Cognitive enhancement is any form of intervention targeted at augmentation of one or several of the key information processing systems of the brain, including those responsible for memory, attention, perception, reasoning, motor function and conceptualization . Cognitive enhancement is possible because of neuroplasticity – brain’s ability to evolve and change its structure even late into adulthood. Therapeutic stimulation of the brain is used in a wide range of neurological and psychiatric diseases, such as stroke, Alzheimer’s disease, schizophrenia, autism and Parkinson’s disease. Furthermore, brain enhancement can be effectively used to boost cognition in healthy individuals, particularly, the elderly ones. In the pre-TMS era, brain enhancement was mainly attempted through transcranial direct current stimulation (tDCS), though with varying degrees of efficacy. “Brain boosting” drugs, such as gingko biloba or piracetam, had also been popular for quite a while, but evidence of their effectiveness is inconsistent and their mechanisms of action are poorly understood .
Why TMS for Cognitive Enhancement
Transcranial magnetic stimulation (TMS) of the brain emerged in the mid-1980s as an innovative and highly promising alternative to more conventional techniques such as motor cortex stimulation (MCS) and deep brain stimulation (DBS). Since then, the method has gained massive recognition, receiving FDA’s approval for the use in major depressive disorder and migraine and being selected as a treatment of choice for PTSD, stress, and depression by the U.S. Navy . On top of that, significant body of evidence suggests high therapeutic potential of rTMS (repetitive TMS) for cognitive enhancement.
How TMS Works to Enhance Cognition?
TMS employs induced electromagnetic currents to modulate focal brain activity. Conducting rTMS at low (B1 Hz) or high frequency (C5 Hz), it is possible to either depress or stimulate the underlying cortical activity, depending on the desired therapeutic outcome .
Cognitive Enhancement in Healthy Individuals
A number of large-scale studies in the recent decades have been indicative of a marked beneficial effect of rTMS on cognitive function in healthy individuals. In 2005, Sole-Padulles et al. studied the effect of rTMS on brain activity in 40 individuals aged 50 or above. Except for minor memory impairment, none of the enrollees suffered from other psychiatric or neurological condition. Before the experiment, the participants were randomly split into two groups, one of which was assigned to rTMS while the other received placebo treatment. Baseline brain activation patterns were studied with fMRI and then compared to such post-treatment. Brain activity was no different before and after the experiment among the placebo group. In contrast, fMRI indicated significant improvement among rTMS group, with the most notable changes in the right middle frontal gyrus and the right medial frontal lobe. On top of that, the results of neuropsychological testing showcased substantial improvement of memory function in rTMS group, compared to no change in sham group .
What Scientists Say?
Between 1999 and 2011, a total of 34 studies were conducted to evaluate cognitive after-effects of rTMS in patients with depression . Of these, 12 studies reported no deterioration of cognitive function while 22 (65%) reported improvement. Most of the open studies indicated improvement in one or more cognitive spheres, such as concentration, verbal fluency, working memory, learning ability, emotional processing, etc. Highly successful is the use of rTMS in patients with schizophrenia: of those studies done to date, many have recorded significant amelioration of either working memory, word memorization or sustained attention. Similarly positive results have been achieved in patients with autism, Alzheimer’s disease (AD), and attention deficit hyperactivity syndrome. Although more research needs to be done in this direction, potential application of rTMS in AD is particularly promising, as the technique facilitates the plasticity mechanisms in the brain that are impaired in patients with this condition .
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