"Despite its often-remarkable
efficacy, [shock therapy] remains a crude technique, analogous
to sculpting rock with explosive charges." So wrote McMaster
mood disorder expert Dr Gary Hasey back in 1999 by way
of introducing a new, more precise treatment for neurological
disorders, called repetitive transcranial magnetic stimulation
(rTMS).
When it was first discovered rTMS
was hailed as a safe, noninvasive alternative to such
'crude techniques.' But though the procedure, which
involves stimulating the brain through a magnetic coil
held outside of the skull, had shown early promise in
treating depression, Parkinson's and epilepsy, it only
ever yielded transient results.
Electroconvulsive therapy (ECT)
on the other hand has a proven track record in treating
severe depression — but it's unclear if it can
do much for symptoms other than depression in Parkinson's
or epilepsy. Memory deficits and the history of abuse
linked to ECT make it the most controversial treatment
in psychiatry. So, it's no surprise that researchers
weren't too hasty to give up on rTMS as a safer alternative.
Now a group of British researchers,
writing in the January 20 issue of Neuron, have
pioneered a rTMS protocol that leads to controllable
changes in the brain that last 60 minutes or more following
treatment.
MAGNETIC
PULSES
In the study, the scalps of nine healthy volunteers
were subjected to various patterns of magnetic pulses.
The researchers found that using short bursts of low-intensity
pulses aimed at the motor cortex for a period of 20
to 190 seconds resulted in significant changes to the
electrical activity in hand muscles.
The pulses were aimed at the portion
of the motor cortex that controls hand movement, and
the results were obtained by objectively measuring the
amount of electrical muscle response to the hand.
"We have found these stimulation
paradigms to be safe in normal subjects and capable
of producing consistent, rapid, and controllable electrophysiological
and behavioural changes in the function of the human
motor system that outlast the period of stimulation
by more than 60 minutes," explains study co-ordinator
Dr John Rothwell, of University College London's Institute
of Neurology. The effects are so powerful, in fact that
they can last up to 90 minutes.
Besides potential therapeutic benefits,
the team is hopeful the method might be a useful tool
for shedding light on other complex brain functions.
The authors predict that their protocol could be applied
to "other regions of the brain for both the study of
normal human physiology and for therapeutic manipulation
of brain plasticity."
Neuron Jan 20, 2005;45(2):201-6
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