Connectivity Between Posterior Parietal Cortex and Ipsilateral Motor Cortex Is Altered in Schizophrenia

• Published in: Biological psychiatry (1969) Vol. 64; no. 9; pp. 815 - 819
• Main Authors: Koch, Giacomo, Ribolsi, Michele, Mori, Francesco, Sacchetti, Lucia, Codecà, Claudia, Rubino, Ivo Alex, Siracusano, Alberto, Bernardi, Giorgio, Centonze, Diego
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2008
• Subjects: Adult; Brain Mapping; Case-Control Studies; Connectivity; Electric Stimulation - methods; Electromyography - methods; Evoked Potentials, Motor - physiology; Female; Humans; Male; Motor Cortex - pathology; Motor Cortex - physiopathology; Neural Pathways - physiopathology; parietal cortex; Parietal Lobe - pathology; Parietal Lobe - physiopathology; Psychiatric/Mental Health; schizophrenia; Schizophrenia - pathology; TMS; Transcranial Magnetic Stimulation; Young Adult; Connectivity; parietal cortex; schizophrenia; TMS; transcranial magnetic stimulation
• ISSN: 0006-3223; 1873-2402; 1873-2402
• DOI: 10.1016/j.biopsych.2008.05.026

Recent advances have highlighted the hypothesis of schizophrenia as a disorder causing defective connectivity among distinct cortical regions. Neurophysiological evidence supporting this hypothesis, however, is still lacking. In the present study, we used a novel twin-coil transcranial magnetic stimulation (tcTMS) approach to investigate ipsilateral parieto-motor connectivity in 20 schizophrenic patients (14 medicated, 6 unmedicated) and in 15 healthy age-matched volunteers. In healthy subjects, a conditioning TMS pulse applied over the ipsilateral posterior parietal cortex (PPC) at 90% of resting motor threshold (RMT) intensity was able to increase the excitability of the hand area of the right primary motor cortex, with peaks at interstimulus intervals (ISIs) of 4 and 15 msec. This paradigm of stimulation failed to reveal any facilitatory parieto-motor interaction in medicated and unmedicated schizophrenic patients. The between-group difference in paired-pulse facilitation was not ISI-specific. In following analyses, we found that the effects across ISIs induced by PPC conditioning at 90% RMT correlated with the Global Assessment Functioning score and with the negative subscale of the Positive and Negative Syndrome Scale, showing that patients with a better global functioning and lower negative symptoms had less impaired connectivity. Moreover the same parameter correlated with illness duration. Parieto-motor connectivity is impaired in schizophrenia. Cortico–cortical disconnection might be a core feature of schizophrenia.