Neurocognitive Basis of Attention and Eye Movement Guidance in the Real World Scenes

Study Overview
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Brief Summary
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The objective of this study is to determine the effects of electrical brain stimulation (EBS) on visual search in natural scenes in humans.

Detailed Description
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The ability to conduct a visual search for an object in a naturalistic scene is a crucial component of everyday interactions with the environment. This process requires the recognition of different items, accessing stored semantic knowledge about those items and their relationships with other objects, and guiding vision based on that knowledge. Classical models of attention emphasize low-level visual salience maps for attentional guidance. However, behavioral studies increasingly support a role for object knowledge in guiding attention and eye movements. Despite strong behavioral evidence that conceptual information about objects and scenes is critical for real world guidance of attention, very little is known about the neural basis of the guidance of attention based on meaning. Previous human imaging studies have identified several brain regions that represent object and scene/context knowledge as it relates to visual recognition. In particular, regions of the temporal lobes (inferior temporal regions (ITC), parahippocampal cortex (PHC), and the hippocampus) are critical for perceiving and understanding objects, but little is known about the role of these individual regions in how they interact to guide attention and eye movements in real-world scenes. Electrical brain stimulation is routinely performed clinically in the surgical treatment of epilepsy patients, both intraoperatively and using implanted electrodes. It is used as standard of care both to map eloquent brain function prior to surgical treatment for epilepsy and to map the seizure network. The purpose of this study is to gain a better understanding of the information flow and neural dynamics of the brain, examining the impact of electrical brain stimulation on stimulus search time, accuracy, and eye movement trajectories.

Official Title
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Neurocognitive Basis of Attention and Eye Movement Guidance in the Real World Scenes

Conditions
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Cognition, Attention, Eye Movements

Intervention / Treatment
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* Device: Electrical Brain Stimulation
* Device: Sham Electrical Brain Stimulation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Have intracranial EEG electrodes implanted for stage II epilepsy planning. Have adequate cognitive and communication ability to give informed consent, understand instructions, and follow direction. Be able to understand the tasks and provide responses. IQ > 75 (done as part of standard-of-care neuropsychological testing as part of the surgical treatment for epilepsy) Speak English Exclusion Criteria: Inability to understand or perform the tasks outlined in this protocol In excessive postoperative discomfort.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Interventional Model Description: All participants will undergo both electrical brain stimulation (EBS) and sham electrical brain stimulation (SEBS) at brain locations where alteration of visual attention behavior is expected to occur, as well as at control locations. The participants will be informed that they will receive both EBS and SEBS, but blinded to the location of each trial and whether the trial is EBS or SEBS. Participants will also be blinded to the objectives of stimulation. The order of stimulation locations and whether the trial is EBS or SEBS will be randomized.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Electrical and Sham Electrical Brain Stimulation<br>Electrical brain stimulation and sham electrical brain stimulation will be administered to all participants. | Device: Electrical Brain Stimulation<br>* Electrical Brain Stimulation (EBS) will be used to disrupt local neural activity in inferior temporal regions (ITC), parahippocampal cortex (PHC), the hippocampus, and control regions. The effects of EBS will be examined on attention and eye movement behavior, and all participants will receive both EBS and sham electrical brain stimulation.<br>Device: Sham Electrical Brain Stimulation<br>* Sham electrical brain stimulation (SEBS) will be applied to inferior temporal regions (ITC), parahippocampal cortex (PHC), the hippocampus, and control regions. The effects of SEBS will be examined on attention and eye movement behavior, and all participants will receive both SEBS and EBS.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Incidence of eye fixations during electrical brain stimulation (EBS) vs. sham electrical brain stimulation (SEBS). | Eye fixations will be assessed using an eye tracking device, which collects videos of eye movements. Participants will be presented with an image of a scene, and asked to locate a target object. The incidence of eye fixations occurring before participants locate the target object will be measured at preferred and control brain regions during EBS and SEBS. | Eye fixation incidence will be assessed during the intervention, through study completion, up to 1 week on average. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Search time for target object during EBS vs. SEBS. | Visual search time will be assessed by asking participants to answer a simple question about a target object in an image of a scene as quickly and accurately as possible. The question will presented to the participants, followed by the image of the scene. The search time to locate the target object and respond to the question will be measured at preferred and control brain regions during EBS and SEBS. | Search Time will be assessed during the intervention, through study completion, up to 1 week on average. | 
| Identification accuracy during EBS vs. SEBS. | Identification accuracy rate will be assessed based on the participants' correct responses for identifying a target object in an image of a scene (described in Outcomes 1 and 2). The search time to locate the target object will be measured at preferred and control brain regions during EBS and SEBS. | Identification accuracy will be assessed during the intervention, through study completion, up to 1 week on average. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Visual Attention, Naturalistic Vision, Intracranial Electroencephalography, Electrical Brain Stimulation