Visual working memory: Study one Task fMRI and Behavioural response
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Subjects and MRI protocol ------------------------------------- Nineteen right-handed healthy adults (6 female, mean age 22.368, range 18-28 years of age) participated in this study on the same 3 T MRI scanner (TrioTim, software version syngo MR B17, Siemens, London,Ontario,Canada) by acquiring: - axial 3D T1-weighted images usign an MPRAGE sequence [echo time (TE) = 2.9 ms, inversion time = 900 ms, flip angle = 9°, slice thickness=1 mm, matrix size=256 x 240 x 384; - three runs of bold task fMRI images using a T2*-weighted echo-planar imaging (EPI) sequence (TR=2000 ms, TE=30 ms, flip angle=45°, slice thickness=3 mm; FOV=240 mm×240 mm, matrix size 80×80; number of slices=36; interleaved slice acquisition). Task protocol ------------------------------------ Participants were required to encode and maintain a set of features from an array of compound stimuli, composed of a pseudo-randomly selected numbers and fractals placed at random spatial positions within a 4 * 4 grid. Each trials began with a pre-encoding cue directing participants to focus on features from one of these three stimulus domains (number, fractal or spatial). Then, three, five or seven compound stimuli were presented within the 4 * 4 grid. After 10 seconds of encoding, stimuli were removed, and participants were required to maintain the features from the cued domain for 10 seconds. Subsequently, participants were presented with a probe array where one each of the numbers, fractals and locations had been shuffled. They were required to indicate within a 10s timeframe the location of the shuffled item that was within the currently maintained domain. The trial terminated at the point in time when the participant responded and the next trial began after a 10-second inter-trial-interval (ITI), during which a fixation cross was displayed and they were instructed to rest. In the imaging analysis, this (ITI) provided the baseline for comparing all other events, i.e., where no overt processing of the WM task was required. Defacing ------------------------------------ spm_deface was used on all anatomical images to ensure de-identification of subjects.
受试者与MRI扫描方案 ------------------------------------- 19名右利手健康成年人（6名女性，平均年龄22.368岁，年龄范围18~28岁）参与本研究，所有扫描均在同一台3T磁共振扫描仪（TrioTim型号，软件版本为syngo MR B17，西门子医疗，加拿大安大略省伦敦市）上完成，采集的图像包括： - 轴位3D T1加权成像：采用MPRAGE序列，参数为：回波时间（echo time, TE）=2.9 ms，反转时间（inversion time）=900 ms，翻转角（flip angle）=9°，层厚=1 mm，矩阵尺寸=256×240×384； - 三组血氧水平依赖（Blood Oxygenation Level Dependent, BOLD）任务态功能磁共振成像（functional magnetic resonance imaging, fMRI）：采用T2*加权回波平面成像（echo-planar imaging, EPI）序列，参数为：重复时间（repetition time, TR）=2000 ms，回波时间（echo time, TE）=30 ms，翻转角（flip angle）=45°，层厚=3 mm，视野（field of view, FOV）=240 mm×240 mm，矩阵尺寸80×80，扫描层数36层，采用交错层序采集模式。 任务范式 ------------------------------------- 受试者需编码并维持一组复合刺激阵列中的特征信息，该复合刺激由伪随机选取的数字与分形图形组成，随机放置于4×4网格的任意空间位置。每个试次首先呈现编码前置提示，指示受试者关注数字、分形图形或空间位置三个刺激域之一的特征。随后，在4×4网格中呈现3、5或7个复合刺激。经过10秒的编码阶段后，刺激消失，受试者需维持提示域的特征信息达10秒。之后向受试者呈现探测阵列，其中数字、分形图形与空间位置各有一项被打乱。受试者需在10秒内指出当前维持域内被打乱项目的对应位置。试将于受试者做出反应时即刻终止，随后进入10秒的试间歇期（inter-trial-interval, ITI），期间呈现注视十字，要求受试者放松休息。在磁共振成像分析中，该试间歇期作为基线条件，用于对比所有其他任务事件，即此时无需对工作记忆（working memory, WM）任务进行外显加工。 图像去标识 ------------------------------------- 对所有解剖图像使用spm_deface工具进行处理，以确保受试者的身份信息完全去标识化。
