Obsesif kompulsif bozukluğun iki hemisferli model ile açıklanması
Özet
Studies regarding obsessive compulsive disorder (OCD) pathogenesis showed dysfunction in prefrontal subcortical networks of both hemispheres. At the same time the corpus callosum (CC) abnormalities were reported in OCD patients. All these findings and the similarity between clinical picture of OCD and intentional conflict observed in patients with isolated lesion of CC suggests a dysfunction in hemispheric coordination in OCD. The aim of this study was to examine this possible disturbance in hemispheric coordination in OCD patients and to determine the relationship between this coordination problem and the clinical findings.Study comprised two phases: In the first phase, hemispheric coordination of healthy volunteers and OCD patients were compared by a paradigm that was designed according to the fact that right hemisphere was more involved in processing of emotional prosody and left hemisphere was more involved in processing of semantic content. In the designed paradigm, commands in anxious and relaxed emotional tones were read and participants were asked to obey the commands as fast as possible. From mean reaction time (RT)/ mean command time (CT) ratio decision time (DT) was calculated for both relaxed emotional prosody and anxious emotional prosody. It was assumed that significant difference of mean DT to commands with different prosodies between OCD group and controls was associated with stronger coordination disturbance. In addition participants received a questionnaire of sociodemographic variables, state and trait anxiety inventory (STAI), hand prefence questionnaire. Stroop Test was administered.In the phase of testing the experiment paradigm, control group had faster DT?s than OCD group in both anxious and relax commands. OCD patients showed high trait anxiety while stroop interference and state anxiety values did not differ between groups.In the second phase, the same experimental paradigm was applied while EEG was recorded for event related coherence analysis. After the record of EEG during the experimental paradigm, a resting EEG was recorded. Because of vast artifact in EEG record with the experiment, coherence data from resting EEG and parameters of the experiment were involved in the statistical analysis.Position of electrodes used in the study were Fp1, Fp2, F3, F4, F7, F8, T3, T4, T5, T6, C3, C4, P3 ve P4. EEG signal was decomposed into delta, theta, alpha, beta bands. Electrode pairs that coherence estimated between two signals were attained to one of six electrode pair regions named as anterior left, anterior right, anterior left-right, posterior left, posterior right, posterior left right. To examine potential group differences in terms of coherence values MANOVA was conducted wıth two groups (OCD and controls) and six electode pair regions as independent variable and coherence values of electrode pairs in delta, teta, alpha and beta bands as dependent variables.In phase 2, group main effect (OCD group had significantly decreased coherence in global manner) and group X electrode pair region interactions were observed. Obsessives? posterior left-right coherence had been significantly lower than controls?. decreased coherence in posterior left-right. There were also significant positive correlations in OCD group between reaction time and coherence values.These results suggest that disturbance in interhemispheric coordination have a role in OCD pathogenesis, and behavioral consequences of this disturbance may be reflection of processes compensating problems associated with decreased coherence.