The photoparoxysmal response reflects abnormal early visuomotor integration in the human motor cortex

A. Suppa, L. Rocchi, P. Li Voti, O. Papazachariadis, S. Casciato, C. Di Bonaventura, A. T. Giallonardo, A. Berardelli

Research output: Contribution to journalArticlepeer-review


Background Visual-paired associative stimulation (V-PAS) is a transcranial magnetic stimulation (TMS) technique able to investigate long-term potentiation (LTP) and depression (LTD)-like plasticity in the primary motor cortex (M1) arising through early visuomotor integration. Objective/hypothesis Abnormal early visuomotor integration might contribute to the pathophysiology of intermittent photic stimulation (IPS)-induced photoparoxysmal response (PPR). Methods We applied V-PAS in 25 healthy subjects (HS), 25 PPR-positive patients, with and without idiopathic generalized epilepsy (IGE), and 8 PPR-negative patients with IGE. V-PAS consisted of primary visual area activation achieved by visual evoked potentials coupled with TMS-induced M1 activation at 100 ms interstimulus interval (ISI) (V-PAS100). Before and after V-PAS, we measured changes in motor evoked potentials (MEPs). We compared MEPs after 1 Hz repetitive TMS (rTMS) and 0.25 Hz-V-PAS100. To examine possible V-PAS-induced after-effects at other ISIs, we delivered V-PAS at 40 (V-PAS40) and 140 ms ISIs (V-PAS140). To clarify whether V-PAS100 increases parieto-/premotor-to-M1 connectivity, before and after V-PAS100, we examined MEPs evoked by paired-pulse techniques. Results V-PAS100 increased MEPs more in PPR-positive patients than in HS. PPR-negative patients had normal response to V-PAS100. 1 Hz-rTMS, 0.25 Hz-V-PAS100 and V-PAS40 elicited similar responses in HS and PPR-positive patients, whereas V-PAS140 induced stronger after-effects in PPR-positive patients than HS. After V-PAS, MEPs elicited by facilitatory paired-pulse protocols decreased similarly in HS and PPR-positive patients. Conversely, MEPs elicited by inhibitory protocols decreased in HS, whereas in PPR-positive patients, they turned from inhibition to facilitation. Conclusion We suggest that abnormal early visuomotor integration contributes to the pathophysiology of PPR.

Original languageEnglish
Pages (from-to)1151-1161
Number of pages11
JournalBrain Stimulation
Issue number6
Publication statusPublished - Nov 1 2015


  • Epilepsy
  • Paired associative stimulation
  • Photoparoxysmal response
  • Primary motor cortex
  • Visuomotor integration

ASJC Scopus subject areas

  • Clinical Neurology
  • Neuroscience(all)
  • Biophysics


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