, 2006; Hoogendam et al., 2010; Ziemann et al., 2008 for review). The theta-burst stimulation (TBS) protocol has been proposed as a putative measure of synaptic plasticity (Huang et al., 2005). When applied over the motor cortex, and depending on the stimulation parameters, TBS can induce a transient suppression of corticospinal excitability

(following continuous TBS; cTBS), or an enhancement (following intermittent TBS; iTBS). Suppression of corticospinal excitability by cTBS and its learn more enhancement by iTBS appear to be mediated by cortical processes (Di Lazzaro et al., 2011), are considered indices of long-term depression (LTD)- and long-term potentiation (LTP)-like mechanisms (Huang et al., 2005; Huerta & Volpe, 2009), and have been shown to involve GABAergic and glutamatergic NMDA receptor pathways respectively (Huang et al., 2007; Stagg et al., 2009). Here we used single-pulse TMS to assess corticospinal excitability in 20 individuals with Asperger’s syndrome (AS) and 20 age-, gender- and IQ-matched neurotypical controls before and after cTBS and iTBS. We hypothesised that in individuals with AS the effects of cTBS and iTBS upon TMS-induced motor evoked potentials (MEPs) would be significantly enhanced, possibly reflecting a human correlate of the alterations in LTD and LTP mechanisms found in animal models of ASD (Rinaldi et al., 2007; Bassell & Warren, 2008). Following the results

of our first experiment, in order to evaluate the reliability of this TMS measure and its diagnostic Methocarbamol potential

SCH772984 concentration we evaluated a separate cohort of 15 individuals with AS and 15 matched controls participants with the same cTBS protocol. We studied two cohorts of participants with AS and matching neurotypical controls. Data from cohort one was collected in Boston, Massachusetts, and was composed of 20 individuals with AS [16 male (M), four female (F); age 18–64 (mean ± SD, 34.3 ± 16.4) years; mean ± SD IQ, 118.2 ± 17.3)] and 20 age-, gender- and full-scale IQ-matched typically developing (TD) individuals (16 M, four F; mean age, 34.9 ± 16.2 years; mean IQ, 112.0 ± 13.0). All participants in cohort one completed the cTBS protocol. A subset of these individuals (nine with AS and nine of their matched TD participants) also underwent the iTBS protocol (AS: seven M, two F; mean age 40.7 ± 18.02 years; mean IQ, 117.2 ± 21.8; TD: eight M, two F; mean age, 41.3 ± 17.4 years; mean IQ, 111.5 ± 12.92). For those who participated in both the cTBS and iTBS protocols, the two sessions were separated by at least 1 week. Not all participants consented to come back for the iTBS session. Data from the second cohort was collected in Barcelona, Spain, and was composed of 15 individuals with AS [(14 M, one F; mean age, 42.4 ± 7.36 years; mean IQ, 110.4 ± 18.75) and 15 age-, gender- and IQ-matched TD individuals (14 M, one F; mean age, 42.4.1 ± 7.36 years; mean IQ, 115.