At the Berenson-Allen Center for Noninvasive Brain Stimulation that I direct we have three distinct missions: (1) Research explores brain-behavior relations, brain plasticity and its modulation, employing different noninvasive brain stimulation techniques combined with careful task design, electroencephalography, and functional brain imaging. (2) Educational efforts feature an intensive course in noninvasive brain stimulation offered three times per year as part of Harvard’s Continuing Medical Education program. (3) Clinical work includes diagnostic studies therapeutic applications of noninvasive brain stimulation for treatment of neuropsychiatric disorders.
My work has been fundamental in establishing transcranial magnetic stimulation (TMS) as a tool capable of revealing causal brain-behavior relations and the timing of information flow and dynamic adaptation in neural networks. My laboratory has contributed to increasing the knowledge about the mechanisms of action and improving the methodology of TMS and its combination with other neurophysiologic and brain imaging methods. For example we developed a method to interface TMS with EEG to allow the study of the effects of brain stimulation on ongoing brain activity and ultimately enable the use of EEG activity as a means of controlling the stimulation applied, and a novel methodology to introduce TMS into the MRI scanner in order to be able to study the neural activity evoked by TMS and thus correlate behavioral with underlying neurophysiologic effects.
I was the first to show that trains of repetitive TMS can be reliably and safely disrupt the activity of a given brain region transiently and thus provide insights about the causality of brain activity in behavior. I demonstrated the rapid plasticity of motor cortical outputs during motor learning, the requirement of visual cortex input for tactile Braille reading in the blind, the causal role of primary visual cortex and the dynamics of interhemipheric compensatory processes during mental imagery, and the need for fast back-projections in visual awareness tasks. Moreover, coupling TMS with physiologic and imaging techniques, I showed that repetitive TMS can induce lasting changes in regional brain excitability and exert trans-synaptic modulatory effects on neural network activity in animal and human studies. This allows for the investigation of the rapid neuroplastic changes that compensate for brain injury or dysfunction, and permits the model-driven, individually-tailored modulation of disrupted networks for treating common neuropsychiatric conditions. We showed that TMS can aide in the recovery of hand function and aphasia after stroke, the adaptation to blindness, the rehabilitation of neglect, the control of addictive behavior, and the acquisition of language and imitation behavior in autism. My laboratory carried out the first double blind study of rTMS in major depression, and the first proof-of-principle studies suggesting therapeutic possibilities of TMS in epilepsy, Parkinson's disease, visceral pain and dystonia. This work provides support to the notion that modulation of activity along a distributed neural network can induce long-lasting plastic changes, even in the adult brain, and have behavioral consequences, which in certain conditions may be therapeutic.