TMS and the Neurology of Autism
Basic findings
Autism is a neurodevelopmental disorder, the exact mechanism of which is not well understood and individuals may have different levels of severity of autism. It has been suggested that social impairments observed in individuals with autism spectrum disorder can be partly explained by an abnormal mirror neuron system (Théoret et al. 2005). Théoret et al. (2005) found that overall modulation of M1 excitability during action observation is significantly lower in individuals with ASD compared with matched controls. In addition, this study found that basic motor cortex abnormalities do not underlie this impairment.
Ongoing research
Monitoring The Disease
A recent study by Enticott et al. 2010 examined motor cortical inhibition and excitability in high functioning autism (HFA) and Asperger disorder using TMS. Participants with either HFA or Asperger disorder and neurotypical participants were administered a paired-pulse TMS paradigm intended to assess motor cortical inhibition and excitability. Responses to TMS were recorded by electromyography. Their findings provided evidence for a possible neurobiological dissociation between HFA and Asperger disorder based on GABAergic function (Enticott et al. 2010).
Modulating The Disease
Boosting the function of motor neurons may improve the prognosis of autistic spectrum disorders and contribute to diagnostic clarity (Perkins et al., 2010).
Sokhadze et al. 2009 theorised that the neuropathology of autism is characterised by a disturbance of cortical modularity. In their model a decrease in the peripheral neuropil space of affected minicolumns provides for an inhibitory deficit and a readjustment in their signal to noise bias during information processing. In their 2009 study rTMS was used as a way of increasing the surround inhibition of minicolumns in autism. Outcome measures based on event-related potentials, induced gamma activity and behavioural measures showed significant post-TMS improvement. The results suggested that rTMS offers a potential therapeutic intervention for autism (Sokhadze et al. 2009).
Links
References
- Enticott et al., Dev Med Child Neurol, 2010.
- Perkins et al., J Clin Neurosci, 2010.
- Sokhadze et al., Journal of Autism and Developmental Disorders, 2009.
- Théoret, Current Biology, 2005.
