A system comprising: a non-invasive nerve stimulator (10, 100) for peripheral nerves, including the ulnar and/or median nerves, configured to be fitted proximate the left and/or right arm, wrist or hand of a user, to stimulate the median and/or ulnar nerves using at least one stimulus, the nerve stimulator (10, 100) comprising: a stimulus generator to generate at least one stimulus; an applicator (34, 104) to apply the generated stimulus to the arm, wrist or hand of the user, the applicator (34, 104) comprising at least one stimulus interface to apply the stimulus to the user's skin, proximate to the anterior or ventral side of the user's arm, wrist or hand; and at least one user biometric measuring sensor (30, 108), embodied in or proximate the applicator (34, 104), to monitor and determine physiological parameters associated with the user, including any one or more of the following: heart rate, HR, heart rate variability, HRV, temperature, SPO2, galvanic skin response, GSR, and inertial measurement; a controller (12, 106) to control the operation of the stimulus generator and the applicator (34, 104), the controller (12, 106) including a stimulus controller module to control the applied stimulation in accordance with a stimulation profile, the stimulation profile defining the applied stimulus in terms of duration and/or frequency and/or intensity/amplitude and/or width, wherein the stimulus controller module applies a stimulation profile based on the physiological parameters received from the at least one user biometric measuring sensor (30, 108), so as to define a closed-loop feedback arrangement, wherein the stimulus controller module compares the received physiological parameters to a predetermined level or profile, and either selects an alternative stimulation profile or adjusts the existing stimulation profile being used, characterised in that the system includes: a training computer running an interactive computer cognitive training application, which the user is arranged to interact with, the training computer comprising a training processing module, which is arranged to be in communication with the nerve stimulator (10, 100), to coordinate the stimulation of the median and/or ulnar nerves with particular activities or learning elements that the user must engage with, and/or at predetermined times during the training. a stimulus generator to generate at least one stimulus; an applicator (34, 104) to apply the generated stimulus to the arm, wrist or hand of the user, the applicator (34, 104) comprising at least one stimulus interface to apply the stimulus to the user's skin, proximate to the anterior or ventral side of the user's arm, wrist or hand; and at least one user biometric measuring sensor (30, 108), embodied in or proximate the applicator (34, 104), to monitor and determine physiological parameters associated with the user, including any one or more of the following: heart rate, HR, heart rate variability, HRV, temperature, SPO2, galvanic skin response, GSR, and inertial measurement; a controller (12, 106) to control the operation of the stimulus generator and the applicator (34, 104), the controller (12, 106) including a stimulus controller module to control the applied stimulation in accordance with a stimulation profile, the stimulation profile defining the applied stimulus in terms of duration and/or frequency and/or intensity/amplitude and/or width, wherein the stimulus controller module applies a stimulation profile based on the physiological parameters received from the at least one user biometric measuring sensor (30, 108), so as to define a closed-loop feedback arrangement, wherein the stimulus controller module compares the received physiological parameters to a predetermined level or profile, and either selects an alternative stimulation profile or adjusts the existing stimulation profile being used,