Presentation 14

The experiments were run on a Windows computer (HP Z200 SFF; Hewlett-Packard Company, Tokyo, Japan) with a 19-inch CRT monitor (HM903D-A; Iiyama, Tokyo, Japan) using Presentation 14.9 software (Neurobehavioral Systems, San Francisco, CA, USA). The resolution of the monitor was 1024 × 768 pixels, and the refresh rate was 100 Hz, as confirmed by a high-speed camera (1000 frames/s; EXILIM FH100; Casio, Tokyo, Japan). A response box with a 2–3-ms RT resolution was used to obtain responses (RB-530; Cedrus, San Pedro, CA, USA). A chin-and-forehead rest was used to maintain a distance of 0.57-m between the participant and the monitor.

We utilized a Windows-based computer (HP Z200 SFF; Hewlett-Packard Company, Tokyo, Japan) equipped with a 19-inch CRT monitor (HM903D-A; Iiyama, Tokyo, Japan) and operated using Presentation 14.9 software (Neurobehavioral Systems, San Francisco, CA, USA). The monitor had a resolution of 768 vertical × 1024 horizontal pixels and a refresh rate of 100 Hz, verified using a 1000 frames/s camera (EXILIM FH100; Casio, Tokyo, Japan). Rests for the chin and forehead ensured a consistent 0.57 m distance between the participant and the monitor.

Data acquisition was performed in a 3T Tim Trio whole-body scanner (Siemens, Erlangen, Germany) equipped with a 32-channel head coil. Forty transverse slices were acquired in each volume using a T2^*-sensitive gradient EPI sequence (TR = 2.350 s, TE = 27 ms, voxel size 2.3 × 2.3 × 2.3 mm). Additionally, isotropic high-resolution (1 × 1 × 1 mm) T1-weighted coronal-oriented structural images were recorded. The course of the experiment as well as acquisition of the data during the experiment was controlled by Presentation 14.2 (Neurobehavioral Systems). Audio texts were presented using an in-ear sound system (Sensimetrics).

At the beginning of a trial, participants were instructed to memorize faces in scene images. One trial consisted of three images and each image was presented for 1 s. After an 8-second delay with fixation, a probe image for each encoded image was presented and serial recognition was performed by key press on the keyboard. Three recognition probes were presented in the order corresponding to the presentation sequence of the encoding images. Participants were instructed to press the “1” key when they saw the encoded face and to press “3” key when they saw a novel face as accurately and quickly as possible. To avoid a wrong key press, we set the key between the two response keys as invalid. Half of all probes in each condition of the experiment were novel faces. The frequency and the serial order of the novel probes in each trial were counterbalanced. To examine the influence of the context information of the backgrounds on recognition, we established three conditions: “Same,” “Different,” and “NB” (see Figure 1). The details of each condition are as follows:
In each condition, 14 trials were performed. The trials in each condition were randomly presented. Before the experiment began, participants completed a practice session of six trials. The experiment was performed on a Windows XP personal computer using Presentation 14.2 (Neurobehavioral Systems).

Stimulus presentation was controlled by Presentation 14.9 (Neurobehavioral Systems) implemented on a Windows computer (HP Z200 SFF, Hewlett-Packard Company). The stimuli were presented on a 19-inch CRT monitor (HM903D-A, Iiyama) with refresh rates of 150 Hz (Experiment 1) and 100 Hz (Experiment 2) and a resolution of 1024 × 768 pixels. The refresh rate was confirmed by a high-speed camera (EXILIM FH100, Casio) with a temporal resolution of 1000 frames/s.