MOA_Attention_MEG_data
Creators: name: Liu, Chunyu
Publisher: name: figshare
Year: 2023
Subjects: classificationCode: 320904
subject: Computational neuroscience (incl. mathematical neuroscience and theoretical neuroscience)

description: <b>Participants</b>Thirty-three participants (eight males; aged 18-27) were recruited from Peking University, China. Two participants were excluded due to excessive head movements or poor behavior results. All participants were right-handed, had normal or corrected-to-normal vision, and had no history of the neurological or psychiatric disorders. They provided informed consent following the protocol approved by the Human Subject Review Committee of Peking University.<b>Stimuli</b>Stimuli were consisted of four facial images selected from Chinese affective picture system<sup>31</sup>, and four building images chosen from outdoor scenes (http://cvcl.mit.edu/database.htm) (as depicted in <b>Fig 1.A</b>). These facial images belonged to four different individuals (2 males and 2 females), all displaying neutral expressions. To ensure uniformity, all images were converted to grayscale and normalized to a size of 300×300 pixels, with consistent luminance adjustments using the Photoshop toolbox. Subsequently, these images were projected onto a translucent screen using a video projector, operating at a refresh rate of 60HZ and a spatial resolution of 1024 × 768, positioned in front of the MEG scanner. The images subtended a visual angle of 5.82° × 5.41°. For the generation and presentation of these visual stimuli, we utilized the Psychtoolbox, an extension for MATLAB software.<b>Experimental procedure</b>Our experiment comprises of two distinct experimental paradigms. In experimental paradigm 1 (<b>Fig 1. B</b>), we aim to define four object-based attention states concerning two objects. These attention states can be categorized as follow: (1) State 1, paying attention to the facial stimulus on the left screen when only one stimulus is present on the screen. (2) State 2, paying attention to the building stimulus on the right screen when only one stimulus is present on the screen. (3) State 3, paying more attention to the facial stimulus on the left screen when two stimuli are present on the screen. (4) State 4, paying more attention to the building stimulus on the right screen when two stimuli are present on the screen. The experimental paradigm 2 (<b>Fig 1.C</b>) is design to describe the process of the object-based attention when viewing two objects simultaneously. To demonstrate that sample rhythmically between two objects, we incorporate the concept of flash event design introduced by Laudau et al<sup>19</sup>. Where, flash events were employed to reset the attentional focus. In our experiment, a flash event comprised four dots, each briefly presented for 33 milliseconds. Each dot subtended a visual angle of 0.73° × 0.73°.Experiment 1 consists of 4 runs, with each run comprising 25 trials for each attention state, and the trial order was randomized. In each trial, the stimulus for each attention state was presented for a duration of 2 seconds, followed by 2 seconds grey screen. During trials involving the observation of two objects, participants were prompted to focus more on the direction by left or right arrows before the presentation of the two objects. In each run, participants were instructed to press either a right or left button using their right or left index finger if a red square flashed quickly in the right or left the screen. During each trial, participants were directed to concentrate on the fixed point, represented by a green cross, located at the center of the screen. All data from the four runs were combined for analysis.Experiment 2 consists of 2 runs. In each run, there are 50 trails for each condition (right or left reset flash) and the trails order was randomized. Each trail commenced with a 1500ms blank interval, followed by the appearance of two objects (a left face or a right building) on screen for 2 seconds. Subsequently, the flash event (either left or right) occurred. Following that, there was an interval of 4 seconds for both objects to be displayed simultaneously. During each trail, participants were instructed to press either a right or left button using their right or left index finger if a red square flashed quickly in the right or left of the screen. Simultaneously, the participants were asked to maintain their focus on a fixed point represented by a green cross at the center of the screen.<b>MEG data acquisition and preprocessing</b>The ongoing neural response to the stimulus material was collected using a 306-channel whole-head MEG system (Elekta-Neuroimage, Helsinki, Finland) within a magnetically shield room. The Dewar helmet was lined with foam wedges before being placed on the subject’s head to ensure stability. The positions of the four head position indicator coil were measure at the beginning of each run. A wooden head supporter was employed to ensure the head displacements between runs remained under 5 mm. MEG data were sampled at 1000Hz. Structural of MRI of all participants’ heads were acquired using a Siemens Magnetom Prisma 3-T MRI system at Peking University. A 3D magnetization-prepared rapid gradient echo T1-weighted sequence was utilized to obtain anatomical image with a resolution of 1× 1 × 1.33 mm<sup>3</sup>.