The fMRI experiment consisted of an encoding phase, and a retrieval phase the next day. The encoding task consisted of six experimental runs, each containing 76 trials, yielding a total of 456 trials. Each trial consisted of three parts, a 1-second cue phase, a 3-second encoding period, and a 1.5-sec rating period (Figure 1). During the cue phase, a word was shown in the middle of the screen together with one of four icons, which indicated the specific trial condition. During the 3-second encoding period, subjects either imagined an image or sound (Internal encoding orientation – Int-Enc) associated with the cue word, or perceived an image or sound (Internal encoding orientation – Ext-Enc) associated with the cue word. During the rating period, participants rated on a 4-point scale (1 = low, 4 = high) either the subjective quality of the imagery experience during Int-Enc trials or the perceptual richness of the stimulus during Ext-Enc trials. For the purpose of the present study, these ratings were not used in the fMRI analyses. Individual encoding trials were jittered between 100 and 2100 msecs.
