Visual Features for Neural Representations of Location

Overseen ByEmily Machniak

Age: 18 - 65

Sex: Any

Trial Phase: Academic

Sponsor: University of California, Santa Barbara

Disqualifiers: Neurological disease, Implanted devices, Pregnancy, others

No Placebo GroupAll trial participants will receive the active study treatment (no placebo)

Trial Summary

What is the purpose of this trial?

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.

Do I need to stop my current medications for this trial?

The trial information does not specify whether you need to stop taking your current medications.

What data supports the effectiveness of the treatment Stimulus properties: task-defining feature?

Research suggests that visual memory can be formed without specific spatial details, and certain neurons in the brain can recognize objects regardless of changes in size, position, or angle. This indicates that focusing on specific features, like color, can help in accurately identifying and remembering visual targets, which supports the idea that task-defining features can enhance visual processing and memory.¹ ² ³ ⁴ ⁵

How does the treatment 'Stimulus properties: task-defining feature' differ from other treatments for visual location representation?

This treatment is unique because it focuses on the specific visual features that define a task, rather than relying on spatial location information. It explores how visual events can be remembered without precise spatial coordinates, which is different from traditional methods that emphasize spatial location in visual processing.¹ ⁶ ⁷ ⁸ ⁹

Research Team

Tommy C Sprague

Principal Investigator

University of California, Santa Barbara

Eligibility Criteria

This trial is for healthy individuals interested in how the brain processes visual information. Participants should be willing to undergo fMRI scans and perform visual tasks that involve discriminating colors or motion of stimuli. Specific eligibility criteria are not provided, but typically participants would need to have no contraindications to fMRI.

Inclusion Criteria

My vision is normal or corrected to normal with glasses or contacts.

Exclusion Criteria

Non-removable metallic piercings

Pregnant or have a chance of being pregnant (if female)

Implanted medical devices (e.g., cardiac pacemaker; metallic aneurism clip)

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Timeline

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Anatomical & Retinotopic Mapping

Participants undergo anatomical and retinotopic mapping to identify brain regions for further analysis

2 hours

1 visit (in-person)

Experimental fMRI Sessions

Participants engage in visual attention tasks during fMRI scanning to study feature dimension maps

3-4 hours

2 visits (in-person)

Follow-up

Participants are monitored for safety and effectiveness after the experimental sessions

2 weeks

Treatment Details

Interventions

Stimulus properties: task-defining feature

Trial Overview The study examines how certain brain regions process and prioritize visual features like color or motion when performing a task. Using advanced imaging (fMRI) and analysis techniques, researchers will track how these regions create 'feature dimension maps' that guide attention in complex scenes.

Participant Groups

1Treatment groups

Experimental Treatment

Group I: Manipulations of task demands (Expt 2.1)Experimental Treatment1 Intervention

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.