To compare the results of the MEG measurements with the scale values of the subjective preference, combinations of a reference stimulus (Δt1=0 ms) and test stimuli (Δt1=0, 5, 20, 60, and 100 ms) were presented alternately 50 times, and the MEGs were analyzed.
Five rounds of 70 to 120 dB white noise stimuli (in 5 or 10 dB increments, 40 ms) were presented in quasi-random order and random ITI.
Stimuli of 500 ms were presented in ascending order of dosage with 30 s inter-stimuli intervals, using a stimulus controller (CS-55, Syntech).
Experimental session began after the mouse was acclimatized to the environment for five min. In the first session, only startle stimuli (SS, 120 dB, 40 ms) were presented for ten times in random inter-trial intervals (ITI, 10 20 s).
Five times of 70 to 120 dB (70, 75, 80, 85, 90, 95, 100, 110, 120 dB) white noise stimuli (40 ms) were presented in quasi-random order and random inter-trial intervals (10 20 sec).
During the measurement, each trial proceeded as follows: First, a fixation stimulus (a 2×2 pixel central square and a 1-pixel-wide circle with a diameter of 1.6 deg, luminance 80% of background, duration 200 ms) and a subsequent blank period (300 ms) were presented twice.
A comparison stimulus (100 ms) was presented 1800 ms after the luminance change.
In each trial, a flash of constant brightness with a duration of 250 ms was presented 200 times.
A blank screen of 200 ms was presented between the response and the start of the next trial.
Finally, an intertrial interval (ITI) that was drawn from a randomly generated exponential function with a mean of 5000 ms (range: 3000 10000 ms) was presented.
In the first session, a 120-dB startle stimulus (40 ms) was presented to the mouse 10 times at random intertrial intervals (10 20 s).
