Brain Networks in TMS for Combined PTSD and Major Depression

Everything we do, every thought we’ve ever had, is produced by the human brain. But exactly how it operates remains one of the biggest unsolved mysteries, and it seems the more we probe its secrets, the more surprises we find.

— Neil deGrasse Tyson

Transcranial magnetic stimulation (TMS) uses repeating strong magnetic pulses to change the activities of neurons. TMS gives us the ability to directly influence brain activity in a highly selective manner, enabling an unprecedented degree of control over how our minds function — for clinical and other applications (e.g. forensic, performance enhancement, etc.).

When applied across the skull to different areas of the cortex of the brain, TMS can have varying effects. The effect of the TMS depends on what areas are targeted, including the depth into the brain, whether the stimulation is used to increase or suppress activity in that area, and how changing activity in that brain area affects the overall function of the brain, and the subjective experience of the individual. As TMS therapy has been officially used in the U.S. since 2008 for the treatment of major depressive disorder unresponsive to at least one medication, using a rather basic protocol, the future use of TMS (and related neuromodulation techniques such as transcranial direct current stimulation, tDCS) will depend on developing more sophisticated understanding of how the brain works.

By forcing neurons to fire using a moving magnetic field to push electrical charge within the cells themselves, the overall activity of the brain can be shifted from one state to another, in some cases. Thus it is possible to shift the brain from a depressed to a healthy pattern, or shift patterns of disordered cognition or emotion processing in PTSD to restore proper function, or slow down activity in motor areas in the brain to interfere with hyperactive circuits in obsessive compulsive disorder, or reduce activity in the auditory cortex to quell hallucinations, and so on. Understanding the brain from a network point of view provides the information required to design better treatment protocols and build more accurate models and sims.

Traditionally, brain function has looked at the biology and electrophysiology of neurons, and used…