Protocol details. Panel A: Two sequential vibrotactile pulses were delivered during the Stimulus Interval, one to each of either skin site A or B. Subject was queried as to which skin site received the first pulse during the Response Interval, and this was followed by a 5 sec delay before the onset of the subsequent trial. Panel B: Pulse delivery sequence for the TOJ and TDT tasks during each 1 sec Stimulus Interval. Order of delivery (skin site A or B) was randomized on a trial-by-trial basis, and inter-pulse interval was decreased or increased, depending on subject response. Panel C: Exemplary 25 Hz conditioning stimulus delivered concurrently with TOJ/TDT task. Panel D: Two non-periodic asynchronous stimuli were delivered concurrently with the TOJ and TDT tests. Panel E: Two non-periodic but synchronous stimuli were delivered concurrently with the TOJ and TDT tests.