Purpose: In this study, the investigators will provide causal evidence for the role of alpha
      and theta oscillations in cognitive control.

      Participants: Participants must be healthy, between the ages of 18 and 35, right handed, able
      to provide informed consent, willing to comply with all study procedures, and be available
      for the duration of the study, speak and understand English.

      Procedures: Alpha and theta brain oscillations will be measured and then entrained using
      frequency specific rhythmic TMS during a retrospective cued cognitive control task.

Modulation of Cognitive Control Signals in Prefrontal Cortex by Rhythmic Transcranial Magnetic Stimulation

Executive Function

Neural oscillations are proposed to be a mechanism of coordinating information processing
      across distributed regions of cortex. Different neural oscillations may correspond to
      different underlying neural computations. Noninvasive brain stimulation allows experimenters
      to modulate specific neural oscillations by targeting particular frequency bands. By
      collecting simultaneous electroencephalography (EEG), rhythmic transcranial magnetic
      stimulation (TMS) has been previously demonstrated to entrain neural oscillations at the
      frequency of stimulation. Furthermore, when the frequency of entrained neural oscillations is
      matched to the frequency of endogenous activity in a cognitive task, the brain stimulation
      improves behavioral performance. Therefore, noninvasive brain stimulation is a promising tool
      for improving cognition by inducing optimal neural activity via externally applied
      electromagnetic fields; e.g. cognitive control improvements.

      Previous evidence has implicated neural activity in the alpha band (8-12 Hz) in information
      suppression and activity in the theta band (4-7 Hz) in information prioritization. Cognitive
      control task paradigms have been shown to elicit distinct activity in both of these bands. In
      this task, the stimuli are lateralized to the right and left visual field during encoding.
      After a short delay, a cue informs participants which stimuli (right or left) will be tested.
      Previous evidence found that alpha activity in parietal cortex is generated contralateral to
      irrelevant stimuli-supporting the role of alpha in information suppression-while theta
      activity in frontal cortex increases with the number of stimuli to be remembered-supporting
      the role of theta in information prioritization.

      For the current study, the investigators propose to deliver rhythmic trains of TMS in either
      alpha frequency, theta frequency, or an arrhythmic control to modulate neural processing
      during a cognitive control task. By collecting simultaneous EEG with TMS, the investigators
      will be able to measure the entrained oscillations from rhythmic TMS. The goal of this
      experiment is to enhance the observed theta and alpha activity that is seen with the
      successful prioritization and suppression of information. To provide causal evidence that
      parietal cortex generates alpha activity and frontal cortex generates theta activity, the
      investigators will apply rhythmic TMS stimulation to two scalp locations: the anterior middle
      frontal gyrus and inferior intraparietal sulcus. By applying alpha frequency, theta
      frequency, and arrhythmic TMS at each location, the investigators will be able to examine the
      causal relationship of frontal theta oscillations in information prioritization and parietal
      alpha oscillations in information suppression.

Theta TMS

Alpha TMS

Arrhythmic TMS

Modulation of Alpha and Theta Oscillations in a Cognitive Control Retrospective Cue Task With Frequency Specific Rhythmic Transcranial Magnetic Stimulation

Participants make a button press on a keyboard to indicate if the probed items are matched or non-matched to the items held in memory after a retrospective cue is presented. The investigators calculate the percent correct for non-match conditions, defined as the hit rate, and the percent incorrect for match conditions, defined as the false alarm rate. The number of remembered items, often referred to as working memory capacity, is calculated as the number of items to be remembered (2, 3, or 4) times the hit rate minus the false alarm rate, divided by one minus the false alarm rate. The range of values is 0 to 4 where larger values mean better performance. For TMS to frontal cortex, working memory capacity is reported when the participant was cued to the right. For TMS to parietal cortex, working memory capacity is reported when the participant was cued to the left.

The electrical activity of the brain is recorded during performance of the task and brain stimulation. The investigators will perform Morlet wavelet convolution on the recorded electrical signal to calculate the amplitude of neural oscillations in the frequency bands: theta (4-7 hertz) and alpha (8-12 hertz). The amplitude of neural oscillations is reported during the second half of stimulation in the region that is being stimulated. The amplitude is normalized for each participant as the percent change from the amplitude during the baseline period (before the task begins). For TMS to frontal cortex the amplitude of theta oscillations are reported and for TMS to parietal cortex the amplitude of alpha oscillations are reported.

Participants make a button press on a keyboard to indicate if the probe items are matched or non-matched to the items held in memory after a retrospective cue is presented. The investigators will calculate the response time of this choice as the difference between the time of the button press and presentation of the probe. For TMS to frontal cortex, response time is reported when the participant was cued to the right. For TMS to parietal cortex, response time is reported when the participant was cued to the left.

Participants will receive TMS while performing a cognitive control task. In their first stimulation session, the TMS coil will be placed over the frontal cortex on the scalp. In their second session, the TMS coil will be placed over the parietal cortex on the scalp. During every session, subjects receive Theta TMS, Alpha TMS, and Arrhythmic TMS.

Participants will receive TMS while performing a cognitive control task. In their first stimulation session, the TMS coil will be placed over the parietal cortex on the scalp. In their second session, the TMS coil will be placed over the frontal cortex on the scalp. During every session, subjects receive Theta TMS, Alpha TMS, and Arrhythmic TMS.

Modulation of Cognitive Control Signals in Prefrontal Cortex by Rhythmic Transcranial Magnetic Stimulation

About this trial

Study ID

Status

Type

Phase

Placebo

Accepting

Trial Timing

What is this trial about?

What are the participation requirements?