The effect of mastication on human cognitive processing: A study using event-related potentials

Protocol for the Mastication and Control conditions in Experiment 1, and the Jaw Movement and Finger Tapping conditions in Experiment 2. In each condition, the subjects performed four oddball sessions. In Mastication, the subjects were asked to chew a gum base that was odorless and tasteless during the intervals between sessions for five minutes. In Control, the subjects were instructed to relax without gum-chewing during the intervals. In Jaw Movement, the subjects were asked to open and close their jaw during the intervals between sessions for five minutes. In Finger Tapping, the subjects were instructed to tap their right index finger during the intervals.

Upper figures: (A) Mean reaction time (RT) for the Mastication and Control conditions in Experiment 1. (B) The value of differences between the pre and post conditions. The value for Pre is set at 0ms. Black circles indicate the RT in Mastication, and gray squares show the RT in Control. Bars indicate standard errors. A significant effect of Condition–Session was found. Lower figures: (A) Mean RT in the Jaw Movement and Finger Tapping conditions in Experiment 2. (B) The value of differences between pre and post conditions. White circles indicate the RT in Jaw Movement, and black squares show the RT in Finger Tapping. There was a significant main effect of Session.

Grand-averaged waveforms of P300 at Pz for the Mastication and Control conditions in Experiment 1. Figures on the left show the waveforms in Mastication, with black triangles indicating the peak latency of P300. The dotted-line indicates the peak latency of P300 in Pre. of note, the peak clearly occurs earlier in Post 3 than in Pre. Figures on the right show the waveforms in Control, with gray triangles indicating the peak latency of P300. Again the dotted-line indicates the peak latency of P300 in Pre. The peak is almost the same among sessions or a little longer in the Post sessions than in Pre.

Grand-averaged waveforms of the target N100 component at Cz in Mastication and Control across all subjects. Figures on the left show the waveforms in Mastication, with black triangles indicating the peak latency of N100. The dotted-line indicates the peak latency of N100 in Pre. of note, the latency is clearly shorter in the Post sessions than in Pre. Figures on the right show the waveforms in Control, with gray triangles indicating the peak latency of N100. Again the dotted-line indicates the peak latency of N100 in Pre. The peak latencies are similar among sessions.

Upper figures show the mean peak latency of P300 at Pz and Cz in Experiment 1. Black circles and gray squares demonstrate Mastication and Control, respectively. The value was set at 0ms, based on the Pre session. Bars indicate standard errors. The ANOVAs for the peak latency of P300 revealed a significant effect of Condition–Session. Lower figures show the mean peak latency of target N100 at Fz and Cz. ANOVAs for the peak latency of target N100 also revealed a significant effect of Condition–Session.

Grand-averaged waveforms of P300 at Pz for the Jaw Movement and Finger Tapping conditions in Experiment 2. Figures on the left show the waveforms in Jaw Movement, with black triangles indicating the peak latency of P300. The dotted line indicates the peak latency of P300 in Pre. Figures on the right show the waveforms in Finger Tapping, with gray triangles indicating the peak latency of P300. Again, the dotted line indicates the peak latency of P300 in Pre.

Upper figures show the mean peak latency of P300 at Pz and Cz in Experiment 2. White circles and black squares demonstrate Jaw Movement and Finger Tapping, respectively. The value was set at 0ms, based on the Pre session. Bars indicate standard errors. ANOVAs for the peak latency of P300 revealed a significant main effect of Session.

Grand-averaged waveforms of the target N100 component at Cz in Jaw Movement and Finger Tapping across all subjects. Figures on the left show the waveforms in Jaw Movement, with black triangles indicating the peak latency of N100. The dotted line indicates the peak latency of N100 in Pre. Figures on the right show the waveforms in Finger Tapping, with gray triangles indicating the peak latency of N100. Again, the dotted line indicates the peak latency of N100 in Pre.

Individual waveforms of Finger Tapping at Post 3 recorded at Pz. Gray triangles show the determined P300. In subject 9, a black triangle is shown, but this latency was out of definition for P300. The dotted line indicates stimulus onset.