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Purpose

The study is a multi-site study and will be conducted at up to 11 investigative sites in the United States. The study will investigate subcortical arousal circuits in visual perception using techniques with complementary strengths based on promising initial studies.

Condition

Eligibility

Eligible Ages
Over 13 Years
Eligible Sex
All
Accepts Healthy Volunteers
No

Inclusion Criteria

  • normal vision with or without the use of corrective lenses

Exclusion Criteria

  • severe vision impairment even with correction preventing ability to see stimuli (prevents accurate pupil and eye gaze measurements) - unable to perform the perception task due to cognitive impairment. All participants must be capable of consenting for themselves. The following are the inclusion/exclusion criteria for epilepsy patients with thalamic electrodes age 18 years and up (Aim 2): Inclusion Criteria: - normal vision with or without the use of corrective lenses - a female subject must have a negative pregnancy test and if sexually active, must be using a reliable form of birth control for the duration of the trial, be surgically sterile, or be at least two years post-menopausal. Exclusion Criteria: - severe vision impairment even with correction preventing ability to see stimuli (prevents accurate pupil and eye gaze measurements) - unable to perform the perception task due to cognitive impairment. All participants must be capable of consenting for themselves. - pregnancy

Study Design

Phase
N/A
Study Type
Interventional
Allocation
Non-Randomized
Intervention Model
Parallel Assignment
Primary Purpose
Treatment
Masking
None (Open Label)

Arm Groups

ArmDescriptionAssigned Intervention
Experimental
Thalamic Recording (Aim 1) 		Participants will perform the visual behavioral task with intracranial electroencephalogram (EEG) brain recordings carried out in parallel with surface EEG recordings. For Aim 1, we will analyze thalamic event related potentials in perceived vs not perceived stimuli, classified as in perception of no report visual stimuli based on eye metrics.
  • Device: EEG
    Participants will have scalp EEG recorded with the international 10-20 system sampled at 256Hz using EEG amplifiers for purposes of surface event related potential analysis
  • Device: Eye Tracking
    An eye-tracking device may be used during the perceptual awareness task. Pupillary and gaze location measurements are recorded using either a ViewPoint~VoltagePro.EyeLink 1000 Plus system, or Argus Science ETVision system. If using the ViewPoint~VoltagePro system or the Argus Science ETVision system, participants will be asked to wear an eye tracker during the perceptual awareness task (similar to wearing sunglasses). If using the EyeLink 1000 Plus system, participants may be asked to place their head inside of a padded head-chin rest to stabilize head position
  • Device: Behavioral task
    For the visual perceptual awareness task, the participant will be presented with barely perceptible visual stimuli. After a variable delay, the participant will be asked to report perception of each stimulus and identify its location.
Experimental
Thalamic Stimulation (Aim 2) 		We will test participants during the Visual Report Paradigm, while recording from the intralaminar thalamus with simultaneous scalp EEG as in Aim 1. Three thalamic stimulation conditions will be tested, randomized across trials: 1. No stimulation; 2. Stimulation Concurrent with visual stimuli; 3. Stimulation Delayed to 2s after visual stimuli. Stimulation will be a 100Hz train lasting 300ms, with biphasic square wave pulses 120μs per phase, current adjusted previously by clinicians to maximum tolerated level without side effects (typically ~3mA). The electrical stimulation is being delivered for research purposes to understand the causal role of thalamus in regulating visual perception.
  • Device: EEG
    Participants will have scalp EEG recorded with the international 10-20 system sampled at 256Hz using EEG amplifiers for purposes of surface event related potential analysis
  • Device: Eye Tracking
    An eye-tracking device may be used during the perceptual awareness task. Pupillary and gaze location measurements are recorded using either a ViewPoint~VoltagePro.EyeLink 1000 Plus system, or Argus Science ETVision system. If using the ViewPoint~VoltagePro system or the Argus Science ETVision system, participants will be asked to wear an eye tracker during the perceptual awareness task (similar to wearing sunglasses). If using the EyeLink 1000 Plus system, participants may be asked to place their head inside of a padded head-chin rest to stabilize head position
  • Device: Behavioral task
    For the visual perceptual awareness task, the participant will be presented with barely perceptible visual stimuli. After a variable delay, the participant will be asked to report perception of each stimulus and identify its location.

Recruiting Locations

University of Kansas Medical Center
Kansas City, Kansas 66160
Contact:
Laura Crabtree
lcrabtree2@kumc.edu

More Details

Status
Recruiting
Sponsor
Yale University

Study Contact

Hal Blumenfeld, MD, PHD
(203) 785-3865
Hal.blumenfeld@yale.edu

Detailed Description

The study will investigate subcortical arousal circuits in visual perception using techniques with complementary strengths based on promising initial studies. This study is expected to shed important light on the precise relationship between transient increases in subcortical arousal and perceptual awareness, generalizable across the visual modality. This research will therefore provide important general potential benefits, including 1. Identification of subcortical arousal systems in perception, which can benefit treatment of many disorders where perceptual deficits are common, e.g. traumatic brain injury, Alzheimer's disease, stroke, developmental disorders, schizophrenia, epilepsy and others. 2. Understanding the role of specific subcortical arousal circuits in perception may help target improved treatments, including transient thalamic stimulation like that planned for the present investigations, or less invasive treatments (TMS, tDCS, designer drugs) to improve function of these circuits. 3. The planned no-report paradigms may detect perceptual awareness in severe brain damage and anesthesia, where people are unable to overtly respond. The main hypotheses are that 1. the thalamic awareness potential (TAP) will be associated with visual perception independent of report, and 2. thalamic intralaminar stimulation at the time of stimulus presentation will augment the probability of perceptual awareness.

Notice

Study information shown on this site is derived from ClinicalTrials.gov (a public registry operated by the National Institutes of Health). The listing of studies provided is not certain to be all studies for which you might be eligible. Furthermore, study eligibility requirements can be difficult to understand and may change over time, so it is wise to speak with your medical care provider and individual research study teams when making decisions related to participation.