title: Impaired induction of long-term potentiation-like plasticity in patients with high-functioning autism and Asperger syndrome.
abstract: OBJECTIVE
  We aimed to investigate the induction of long-term potentiation (LTP)-like plasticity by paired associative stimulation (PAS) in patients with high-functioning autism and Asperger syndrome (HFA/AS).
  
  
  METHODS
  PAS with an interstimulus interval between electrical and transcranial magnetic stimulation of 25 ms (PAS(25)) was performed in patients with HFA/AS (n=9; eight males, one female; mean age 17 y 11 mo, SD 4 y 5 mo) and in typically developing age-matched volunteers (n=9; five males, four females; mean age 22 y 4 mo, SD 5 y 2 mo). The amplitude of motor-evoked potentials was measured before PAS(25), immediately after stimulation, and 30 minutes and 60 minutes later. A PAS protocol adapted to individual N20 latency (PAS(N20+2)) was performed in six additional patients with HFA/AS. Short-interval intracortical inhibition was measured using paired-pulse stimulation.
  
  
  RESULTS
  In contrast to the typically developing participants, the patients with HFA/AS did not show a significant increase in motor-evoked potentials after PAS(25). This finding could also be demonstrated after adaptation for N20 latency. Short-interval intracortical inhibition of patients with HFA/AS was normal compared with the comparison group and did not correlate with PAS effect.
  
  
  CONCLUSIONS
  Our results show a significant impairment of LTP-like plasticity induced by PAS in individuals with HFA/AS compared with typically developing participants. This finding is in accordance with results from animal studies as well as human studies. Impaired LTP-like plasticity in patients with HFA/AS points towards reduced excitatory synaptic connectivity and deficits in sensory-motor integration in these patients.
authors.affiliation: Department of Paediatrics, Technical University Munich, Munich, Germany.
authors.forename: Nikolai H
authors.initials: NH
authors.lastname: Jung
authors.forename: Wibke G
authors.initials: WG
authors.lastname: Janzarik
authors.forename: Igor
authors.initials: I
authors.lastname: Delvendahl
authors.forename: Alexander
authors.initials: A
authors.lastname: Münchau
authors.forename: Monica
authors.initials: M
authors.lastname: Biscaldi
authors.forename: Florian
authors.initials: F
authors.lastname: Mainberger
authors.forename: Tobias
authors.initials: T
authors.lastname: Bäumer
authors.forename: Reinhold
authors.initials: R
authors.lastname: Rauh
authors.forename: Volker
authors.initials: V
authors.lastname: Mall
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D020817:Asperger Syndrome / Q000473:pathology* / Q000503:physiopathology; D001321:Autistic Disorder / Q000473:pathology* / Q000503:physiopathology; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D017774:Long-Term Potentiation / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology*; D009433:Neural Inhibition / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult