title: The Photoparoxysmal Response Reflects Abnormal Early Visuomotor Integration in the Human Motor Cortex.
abstract: 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
  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.
  
  
  CONCLUSIONS
  We suggest that abnormal early visuomotor integration contributes to the pathophysiology of PPR.
authors.affiliation: IRCCS Neuromed Institute, 86077 Pozzilli, IS, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Suppa
authors.affiliation: Department of Neurology and Psychiatry, "Sapienza" University of Rome, 00185 Rome, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Rocchi
authors.affiliation: Department of Neurology and Psychiatry, "Sapienza" University of Rome, 00185 Rome, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Li Voti
authors.affiliation: Department of Physiology and Pharmacology, "Sapienza" University of Rome, 00185 Rome, Italy.
authors.forename: O
authors.initials: O
authors.lastname: Papazachariadis
authors.affiliation: Department of Neurology and Psychiatry, "Sapienza" University of Rome, 00185 Rome, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Casciato
authors.affiliation: Department of Neurology and Psychiatry, "Sapienza" University of Rome, 00185 Rome, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Di Bonaventura
authors.affiliation: Department of Neurology and Psychiatry, "Sapienza" University of Rome, 00185 Rome, Italy.
authors.forename: A T
authors.initials: AT
authors.lastname: Giallonardo
authors.affiliation: IRCCS Neuromed Institute, 86077 Pozzilli, IS, Italy; Department of Neurology and Psychiatry, "Sapienza" University of Rome, 00185 Rome, Italy. Electronic address: alfredo.berardelli@uniroma1.it.
authors.forename: A
authors.initials: A
authors.lastname: Berardelli
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D004831:Epilepsies, Myoclonic / Q000503:physiopathology*; D004829:Epilepsy, Generalized / Q000503:physiopathology*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D010775:Photic Stimulation; D010787:Photosensitivity Disorders / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation; D014793:Visual Cortex / Q000502:physiology*; D055815:Young Adult
keywords: Epilepsy; Paired associative stimulation; Photoparoxysmal response; Primary motor cortex; Visuomotor integration