Resting State Dense Array Gamma Oscillatory Activity as a Response Marker for Cerebellar-Repetitive Transcranial Magnetic Stimulation (rTMS) in Schizophrenia.BACKGROUND
 As cerebellum and its abnormalities have been implicated in the pathophysiology of schizophrenia, repetitive transcranial magnetic stimulation (rTMS) of this alternate site has been suggested as a novel target for treating patients with this disorder.  As resting state gamma activity measures functional brain connectivity, it could be used as a specific treatment marker.


 To investigate the effect of cerebellar-rTMS on resting state gamma activity, while studying its efficacy in recent onset schizophrenia patients.


 This rater-blinded prospective study was completed by 11 schizophrenia patients.  They received 10 sessions of high-frequency (theta patterned) rTMS to midline cerebellum over 2 weeks.  Resting state EEG was recorded using high (192-channel) resolution EEG at baseline and post rTMS.  Gamma spectral power was calculated using fast Fourier transformation, Hanning window averaged over 8 scalp segments corresponding 8 lobes.  Clinical improvement rated on the Positive and Negative Syndrome Scale and depressive symptoms assessed using the Calgary Depression Scale for Schizophrenia were other outcome variables.  Nonparametric statistics were used.


 Over the treatment course, significant reduction was seen on negative syndrome and depression scores.  Gamma spectral power in left frontal and temporal segments reduced significantly.  Spearman correlation analysis showed that percentage reduction in psychopathology scores had significant positive correlation with percentage reduction in gamma spectral power.


 CONCLUSIONS
 Cerebellar-rTMS might be an effective adjunct to treat intricate and lingering negative and affective symptoms.  Resting state gamma spectral power in frontal and temporal regions might be used as a biomarker for treatment response.
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