About

Megan A Boudewyn is the Principal Investigator of the Cognitive Neuroscience Lab at UCSC. Her research focuses on understanding how we comprehend meaning within language, particularly the cognitive processes that facilitate this comprehension. She is especially interested in how individuals deal with ambiguous referential processing during discourse. To investigate these questions, her research utilizes electrophysiology and brain stimulation techniques to examine both neurotypical and clinical population samples, aiming to deepen the understanding of language comprehension mechanisms. Prior to joining UCSC, Megan Boudewyn completed her Bachelor of Science degree in psychology at the University of Utah, where she also minored in Cognitive Science and earned a certification in Human Factors. She is originally from Chicago. Outside of her academic pursuits, she enjoys reading and writing, climbing, and spending time with her dog.

Research topics

• Computer Science
• Artificial Intelligence
• Natural Language Processing
• Psychology
• Data science
• Audiology
• Neuroscience
• Engineering
• Psychiatry
• Medicine
• Linguistics
• Systems engineering
• Cognitive psychology

Selected publications

• Dissecting Neurocomputational Mechanisms of Impaired Instrumental Learning Across Psychopathologies Using Integrative Model-Based EEG Phenotyping

  Biological Psychiatry · 2025-04-09 · 1 citations

  article
  PublisherDOI

• Neuromodulation of prefrontal cortex promotes deep processing during language comprehension: a tDCS/EEG study

  Cognitive Affective & Behavioral Neuroscience · 2025-08-13

  articleOpen access1st authorCorresponding

  In this study, we used transcranial direct current stimulation (tDCS), a noninvasive neuromodulation technique, to test a set of hypotheses about the extent to which the prefrontal cortex (PFC) contributes to revision and updating processes during language comprehension. Following 20 min of PFC-targeted, Active Control, or Sham tDCS, EEG was recorded while participants performed a widely used paradigm in which they read sentences containing plausible and implausible thematic roles (e.g. The actress/film-maker was directed by the film-maker/actress on set). This linguistic manipulation allowed us to examine comprehension under conditions when shallow processing and deeper processing yield conflicting meaning representations, which previous work has shown often engages revision and updating processes upon detection of the conflict. A different pattern of event-related potential responses was elicited when the same participants encountered implausible thematic roles during reading after receiving Sham compared with PFC-targeted tDCS. Specifically, N400 effects were found after Sham tDCS, whereas robust P600 effects were found after PFC-targeted tDCS (and to a significantly lesser extent, after Active Control tDCS). This suggests that while readers tended to treat implausible thematic roles as semantic anomalies after Sham tDCS, those same readers were more likely to detect conflict and engage in revision and updating in response to implausible thematic roles when in a state of heightened PFC stimulation. These results provide a novel demonstration of within-individual variability in language processing depending on current neurocognitive state and have implications for psycholinguistic theory about PFC contributions to revision and updating processes during language comprehension.

  PublisherOA PDFDOI

• Common sources of linguistic conflict engage domain-general conflict control mechanisms during language comprehension

  Cognitive Affective & Behavioral Neuroscience · 2025-02-12 · 2 citations

  articleOpen access1st authorCorresponding

  The current study tested the hypothesis that lexical ambiguity, a common source of representational conflict during language comprehension, engages domain-general cognitive control processes that are reflected by theta-band oscillations in scalp-recorded electroencephalograms (EEG). In Experiment 1, we examined the neural signature elicited by lexically ambiguous compared to unambiguous words during sentence comprehension. The results showed that midfrontal theta activity was increased in response to linguistic conflict (lexical ambiguity). In Experiment 2, we examined postconflict adaptation effects by comparing temporarily ambiguous sentences that followed previous instances of conflict (other temporarily ambiguous sentences) to those that followed a previous low-conflict (unambiguous) sentence. A midfrontal theta effect associated with linguistic conflict was again found in Experiment 2, such that theta was increased for temporarily ambiguous sentences that followed previous low-conflict (unambiguous) sentences compared with those that followed previous high-conflict (temporarily ambiguous) sentences. In both experiments, facilitated lexical semantic processing was also observed for words that came after the point of conflict, which may reflect a downstream "benefit" of cognitive control engagement. Overall, our results provide novel insights into the neurocognitive mechanisms underlying conflict processing in language comprehension and suggest that the same neural computations are involved in processing nonlinguistic and linguistic conflict.

