Person: Fedorenko, Evelina
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Fedorenko
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Evelina
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Fedorenko, Evelina
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Publication Single-Neuronal Predictions of Others’ Beliefs in Humans(Springer Science and Business Media LLC, 2021-01-27) Jamali, Mohsen; Grannan, Benjamin; Fedorenko, Evelina; Saxe, Rebecca; Báez-Mendoza, Raymundo; Williams, Ziv M.Human social behavior crucially depends on our ability to reason about others. This capacity for ‘theory of mind’ plays a vital role in social cognition because it allows us not only to form a detailed understanding of the hidden thoughts and beliefs of other individuals but to also understand that they may differ from our own 1-4. Although a number of areas in the human brain have been linked to social reasoning 5-8 and its disruption across a variety of psychosocial conditions 9-12, the basic cellular mechanisms that underlie human theory of mind remain undefined. Using a rare opportunity to acutely record from single cells in the human dorsomedial prefrontal cortex, we discover neurons that reliably encode information about others’ beliefs across richly varying scenarios and that distinguish self- from other-belief related representations. By further following their encoding dynamics, we show how these cells represent the contents of the other’s beliefs and accurately predict whether they are true or false. We also show how they track beliefs from another’s perspective and how their activities relate to behavioral performance. Together, these findings reveal a detailed cellular process in the dorsomedial prefrontal cortex for representing another’s beliefs and identify candidate neurons that could support human theory of mind.Publication Neural encoding and production of functional morphemes in the posterior temporal lobe(Nature Publishing Group UK, 2018) Lee, Daniel; Fedorenko, Evelina; Simon, Mirela; Curry, William; Nahed, Brian; Cahill, Dan P.; Williams, ZivMorphemes are the smallest meaning-carrying units in human language, and are among the most basic building blocks through which humans express specific ideas and concepts. By using time-resolved cortical stimulations, neural recordings, and focal lesion evaluations, we show that inhibition of a small cortical area within the left dominant posterior–superior temporal lobe selectively impairs the ability to produce appropriate functional morphemes but does not distinctly affect semantic and lexical retrieval, comprehension, or articulation. Additionally, neural recordings within this area reveal the localized encoding of morphological properties and their planned production prior to speech onset. Finally, small lesions localized to the gray matter in this area result in a selective functional morpheme-production deficit. Collectively, these findings reveal a detailed division of linguistic labor within the posterior–superior temporal lobe and suggest that functional morpheme processing constitutes an operationally discrete step in the series of computations essential to language production.Publication Functional Network Dynamics of the Language System(Oxford University Press, 2016) Chai, Lucy R.; Mattar, Marcelo G.; Blank, Idan Asher; Fedorenko, Evelina; Bassett, Danielle S.During linguistic processing, a set of brain regions on the lateral surfaces of the left frontal, temporal, and parietal cortices exhibit robust responses. These areas display highly correlated activity while a subject rests or performs a naturalistic language comprehension task, suggesting that they form an integrated functional system. Evidence suggests that this system is spatially and functionally distinct from other systems that support high-level cognition in humans. Yet, how different regions within this system might be recruited dynamically during task performance is not well understood. Here we use network methods, applied to fMRI data collected from 22 human subjects performing a language comprehension task, to reveal the dynamic nature of the language system. We observe the presence of a stable core of brain regions, predominantly located in the left hemisphere, that consistently coactivate with one another. We also observe the presence of a more flexible periphery of brain regions, predominantly located in the right hemisphere, that coactivate with different regions at different times. However, the language functional ROIs in the angular gyrus and the anterior temporal lobe were notable exceptions to this trend. By highlighting the temporal dimension of language processing, these results suggest a trade-off between a region's specialization and its capacity for flexible network reconfiguration.Publication Toward a universal decoder of linguistic meaning from brain activation(Nature Publishing Group UK, 2018) Pereira, Francisco; Lou, Bin; Pritchett, Brianna; Ritter, Samuel; Gershman, Samuel; Kanwisher, Nancy; Botvinick, Matthew; Fedorenko, EvelinaPrior work decoding linguistic meaning from imaging data has been largely limited to concrete nouns, using similar stimuli for training and testing, from a relatively small number of semantic categories. Here we present a new approach for building a brain decoding system in which words and sentences are represented as vectors in a semantic space constructed from massive text corpora. By efficiently sampling this space to select training stimuli shown to subjects, we maximize the ability to generalize to new meanings from limited imaging data. To validate this approach, we train the system on imaging data of individual concepts, and show it can decode semantic vector representations from imaging data of sentences about a wide variety of both concrete and abstract topics from two separate datasets. These decoded representations are sufficiently detailed to distinguish even semantically similar sentences, and to capture the similarity structure of meaning relationships between sentences.