenia as a misconnection syndrome or cognitive dysmetria induced by dysfunction of the cortico-cerebellar-thalamic-cortical circuit (CCTCC).