Criticality, Working Memory, and Effort

Brown University

Status: Completed

Conditions: Healthy

Treatments: Device: transcranial magnetic stimulation

Study type: Interventional

Funder types: Other; NIH

Identifiers

NCT05797636

K99MH125021 (U.S. NIH Grant/Contract)

2106003016

Details and patient eligibility

About

The project examines electroencephalography, MRI, and behavioral measures indexing flexibility (critical state dynamics) in the brain when healthy young adults do demanding cognitive tasks, and in response to transcranial magnetic stimulation.

Full description

The healthy human brain is a complex, dynamical system which is hypothesized to lie near a phase transition at rest - at the boundary between order and chaos. Proximity to this critical point is functionally adaptive as it affords maximal flexibility, dynamic range, and information handling capacity, with implications for working memory function. Divergence from this critical point has become correlated with diverse forms of psychopathology and neuropathy suggesting that distance from a critical point is both a potential biomarker of disorder and also a target for intervention in disordered brains. The Investigators have further hypothesized that subjective cognitive effort is a reflection of sub-criticality induced by engagement with demanding tasks.

A key control parameter determining distance from criticality in a resting brain is hypothesized to be the balance of cortical excitation to inhibition (the "E/I balance"). Transcranial magnetic stimulation is a widely used experimental and clinical tool for neuromodulation and theta-burst stimulation (TBS) protocols are thought to modulate the E/I balance. Here the Investigators test whether cortical dynamics can be systematically modulated away from the critical point with continuous theta-burst stimulation (cTBS), which is thought to decrease the E/I balance, and thereby impact on working memory function and subjective cognitive effort during performance of the working memory tasks.

Enrollment: 30 patients

Sex: All

Ages: 18 to 45 years old

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

1. Provision of signed and dated informed consent form
2. Stated willingness to comply with all study and availability for the duration of the study
3. Males and females; Ages 18-45
4. Healthy, neurologically normal with no diagnosed mental or physical illness
5. Willingness to adhere to the MRI and two session stimulation protocol
6. Fluent in English
7. Normal or corrected to normal vision
8. At least twelve years of education (high school equivalent)
9. Right-handed

Exclusion criteria

1. Ongoing drug or alcohol abuse
2. Diagnosed psychiatric or mental illness
3. Currently taking psychoactive medication
4. Prior brain injury
5. Metal in body
6. History of seizures or diagnosis of epilepsy
7. Claustrophobia
8. Pregnant or possibly pregnant
9. Younger than 18 or older than 45
10. Use of medications which potentially lower the usage threshold

Trial design

Primary purpose: Basic Science

Allocation: N/A

Interventional model: Single Group Assignment

Masking: None (Open label)

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30 participants in 1 patient group

Transcranial magnetic stimulation participants

Experimental group

Description:

All participants will be recruited into a single arm where, across two sessions they will receive transcranial magnetic stimulation in separate session to either the dorsolateral prefrontal cortex or the angular gyrus. Session order will be counter-balanced across participants, and stimulation target will be blinded to the participants until after their participation is complete.

Treatment:

Device: transcranial magnetic stimulation