PMC:2813722 / 8409-14158
Annnotations
{"target":"http://pubannotation.org/docs/sourcedb/PMC/sourceid/2813722","sourcedb":"PMC","sourceid":"2813722","source_url":"https://www.ncbi.nlm.nih.gov/pmc/2813722","text":"Materials and Methods\n\nParticipants\nParticipants were 37 English-speaking 5-year-olds (M age = 5.28 years, SD = 0.54, Range = 4.10–6.00), including 20 children (9 boys and 11 girls) from a European-Canadian background (M age = 5.38 years, SD = 0.41) and 17 children (5 boys and 12 girls) from a Chinese-Canadian background (M age = 5.18 years, SD = 0.65), who were recruited through a computerized database containing names of parents who have expressed interest in their child's participation in research. Children from the two cultural groups did not differ in age, t(35) = 1.13, p \u003e 0.26, or in the proportion of boys in the group, χ2(1, N = 37) = 0.36, p \u003e 0.55. Chinese-Canadian children were second-generation immigrants from China and European-Canadian children were second-generation (or more) immigrants from Europe. Five of the European-Canadian parents and 15 of the Chinese-Canadian parents indicated that more than one language was spoken in the home. Most European-Canadian parents had post-secondary education (mothers 85%; fathers 65%) and were mostly employed in managerial and professional, clerical, sales, and entertainment occupations. All of the Chinese-Canadian parents had post-secondary education and were mostly employed in managerial and professional, sales, and industrial processing occupations. In addition, parents were administered an individualism–collectivism questionnaire (Triandis, 1995), and no significant difference was found between the two cultural groups on either the individualism, F(1, 33) = 2.89, p \u003c 0.10, ηp2=0.08, or collectivism, F(1, 33) = 0.00, p \u003c 0.98, ηp2=0.00, dimension. All children had normal or corrected-to-normal vision, and were free of any psychiatric diagnoses or medication. An additional 17 participants were tested but eliminated from the final analysis because (a) they refused to wear the EEG net (see below), n = 7, (b) they had fewer than 11 correct no-go trials that that were free of eye blinks or movement artifacts, n = 9, or (c) their data were not recorded due to technical difficulties, n = 1. Recruitment and all procedures were approved by the appropriate Research Ethics Board at the University of Toronto, in accord with the Canadian Tri-Council Policy Statement: Ethical Conduct for Research Involving Humans.\n\nProcedure\nChildren were given a brief introduction to the testing environment and the EEG system, and parental informed consent (and child assent) was obtained for all participants. The experimenter then applied a 128-channel HydroCel Geodesic Sensor Net to the child's head, the child was seated in front of a computer monitor with the distance and alignment to the monitor controlled, and the go/no-go task was administered. This task, which was adapted from Durston et al. (2002b), was presented using E-Prime Version 1.2 (PST, Pittsburgh, PA, USA). On each trial, an animal stimulus (cow, horse, bear, pig, or dog) was presented at a central location on the screen. During a block of 10 practice trials (6 go, 4 no-go), the child was instructed to press a sticker-covered key on a keyboard as soon as they saw each animal (go stimuli) except for the dog (no-go stimulus). They were told not to press when they saw the dog. The practice block was repeated until children were correct on at least 9/10 trials. The task itself consisted of 144 trials divided into four blocks. In each block, 27 (75%) of the trials were go trials and 9 (25%) were no-go trials. This ratio encouraged a pre-potent tendency to respond. No-go trials were preceded by two, three, or four go trials. On each trial, a fixation point in the form of a “pokeball” appeared at a central location on the screen, along with a “ding” sound, and lasted 1500 ms. Next, an animal stimulus was presented for 1500 ms. In order to increase children's motivation to complete the task, feedback was given following each response. Positive feedback following correct responses was provided by a bright yellow smiley face, and negative feedback following incorrect responses, omitted responses, and responses that occurred after the 1500 ms stimulus window, was provided by a red frowning face. Feedback stimuli were shown for 500 ms (see Figure 1 for trial structure). Accuracy on go and no-go trials was recorded, as was reaction time (RT) on correct go trials.\nFigure 1 Go/no-go task trial structure. During the go/no-go task, EEG data were sampled at 1000 Hz using EGI Netstation 4.1.2 software (EGI, Eugene, OR, USA), and impedances were maintained below 40 kΩ. Electrodes were referenced to Cz during recording. Editing of the EEG for eye blinks, eye movements, movement artifacts, signals exceeding 200 μV, and fast transits exceeding 100 μV was carried out offline, and all trials containing more than 20% artifacts were eliminated from analysis. During averaging, all data were re-referenced to the average reference of all 128 sites (Tucker et al., 1993). Data were filtered using a Finite Impulse Response 1–30 Hz bandpass filter. Stimulus-locked data were segmented into epochs ranging from 200 ms prior to stimulus onset to 1000 ms after onset. ERP data from correct trials (go and no-go) were baseline corrected using the first 200 ms of each segment. The N2 was then coded as the largest negative deflection after the P1 with a fronto-central topography and a latency of 250–500 ms post-stimulus. N2 latency was recorded as the latency from stimulus onset to the peak identified in the amplitude analysis. The mean number (and SD) of trials contributing to the N2 was 70.92 (18.93) for go trials and 23.81 (5.98) for no-go trials, and there were no differences in trial count between cultural groups for either go trials, t(35) = −1.02, ns, or no-go trials, t(35) = −0.07, ns.","divisions":[{"label":"title","span":{"begin":0,"end":21}},{"label":"sec","span":{"begin":23,"end":2294}},{"label":"title","span":{"begin":23,"end":35}},{"label":"p","span":{"begin":36,"end":2294}},{"label":"title","span":{"begin":2296,"end":2305}},{"label":"p","span":{"begin":2306,"end":4320}},{"label":"figure","span":{"begin":4321,"end":4361}},{"label":"label","span":{"begin":4321,"end":4329}},{"label":"caption","span":{"begin":4331,"end":4361}},{"label":"p","span":{"begin":4331,"end":4361}}],"tracks":[]}