Intelligent determination of therapeutic stimulation intensity for transcutaneous electrical nerve stimulation

Apparatus for determining a target stimulation intensity level of electrical stimulation to a user that evokes an immediate electrotactile sensation from the user, said apparatus comprising:

• a stimulation unit for electrically stimulating body tissue of the user;
• a control unit for determining an intensity level of a next electrical stimulation to be delivered to the user by the stimulation unit based on a likelihood function that specifies the likelihood of a range of intensity levels to be the target stimulation intensity level;
• an indication unit for the user to indicate when the immediate electrotactile sensation is felt when the stimulation unit stimulates the user at the intensity level;
• and
• a calculation unit for updating the likelihood function for the range of intensity levels to be the target stimulation intensity level based on input to the indication unit from the user;
• wherein the control unit is further configured to update the target stimulation intensity level based on the updated likelihood function, and either (i) establish the updated stimulation intensity level as the target stimulation intensity level for invoking the immediate electrotactile sensation from the user, or (ii) set the updated stimulation intensity level as the intensity level of the next electrical stimulation to be delivered to the user to obtain an additional indication of the immediate electrotactile sensation felt by the user.