Poster C42, Wednesday, August 21, 2019, 10:45 am – 12:30 pm, Restaurant Hall
Towards a functional interpretation of sustained anterior negativities
Aura A L Cruz Heredia1, Bethany Dickerson2, Ellen Lau1;1University of Maryland, Linguistics, 2University of Massachusetts, Amherst
|INTRODUCTION| Prior work in neuroscience has implicated persistent neural activity as an underlying mechanism engaged during working memory (WM) tasks. Nevertheless, what exactly is being encoded by this sustained activity remains a topic of much research and debate. In the language-domain, previous ERP work has observed a sustained anterior negativity (SAN) during the processing of filler-gap dependencies – which are widely regarded as being taxing on WM resources – relative to sentences with no such dependencies. While the SAN have been interpreted as an index of WM, exactly what mechanism drives the response is still underspecified. One popular proposal has been that SANs index the carrying forward of filler-related information until a gap is encountered. Here, we explore this hypothesis, as well as one that emphasizes syntactic predictions, across three EEG and one MEG experiment, in order to replicate and evaluate the response’s functional profile and neural generators. |METHODS| All experiments use RSVP of the sentences at a rate of 500-600ms per word. For experiments involving matrix WH-questions, subjects were tasked with evaluating whether a follow-up was a good response to the given question or sentence. In the embedded-WH experiment, subjects answered traditional comprehension questions. For EEG, SANs were evaluated as an interaction between condition and anterior electrodes such that these appear more negative in the dependency’s time-window relative to controls. |RESULTS| Across our experiments we found that: (1) SANs can be observed for short dependencies in fairly simple sentences. In two EEG experiments (n=14, n=22) we observed significant sustained negativities for simple (WH) object questions during the dependency region ('What did *the cover of the magazine* feature?') as compared to a yes/no control. (2) SANs do not seem to be a simple function of syntactic dependency or syntactic prediction. In a third EEG experiment (n=25), we failed to observe a SAN for similar, but embedded, object questions, relative to a complement clause control (‘John asked *what…’ vs ‘John asked *whether…’) (see also Sprouse et al. in prep. for similar results). We also failed to observe a SAN in response to a different kind of syntactic prediction – that of an additional clause after a subordinating adverb relative to a temporal adverb ('Although...' vs. 'Today...') – while still observing the response to the matrix object questions (n=22). Finally, we are currently collecting MEG data to determine the neural generators of the SAN response as a way to constrain the hypothesis-space. An early analysis of the first set of participants (n=12) reveals a significant cluster localized to left inferior/middle frontal cortex. |CONCLUSION| These results motivate several new research questions: if the SAN does not index syntactic WM per se, then what does it index? And what governs its presence or absence across different paradigms? In line with a suggested non-syntactic component for the SAN from Yano and Koizumi (2018), we suspect that the SAN may be related to interpretive processes, such as creating a richer situation model in order to more rapidly answer an open-ended question, or to understand complex scenarios.
Themes: Syntax, Meaning: Discourse and Pragmatics
Method: Electrophysiology (MEG/EEG/ECOG)