Christopher Beckett and Dr. Bruce Brown, Department of Psychology

Introduction

The event-related potential (ERP) method has led to major advances in the experimental exploration of the neurological correlates of human cognition (Luck, 2005). The usual process is to take EEG (electroencephalographic) recordings during a cognitive task. The recording is timelocked to a stimulus so that multiple trials can be averaged to amplify the signal of the resulting cognitive process. In past research studies, faculty and students in our Quantitative EEG Lab (qEEG) have discovered a way to isolate individual cognitive “bands” within a set of ERP waves. These cognitive bands have diagnostic utility. They can be used to identify personal characteristics such as male versus female, healthy controls versus a variety of neurological and psychiatric disorders, and academically strong students versus students on academic probation. In a recent study (Brown, et al., 2016) we were able to discriminate significantly between 75 subjects with mild Alzheimer’s disease and 95 healthy controls (Wilks’ lambda=.4297, p<.0001, R2=.5703). We found that the ability to discriminate between categories of persons is highly dependent on the kind of cognitive task used in the ERP studies. Unfortunately, the vast majority of ERP studies of cognition use the Oddball Paradigm, a task that is primarily visual and gives limited cognitive information. We found, for example, that the Sternberg Memory Search Paradigm, a better task for measuring cognition (Sternberg, 1966), is substantially stronger in identifying gender differences (R2=.946) among subjects, than is the Oddball Paradigm (R2=.803) in a comparable study. In looking for an additional cognitive task for use in our future studies, the NBack Task seems to be a good candidate. The goal of our research and development in the qEEG Lab is to find a biological marker of Alzheimer’s disease in its early stages, and this study should move us closer to that goal by finding a stronger cognitive task for investigating precisely the quantitative microstructure of cognitive processes in the brain.

Methodology

This summer we developed our Visual N-Back Task using the psychological software tool EPrime. E-prime is used to design experiments as well as collect and prepare data for analysis. We will be using it in combination with the Emotiv Pure EEG software. As well, we are also currently in the process of creating the E-Prime code for the Sternberg Memory Search Paradigm for comparison with the N-Back Task. For the rest of this summer term we will be finishing and fine-tuning the tasks. I have now graduated from BYU and will be entering a graduate program at Utah State University in the fall. My co-investigator Ryan Wells will be assuming the leadership responsibilities for the study and together with several additional undergraduate student investigators will be collecting data from 56 participants.

On the day of the research, participants will sign up through SONA, and arrive on their scheduled date in 221 of the Richards Building. Here they will receive instructions and fill out the IRB stamped Consent form. They will also indicate whether they would like to be considered for a future toxicology study that will be linked to the results of this study. Following, they will fill out the short Demographics questionnaire using a Qualtrics based survey. Then, they will complete two tasks, first the N-Back Task, then the Sternberg Memory Search Paradigm, always in the same order. The EEG data will be collected by an Emotiv EEG headset, a much less intrusive method for obtaining EEG measurements without gel or barbs.

First, subjects will complete the N-Back Task. For each of the rounds, single digits will be displayed in succession on the screen. First, the subject will complete the “1-back presenceresponding task,” meaning they will need to press the response button each time as digit is a repeated of a previous digit. Next, the participant will do the “2-back presence-responding task,” meaning they are to press the response button when a digit is a repeat of a digit given two digits ago. For example, if a 1, then a 2, then a 1, appears in succession, the subject will press the response button when the second 1 appears. Third, the subject will do the “1-back absenceresponding task,” meaning they will press the response button whenever a digit is NOT repeated. Finally, the subject will complete the “2-back absence-responding task,” meaning they will press the response button whenever a number is NOT a repeat of the digit given two digits ago.

Next, the subject will complete the Sternberg Task. Participants will be doing the Sternberg task in each of two response sets: presence-responding and absence-responding. Within each response set they will be given each of three memory-load conditions. The first will be a memory-load of two, where they will be instructed to, for example, “press the button if the digit 2 or the digit 7 appears.” The next condition will be presence-responding with a memory load of four (for example, “press the button if the digits 1, 4, 8, or 9 appears”), followed by the final presenceresponding trial with a memory load of six. They will then be given absence-responding trials for memory-load conditions of two, four, or six digits held in memory. For example, for the absence-responding condition for a memory-load of four, they might be instructed “do NOT press the button if a 0, 3, 5, or 8 appears, otherwise do.”

At the conclusion of both cognitive tasks, which will all together will take a little less than an hour, each participant will sign up for a 2-week follow-up to repeat the same tasks a second time. Once the collection of all data is complete, it will be analyzed to compare the Sternberg Memory Search Paradigm results with the N-Back Task results, and with Oddball Paradigm results from previous studies in our lab. The results will be written up for submission to a journal.

Results

The research group are now ready to begin recruiting subjects at the beginning of fall semester. Our plan is to complete the testing of subjects by the end of October and to have the data analyzed by November 30th and the initial paper written by the end of fall semester.

Discussion and Conclusion

Using the data we gather from this research, we expect to find that, even as the Sternberg Memory Search Task is superior to the Oddball Paradigm Task in classifying persons by gender, the N-Back Task will be superior to both of them.