Operant Up-Conditioning of the Tibialis Anterior Motor-Evoked Potential in Multiple Sclerosis: Feasibility Case Studies

Figure 1

(a) Session schedule. Six baseline sessions are followed by 24 conditioning sessions. (b) Composition of baseline and conditioning sessions. (c) Setup view. The subject sits in a chair with hip, knee, and ankle angles fixed at ≈100°, ≈120°, and ≈110°, respectively, in a custom-made apparatus. (d) Visual feedback screens for control and conditioning trials. In all trials, the number of the current trial within its block is displayed, and the background EMG panel shows the correct range (shaded) and the current value (green vertical bar, updated every 200 ms). If TA EMG activity stays in the correct range for at least 2 s and at least 5.5 s has passed since the last trial, an MEP is elicited. In control trials (left), the MEP panel is not shown. In conditioning trials (right), the shading in the MEP panel indicates the rewarded MEP range for up-conditioning. The dark horizontal line is the average MEP size of the baseline sessions, and the vertical bar is the MEP size (i.e., the average rectified EMG in the MEP interval (e.g., 45–75 ms after TMS)) for the most recent trial (it appears 200 ms after TMS). If that MEP size reaches into the shaded area, the bar is green and the trial is a success. If it falls below the shaded area, the bar is red and the trial is a not a success. The running success rate for the current block is shown at the bottom.

(a) Session schedule

(b) Session composition

(c) Setup view

(d) Visual feedback screens