Posttraumatic stress disorder can be viewed as a disorder of fear dysregulation. An abundance of research suggests that the prefrontal cortex is central to fear processing—that is, how fears are acquired and strategies to regulate or diminish fear responses. The current review covers foundational research on threat or fear acquisition and extinction in nonhuman animals, healthy humans, and patients with posttraumatic stress disorder, through the lens of the involvement of the prefrontal cortex in these processes. Research harnessing advances in technology to further probe the role of the prefrontal cortex in these processes, such as the use of optogenetics in rodents and brain stimulation in humans, will be highlighted, as well other fear regulation approaches that are relevant to the treatment of posttraumatic stress disorder and involve the prefrontal cortex, namely cognitive regulation and avoidance/active coping. Despite the large body of translational research, many questions remain unanswered and posttraumatic stress disorder remains difficult to treat. We conclude by outlining future research directions related to the role of the prefrontal cortex in fear processing and implications for the treatment of posttraumatic stress disorder.

Highlights• Electroencephalogram (EEG) was concurrently recorded in a simulated classroom from groups of four students and a teacher.• Alpha-band (8-12Hz) brain-to-brain synchrony predicted students' performance in a delayed post-test.• Moment-to-moment variation in alpha-band brain-to-brain synchrony indicated what specific information was retained by students.• Whereas student-to-student brain synchrony best predicted learning at a zero time lag, student-to-teacher brain synchrony best predicted learning when adjusting for a ~200 millisecond lag in the students' brain activity relative to the teacher's brain activity. SummaryLittle is known about the brain mechanisms that underpin how humans learn while interacting with one another in ecologically-valid environments (1-3). This is because cognitive neuroscientists typically measure one participant at a time in a highly constrained environment (e.g., inside a brain scanner). In the past few years, researchers have begun comparing brain responses across individuals (4-6) demonstrating that brain-to-brain synchrony can predict subsequent memory retention (7-9). Yet previous research has been constrained to noninteracting individuals. Surprisingly, the one study that was conducted in a group setting found that brain synchrony between students in a classroom predicted how engaged the students were, but not how much information they retained (10). This is unexpected because brain-to-brain synchrony is hypothesized to be driven, at least partially, by shared attention (11,12), and shared attention has been shown to affect subsequent memory (13). Here we used EEG to 3 simultaneously record brain activity from groups of four students and a teacher in a simulated classroom to investigate whether brain-to-brain synchrony, both between students and between the students and the teacher, can predict learning outcomes (Fig. 1A). We found that brain-tobrain synchrony in the Alpha band (8-12Hz) predicted students' delayed memory retention.Further, moment-to-moment variation in alpha-band brain-to-brain synchrony discriminated between content that was retained or forgotten. Whereas student-to-student brain synchrony best predicted delayed memory retention at a zero time lag, student-to-teacher brain synchrony best predicted memory retention when adjusting for a ~200 millisecond lag in the students' brain activity relative to the teacher's brain activity. These findings provide key new evidence for the importance of brain data collected simultaneously from groups of individuals in ecologicallyvalid settings. Results and DiscussionBehavioral results. Students' content knowledge was assessed a week before the EEG session, immediately following each one of four mini-lectures, and one week later ( Fig. 1B; See Methods). As expected, students' content knowledge significantly increased from the pre-test (0.43±0.02; mean ± standard deviation of the mean) to the immediate post-test (0.73±0.02; F(1,30)=210.76; p<10 -13 ), and from the pre-test to the delayed post-test (0.64±0.02; F(1,30)=...

Larval zebrafish possess a number of molecular and genetic advantages for rigorous biological analyses of learning and memory. These advantages have motivated the search for novel forms of memory in these animals that can be exploited for understanding the cellular and molecular bases of vertebrate memory formation and consolidation. Here, we report a new form of behavioral sensitization in zebrafish larvae that is elicited by an aversive chemical stimulus [allyl isothiocyanate (AITC)] and that persists for ≥30 min. This form of sensitization is expressed as enhanced locomotion and thigmotaxis, as well as elevated heart rate. To characterize the neural basis of this nonassociative memory, we used transgenic zebrafish expressing the fluorescent calcium indicator GCaMP6 ( Chen et al., 2013 ); because of the transparency of larval zebrafish, we could optically monitor neural activity in the brain of intact transgenic zebrafish before and after the induction of sensitization. We found a distinct brain area, previously linked to locomotion, that exhibited persistently enhanced neural activity following washout of AITC; this enhanced neural activity correlated with the behavioral sensitization. These results establish a novel form of memory in larval zebrafish and begin to unravel the neural basis of this memory.

Much of human learning happens through interaction with other people, but little is known about how this process is reflected in the brains of students and teachers. Here, we concurrently recorded electroencephalography (EEG) data from nine groups, each of which contained four students and a teacher. All participants were young adults from the northeast United States. Alpha-band (8–12 Hz) brain-to-brain synchrony between students predicted both immediate and delayed posttest performance. Further, brain-to-brain synchrony was higher in specific lecture segments associated with questions that students answered correctly. Brain-to-brain synchrony between students and teachers predicted learning outcomes at an approximately 300-ms lag in the students’ brain activity relative to the teacher’s brain activity, which is consistent with the time course of spoken-language comprehension. These findings provide key new evidence for the importance of collecting brain data simultaneously from groups of learners in ecologically valid settings.

Neuroscience is one of the fastest-growing STEM fields, yet its presence in K-12 science education is very limited, partially due to the lack of accessible teaching materials and tools. Here, we describe a new high school neuroscience curriculum ("BrainWaves"), where students utilize recent advances in low-cost, portable Electroencephalography (EEG) technology to investigate their own brain activity. This semester-long curriculum is supported by science mentors and an educational application that guides students through the process of recording and analyzing their own brain activity. Evaluation data collected in 5 public New York City schools in 2018/19 indicate significant positive shifts in content knowledge and self-efficacy among students who participated in BrainWaves compared to students in other courses of the same teacher. The quantitative findings are supported by interviews, where students reported increased appreciation for neuroscience and college readiness as well as the benefits of collaborating with scientists and using portable brain technology in classrooms.