Modulation of Cognitive Control Signals in Prefrontal Cortex by Rhythmic Transcranial Magnetic Stimulation
Condition: Executive Function
Study type: Interventional

Summary: 
      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.
    

Detailed description: 
      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.
    

Intervention name(s): Theta TMS; Alpha TMS; Arrhythmic TMS
Intervention type(s): Device; Device; Device
Intervention description(s): TMS will be administered at the frequency of each subject's endogenous theta oscillation (4-7Hz); TMS will be administered at the frequency of each subject's endogenous alpha oscillation (8-12 Hz); TMS will be administered arrhythmically; i.e. a sequence of pulses with randomized timing
Other intervention name(s): MagProX100; MagProX100; MagProX100
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Basic Science