Impaired inter-hemispheric facilitatory connectivity in schizophrenia.

Clinica Psichiatrica, Dipartimento di Neuroscienze, Università Tor Vergata, Rome, Italy.
Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology (Impact Factor: 3.12). 03/2011; 122(3):512-7. DOI: 10.1016/j.clinph.2010.08.013
Source: PubMed

ABSTRACT To investigate the inter-hemispheric connections between the dorsal premotor cortex (dPM) and contralateral primary motor cortex (M1) in schizophrenia.
Sixteen medicated, nine unmedicated schizophrenia patients and 20 healthy age-matched subjects were studied by twin-coil Transcranial Magnetic Stimulation. To activate distinct facilitatory and inhibitory transcallosal pathways between dPM and the contralateral M1, the intensity of dPM stimulation was adjusted to be either suprathreshold (110% of resting motor threshold) or subthreshold (80% of active motor threshold). Interstimulus intervals between conditioning stimulus and test stimulus were 6, 8 and 15 ms.
Schizophrenia patients had comparable efficacy of the inhibitory pathway. On the other hand, medicated patients showed less facilitation of contralateral M1 following dPM stimulation at 80% of active motor threshold, at interstimulus interval=8 ms. The individual amount of facilitation induced by dPM conditioning at 80% of active motor threshold at interstimulus interval=8 ms correlated negatively with negative symptoms.
Inter-hemispheric facilitatory dPM-M1 connectivity is selectively altered in schizophrenia.
This study produced evidence that dPM-M1 connectivity is dysfunctional and that correlates with negative symptoms. These results converge with previous studies which strongly hypothesize that inter- and intra-hemispheric connectivity disturbances may play a major role in schizophrenia.

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