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Investigating Midfrontal Theta Signal and Learning

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Abstract:
Authors: Tiantian Li, Meera Singh, Rasmus Bruckner, Michael J. Frank, Matthew Nassar. An increase in midfrontal theta signal (4-7 Hz) in the brain has been previously observed in surprising situations requiring learning, leading to the proposal that theta may be a learning signal. Conversely, theta could also relate to latent states, which inform the brain about the current context and help us make decisions accordingly. To determine whether theta relates to learning or latent state representation, we re-analyzed data from a predictive inference task requiring participants to block cannonballs on a computer screen by predicting where the cannonball would strike. The task contained two blocks with differing statistical contexts that helped inform predictions. One context (“changepoint”) featured persistent changes in cannonball location, i.e. cannonballs would strike in one location for some time, then switch to a new location for some time, and so on. Thus, a change in cannonball location should prompt subjects to update their predictions. The other context (“oddball”) featured transient changes in cannonball location; the cannonball would generally strike in the same area, with an occasional cannonball strike in a different location. Here, changes in cannonball location should not prompt prediction updates. We used time-frequency decomposition to extract theta frequency from EEG data collected during the task. We then performed two regressions, one to analyze theta signal strength during surprising trials (trials with a change in cannonball location), and one to analyze the relationship between theta strength and learning (prediction updates). We found that theta signal strength increases during surprising trials compared to regular trials for both statistical contexts. Additionally, during changepoint blocks, a larger theta signal corresponded to an increase in learning, while during oddball blocks, a larger theta signal corresponded with a decrease in learning. These results suggest that theta is not a direct learning signal as previously speculated, but rather may play a role in modulating latent state representation. Our most recent analysis shows that these basic relations between theta and learning are not exclusive to theta, but extend across other frequency bands such as delta, which we are currently investigating.

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Citation

Meera Singh, Li, Tiantian, Bruckner, Rasmus, et al., "Investigating Midfrontal Theta Signal and Learning" (2021). Summer Research Symposium. Brown Digital Repository. Brown University Library. https://doi.org/10.26300/75r8-5y62

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  • Summer Research Symposium

    Each year, Brown University showcases the research of its undergraduates at the Summer Research Symposium. More than half of the student-researchers are UTRA recipients, while others receive funding from a variety of Brown-administered and national programs and fellowships and go …
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