Task irrelevant Affective Processing--论文代写范文精选

  简单的几何数据作为标准，刺激被分配到四块,异常刺激包含10类,每次都完全重复一次任务。正如所料,其事后测试显示,由于主观评级差异,唤起快乐的照片最初作为协变量,对ERP分析有重大影响。下面的report代写范文进行了详述。

  Abstract
  Participants :Sixteen younger adults(mean age=21.6, SD=3.89; range: 17～26 years; eight females) and sixteen older adults (mean age=69.7, SD=3.20; range: 61～75 years; nine females) participated in the ERP study and received monetary compensation for their participation. Younger adults were recruited from two local universities, and older adults were from the community centers nearby. All were right-handed with normal or corrected-to-normal vision and had no known reading or neurological disorders, and older adults had high scores on the Mini-Mental Status Examination [14] (mean score = 28.75, SD = 1.44), consistent with intact cognitive function. 

  Older adults scored significantly lower than the young on the depression and anxiety emotional measurements (CES-D, STAI-State, and STAI-Trait)[15-16] , indicating that older adults had less negative feelings in daily life. In addition, older adults showed some signs of deteriorated cognitive ability in terms of reduced processing speed (Trail making A) [17] and fluidThis study was approved by the ethics committees of the Institute of Psychology, Chinese Academy of Sciences. Signed informed consent has been obtained from each participant, and for one participant aged 17 also has informed consent signed by her parents.

  Stimuli The task used a total of 800 stimuli of three types: simple geometric figures served as standard items (n = 560, 70%), similar geometric figures 20% larger than the standard items served as targets (n = 120, 15%), and images from the normalized Chinese Affective Picture System (CAPS)[19] served as deviants (n = 120, 15%). The stimuli were assigned to four blocks, and within each block standard stimuli were one of four blue geometric figures (i.e. square, circle, triangle, or diamond). The deviant stimuli contained 10 each of three kinds of valenced stimuli (i.e. neutral, happy, and sad faces) in each block, and each deviant stimulus was repeated exactly once in the task. Although these pictures had been normalized, in the present study they were selected out of CAPS on the basis of re-normalized valence and arousal ratings from both younger (n = 15) and older adults (n = 15) who did not participate in the ERP experiment. Valence rating was comparable for both younger and older adults, and the valence effect was significant (F (2, 76) = 1492.44, P < 0.001). 

  As expected, post-hoc tests revealed that the lowest valence was assigned to sad pictures, an intermediate valence was assigned to neutral ones, and the highest valence was assigned to happy ones, all P < 0.001 . For arousal ratings, there was a significant interaction between age and valence (F (2, 76) = 9.24, P < 0.001 ). For the happy pictures, older adults reported higher arousal than younger adults (F (1, 38)= 16.32, P < 0.001), while the sad and neutral faces were comparably-rated between groups (sad, F (1, 38) = 1.91, P = 0.175; neutral, F (1, 38) = 0.03, P = 0.855). 

  To summarize, in the valence dimension, the two groups had the same across-category valence judgments; in the arousal dimension, older adults reported more arousal for the happy pictures than did the young (Table 2). Because of this subjective rating differences, arousal rating for happy pictures were initially included as a covariate in group comparisons, but they were later dropped from the analyses because they were not found to exert any significant effects on ERP analyses. All the stimuli were pseudo-randomized within each block for each participant, such that (1) the mean ratings of valence and arousal of three kinds of affective faces did not differ from one block to another; (2) neither target nor deviant stimuli occurred as the initial item in any presented series; (3) neither target nor deviant stimulus categories occurred more than three times consecutively.

  Procedure After participants signed an informed consent form and received applications for ERP recording, they were seated in a comfortable chair approximately 60 cm from the computer screen in a dimly-lit, sound-attenuated room. They were asked to react as quickly as possible by pressing the spacebar when they detected geometric figures larger than the standard ones. Participants were not asked to judge or otherwise respond to the deviant stimuli. Each stimulus was displayed sequentially on the center of the computer screen (17义) on a black background. The standard and target stimuli were presented for 500 ms, occupying about 5毅 of horizontal visual angle, while the deviant pictures were presented for 750 ms, occupying about 10毅 of horizontal visual angle [20] . The stimulus-onset asynchrony (SOA) varied randomly between 900 ～ 1 000 ms. Example trails from the oddball task are shown in Figure 1. Prior to the experimental blocks, participants received two practice blocks including 30 items. The experimental session lasted about 30 min.

  ERP recording and analysis 
  The EEG was recorded from 64 Ag/AgCl electrodes mounted in an elastic cap (Quick-Cap, NeuroScan Inc., USA). Recordings were referenced to the left mastoid, but re-referenced to linked mastoids offline. The horizontal electrooculogram (EOG) was recorded from electrodes placed at the outer canthus of each eye, and the vertical EOG was recorded from electrodes placed above and below the participants' left eye. Electrode impedances were kept below 5 k赘. The EEG and EOG were amplified with online high-low band pass filtering (0.05 ～100 Hz) and recorded continuously with a digitization rate of 1 000 Hz. ERPs were computed for each participant, condition, and electrode site. 

  A 30 Hz low-pass filter was applied offline to the continuous EEG data. The epoch interval was 1 000 ms, ranging from 100 ms before the onset of the deviant stimuli to 900 ms after it. Epochs with EEG exceeding 依100 滋V were excluded from the averages through artifact rejection. The overall rejection rate was 4.32% for younger adults and 3.86% for the older ones, equal for all three kinds of affective pictures in both groups (younger adults, Happy: 5.31% , Neutral: 4.06% , Sad: 3.75% ; older adults, Happy: 4.84%, Neutral: 2.97%, Sad: 2.97%). Two time windows were chosen on the basis of visual inspection and earlier studies: (a) 270 ～420 ms in younger adults and 320 ～470 ms in older adults for P3a effects and (b) 500～700 ms in younger adults and 650～850 ms in older adults for positive slow wave (PSW) of deviant stimuli. 

  All statistical analyses were performed on the mean amplitudes in the selected time windows. ERPs were analyzed separately for midline and lateral electrodes. Omnibus ANOVAs for lateral electrodes included four within-subject factors: time window (P3a, PSW), hemisphere (left, right), region (frontal, central, parietal), and valence (happy, neutral, sad); and one between-subject variable age group (older adults, younger adults). Crossing the variables of region and hemisphere yielded six regions of interest (ROIs), with two electrodes for each ROI: left frontal (F3, F5); left central (C3, C5); left parietal (P3, P5); right frontal (F4, F6); right central (C4, C6); and right parietal (P4, P6). Omnibus ANOVAs for midline electrodes included three within-subject factors: electrode (Fz/Cz/Pz), time window, and valence; and one between-subject variable age group. Only effects involving valence are reported.(paper代写)

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