Review article
Neuropsychological and neurobiological aspects of working memory

Working memory means an abilities to keep information for a short-time and to manipulate them. Working memory play a significant role in the organization of complex cognitive functions, adaptational processes, mental plasticity and consciousness. Working memory is connected with the activity of dorsolateral prefrontal cortex of the brain and with the activity of different neurotransmitter systems, especially with dopaminergic, glutamatergic and BDNF systems. Molecular genetics studies show an association between working memory abilities and polymorphism of dopaminergic system genes in schizophrenia and polimorphism of BDNF gene in bipolar disorder. The working memory disturbances are presented in schizophrenia and bipolar disorder and also in healthy first degree relatives of patients with schizophrenia and bipolar disorder. Currently they are known as an cognitive endophenotypic marker of vulnerability to these illnesses. In schizophrenia, working memory disturbances are core and enduring deficits, and may increase during the course of the illness. Working memory dysfunctions are connected with structural and functional abnormalities in prefrontal cortex of schizophrenic patients. In bipolar disorder during depressive episodes working memory disturbances may achieve a similar level as in schizophrenia. The most useful neuropsychological methods for working memory assessment are Wisconsin Card Sorting Test and N-back test. The performance on these tests is connected with the level of prefrontal cortex dysfunctions. These tests are particularly useful in neuroimaging studies performed during cognitive stimulation.