The validity of the positive and negative construct has been challenged by factor analysis studies observing a three dimension grouping of symptoms.
Different terminology is used, but a dimension for hallucinations, a dimension for disorganization, and a dimension for negative symptoms are usually described.
Reduced NMDA receptor signalling is suggested by multiple lines of evidence.
Studies demonstrate reduced NMDA receptor expression and NMDA receptor blockers mimic both schizophrenia symptoms and the physiological abnormalities associated with schizophrenia. The subsets of interneurons that are abnormal in schizophrenia are responsible for the synchronizing of neural ensembles that is necessary during working memory tasks, a process that is electrophysiologically reflected in gamma frequency (30–80 Hz) oscillations.
Efforts to improve learning ability in people with schizophrenia using a high- versus low-reward condition and an instruction-absent or instruction-present condition revealed that increasing reward leads to poorer performance while providing instruction leads to improved performance, highlighting that some treatments may exist to increase cognitive performance.
Training people with schizophrenia to alter their thinking, attention, and language behaviors by verbalizing tasks, engaging in cognitive rehearsal, giving self-instructions, giving coping statements to the self to handle failure, and providing self-reinforcement for success, significantly improves performance on recall tasks.The extent of the cognitive deficits someone experiences is a predictor of how functional they will be, the quality of occupational performance, and how successful they will be in maintaining treatment.Deficits in verbal memory are the most pronounced in someone with schizophrenia, and are not accounted for by deficit in attention.A subgroup of persons with schizophrenia present an immune response to gluten different from that found in people with celiac, with elevated levels of certain serum biomarkers of gluten sensitivity such as anti-gliadin Ig G or anti-gliadin Ig A antibodies.Abnormal dopamine signalling has been implicated in schizophrenia based on the usefulness of medications that effect the dopamine receptor and the observation that dopamine levels are increased during acute psychosis.Positive symptoms are those that most people do not normally experience, but are present in people with schizophrenia.They can include delusions, disordered thoughts and speech, and tactile, auditory, visual, olfactory and gustatory hallucinations, typically regarded as manifestations of psychosis.A number of potential explanations have been proposed, including that alleles associated with schizophrenia risk confers a fitness advantage in unaffected individuals.Maternal nutritional deficiencies, such as those observed during a famine, as well as maternal obesity have also been identified as possible risk factors for schizophrenia.Although these functions are dissociable, their dysfunction in schizophrenia may reflect an underlying deficit in the ability to represent goal related information in working memory, and to utilize this to direct cognition and behavior.These impairments have been linked to a number of neuroimaging and neuropathological abnormalities.