Brain Networks and Consciousness

Subcortical-cortical Network Dynamics of Anesthesia and Consciousness

General anesthesia (GA) is a medically induced state of unresponsiveness and unconsciousness, which millions of people experience every year. Despite its ubiquity, a clear and consistent picture of the brain circuits mediating consciousness and responsiveness has not emerged. Studies to date are limited by lack of direct recordings in human brain during medically induced anesthesia. Our overall hypothesis is that the current model of consciousness, originally proposed to model disorders and recovery of consciousness after brain injury, can be generalized to understand mechanisms of consciousness more broadly. This will be studied through three specific aims. The first is to evaluate the difference in anesthesia sensitivity in patients with and without underlying basal ganglia pathology. Second is to correlate changes in brain circuitry with induction and emergence from anesthesia. The third aim is to evaluate the effects of targeted deep brain stimulation on anesthesia induced loss and recovery of consciousness. This study focuses on experimentally studying these related brain circuits by taking advantage of pathological differences in movement disorder patient populations undergoing deep brain stimulation (DBS) surgery. DBS is a neurosurgical procedure that is used as treatment for movement disorders, such as Parkinson's disease and essential tremor, and provides a mechanism to acquire brain activity recordings in subcortical structures. This study will provide important insight by using human data to shed light on the generalizability of the current model of consciousness. The subject's surgery for DBS will be prolonged by up to 40 minutes in order to record the participant's brain activity and their responses to verbal and auditory stimuli.

Study Overview

• Status: Terminated
• Conditions: Parkinson Disease; Anesthesia; Essential Tremor; Loss of Consciousness
• Intervention / Treatment: Drug: Propofol

• Study Type: Observational
• Enrollment (Actual): 57

Contacts and Locations

Study Locations

• United States
  • Texas
    • Dallas, Texas, United States, 75235
      • Nader Pouratian

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

• Sampling Method: Probability Sample

Study Population

Study participants are Parkinson's disease and essential tremor patients undergoing revision/replacement of an implantable pulse generator for DBS, or initial DBS implantation.

Description

Inclusion Criteria:

• Willingness and ability to cooperate during conscious operative procedure for up to 40 minutes
• Clinical diagnosis of Parkinson's disease or essential tremor
• Preoperative MRI without evidence of cortical or subdural adhesions or vascular abnormalities

Exclusion Criteria:

• Patients with recent use (within one week) of anticoagulant or antiplatelet agent use
• Neurocognitive testing indicating amnestic cognitive deficits
• History of intolerance of propofol or medical indications to use an anesthetic other than propofol

Study Plan

How is the study designed?

Design Details

• Observational Models: Case-Control
• Time Perspectives: Prospective

Number of groups / cohorts

7

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Parkinson's Disease patients with DBS, no stimulation; This cohort will serve as as the observed group, displaying basal ganglia pathology. A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Experiments will be completed with DBS off.	Drug: Propofol; Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Essential Tremor patients with DBS; This cohort will serve as a control group (no basal ganglia pathology). A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a TCI system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Experiments will be completed with DBS off.	Drug: Propofol; Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Parkinson's Disease patients with DBS, Gpi stimulation; This cohort will serve as as the observed group, displaying basal ganglia pathology. A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Participants will be stimulated at the Gpi via DBS leads during propofol induced loss of consciousness.	Drug: Propofol; Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Parkinson's Disease patients with DBS, Gpe stimulation; This cohort will serve as as the observed group, displaying basal ganglia pathology. A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Participants will be stimulated at the Gpe via DBS leads during propofol induced loss of consciousness.	Drug: Propofol; Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Parkinson's Disease patients undergoing DBS surgery, Gpe stimulation; A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Participants will be stimulated at the Gpe via DBS leads, and cortical activity will be recorded via ECoG during propofol induced loss of consciousness.	Drug: Propofol; Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Parkinson's Disease patients undergoing DBS surgery, Gpi stimulation; A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Participants will be stimulated at the Gpi via DBS leads, and cortical activity will be recorded via ECoG during propofol induced loss of consciousness.	Drug: Propofol; Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.
Parkinson's Disease patients undergoing DBS surgery, no stimulation; A syringe pump controlled by Stanpump implementing the Eleveld Pharmacokinetics-Pharmacodynamics (PK-PD) model for propofol will be used as a targeted controlled infusion (TCI) system to achieve plasma target propofol concentrations. Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved. Participants will not receive any stimulation via DBS leads, and cortical activity will be recorded via ECoG during propofol induced loss of consciousness.	Drug: Propofol; Target effect-site concentration of propofol will be started at 1.4 μg/mL and will be increased by 0.3 μg/mL with reassessment until endpoints are achieved.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Propofol Dose Response Curve	Average targeted serum dose of propofol at which 50% of patients had loss of behavioral responses	Baseline visit
Behavioral Assessment of Propofol Induced Loss / Recovery of Consciousness and Responsiveness	Number of participants with loss of at least 50% of behavioral responses at a targeted serum concentration of 1.5 ug/mL using the following three behavioral responses will be evaluated: (1) loss/recovery of spontaneous movement (i.e., loss and recovery of responsiveness) (2) loss/recovery of movement in response to stimuli (separately to clicks [non-salient] and verbal stimuli [salient]), and (3) loss/recovery of movement to command (verbal command with patient name with instruction to open their eyes, as proxy of loss/recovery of consciousness).	baseline
Electrocorticogram (ECoG) and Pallidal Local Field Potential (LFP) Recordings	Oscillatory frequency at which maximal power changes occur with inducing loss of consciousness, as measured using ECoG and Globus Pallidus internus / Globus Pallidus externus (GPi/GPe) LFP recordings during DBS implantation surgery with target-controlled infusion of propofol. This is not an average frequency but a single peak value based on population spectra at which maximal changes are noted. The number reported is not an average of peaks across patients, but the peak identified after integrating data across the population studied. There is no corresponding measure of dispersion or prevision based on the way the value is identified. Rather, it is a single peak value.	Baseline

Collaborators and Investigators

• Sponsor: University of Texas Southwestern Medical Center
• Collaborators: University of California, Los Angeles
• Investigators: Principal Investigator: Nader Pouratian, MD, PhD, University of Texas Southwestern Medical Center

Study record dates

Study Major Dates

• Study Start (Actual): October 15, 2020
• Primary Completion (Actual): November 14, 2024
• Study Completion (Actual): December 31, 2025

Study Registration Dates

• First Submitted: July 30, 2020
• First Submitted That Met QC Criteria: August 4, 2020
• First Posted (Actual): August 6, 2020

Study Record Updates

• Last Update Posted (Actual): June 8, 2026
• Last Update Submitted That Met QC Criteria: June 4, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: deep brain stimulation; general anesthesia; basal ganglia; sensorimotor cortex; thalamus
• Additional Relevant MeSH Terms: Synucleinopathies; Neurologic Manifestations; Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Neurobehavioral Manifestations; Neurodegenerative Diseases; Movement Disorders; Parkinsonian Disorders; Basal Ganglia Diseases; Consciousness Disorders; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Parkinson Disease; Essential Tremor; Unconsciousness; Organic Chemicals; Hydrocarbons; Hydrocarbons, Cyclic; Hydrocarbons, Aromatic; Phenols; Benzene Derivatives; Propofol
• Other Study ID Numbers: STU-2021-0396

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes