Consciousness Transcranial Alternative Electric STimulation

NCT03574883 | Completed

• 2 other identifiers: C17-222017-A02761-52
• Study Type: interventional
• Target: 67
• Locations: 1 country
• Sites: 1

Brief Summary

The aim of this study is to investigate the effect of transcranial Alternating Current Stimulation (tACS) at theta frequency and the the effect of transcranial Direct Current Stimulation (tDCS) on the conscious access to visual stimuli. tACS and tDCS are non-invasive stimulation techniques that are used to induce brain oscillations at certain frequency or to increase the brain activity in applied region. Healthy participants will perform a behavioral task measuring conscious access (visual backward metacontrast masking task) before, during and after fronto-parietal tACS or tDCS stimulation which will increase neural activity in the two sites. This will allow us to examine online and remaining effects of the stimulation and the causal role of fronto-parietal activity on conscious access.

Conditions

Healthy

Keywords

Conscious access; transcranial electric stimulation; tACS; Global neuronal workspace; Masking paradigm; tDCS

Outcome Measures

Primary Outcomes (1)

• Change in subjective performance on the behavioral task (% of seen masked target) between before and after stimulation.

  Change in the percentage of the correct responses on the subjective evaluation, that is the percentage of seen masked target at each SOA over all masked target presented, between before and after stimulation, for each stimulation modality (inphase theta, antiphase theta, sham).

  Measured at each stimulation sessions (three sessions in a randomized cross-over order) for each participant. The three sessions will span in an average of two weeks.

Secondary Outcomes (3)

• Change in visual evoked potentials between before and after stimulation.

  Measured at each stimulation sessions (three sessions in a randomized cross-over order) for each participant. The three sessions will span in an average of two weeks.

• Change in quantitative EEG measures between before and after stimulation.

  Measured at each stimulation sessions (three sessions in a randomized cross-over order) for each participant. The three sessions will span in an average of two weeks.

• Change in objective performance on the behavioral task (% of correct response on the number comparison task for masked target) between before and after stimulation.

  Measured at each stimulation sessions (three sessions in a randomized cross-over order) for each participant. The three sessions will span in an average of two weeks.

Study Arms (5)

In-phase tACS

EXPERIMENTAL

6 Hz stimulation (1000 μA) will be applied simultaneously over the left prefrontal dorso-lateral cortex (F3 of the 10-20 international scalp EEG system) and the left parietal cortex (P3) for 20 minutes using an 8-channels stimulator. The phase difference between the two stimulation sites will be 0°.

Device: tACS

Anti-phase tACS

ACTIVE COMPARATOR

6 Hz stimulation (1000 μA) will be applied simultaneously over the left prefrontal dorso-lateral cortex (F3 of the 10-20 international scalp EEG system) and the left parietal cortex (P3) for 20 minutes using an 8-channels stimulator. The phase difference will be 180°,

Device: tACS

Sham tACS

SHAM COMPARATOR

The stimulation (anti-phase) will start with a current intensity of 1000 μA lasting for 30 seconds. Afterwards, the intensity will progressively decrease over 20 seconds until cessation.

Device: tACS

Active tDCS

EXPERIMENTAL

1000 μA tDCS stimulation will be applied simultaneously over the left prefrontal dorso-lateral cortex (F3 of the 10-20 international scalp EEG system) and the left parietal cortex (P3) for 20 minutes using an 8-channels stimulator

Device: tDCS

Sham tDCS

SHAM COMPARATOR

The stimulation will start with a current intensity of 1000 μA lasting for 30 seconds. Afterwards, the intensity will progressively decrease over 20 seconds until cessation.

Device: tDCS

Interventions

tACS DEVICE

tACS is a non-invasive stimulation technique that works by delivering a weak sinusoidally oscillating electrical current to the surface of the skull to entrain oscillations in the brain.

Anti-phase tACS; In-phase tACS; Sham tACS

tDCS DEVICE

tDCS is a form of neuromodulation method where very low levels of constant current are delivered to specifically targeted areas of the brain

Active tDCS; Sham tDCS

Eligibility Criteria

• Age: 18 Years - 60 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• French social security affiliation
• Absence of neurological and psychiatric disorders
• Absence of antiepileptic treatment
• Normal vision (with or without correction)
• Age between 18 and 60 years
• Right-handedness
• Signed informed consent to participate

You may not qualify if:

• Person under legal protection (legal guardian, tutor, curator)
• Past medical history of epilepsy
• Past medical history of neurological or psychiatric disorders
• Electrical stimulation contraindication (metallic intra-cranial implants, pacemaker or implantable cardioverter-defibrillator, cranial prosthesis)
• Antiepileptic and other psychotropes treatment
• Pregnant, parturient or breastfeeding women
• Left-handedness

Sponsors & Collaborators

• Institut National de la Santé Et de la Recherche Médicale, France: lead

Study Sites (1)

Institut du Cerveau et de la Moelle - CR-ICM U 975 / UMRS INSERM 1127

Paris, 75013, France

Location

Related Publications (2)

• Del Cul A, Baillet S, Dehaene S. Brain dynamics underlying the nonlinear threshold for access to consciousness. PLoS Biol. 2007 Oct;5(10):e260. doi: 10.1371/journal.pbio.0050260.

  PMID: 17896866 BACKGROUND

• Polania R, Nitsche MA, Korman C, Batsikadze G, Paulus W. The importance of timing in segregated theta phase-coupling for cognitive performance. Curr Biol. 2012 Jul 24;22(14):1314-8. doi: 10.1016/j.cub.2012.05.021. Epub 2012 Jun 7.

  PMID: 22683259 BACKGROUND

MeSH Terms

Interventions

Transcranial Direct Current Stimulation

Intervention Hierarchy (Ancestors)

Electric Stimulation Therapy; Therapeutics; Convulsive Therapy; Psychiatric Somatic Therapies; Behavioral Disciplines and Activities; Electroshock; Psychological Techniques

Study Officials

• Lionel NACCACHE, MD, PhD

  CR-ICM U 975 /UMRS INSERM 1127

  PRINCIPAL INVESTIGATOR

• Jacobo D SITT, MD, PhD

  CR-ICM U 975 /UMRS INSERM 1127

  PRINCIPAL INVESTIGATOR

• Bertrand HERMANN, MD

  CR-ICM U 975 /UMRS INSERM 1127

  STUDY CHAIR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, INVESTIGATOR
• Masking Details: Study will be double-blind : neither participant nor the investigator will know which stimulation type (in-phase active, anti-phase active or sham) is on.
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER GOV
• Responsible Party: SPONSOR

Model Details: This study is composed of two independent sub-studies, one exploring the effects of tACS and the other the effects of tDCS, with different participants assigned to the two sub-studies. There will be 3 arms in tACS group and 2 arms in tDCS group. Among each sub-study, all participants will participate in all arms (hence the cross-over design).

Study Record Dates

• First Submitted: April 19, 2018
• First Posted: July 2, 2018
• Study Start: April 23, 2018
• Primary Completion: July 16, 2021
• Study Completion: July 16, 2021
• Last Updated: May 16, 2025

Record last verified: 2025-03

Data Sharing

• IPD Sharing: Will not share

Locations

FR (1)