The neural representation of plural discourse entities

Neural correlates of pronoun processing: An activation likelihood estimation meta-analysis

Pronouns are unique linguistic devices that allow for the expression of referential relationships. Despite their communicative utility, the neural correlates of the operations involved in reference assignment and/or resolution, are not well-understood. The present study synthesized the neuroimaging literature on pronoun processing to test extant theories of pronoun comprehension. Following the PRISMA guidelines and thebest-practice recommendations for neuroimaging meta-analyses, a systematic literature search and record assessment were performed. As a result, 16 fMRI studies were included in the meta-analysis, and were coded in Scribe 3.6 for inclusion in the BrainMap database. The activation coordinates for the contrasts of interest were transformed into Talairach space and submitted to an Activation Likelihood Estimation (ALE) meta-analysis in GingerALE 3.0.1. The results indicated that pronoun processing had functional convergence in the left posterior middle and superior temporal gyri, potentially reflecting the retrieval, prediction and integration roles of these areas for pronoun processing.

The spatiotemporal dynamics of semantic integration in the human brain

Language depends critically on the integration of lexical information across multiple words to derive semantic concepts. Limitations of spatiotemporal resolution have previously rendered it difficult to isolate processes involved in semantic integration. We utilized intracranial recordings in epilepsy patients (n = 58) who read written word definitions. Descriptions were either referential or non-referential to a common object. Semantically referential sentences enabled high frequency broadband gamma activation (70-150 Hz) of the inferior frontal sulcus (IFS), medial parietal cortex, orbitofrontal cortex (OFC) and medial temporal lobe in the left, language-dominant hemisphere. IFS, OFC and posterior middle temporal gyrus activity was modulated by the semantic coherence of non-referential sentences, exposing semantic effects that were independent of task-based referential status. Components of this network, alongside posterior superior temporal sulcus, were engaged for referential sentences that did not clearly reduce the lexical search space by the final word. These results indicate the existence of complementary cortical mosaics for semantic integration in posterior temporal and inferior frontal cortex.

Syntax response-space biases for hands, not feet

A number of studies have shown a relationship between comprehending transitive sentences and spatial processing (e.g., Chatterjee, Trends in Cognitive Sciences, 5(2), 55-61, 2001), in which there is an advantage for responding to images that depict the agent of an action to the left of the patient. Boiteau and Almor (Cognitive Science, 2016) demonstrated that a similar effect is found for pure linguistic information, such that after reading a sentence, identifying a word that had appeared earlier as the agent is faster on the left than on the right, but only for left-hand responses. In this study, we examined the role of lateralized manual motor processes in this effect and found that such spatial effects occur even when only the responses, but not the stimuli, have a spatial dimension. In support of the specific role of manual motor processes, we found a response-space effect with manual but not with pedal responses. Our results support an effector-specific (as opposed to an effector-general) hypothesis: Manual responses showed spatial effects compatible with those in previous research, whereas pedal responses did not. This is consistent with theoretical and empirical work arguing that the hands are generally involved with, and perhaps more sensitive to, linguistic information.

Bilateral parietal contributions to spatial language

It is commonly held that language is largely lateralized to the left hemisphere in most individuals, whereas spatial processing is associated with right hemisphere regions. In recent years, a number of neuroimaging studies have yielded conflicting results regarding the role of language and spatial processing areas in processing language about space (e.g., Carpenter, Just, Keller, Eddy, & Thulborn, 1999; Damasio et al., 2001). In the present study, we used sparse scanning event-related functional magnetic resonance imaging (fMRI) to investigate the neural correlates of spatial language, that is; language used to communicate the spatial relationship of one object to another. During scanning, participants listened to sentences about object relationships that were either spatial or non-spatial in nature (color or size relationships). Sentences describing spatial relationships elicited more activation in the superior parietal lobule and precuneus bilaterally in comparison to sentences describing size or color relationships. Activation of the precuneus suggests that spatial sentences elicit spatial-mental imagery, while the activation of the SPL suggests sentences containing spatial language involve integration of two distinct sets of information - linguistic and spatial.

Language in context: Characterizing the comprehension of referential expressions with MEG

A critical component of comprehending language in context is identifying the entities that individual linguistic expressions refer to. While previous research has shown that language comprehenders resolve reference quickly and incrementally, little is currently known about the neural basis of successful reference resolution. Using source localized MEG, we provide evidence across 3 experiments and 2 languages that successful reference resolution in simple visual displays is associated with increased activation in the medial parietal lobe. In each trial, participants saw a simple visual display containing three objects which constituted the referential domain. Target referential expressions were embedded in questions about the displays. By varying the displays, we manipulated referential status while keeping the linguistic expressions constant. Follow-up experiments addressed potential interactions of reference resolution with linguistic predictiveness and pragmatic plausibility. Notably, we replicated the effect in Arabic, a language that differs in a structurally informative way from English while keeping referential aspects parallel to our two English studies. Distributed minimum norm estimates of MEG data consistently indicated that reference resolution is associated with increased activity in the medial parietal lobe. With one exception, the timing of the onset of the medial parietal response fell into a mid-latency time-window at 350-500ms after the onset of the resolving word. Through concurrent EEG recordings on a subset of subjects we also describe the EEG topography of the effect of reference resolution, which makes the result available for comparison with a larger existing literature. Our results extend previous reports that medial parietal lobe is involved in referential language processing, indicating that it is relevant for reference resolution to individual referents, and suggests avenues for future research.

Language in Context: MEG Evidence for Modality-General and -Specific Responses to Reference Resolution

Successful language comprehension critically depends on our ability to link linguistic expressions to the entities they refer to. Without reference resolution, newly encountered language cannot be related to previously acquired knowledge. The human experience includes many different types of referents, some visual, some auditory, some very abstract. Does the neural basis of reference resolution depend on the nature of the referents, or do our brains use a modality-general mechanism for linking meanings to referents? Here we report evidence for both. Using magnetoencephalography (MEG), we varied both the modality of referents, which consisted either of visual or auditory objects, and the point at which reference resolution was possible within sentences. Source-localized MEG responses revealed brain activity associated with reference resolution that was independent of the modality of the referents, localized to the medial parietal lobe and starting ∼415 ms after the onset of reference resolving words. A modality-specific response to reference resolution in auditory domains was also found, in the vicinity of auditory cortex. Our results suggest that referential language processing cannot be reduced to processing in classical language regions and representations of the referential domain in modality-specific neural systems. Instead, our results suggest that reference resolution engages medial parietal cortex, which supports a mechanism for referential processing regardless of the content modality.