Stim2

Stimuli consisted of five commonly used short phrases borrowed from the list used in alternative and augmented communication: 1. Do you understand me; 2. That’s perfect; 3. How are you; 4. Good-bye; 5. I need help. These were used as visual stimuli, displayed on a screen, one at a time, written in English. A stimulus dedicated computer running the STIM2 software (Compumedics, LTD) connected to a high-quality DLP projector was used to display the stimuli onto a back-projection screen situated at 90cm from the subjects.

Although the ultimate goal of this research is targeted for locked-in patients, it is essential to first learn whether a NeuroVAD system is possible for healthy subjects before moving on to ALS patients. Hence, to show the first proof of concept of NeuroVAD with non-invasive neural signals, in this study we used data from 8 healthy subjects (3 females and 5 males; age 41 ± 14 years) without a history of vision, speech, and auditory or cognitive disorder. Prior written consent was obtained from each subject in compliance with the institutional review boards of UT Dallas, UT Austin, Dell Children’s Medical Center, and Cook Children’s Medical Center. A set of 5 commonly used phrases used in augmentative and alternative communication (AAC) were chosen as the stimuli for this study. They are: 1. Do you understand me, 2. That’s perfect, 3. How are you, 4. Good-bye, and 5. I need help. A stimulus dedicated computer running the STIM2 software (Compumedics, LTD) and connected to a high-quality DLP projector was used to visually display the phrase stimuli onto a back-projection screen situated at about 90 cm from the subjects.

The experiment consisted of 2 blocks separated by a break. All trials were presented in a pseudo-randomized order. Each block consisted of 80 congruent or incongruent trials (20 statement-statement pairs, 20 statement-question pairs, 20 question-question pairs, and 20 question-statement pairs). Prior to the testing, participants completed 4 practice trials to familiarize themselves with the stimuli and task. Feedback was provided in the practice but not the experimental trials. For stimulus presentation and data collection, we employed the software Stim2 (Compumedics Neuroscan, USA).

The EEG paradigm included one 4-min resting condition with eyes open as the baseline, and two experimental conditions (aesthetic judgment of paintings vs. fashion window displays). The sequence of the two experimental conditions was randomized and counterbalanced among the 20 participants. During the EEG recording, the participants performed aesthetic judgments of the 80 paintings and 80 fashion window displays, which were presented for 5 s with an inter-trial interval of 5.5 s. The visual stimuli were generated, controlled, and presented using software called STIM2 (Compumedics Neuroscan, El Paso, TX, United States). The participants were invited to assess the perceived visual stimuli as either “beautiful” or “not beautiful” by pressing the corresponding buttons of the STIM2 Response Pad. The stimuli of paintings and fashion windows displays were randomly presented (Figure 1). Besides EEG signals, the behavioral measures included the time taken by the participants to make aesthetic judgments and the number of visual stimuli perceived as beautiful or not beautiful. After two trials of the experimental conditions, the participants fully relaxed with eyes open for 4 min as the baseline measurement.

We used an auditory oddball task, which involved presenting standard stimuli (85%, 2000 Hz) and target stimuli (15%, 1000 Hz) in a pseudorandomized order. In total, 300 stimuli were delivered binaurally using a sound generator (STIM 2; Compumedics, El Paso, TX). Insert earphones were used to present the auditory stimuli. The loudness of the stimuli was 85 dB sound pressure level (SPL). All stimuli were presented for 100 milliseconds (including 10-millisecond rise and fall times) with fixed inter-trial intervals of 1250 milliseconds. The task required subjects to press a button with their right hand as quickly and accurately as possible only when target stimuli were presented. All participants were given the opportunity to practice before the actual task started. Participants completed 3 blocks of 100 trials while seated in a comfortable chair. A detailed description of the experimental procedure was described in our previous report.^{[21 (link)]}

Patients were seated in a dimly lit room, in front of a computer monitor placed at a distance of 70 cm. The stimuli were presented with STIM software (Stim2, Compumedics Neuroscan, Charlotte, NC, USA) running on a 15-inch. screen. Participants were asked to observe each stimulus during the EEG/fNIRS recording for the entire time of exposition. Pictures were presented randomly at the center of a computer monitor for 6 s, with an inter-stimulus interval of 12 s. One-hundred and twenty seconds eyes-closed and 120 eyes-open resting baseline were registered at the beginning of the experiment before picture presentation. After the experimental phase, patients had time to rate their emotional experience on the SAM scale (see Figure 1).