Objective: Altered cortical connectivity and plasticity seems to be asymmetrical between the hemispheres in patients with schizophrenia (SCZ). We evaluated long-term potentiation (LTP) in parietal-frontal circuits of both hemispheres using a cortico-cortical Paired Associative Stimulation (cc-PAS) protocol testing the rules of Hebbian-like spike timing dependent plasticity (SPTD).
Methods: 12 SCZ and 12 healthy subjects (HS) underwent a cc-PAS protocol to activate, by means of paired pulses of transcranial magnetic stimulation (TMS), the short-latency connection between posterior parietal cortex (PPC) and primary motor cortex (M1) of both hemispheres. Motor-evoked potentials (MEPs) were collected to assess the time course of the after effects of cc-PAS protocol measuring MEP amplitude as index of cortico-cortical associative plasticity.
Results: While HS showed a similar time course of LTP-like plasticity in the two hemispheres, SCZ revealed a weaker late-LTP-like plasticity in the left compared to the right hemisphere after cc-PAS protocol.
Conclusions: SCZ failed to show the typical long-lasting increase of M1 excitability observed after cc-PAS protocol in both hemispheres, with a greater reduction in the left one.
Significance: Our findings provide novel neurophysiological evidence for an asymmetric impairment of the left parietal-frontal network in SCZ patients.
Keywords: Connectivity; Paired associative stimulation; Parietal cortex; Plasticity; Schizophrenia; Stimulation; Transcranial magnetic.
Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.