Fig. 2.

Experimental design and results. (A) Recordings for all subjects were made via a microphone (Mic) in the ear canal set into a custom-fit ear bud. On each trial, a subject fixated on a central LED and then made a saccade to a target LED (−24° to +24° horizontally in 6° increments and 6° above the fixation point) without moving his/her head. The ±24° locations were included on only 4.5% of trials and were excluded from analysis (Methods); other target locations were equally likely (∼13% frequency). (B) Humans (black text) received randomly interleaved silent and click trials (50% each). Clicks were played via a sound transducer coupled with the microphone at four times during these trials: during the initial fixation and saccade and at 100 ms and 200 ms after target fixation. Monkeys’ trials had minor timing differences (red text), and all trials had one click at 200–270 ms after target fixation (red click trace). (C) Average eye trajectories for one human subject and session for each of the included targets are shown; colors indicate saccade target locations from ipsilateral (blue) to contralateral (red). deg, degrees; Horiz., horizontal; Vert., vertical. Mean eye position is shown as a function of time, aligned on saccade onset (D) and offset (E). H, horizontal; V, vertical. Mean microphone recordings of air pressure in the ear canal, aligned on saccade onset (F) and offset (G), indicate that the eardrum oscillates in conjunction with eye movements. The phase and amplitude of the oscillation varied with saccade direction and amplitude, respectively. The oscillations were, on average, larger when aligned on saccade onset than when aligned on saccade offset.