Probing the Role of Feature Dimension Maps in Visual Cognition: Impact of Task Demands (Expt 2.1)

NCT ID: NCT06281457

Last Updated: 2024-08-21

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

ENROLLING_BY_INVITATION

Clinical Phase

NA

Total Enrollment

10 participants

Study Classification

INTERVENTIONAL

Study Start Date

2024-04-01

Study Completion Date

2025-06-30

Brief Summary

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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.

Detailed Description

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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.

STATISTICAL DESIGN \& POWER

The fMRI studies described in this study record employ an inverted encoding model (IEM) for spatial position to quantify stimulus representations in reconstructed spatial maps of the visual field based on activation patterns measured in retinotopic feature-selective ROIs. The investigators rigorously identify ROIs using independent retinotopic mapping and localizer techniques, and use a 'mapping' task to estimate a 'fixed' encoding model for use across all conditions in each Experiment reported. These design decisions ensure that the investigators can maximize their ability to detect effects of their manipulations of interest within individual participants and brain regions and maximize the statistical power. The investigators use a compromise between deep imaging of several experimental and stimulus conditions within individual participants and aggregation of data across a moderate sample of these deeply-imaged participants (n = 10; see below). This allows the investigators to attain high-quality, reproducible estimates of model-based stimulus representations across task and stimulus manipulations within individual participants and conduct statistical inference on these measurements across the study sample.

fMRI analyses will be conducted within each participant's individual brain, and voxels are assigned 'region' labels according to independent criteria (functional retinotopic mapping). Accordingly, there are no comparisons that require precise alignment of brain tissue between participants, and no generation of group-averaged 'maps' of brain activation. As such, concerns about reproducibility of brain maps and associated statistical power concerns are irrelevant to this study design.

The statistical design of the study is a repeated-measures design, whereby each participant is exposed to all manipulations in the study. The order of manipulations each participant experiences is randomized across participants. The investigators will employ nonparametric randomization tests for all statistical comparisons whereby they will conduct hypothesis testing (e.g., repeated-measures analysis of variance) using 'shuffled' data (misaligned condition labels relative to measured map activation on each trial) to generate a null distribution of test statistics under the null hypothesis of no effect of their independent variable(s). Once this procedure is repeated extensively (1,000 times) per test, the p-value can be estimated by comparing the test statistic computed using intact labels to this null distribution, and corrected for multiple comparisons as appropriate (e.g., via false discovery rate). Using permutation procedures to generate a null distribution minimizes reliance on parametric assumptions.

Additionally, the experiments within the study are designed such that sufficient data will be acquired that data from each individual participant can be used to test the effects of interest. Accordingly, each participant can be considered independent 'replication' of each other participant. Previous studies adopting a similar methodology whereby IEM-based reconstructions of visual stimuli are compared between conditions have employed relatively small sample sizes (n = 7-8). Other studies using population receptive field models or location-specific functional localizer, which are in principle very similar to the approach employed here, have used smaller sample sizes (e.g., n = 6).

Sample size \& statistical power:

In this study, the investigators will acquire an intermediate sample size with extensive data per task condition (n = 10; 2 experimental fMRI sessions, each 1.5-2 hrs, for each participant; along with a 2-hr anatomical imaging and retinotopic mapping fMRI session). Of particular interest, one study used n = 6 participants to establish with a large effect size dz = 3.52 that V1 voxels tuned to a stimulus location where a salient stimulus was defined by feature contrast respond more strongly than when feature contrast is absent. In another study, similar effect sizes were reported by this group in a color-selective ROI known as hV4 (n = 6; dz = 1.06 and 1.80 for orientation- and motion-based contrast, respectively).

Accordingly, assuming a conservative effect size of 0.90 (based on those reported previously), the investigators expect a sample size of n = 10 will allow the study to be well-powered (80%, α = 0.05) to detect a similar change in Experiment 1.1, which is most analogous to this study (one-tailed paired T-test).

Additionally, the investigators used their pilot data (n = 3) to measure the effect size for the critical comparison between salience-related modulations between feature-selective regions to be dz = 3.10 for the salience-defining feature. These values are commensurate with those cited above, and further support the selection of sample size. If analyses of data acquired during further pilot testing \& experiment refinement suggest smaller effect sizes, the investigators will refine the power analyses and adjust the projected enrollment accordingly to ensure robust and reproducible results. Note that this power analysis relies on parametric assumptions which will not be required for the proposed analyses, which invoke randomization methods to compute empirical null distributions.

Conditions

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Basic Science: Visual Attention in Healthy Participants Basic Science: Neural Representations of Location

Study Design

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Allocation Method

NA

Intervention Model

SINGLE_GROUP

This is a basic science study in which all participants will participate in all task conditions within each experiment (repeated-measures design).
Primary Study Purpose

BASIC_SCIENCE

Blinding Strategy

NONE

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).

Study Groups

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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.

