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Impaired induction of long-term potentiation-like plasticity in patients with high-functioning autism and Asperger syndrome.
JUNG, NIKOLAI H 1,2; JANZARIK, WIBKE G 2; DELVENDAHL, IGOR 2,3; MUNCHAU, ALEXANDER 4; BISCALDI, MONICA 5; MAINBERGER, FLORIAN 2; BAUMER, TOBIAS 4; RAUH, REINHOLD 5; MALL, VOLKER 1,2
[Article] Developmental Medicine & Child Neurology. 55(1):83-89, January 2013.

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AIM: 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).

METHOD: PAS with an interstimulus interval between electrical and transcranial magnetic stimulation of 25 ms (PAS25) was performed in patients with HFA/AS (n=9; eight males, one female; mean age 17y 11mo, SD 4y 5mo) and in typically developing age-matched volunteers (n=9; five males, four females; mean age 22y 4mo, SD 5y 2mo). The amplitude of motor-evoked potentials was measured before PAS25, immediately after stimulation, and 30 minutes and 60 minutes later. A PAS protocol adapted to individual N20 latency (PASN20 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 PAS25. 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.

INTERPRETATION: 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.