Review written by Jess Breda (PNI)
Have you ever wondered how information is transferred from one brain to another? This process can occur in a variety of ways, from verbal storytelling to simple hand gestures, and across different backgrounds, such as a flight attendant instructing a first time flyer, or a casual conversation with a friend. We gain information from others on a daily basis. However, to study this on a biological level requires the complicated task of recording from two brains experiencing the same stimuli and aligning their activity in time.
Previous work from the Hasson Lab at Princeton University established a technique to achieve this dual recording of two brains in a naturalistic way. The researchers performed functional magnetic resonance imaging (fMRI) scans on ‘speakers’, who read 15 minute narratives, and ‘listeners’, who listened to the narratives. They found neural activity in speaker-listener brains was correlated in higher-order processing areas when the narrative was the same for the speaker and the listener (as opposed to when the speaker reads narrative A and the listener hears narrative B). This coupling of brain activity (i.e. similar responses in similar regions during stimulus presentation) is thought to be driven by a shared understanding of the narrative. Given the complexities of communication, could correlated brain activity explain the transfer of information when the content is abstract, or background knowledge is dissimilar across participants?
To address this question, graduate student Mai Nguyen and colleagues from the Princeton Psychology Department investigated if the brains of teachers and students are coupled during lectures, and if couplingmagnitude predicts learning outcomes. The team performed fMRI scanning on a teacher as they presented a 30-minute scientific lecture with slides, and on students as they watched the lecture. There were two student conditions: an ‘intact’ group where the lecture was delivered in its entirety and a ‘scrambled’ group where the lecture audio was scrambled at the sentence level and the slide text was scrambled at the world level. This experimental design allowed the researchers to distinguish between correlated activity due to shared sensory input and correlated activity driven by a shared understanding of the material. Additionally, students took pre- and post-lecture tests to determine baseline knowledge and measure learning.
The team found alignment in brain activity between the teacher and ‘intact’ students in multiple regions, including a collection of higher-order brain regions called the default mode network (DMN). While the known function of the DMN is continually evolving (see here), coupling in this area is associated with listener comprehension in narrative story telling. This suggests the alignment of activity between teacher (expert) and student (novice) in Nguyen et al.’s research could represent shared knowledge. Moreover, the team found that increased correlation between teacher and student brain activity in the posterior medial cortex (PMC) of the DMN predicted learning outcomes: the more coupled the student’s PMC was to the teacher’s, the greater their improvement was between pre- and post-lecture tests.
Interestingly, the team also found alignment in an area not found to be active in other narrative storytelling studies: the superior parietal lobule (SPL). This brain region is associated with mental rotation and math, and given the scientific nature of the lecture, this finding suggests that brain activity coupling during information transfer is content specific; the coupling locations are dependent on the task type.
All together, Nyguen et al. is the first fMRI study to examine neural coupling between teachers and students in a naturalistic setting. They revealed that neural coupling between teachers and students can be used as a marker of learning: teachers may be more effective in teaching, and students may learn better, when their brain activity is similar. When considering that shared brain activity is related to learning outcomes, this study suggests that shared understanding (measured neurally here) is critical in promoting learning in students. Thus, their research has significant implications in determining effective pedagogical strategies, and has laid a strong foundation to further investigate neural activity during teacher-student communication.
Mai Nguyen, first author and graduate student in the Hasson lab, noted that, “while the field is starting to shift towards more ‘real-life neuroscience’, scanning people while freely talking and viewing is still highly unusual - except at Princeton.” She attributed this to the technique being pioneered by Uri Hasson, Professor of Psychology and Neuroscience at Princeton, as well as the accessibility of specialized fMRI machines in Princeton’s Bezos Imaging Center.
This original preprint was submitted to bioRxiv on May 7, 2020. Please follow this link to view the full version.