Specific characteristics of prefrontal cortex functions in multiple sclerotic patients

Abstract

Cognitive dysfunction is common in MS and can cause poor quality of life. Physical examination and EDSS can not reliably predict cognitive impairments. Frontal cortex atrophy predicts cognitive impairment in MS. Dorsolateral prefrontal cortex (DLPFC) processes logical thinking, working memory, attention and executive functions and ventro-medial pre-frontal cortex (VMPFC) processes emotional evaluations, social cognition and response inhibition. We assessed DLPFC and VMPFC dysfunctions in MS patients with neuropsychological assessment tasks.Material and methods:40 patients (27 female) and 40 healthy, age, sex and IQ matched controls were included. The MS clinical manifestations were evaluated according to EDSS by a qualified neurologist. Beck depression inventory II was used for depression. We used Wisconsin Card Sorting Task (WCST) and Time Perception Task (TPT) for DLPFC and Iowa Gambling Task (IGT), Delayed Discounting Task (DDT) and Balloon Analogue Risk Task (BART) for assessment of VMPFC functions.Results:MS patients had more perseveration errors (15.49 VS 8.77) (P=0.007) in WCST. In TPT patients tend to over-estimate and over-reproduce time intervals. MS patients have more delay in selection of risky choices cards on IGT, (3.39 seconds vs 2.48 seconds). In DDT patients have lower discounting amounts over delays. In Bart patients have lower levels of risky behavior tendency.Conclusion:Decision making is being processed logically in dorsolateral and emotionally in ventromedial parts of prefrontal cortex. According to our study, MS patients follow a conservative strategy in their decision makings both logically and emotionally. This may be explained by “multiple disconnection syndrome” seen in MS particularly in frontal lobes or because of the specific effects of disease-stigma burden on patients' behavior.slowing of information processing speed as a primary causative factor must be mentioned.