Causal Role of Top-Down Theta Oscillations in Prioritization
At a glance
Conditions
Where it's being run
1 sites across 1 statesStudy leadership
- Flavio Frohlich, PhD · PRINCIPAL_INVESTIGATOR · UNC Chapel Hill
Who to contact
This trial hasn't published a contact. View it on ClinicalTrials.gov
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What this trial measures
- Change in Working Memory Task Performance - Pashler's working memory capacity metric (k)During the 1- to 1.5-hour test at Baseline and Stimulation Session conducted over a 1 to 2 day period
The participant will be presented with three colored squares in both visual fields during a practice session. Then the participant is presented with an informative retro-cue, an arrow to the left or right, that is 100% predictive of the upcoming probe, or an uninformative neural cue, an arrow pointing in both directions. Finally, in the probe epoch participants are presented with an array of squares on the left or the right side of the screen. Participants must determine if the array of colored squares is the same or different from those held in memory. Performance will be defined as: k=N\*(HR\*FA)/(1-FA) where N is the number of the items that are held in memory. HR is the hit rate defined as the percent correct for trials where the probe does not match the encoding array. FA is the false alarm rate defined as the percent incorrect for trials where the probe does match the encoding array.
- Change in Working Memory Task Performance - Reaction TimeDuring the 1- to 1.5-hour test at Baseline and Stimulation Session conducted over a 1 to 2 day period
The participant will be presented with three colored squares in both visual fields during a practice session. Then the participant is presented with an informative retro-cue, an arrow to the left or right, that is 100% predictive of the upcoming probe, or an uninformative neural cue, an arrow pointing in both directions. Finally, in the probe epoch participants are presented with an array of squares on the left or the right side of the screen. Participants must determine if the array of colored squares is the same or different from those held in memory. Reaction times will be quantified in milliseconds.
- Intracranial EEG Multi-taper fftDuring the 1- to 1.5-hour test at Baseline and Stimulation Session conducted over a 1 to 2 day period
Time-frequency analysis of electrophysiology data will be performed using methods like multi-taper fft. This will be compared between sham (arrhythmic) and stimulation trials to identify if stimulation enhances neuronal entrainment.
- Intracranial EEG weighted phase lag index (wPLI)During the 1- to 1.5-hour test at Baseline and Stimulation Session conducted over a 1 to 2 day period
Functional connectivity will be measured using weighted phase lag index (WPLI). To calculate WPLI, first Morlet wavelet convolution is performed to extract instantaneous phase and amplitude for the frequency of interest for the two target sites. Next, the cross-spectral density is calculated (one signal multiplied by the complex conjugate of the other). From the cross-spectral density the imaginary component of the resulting signal is extracted. Then those imaginary values are averaged over the time frame of instance (here, the second half of the stimulation train). Finally, the magnitude of the resulting vector is taken to be the wPLI. This metric quantifies the consistency of phase lag between the two target regions and is weighted towards signals with a 90 or 270 degree offset to address a common confound in electrophysiology, volume conduction.