71

One serotonergic receptor, the 5-HT2A subtype, is of relevance for the pathophysiology of psychosis.72 Hallucinogens, eg, lysergic acid diethylamide (LSD), act as agonists at the 5-HT2A receptor and several antipsychotic compounds, especially the atypical neuroleptics, block the activity of the 5-HT2A receptor. Several postmortem studies have reported a decrease in 5-HT2 receptors in schizophrenia, but others have not.73,74 A recent PET study of neuroleptic-free patients with schizophrenia did not find any differences in the expression of cortical 5-HT2 receptors in Inhibitors,research,lifescience,medical several cortical areas.74 Cortical function Neuroimaging studies have revealed dysfunctional cortical networks in schizophrenia.75-79 Inhibitors,research,lifescience,medical Regional cerebral blood flow (rCBF) and glucose metabolism were found to be abnormal in frontal cortex and temporal lobe structures at rest as well as during the performance of cognitive tasks. There is, however, no pattern that is diagnostic for schizophrenia. For example, frontal cortical activity at rest was found to be lower by some investigators80-95 but not by others,96-113 and temporal lobe activity at rest was found’ to be decreased,91,104,109,114 normal,95 or increased.113,115 Similarly, frontal cortical recruitment during task performance was found to be decreased in some studices80,84,85,106,112,116-122

but not in others.123-125 Inhibitors,research,lifescience,medical The clinical Inhibitors,research,lifescience,medical heterogeneity of schizophrenia might explain why schizophrenia as a whole is not associated with a pathognomonic abnormality of brain function. When the signs and symptoms of schizophrenia are used to categorize patients into two groups (positive and negative syndrome) or into distinct clusters, a more consistent pattern of neural dysfunction in

schizophrenia emerges. Frontal cortex activity at rest correlates inversely with the degree of negative symptoms,29,95,114,126-130 and left medial temporal lobe activity at rest correlates positively with the severity of psychopathology115,131 or the degree of reality Inhibitors,research,lifescience,medical distortion.29,130 Similarly, decreased frontal cortex recruitment during the performance of some cognitive tasks occurs primarily in patients with negative symptoms.80,119 Thalamus The thalamus serves several important functions in information processing in the human brain.132 First, the relay nuclei (ventral posterior lateral promotion information nucleus [VPL], Dacomitinib medial Palbociclib order geniculate nucleus [MGN], lateral geniculate nucleus [LGN ]) relay sensory information from the sensory organs to the appropriate areas of the primary sensory cortex (SI, Al, and VI). Second, the association nuclei, especially the mediodorsal (MD) nucleus, establish reciprocal connections with the association cortex. Third, the motor nuclei (ventral) relay input from the basal ganglia to the motor and premotor cortex.