Akademik Veri Yönetim Sistemi
INTERNATIONAL JOURNAL OF NEURAL SYSTEMS, cilt.25, 2015 (SCI-Expanded)
https://pubmed.ncbi.nlm.nih.gov/25804351/
https://www.worldscientific.com/doi/abs/10.1142/S0129065715500100
ABSTRACT
In the present study, both single channel
electroencephalography(EEG)complexity and two channel interhemispheric
dependency measurements have newly been examined for classification of patients
with obsessive-compulsive disorder (OCD) and controls by using support vector
machine classifiers. Three embedding entropy measurements (approximate entropy,
sample entropy, permutation entropy (PermEn)) are used to estimate single
channel EEG complexity for 19-channel eyes closed cortical measurements. Mean
coherence and mutual information are examined to measure the level of
interhemispheric dependency in frequency and statistical domain, respectively
for eight distinct electrode pairs placed on the scalp with respect to the international
10-20 electrode placement system. All methods are applied to short EEG segments
of 2 s. The classification performance is measured 20 times with different
2-fold cross-validation data for both single channel complexity features (19
features) and interhemispheric dependency features (eight features). The
highest classification accuracy of 85 +/- 5.2% is provided by PermEn at
prefrontal regions of the brain. Even if the classification success do not
provided by other methods as high as PermEn, the clear differences between
patients and controls at prefrontal regions can also be obtained by using other
methods except coherence. In conclusion, OCD, defined as illness of
orbitofronto-striatal structures [Beucke et al., JAMA Psychiatry 70 (2013) 619-629;
Cavedini et al., Psychiatry Res. 78 (1998) 21-28; Menzies et al., Neurosci.
Biobehav. Rev. 32(3) (2008) 525-549], is caused by functional abnormalities in
the pre-frontal regions. Particularly, patients are characterized by lower EEG
complexity at both pre-frontal regions and right fronto-temporal locations. Our
results are compatible with imaging studies that define OCD as a sub group of
anxiety disorders exhibited a decreased complexity (such as anorexia nervosa
[Toth et al., Int. J. Psychophysiol. 51(3) (2004) 253-260] and panic disorder
[Bob et al., Physiol. Res. 55 (2006) S113-S119]).
CONCLUSION
Studies on other neuropsychiatric disorders haveshown
different patterns of complexity. An increasedcomplexity has been observed in
relatively youngerpatients with recent-onset schizophrenia with posi-tive
symptoms, whereas relatively older schizophren-ics with negative symptoms and
chronic illnessexhibited a decreased complexity. Clinical studieshave
demonstrated a higher complexity in severaldisorders such as depression, major
depressive dis-order, a manic episode of bipolar mood disorder and attention
deficit hyperactivity, however, sev-eral studies have reported a lower
complexity in other psychiatric disorders such as dissociative states, anorexia
nervosa and panic disorder. The lasttwo, with which OCD was classified among
anxiety disorders until recently, have the common character-istic of decreased
complexity as in OCD. Our finding that EEG differences are most obvi-ous in the
prefrontal areas is consistent with liter-ature showing that primarily
orbito-frontal cortexand basal ganglia is involved in OCD. Since thebasal
ganglia are deep in the brain and EEG recordsthe cortical activity, striatal
pathology may be over-looked by EEG and only frontocortical pathologycan be
apparent. Studies using functional MRI havefounded a high degree of
connectivity or hyperactivity in the orbito-frontal cortex and the basal gangliain
un-medicated OCD patients. The fact that our patients were drug-naive
isimportant in that suspicion about the modifying effect of medications on brain
function has alreadybeen relieved. EEG studies on schizophrenia andfMRI studies
on OCD have commonly shownthat pharmacotherapy leads to changes in
brainactivities. References 33 and 34 recruited OCDpatients who had been
un-medicated for some time, but not drug-naive. It cannot be excluded, however,
that previous medication leads to changes in func-tional brain activities.
Therefore, the present studyreports clear electrophysiological pathology that
isnot confounded by pharmaco-medical interference. Our small sample size is a
shortcoming of thestudy. Comparisons of drug-naive patients with med-icated and
chronic patients, young and elder, andof pre- and post-treatment results with
regard tocomplexity will be highly valuable in future studies. OCD is a
disorder usually comorbid with a variety ofother mental illnesses, and
therefore the investigationof EEG data that differentiates co-occurring
condi-tions may present interesting knowledge. Comparingthe EEG data of
patients having OCD with thosesuffering from other neuropsychiatric disorders,
suchas schizophrenia, will enhance our understanding ofcomplexity in the
central nervous system