Probing the Role of Feature Dimension Maps in Visual Cognition: Expt 2.1
试验速览
- 阶段
- 不适用
- 状态
- Enrolling By Invitation
- 入组人数
- 10
- 试验地点
- 1
- 主要终点
- Blood Oxygenation Level Dependent (BOLD) fMRI signal
研究概览
简要总结
How does one know what to look at in a scene? Imagine a "Where's Waldo" game - it's challenging to find Waldo because there are many 'salient' locations in the picture, each vying for one's attention. One can only attend to a small location on the picture at a given moment, so to find Waldo, one needs to direct their attention to different locations. One prominent theory about how one accomplishes this claims that important locations are identified based on distinct feature types (for example, motion or color), with locations most unique compared to the background most likely to be attended. An important component of this theory is that individual feature dimensions (again, color or motion) are computed within their own 'feature maps', which are thought to be implemented in specific brain regions. However, whether and how specific brain regions contribute to these feature maps remains unknown.
The goal of this study is to determine how brain regions that respond strongly to different feature types (color and motion) and which encode spatial locations of visual stimuli transform 'feature dimension maps' based on stimulus properties as a function of task instructions. The investigators hypothesize that feature-selective brain regions act as neural feature dimension maps, and thus encode representations of relevant location(s) based on their preferred feature dimension, such that the stimulus representation in the most relevant feature map is up-regulated to support adaptive behavior. The investigators will scan healthy human participants using functional MRI (fMRI) in a repeated-measures design while they view visual stimuli made relevant based on a cued feature dimension (e.g., color or motion). The investigators will employ state-of-the-art multivariate analysis techniques that allow them to reconstruct an 'image' of the stimulus representation encoded by each brain region to dissect how neural tissue identifies salient locations. Each participant will perform a challenging discrimination task based on the cued feature (report motion direction or color of stimulus dots) of a stimulus presented in the periphery, which are identical across trial types. Across trials the investigators will manipulate the attended feature value (color, motion, or fixation point). This manipulation will help the investigators fully understand these critical relevance computations in the healthy human visual system.
详细描述
In this experiment, participants will engage in all task conditions in a repeated-measures design. Participants are not randomly assigned to groups, as all participants will experience the same set of experimental manipulations. In this experiment, participants will engage in a series of challenging visual attention tasks while their eye position is tracked during fMRI scanning.
In all tasks, participants will perform challenging discrimination judgments based on a stimulus presented at the fixation point (discriminate the aspect ratio of a + target - wide or tall?), or a stimulus presented in the periphery (were the dots moving clockwise/counterclockwise? were the dots orange/cyan?). Behavioral responses will be recorded with a button press, which participants will make using a fMRI-compatible button box held in their right hand.
In this Experiment, the investigators will manipulate aspects of the behavioral task while keeping the stimulus display constant. These manipulations will allow the investigators to test the role of feature-selective retinotopic regions of interest (ROIs) in transforming spatial representations of salient locations as a function of task relevance to guide visual attention.
In this Experiment (Experiment 2.1), the investigators will present a single stimulus at a peripheral location on a blank background containing equiluminant colored moving dots (orange and cyan dots, moving both clockwise and counterclockwise around the stimulus center). Participants will be cued at the beginning of each trial to report either the most prominent color of the dots (orange or cyan), the most prominent motion direction (clockwise or counterclockwise), or to perform a fixation task. If attending to a feature dimension modulates the activation profiles within the corresponding dimension map, the investigators expect to see a selective enhancement of the stimulus representation in the dimension map of a region preferring the attended feature.
Participants will also be scanned for an anatomical & retinotopic mapping session, which will allow the investigators to identify brain regions for further analysis using well-established and standardized procedures.
研究设计
- 研究类型
- Interventional
- 分配方式
- Na
- 干预模型
- Single Group
- 主要目的
- Basic Science
- 盲法
- None
盲法说明
Participants will typically be unaware of the conditions presented, though because these involve manipulations of stimuli or task demands, they may be aware of the manipulation. This is not expected to impact the primary outcome measures (e.g., BOLD signal activation patterns).
入排标准
- 年龄范围
- 18 Years 至 55 Years（Adult）
- 性别
- All
- 接受健康志愿者
- 是
入选标准
- •between 18 and 55 years of age
- •normal or corrected-to-normal vision
排除标准
- •neurological disease based on self-report
- •implanted medical devices (e.g., cardiac pacemaker; metallic aneurism clip)
- •non-removable metallic piercings
- •metal fragments in the body (e.g., from welding)
- •pregnant and have a chance of being pregnant (if female)
- •history of claustrophobia
- •history of hearing loss/damage
研究组 & 干预措施
Manipulations of task demands (Expt 2.1)
Participants will view a single stimulus containing dots moving in one of two directions (clock-wise or counterclockwise) and drawn in one of two colors (orange and cyan). To complete the correct task for a trial, a cue at fixation will be manipulated.
干预措施: Stimulus properties: task-defining feature (Other)
结局指标
主要结局
Blood Oxygenation Level Dependent (BOLD) fMRI signal
时间窗: Through study completion, an average of two weeks
The investigators will use BOLD activation patterns measured from each retinotopic ROI to fit quantitative models of spatial encoding. These models will be used to reconstruct stimulus representations on experimental trials to quantify how stimulus representations are encoded in each brain region studied, and how these representations change across experimental manipulations. These measurements will be used to test the impact of stimulus manipulations on stimulus representations in different brain regions.
Behavioral response (button press)
时间窗: Through study completion, an average of two weeks
On attend-fixation trials, participants will be instructed to attend carefully to the fixation point and report the shape of a target '+' (wide or tall) by pressing one of two buttons held in their hand inside the scanner. The left button will indicate wide; the right button will indicate tall. On attend-color trials, participants will report whether more dots of the attended stimulus are orange (left button) or cyan (right button). On attend-motion trials, participants will report whether more of the dots of the attended stimulus are moving counterclockwise (left button) or clockwise (right button). The investigators will ensure participants are performing the task as instructed by assessing the accuracy of their behavioral responses.
Gaze position
时间窗: Through study completion, an average of two weeks
The investigators will use the measured gaze position in (x,y) coordinates to verify stable fixation throughout the experiment. Trials with poor fixation performance may be excluded from further analyses.
次要结局
未报告次要终点