Psychophysiological Assessment
We used the BIOPAC MP150 system (BIOPAC System, Inc., Goleta, CA), a
modular data acquisition and analysis system that is widely used in
psychophysiological research, to assess psychophysiological activation,
alpha asymmetry, and the ERN. We used AcqKnowledge software to filter
and extract data.
Psychophysiological activation. The following measures were
assessed during a 5-minute baseline resting phase and throughout the
discarding and neutral tasks. We assessed skin conductance level (SCL)
through a constant voltage of 0.5 V across two electrodes placed on the
first and second fingers of the left hand. The total number of skin
conductance responses (SCRs), which reflect the peaks in the SCL
waveform, were extracted along with mean SCL. Heart rate variability
(HRV) and heart rate (HR) data were collected via electrocardiogram
(ECG) leads attached to both the left and right wrists, as well as the
left ankle. ETCO2 was collected through nasal cannula
and was measured in real time using the AcqKnowledge software rate
calculation function. This function allowed for breath-by-breath
measurement of ETCO2 percentage which then we
statistically transformed to mmHg.
ERN . EEG data was recorded at 2000hz from six electrodes
[‘Fz’,’O1’, ‘F3’, ‘O2’, ‘F4’, ‘Pz’] with a linked mastoid reference.
All EEG post processing was conducted using the MNE software package
(Gramfort et al., 2013). Data were bandpass filtered from 1 to 17Hz and
EEG was segmented from 500ms before to 350ms after the commission of a
response and baseline corrected from mean activity in the -500 to -100ms
pre-response. Epochs with activity greater than 125mv were excluded for
artifact. The ERN was measured as the difference between incorrect and
correct responses at electrodes F3, Fz, & F4 50 to 150ms post response
in line with prior literature (Gehring et al., 2018; Larson et al.,
2010; Meyer, 2016; Meyer et al., 2020; Riesel, 2019) and confirmed with
visual inspection of grand averaged waveforms.
Resting state alpha asymmetry . Alpha asymmetry was assessed
during the baseline resting phase. Baseline EEG was segmented into 1-sec
epochs. Artifact detection was the same as for ERN analyses.
Artifact-free segments were decomposed into the frequency domain using
multitaper fast fourier transform (FFT) implemented in the MNE software
package. Frontal asymmetry indices were calculated by subtracting the
natural log of the power of the left hemisphere electrode from that of
the homologous right hemisphere electrode (In[right (F4)] – [left
(F3)]).
Quality control . To minimize artifacts, participants were asked
not to move during the study other than to press the appropriate button
on the Go/No Go tasks (see below). They were closely observed by a
research assistant throughout the study. Any movements that occurred
were recorded on a testing form with the specific time that they
occurred. If artifacts appeared in the waveform at those times, the
sections of the waveform that included the artifact were excluded from
the analyses. To ensure reliable data for the EDA analyses, prior to
starting the tasks, we asked participants to hold their breath for a few
seconds to verify that the signal responded to the breath-holding (EDA
waveform should increase with breath-holding). Prior to starting the
tasks, we visually inspected the ECG waveform to ensure that QRS peaks
were being recorded properly. Additionally, during application of the
EEG cap, each electrode was abraded (via a Q-tip) and re-jelled with
abrasive electrolyte-gel up to three times, or until impedances as
determined by an electrode impedance checker were less than 5 kΩ. The
testing room in which the study took place was regulated at a
temperature ranging between 71°F-73°F in order to ensure quality data
collection.
For HRV, we applied a band pass filter (low frequency cutoff = 1 Hz;
high frequency cutoff = 35 Hz; QRS peak threshold = 0.5 mV, which was
adjusted as needed depending on the height of individual participants’
QRS peaks). For EDA, we first applied a low pass filter (1 Hz). The SCR
threshold level was set at 0.02 microsiemens.