The following disclosure describes several methods and apparatus for
intracranial electrical stimulation to treat or otherwise effectuate a
change in neural-functions of a patient. Several embodiments of methods
in accordance with the invention are directed toward enhancing or
otherwise inducing a lasting change in neural activity to effectuate a
particular neural-function. Such lasting change in neural activity is
defined as "neuroplasticity." The methods in accordance with the
invention can be used to treat brain damage (e.g., stroke, trauma, etc.),
brain disease (e.g., Alzheimer's, Pick's, Parkinson's, etc.), and/or
brain disorders (e.g., epilepsy, depression, etc.). The methods in
accordance with the invention can also be used to enhance neural-function
of normal, healthy brains (e.g., learning, memory, etc.), or to control
sensory functions (e.g., pain). Certain embodiments of methods in
accordance with the invention electrically stimulate the brain at a
stimulation site where neuroplasticity is occurring. The stimulation site
may be different than the region in the brain where neural activity is
typically present to perform the particular neural function according to
the functional organization of the brain. In one embodiment in which
neuroplasticity related to the neural-function occurs in the brain, the
method can include identifying the location where such neuroplasticity is
present. In an alternative embodiment in which neuroplasticity is not
occurring in the brain, an alternative aspect is to induce
neuroplasticity at a stimulation site where it is expected to occur.
Several embodiments of these methods that are expected to produce a
lasting effect on the intended neural activity at the stimulation site
use electrical pulses that increase the resting membrane potential of
neurons at the stimulation site to a subthreshold level.