DEAR DOCTOR K: I saw an ad for something called a "tDCS brain-stimulating device." It supposedly helps improve memory and thinking. Is it worth a try?
DEAR READER: Transcranial direct current stimulation (tDCS) transmits a current into the brain through electrodes (little metal plates) on the forehead or scalp. The current is weak; it comes from a 9-volt battery (the size used in a smoke detector). People who undergo tDCS may feel their scalp tingle and hear a humming noise. Doctors can control whether the current activates -- or suppresses -- the neurons in your brain that lie beneath the electrodes.