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• Auditory Perceptual Biases in Schizophrenia: A Case-Control Study Using Sine-Wave Speech

  2025-09-06 · 1 citations

  articleOpen access

  People who hear voices may have strong prior expectations of speech, so that noisy auditory signals are resolved as speech. Data in non-clinical voice hearers suggest that voice hearing may involve sensitivity to speech in degraded stimuli. This has yet to be examined in people with schizophrenia. In this case-control study, we presented sine-wave-speech (SWS; made by replacing the formants in speech with pure tone whistles) to people with schizophrenia (SZ, n=63) and healthy controls (HC; n=27). SWS is typically unintelligible on first exposure. However, once the listener knows that it is potentially intelligible as speech (by exposure to the unaltered speech template, which thus serves as a prior expectation), relatively high levels of comprehension are achieved. Our participants first listened to intelligible and unintelligible SWS and reported whether they heard speech. They were then exposed to the speech templates, and then the first phase was repeated. Compared to HC, people with SZ reported hearing more speech before template exposure. The Reveal increased both groups’ false alarms and reporting of speech, but there was no interaction with group. Change in hit rates after the Reveal correlated with hallucinations, which is consistent with a greater influence of the priors enhancement in SZ patients who hear voices. These findings suggest that people with SZ have stronger expectations of speech. This task has validity for hallucinatory voice hearing. It is also simple and convenient to administer, and may prove useful in detecting prodromal risk, as well as acute exacerbation in voice hearing.

  PublisherDOI

• Leveraging Large Language Models to Characterize Disrupted Speech Patterns in Schizophrenia

  Biological Psychiatry · 2025-12-10

  article1st authorCorresponding
  PublisherDOI

• Model-Based Electroencephalography Phenotyping Uncovers Distinct Neurocomputational Mechanisms Underlying Learning Impairments Across Psychopathologies

  Biological Psychiatry Global Open Science · 2025-11-29

  articleOpen access

  Major depressive disorder (MDD), bipolar disorder (BP), and schizophrenia (SCZ) involve learning impairments with poorly understood mechanisms. Understanding both the similarities and differences in these mechanisms is important to guide the development of new, targeted interventions. 255 participants diagnosed with MDD (n=54), BP (n=47), SCZ (n=67) or without any diagnoses (CTRL; n=87) performed an associative learning task. Computational modeling quantified the mechanistic interplay between working memory (WM) and reinforcement learning (RL). The latent RL and WM signatures in the EEG dynamics showed shared and distinct neurocognitive mechanisms underlying learning. All clinical groups showed learning impairments at the behavioral level. Model-based EEG analyses linked these impairments to distinct patterns in the dynamic interplay between latent RL and WM mechanisms, contrasting with the typical patterns observed in CTRL. SCZ was characterized by reduced neural markers of WM, weakening the cooperative influence of WM onto RL (“reduced WM recruitment”), and reduced integration of negative feedback. Conversely, MDD was characterized by reduced reciprocal influence of RL onto WM, reducing the tendency to upregulate WM contribution with reward history (“impaired WM management”). Finally, BP was characterized by deficits in both WM and RL recruitment, along with higher WM decay. Behavioral learning impairments that appear similar across clinical groups can be linked to distinct neurocognitive mechanisms via integrative neurocomputational modeling. Our approach provides insights into the interplay of underlying learning mechanisms and how they manifest differently across psychopathologies. People with depression, bipolar disorder, and schizophrenia often show learning difficulties but the underlying causes may differ. By combining brain activity recordings with computational models, we identified distinct cognitive mechanisms driving these impairments. Our findings show how modeling and physiology can give insights into hidden decision dynamics behind learning difficulties. We also outline key steps needed to advance computational psychiatry tools toward clinical applications, including their potential use in guiding personalized treatment.

  PublisherDOI

• Model-based EEG phenotyping uncovers distinct neurocomputational mechanisms underlying learning impairments across psychopathologies

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-11-04

  preprintOpen access

  Abstract Background Major depressive disorder (MDD), bipolar disorder (BP), and schizophrenia (SCZ) involve learning impairments with poorly understood mechanisms. Understanding both the similarities and differences in these mechanisms is important to guide the development of new, targeted interventions. Methods 255 participants diagnosed with MDD (n=54), BP (n=47), SCZ (n=67) or without any diagnoses (CTRL; n=87) performed an associative learning task. Computational modeling quantified the mechanistic interplay between working memory (WM) and reinforcement learning (RL). The latent RL and WM signatures in the EEG dynamics showed shared and distinct neurocognitive mechanisms underlying learning. Results All clinical groups showed learning impairments at the behavioral level. Model-based EEG analyses linked these impairments to distinct patterns in the dynamic interplay between latent RL and WM mechanisms, contrasting with the typical patterns observed in CTRL. SCZ was characterized by reduced neural markers of WM, weakening the cooperative influence of WM onto RL (reduced WM recruitment), and reduced integration of negative feedback. Conversely, MDD was characterized by reduced reciprocal influence of RL onto WM, reducing the tendency to upregulate WM contribution with reward history (impaired WM management). Finally, BP was characterized by deficits in both WM and RL recruitment, along with higher WM decay. Conclusions Behavioral learning impairments that appear similar across clinical groups can be linked to distinct neurocognitive mechanisms via integrative neurocomputational modeling. Our approach provides insights into the interplay of underlying learning mechanisms and how they manifest differently across psychopathologies. Citation This manuscript is a preprint version of the later manuscript accepted for publication in Biological Psychiatry: Global Open Science . The content may differ from the final published version following peer review and editorial revisions. Ging-Jehli, N.R., Rac-Lubashevsky, R., Bera, K., Roberts, A., Loder, A., Boudewyn, M.A., Carter, C.S., Erickson, M., Gold, J., Luck, S.J., Ragland, J.D., Yonelinas, A.P., MacDonald III, A.W., Barch, D.M., & Frank, M.J. (2025). Model-based EEG phenotyping uncovers distinct neurocomputational mechanisms underlying learning impairments across psychopathologies. Preprint at bioRxiv.

