Connectivity between posterior parietal cortex and ipsilateral motor cortex is altered in schizophrenia.
BACKGROUND
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
Parieto-motor connectivity is impaired in schizophrenia. Cortico-cortical disconnection might be a core feature of schizophrenia.
Koch
Giacomo
G
Clinica Neurologica, Dipartimento di Neuroscienze, Università Tor Vergata, Rome, Italy. giakoch@libero.it
Ribolsi
Michele
M
Mori
Francesco
F
Sacchetti
Lucia
L
Codecà
Claudia
C
Rubino
Ivo Alex
IA
Siracusano
Alberto
A
Bernardi
Giorgio
G
Centonze
Diego
D
D000328:Adult; D001931:Brain Mapping; D016022:Case-Control Studies; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000473:pathology / Q000503:physiopathology*; D009434:Neural Pathways / Q000503:physiopathology; D010296:Parietal Lobe / Q000473:pathology / Q000503:physiopathology*; D012559:Schizophrenia / Q000473:pathology*; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult