Left hemispheric breakdown of LTP-like cortico-cortical plasticity in schizophrenic patients

Publication date: Available online 14 July 2017
Source:Clinical Neurophysiology
Author(s): Michele Ribolsi, Giulia Lisi, Viviana Ponzo, Alberto Siracusano, Carlo Caltagirone, Cinzia Niolu, Giacomo Koch
ObjectiveAltered 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).Methods12 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.ResultsWhile 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.ConclusionsSCZ 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.Significanceour findings provide novel neurophysiological evidence for an asymmetric impairment of the left parietal-frontal network in SCZ patients.



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