  PublisherOA PDFDOI

• Associations Between Working Memory Contributions to Reinforcement Learning and Mental Health Phenotypes in a Representative Online Hypothesis-Generating Sample

  Biological Psychiatry · 2025-04-09

  article
  PublisherDOI

• Increased Reporting of Speech in Degraded Stimuli in Schizophrenia: A Case Control Study with Sine-Wave-Speech

  Schizophrenia Bulletin · 2025-12-13

  articleOpen access

  BACKGROUND AND HYPOTHESIS: People who hear voices may have strong prior expectations of speech, so that noisy auditory signals are resolved as speech. Data in non-clinical voice hearers suggest that voice hearing may involve sensitivity to speech in degraded stimuli. This has yet to be examined in people with schizophrenia (SZ). STUDY DESIGN: In this case-control study, we presented sine-wave-speech (SWS; made by replacing the formants in speech with pure tone whistles) to people with SZ (n = 63) and healthy controls (HC; n = 27). SWS is typically unintelligible on first exposure. However, once the listener knows that it is potentially intelligible as speech (by exposure to the unaltered speech template, which thus serves as a prior expectation), relatively high levels of comprehension are achieved. Our participants first listened to intelligible and unintelligible SWS and reported whether they heard speech. They were then exposed to the speech templates, and then the first phase was repeated. STUDY RESULTS: Compared to HC, people with SZ reported hearing more speech before template exposure. The Reveal increased both groups' false alarms and reporting of speech, but there was no interaction with group. Change in hit rates after the Reveal correlated with hallucinations, which is consistent with a greater influence of the priors enhancement in SZ patients who hear voices. CONCLUSIONS: These findings suggest that people with SZ have stronger expectations of speech. This task has validity for hallucinatory voice hearing. It is also simple and convenient to administer, and may prove useful in detecting prodromal risk, as well as acute exacerbation in voice hearing.

  PublisherOA PDFDOI

• Age-related differences in memory encoding and retrieval during referential processing: A time–frequency analysis.

  Psychology and Aging · 2024-11-01

  articleOpen access

  We investigated how lexical form similarity of referential candidates and ambiguity of following pronouns impact the encoding and retrieval of words from memory during sentence processing in younger and older adults. Critical sentences included two noun phrases (henceforth NPs) that were either phonologically and orthographically similar (Jason and Jacob/Jade) or dissimilar (Jason and Matt/Hannah), followed by a pronoun (e.g., he) that was either ambiguous or unambiguous (depending on the genders of the preceding NPs). We analyzed brain activity time-locked to the onsets of the second NP (NP2) and the pronoun to investigate the encoding and the retrieval of the NPs, respectively. During encoding NP2, older adults exhibited greater alpha power when NP1 had the same-gender, whereas younger adults showed no such effect, suggesting an increased need for inhibition for older adults during encoding. Moreover, although both groups exhibited an increase in alpha power for similar NPs, only younger adults exhibited a theta power increase, suggesting similarity-induced inhibition for both groups, but an additional maintenance cost only for younger adults. During retrieval (i.e., on the pronoun), we found that both pronominal ambiguity and form similarity resulted in greater theta power for younger adults, suggesting full pronominal processing and therefore more difficult retrieval, but smaller theta/alpha power for older adults, suggesting good-enough processing and therefore easier retrieval. Together with complementary behavioral results, our findings suggest that older adults resort to good-enough referential processing when the retrieval of relevant representations is cognitively demanding. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

  PublisherDOI

Frequent coauthors

• Tamara Y. Swaab

  University of California, Davis

  17 shared

• Cameron S. Carter

  University of California, Davis

  12 shared

• Michael J. Frank

  10 shared

• Debra L. Long

  University of California, Davis

  10 shared

• J. Daniel Ragland

  University of California, Davis

  8 shared

• Steven J. Luck

  University of California, Davis

  8 shared

• Deanna M. Barch

  Washington University in St. Louis

  7 shared

• Matthew J. Traxler

  University of Iowa

  6 shared

Labs

• Cognitive Neuroscience LabPI

Awards & honors

• 2018 NARSAD Young Investigator Award, Brain & Behavior Resea…
• 2020 R21 MH120383, National Institute of Mental Health