Memory Impairment in Schizophrenic Patients

Schizophrenia affects approximately 3.2 million people in the United States, with 200,000 new cases every year. Classified as a mood disorder by the DSM V, schizophrenia is diagnosed based on five primary symptoms: delusions, disorganized speech, catatonic behavior, hallucinations, and associated negative behaviors. The symptoms of schizophrenia can be quite debilitating and can affect the overall quality of one’s life. Although there is no definitive cure, the symptoms can be managed through medications, various forms of therapy, and palliative care. One of the most devitalizing symptoms of the condition is memory impairment; however, there is minimal research regarding the mechanism for this particular feature. Thus, both Dr. Erickson from the University of Chicago and Dr. Van Snellenberg from the Columbia University Medical Center constructed distinct research protocols to uncover the underlying mechanism. Through their research, each investigator discovered a unique, yet complementary mechanism and corresponding anatomical structures related to the cause of this particular symptom.

Dr. Van Snellenberg recognized the dramatic impact memory impairment has on schizophrenic patients. He states that schizophrenic patients often have difficulty maintaining employment and relationships. To progress the research in the field, Dr. Van Snellenberg utilized past hypotheses to develop a concrete procedure. In the past, many scientists have theorized that the memory impairment in schizophrenic patients is related to the dorsolateral prefrontal cortex (DLPFC), yet found no significant correlations. The dorsolateral prefrontal cortex plays a vital role in working memory, as well as attention and higher cognitive functions. Thus, Dr. Van Snellenberg investigated the dorsolateral prefrontal cortex in being a causative factor for memory impairment in schizophrenic patients. He designed a single computerized working memory task that encompassed eight levels of increasing difficulty. The study had 51 schizophrenic patients and 45 control subjects. Twenty-one of the 51 schizophrenic patients were on antipsychotic medications. The participants were given the working memory test, while brain activity was measured using an fMRI. The results indicated that schizophrenic patients, those on medications and those who were not, had a weaker DLPFC activation, as compared to the healthy controls at all eight levels of difficulty. Through his research, Dr. Van Snellenberg successfully identified that the DLPFC is involved in memory impairment in schizophrenic patients, thus pinpointing a specific target.

Interestingly, Dr. Molly Erikson conducted a similar investigation to discover the underlying mechanism for memory impairment and presented with different results. Dr. Erickson proceeded with a change detection task to test her hypothesis. During the task, one to seven squares were flashed on the screen for 200ms, followed by an 800ms delay period. The squares subsequently returned, and the participants were then asked to determine if the pattern was similar or different. Dr. Erickson noticed that the healthy control subjects had an alpha desynchronization signal emanating from their bilateral occipital lobe, while the schizophrenic patients had a diminished signal. This difference in signal intensity indicated that schizophrenic patients have an impairment in their encoding/consolidation process, thus leading to their memory impairment. In addition to Dr. Van Snellenberg, Dr. Erickson discovered an additional cause for memory impairment in schizophrenic patients.  

To this day, schizophrenia continues to be a mysterious condition. The diversity in symptoms makes it nearly impossible to treat, further perpetuating the discomfort patients experience. However, the research in this field is growing at an unprecedented rate, as many investigators are dedicated to discovering the concealed workings. Both Dr. Erickson and Dr. Van Snellenberg successfully identified distinct mechanisms for the memory impairment schizophrenics experience. Their work allows for the development of targeted therapy in treating the cognitive deficits of schizophrenia. Furthermore, their research also carries social implications. Unfortunately, many schizophrenic patients are misunderstood, largely due to public ignorance regarding the condition. Thus, their findings may help reduce the societal stigma surrounding schizophrenics, as a biological and scientific basis has been identified. Furthermore, their conclusions may be applied to discovering treatment methods for other memory-related conditions, such as Alzheimer’s and dementia. Lastly, the findings may even be expanded into treating the other symptoms of schizophrenia, such as hallucinations and delusions. However, due to the complexity of the condition, many barriers exist in the development of new treatments. But, the research that is currently being conducted provides a strong foundation. Ultimately, the studies conducted by Dr. Van Snellenberg and Dr. Erickson has many implications relating to future treatment development, giving hope to the 3.2 million schizophrenic patients in the United States and many more worldwide.

Link to News Article: https://www.sciencedaily.com/releases/2016/04/160404143843.htm

Jared X. Van Snellenberg, Ragy R. Girgis, Guillermo Horga, Elsmarieke van de Giessen, Mark Slifstein, Najate Ojeil, Jodi J. Weinstein, Holly Moore, Jeffrey A. Lieberman, Daphna Shohamy, Edward E. Smith, Anissa Abi-Dargham. Mechanisms of working memory impairment in schizophrenia. Biological Psychiatry, 2016; DOI: 10.1016/j.biopsych.2016.02.017

Erickson, M. A., Albrecht, M. A., Robinson, B., Luck, S. J., & Gold, J. M. (2017). Impaired Suppression of Delay-Period Alpha and Beta Is Associated With Impaired Working Memory in Schizophrenia. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, 2(3), 272-279. doi:10.1016/j.bpsc.2016.09.003