METHODS AND APPARATUS FOR EFFECTUATING A LASTING CHANGE IN A NEURAL-FUNCTION OF A PATIENT
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.
1 - 123 . (canceled)
124 . A method of stimulating the brain of a patient, comprising:
selecting a stimulation site at the cortex of the brain of the patient;
implanting an electrode under the skull of the patient at the stimulation site, wherein the electrode comprises an elongated member having a stimulation portion, and wherein the stimulation portion is positioned within the cortex; and
applying electrical stimulation directly to the stimulation site via the pin such that the electrical stimulation is delivered from within the cortex and below the pial surface.
125 . The method of claim 124 , further comprising estimating a threshold for the individual patient at which an electrical signal directly triggers a neural reaction in response to the electrical signal.
126 . The method of claim 125 wherein the electrical stimulation is applied at a level less than the estimated threshold.
127 . The method of claim 126 wherein the electrical stimulation is applied at a level less than approximately 80% of the estimated threshold.
128 . The method of claim 126 wherein the electrical stimulation is applied at a level less than approximately 60% of the estimated threshold.
129 . The method of claim 126 wherein the electrical stimulation is at a level of approximately 50% of the estimated threshold.
130 . The method of claim 125 wherein estimating the threshold comprises determining a threshold by applying an electrical signal to the stimulation site via the implanted electrode at a level that causes neurons to fire action potentials without additional intrinsic input.
131 . The method of claim 130 wherein the electrical stimulation is applied at a level less than the determined threshold.
132 . The method of claim 124 wherein the patient has been diagnosed with depression and the stimulation site is selected to treat the depression.
133 . The method of claim 132 , further comprising estimating a threshold for the individual patient at which an electrical signal directly triggers a neural reaction in response to the electrical signal, and wherein the electrical stimulation is applied at a level less than the determined threshold.
134 . The method of claim 133 , further comprising inducing a lasting change in neural activity at the stimulation site.
135 . The method of claim 133 wherein the electrical stimulation is applied at a level less than approximately 80% of the estimated threshold.
136 . The method of claim 133 wherein the electrical stimulation is applied at a level less than approximately 60% of the estimated threshold.
137 . The method of claim 133 wherein the electrical stimulation is at a level of approximately 50% of the estimated threshold.