CLINIC
SOURCES OF WORKING MEMORY IMPAIRMENTS IN SCHIZOPHRENIA AN OVERVIEW FOCUSING ON THE IDENTIFICATION OF WORKING MEMORY IMPAIREMENTS AND THEIR CELLULAR BASIS By
Deniz Eracar Shayna Cohen
History of Schizophrenia
Working Memory Processes
Schizophrenia is a neuropsychological disorder which is associated with dramatic impairments in neurocognitive functions such as selective attention and memory. The first accounts that indicate an association between schizophrenia and memory dysfunction date back to Kraepelin’s clinical observations in 1919, which state that patients with schizophrenia “[..](could) not keep a thought in mind” (Kraeoplin, 1919). This observation has paved the way for publications of numerous research studies involving schizophrenic patients and memory tasks. Over time, multiple research groups have realized that the cognitive symptoms, or their lack thereof, of schizophrenic patients were compatible with the presence of an underlying deficit in working memory processes.
By Baddeley and Hitch’s definition (1974), working memory processes describe a limited-capacity “working space” for information processing. The cognitive deficits in working memory in schizophrenia patients appear to reflect a disturbance in executive control and the processes that facilitate complex information processing and behavior, which are, as the research of numerous research groups have indicated, functions that the dorsolateral prefrontal cortex (DLPFC) is responsible for (Carter et al.,1999). Comparably, similarities between schizophrenic symptoms and the symptoms observed in patients with frontal lobe dysfunctions were pointed out almost two decades ago (Park et al., 1992) and made evident through the usage of electrophysiology and
delayed response tasks. In these tasks, non primate subjects were momentarily shown the location of a food item that was then quickly placed behind an opaque screen and tested to see whether they remember the correct location of the food item after a delay period of a few seconds. The studies with delayed-response tasks lead to two significant conclusions: Firstly, It was observed that primates with dorsolateral prefrontal cortex, just like schizophrenics, performed poorly on these tasks (Kojima et al., 1982) and secondly, the tasks demonstrated that the neurons in and around the principal sulcus of the prefrontal cortex became activated during the delay period, hypothetically to keep the presented information in the mind when the visual stimuli leading to that information was kept out of view.
winter 2021 || 19