Group Type EXPERIMENTAL

Stimulus properties: task-defining feature

Intervention Type OTHER

The feature used to determine which stimulus feature to attend to will be varied across trials using a letter cue (M = motion-attend, C = color-attend, F = fixation-attend)

Interventions

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Stimulus properties: task-defining feature

The feature used to determine which stimulus feature to attend to will be varied across trials using a letter cue (M = motion-attend, C = color-attend, F = fixation-attend)

Intervention Type OTHER

Eligibility Criteria

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Inclusion Criteria

* between 18 and 55 years of age
* normal or corrected-to-normal vision

Exclusion Criteria

* 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
Minimum Eligible Age

18 Years

Maximum Eligible Age

55 Years

Eligible Sex

ALL

Accepts Healthy Volunteers

Yes

Sponsors

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National Eye Institute (NEI)

NIH

Sponsor Role collaborator

University of California, Santa Barbara

OTHER

Sponsor Role lead

Responsible Party

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Responsibility Role SPONSOR

Principal Investigators

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Tommy C Sprague

Role: PRINCIPAL_INVESTIGATOR

University of California, Santa Barbara

Locations

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University of California, Santa Barbara

Santa Barbara, California, United States

Site Status

Countries

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United States

References

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Mackey WE, Winawer J, Curtis CE. Visual field map clusters in human frontoparietal cortex. Elife. 2017 Jun 19;6:e22974. doi: 10.7554/eLife.22974.

Reference Type BACKGROUND
PMID: 28628004 (View on PubMed)

Hallenbeck GE, Sprague TC, Rahmati M, Sreenivasan KK, Curtis CE. Working memory representations in visual cortex mediate distraction effects. Nat Commun. 2021 Aug 5;12(1):4714. doi: 10.1038/s41467-021-24973-1.

Reference Type BACKGROUND
PMID: 34354071 (View on PubMed)

Sprague TC, Itthipuripat S, Vo VA, Serences JT. Dissociable signatures of visual salience and behavioral relevance across attentional priority maps in human cortex. J Neurophysiol. 2018 Jun 1;119(6):2153-2165. doi: 10.1152/jn.00059.2018. Epub 2018 Feb 28.

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Sprague TC, Adam KCS, Foster JJ, Rahmati M, Sutterer DW, Vo VA. Inverted Encoding Models Assay Population-Level Stimulus Representations, Not Single-Unit Neural Tuning. eNeuro. 2018 Jun 5;5(3):ENEURO.0098-18.2018. doi: 10.1523/ENEURO.0098-18.2018. eCollection 2018 May-Jun. No abstract available.

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Sprague TC, Boynton GM, Serences JT. The Importance of Considering Model Choices When Interpreting Results in Computational Neuroimaging. eNeuro. 2019 Dec 20;6(6):ENEURO.0196-19.2019. doi: 10.1523/ENEURO.0196-19.2019. Print 2019 Nov/Dec.

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Laumann TO, Gordon EM, Adeyemo B, Snyder AZ, Joo SJ, Chen MY, Gilmore AW, McDermott KB, Nelson SM, Dosenbach NU, Schlaggar BL, Mumford JA, Poldrack RA, Petersen SE. Functional System and Areal Organization of a Highly Sampled Individual Human Brain. Neuron. 2015 Aug 5;87(3):657-70. doi: 10.1016/j.neuron.2015.06.037. Epub 2015 Jul 23.

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Fedorenko E. The early origins and the growing popularity of the individual-subject analytic approach in human neuroscience. Current Opinion in Behavioral Sciences. 2021; 40:105-112.

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Naselaris T, Allen E, Kay K. Extensive sampling for complete models of individual brains. Current Opinion in Behavioral Sciences. 2021; 40:45-51.

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Poldrack RA. Diving into the deep end: a personal reflection on the MyConnectome study. Current Opinion in Behavioral Sciences. 2021; 40:1-4.

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Pritschet L, Taylor CM, Santander T, Jacobs EG. Applying dense-sampling methods to reveal dynamic endocrine modulation of the nervous system. Curr Opin Behav Sci. 2021 Aug;40:72-78. doi: 10.1016/j.cobeha.2021.01.012. Epub 2021 Feb 25.

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PMID: 35369044 (View on PubMed)

Gratton C, Nelson SM, Gordon EM. Brain-behavior correlations: Two paths toward reliability. Neuron. 2022 May 4;110(9):1446-1449. doi: 10.1016/j.neuron.2022.04.018.

Reference Type BACKGROUND
PMID: 35512638 (View on PubMed)

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Reference Type BACKGROUND
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Sprague TC, Serences JT. Attention modulates spatial priority maps in the human occipital, parietal and frontal cortices. Nat Neurosci. 2013 Dec;16(12):1879-87. doi: 10.1038/nn.3574. Epub 2013 Nov 10.

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Itthipuripat S, Vo VA, Sprague TC, Serences JT. Value-driven attentional capture enhances distractor representations in early visual cortex. PLoS Biol. 2019 Aug 9;17(8):e3000186. doi: 10.1371/journal.pbio.3000186. eCollection 2019 Aug.

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Reference Type BACKGROUND
PMID: 28381491 (View on PubMed)

Other Identifiers

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R01EY035300

Identifier Type: NIH

Identifier Source: secondary_id

View Link

5-24-0030: 2.1

Identifier Type: -

Identifier Source: org_study_id

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