For the past 3 years a group of interested researchers have met before IMFAR for a 2-day conference on Transcranial Magnetic Stimulation (TMS) and Autism. This year we had the opportunity to further brainstorm in an opening panel that boasted 4 researchers discussing their work (20 minutes each including question period) and a discussant. Some of the information regarding that panel can be found at Medscape (http://www.medscape.com/viewarticle/863456?src=soc_tw_share). In order to browse the press release you have to join Medscape, but the service is for free. Our own presentation in that panel is summarized in the Medscape press release and in previous blogs in this website (for those interested use the search feature in the home page of corticalchauvinism.com and type TMS).
This blog will summarize one of the presentations. The presentation opened the panel for discussion and was given by Lindsay Oberman from Brown University. Contrary to the other presentations that provided the results of clinical trials, Lindsay decided to introduce in her lecture how TMS worked and some mechanistic studies on brain plasticity.
TMS is a noninvasive technique that creates a changing magnetic field focused on the outer portions of the brain. The large current produced by discharging a bank of supercapacitors across a coil generates a strong magnetic field of the same order of magnitude as that seen in a Magnetic Resonance Imaging (MRI) scanner. The mechanistic studies used by Lindsay were based on single session stimulations whose effects lasted for about 40 minutes. In this regard Lindsay said that the studies were not meant to be therapeutic but rather acted as a probe for studying brain mechanisms During the last few years Lindsay has studied the effects of theta bursts. This variant of stimulation (theta bursts) has advantages over more classic regular pulses as they are able to attain similar results but faster and at a lower intensity of stimulation.
Lindsay went on to examine the question as to whether by using theta bursts treatment on consecutive days would offer benefits to the therapy. Using classical stimulation frequencies (1HZ and lower) our own group has found increased benefits when doing day after stimulations. Lindsay, however, found that a second day of stimulation had diminishing returns in autism spectrum disorder (ASD) patients but an incremental response in controls.
Lindsay continued her presentation by telling the audience 2 interesting facts about her findings. First the response of ASD individuals to theta bursts appeared to be age-dependent. Her studies used primarily adults, and results similar to those in controls appear to be observed in pre-pubertal patients. Second, and lastly, she claimed that there were many paradoxical responses in ASD. Using a therapy protocol that were supposed to be stimulatory to the brain she found marked numbers of individuals that showed an inhibitory response. Similarly when using train of pulses believed to be inhibitory she found a significant percentage of ASD individuals that exhibited an excitatory effect.
Lindsay’s presentation was very interesting and highlighted the need for carefully pacing future studies before establishing major protocols patient treatment.There is a need for control studies pitting classical stimulation techniques against theta bursts on a head to head basis. Other groups need to reproduce reported results and establish their own trials using large samples, broader age groups, and different stimulation sequences.