Ventral and dorsal streams for choosing word order during sentence production.

Proficient language use requires speakers to vary word order and choose between different ways of expressing the same meaning. Prior statistical associations between individual verbs and different word orders are known to influence speakers' choices, but the underlying neural mechanisms are unknown. Here we show that distinct neural pathways are used for verbs with different statistical associations. We manipulated statistical experience by training participants in a language containing novel verbs and two alternative word orders (agent-before-patient, AP; patient-before-agent, PA). Some verbs appeared exclusively in AP, others exclusively in PA, and yet others in both orders. Subsequently, we used sparse sampling neuroimaging to examine the neural substrates as participants generated new sentences in the scanner. Behaviorally, participants showed an overall preference for AP order, but also increased PA order for verbs experienced in that order, reflecting statistical learning. Functional activation and connectivity analyses revealed distinct networks underlying the increased PA production. Verbs experienced in both orders during training preferentially recruited a ventral stream, indicating the use of conceptual processing for mapping meaning to word order. In contrast, verbs experienced solely in PA order recruited dorsal pathways, indicating the use of selective attention and sensorimotor integration for choosing words in the right order. These results show that the brain tracks the structural associations of individual verbs and that the same structural output may be achieved via ventral or dorsal streams, depending on the type of regularities in the input.

Cognitive control during sentence generation.

Sentence generation involves selecting the right words out of multiple co-activated representations for the right utterance positions. This selection process is hypothesized to involve cognitive control. Previous research has linked cognitive control during language processing to regions within the frontal lobe, including the anterior cingulate cortex (ACC) and left ventrolateral prefrontal cortex (VLPFC). We examined the neural correlates of word and sentence generation to determine whether these cognitive control regions were activated more for sentences than words. We also manipulated the phonological overlap between nouns in the sentence to determine whether cognitive control recruitment increased under phonological competition. Whole-brain analysis revealed increased activation in the ACC and bilateral frontal cortex for sentences over words. Region of interest analysis revealed an effect of phonological competition within the ACC. Psychophysiological interaction (PPI) analysis further showed that functional connectivity within a task-maintenance network increased under phonological competition. These results suggest a role for conflict detection and monitoring during sentence generation, which is consistent with a theoretical framework incorporating domain-general cognitive control processes into language processing.

Acquiring and Producing Sentences: Whether Learners Use Verb-Specific or Verb-General Information Depends on Cue Validity.

Learning to produce sentences involves learning patterns that enable the generation of new utterances. Language contains both verb-specific and verb-general regularities that are relevant to this capacity. Previous research has focused on whether one source is more important than the other. We tested whether the production system can flexibly learn to use either source, depending on the predictive validity of different cues in the input. Participants learned new sentence structures in a miniature language paradigm. In three experiments, we manipulated whether individual verbs or verb-general mappings better predicted the structures heard during learning. Evaluation of participants' subsequent production revealed that they could use either the structural preferences of individual verbs or abstract meaning-to-form mappings to construct new sentences. Further, this choice varied according to cue validity. These results demonstrate flexibility within the production architecture and the importance of considering how language was learned when discussing how language is used.

Intrusive effects of semantic information on visual selective attention.

Every object is represented by semantic information in extension to its low-level properties. It is well documented that such information biases attention when it is necessary for an ongoing task. However, whether semantic relationships influence attentional selection when they are irrelevant to the ongoing task remains an open question. The ubiquitous nature of semantic information suggests that it could bias attention even when these properties are irrelevant. In the present study, three objects appeared on screen, two of which were semantically related. After a varying time interval, a target or distractor appeared on top of each object. The objects' semantic relationships never predicted the target location. Despite this, a semantic bias on attentional allocation was observed, with an initial, transient bias to semantically related objects. Further experiments demonstrated that this effect was contingent on the objects being attended: if an object never contained the target, it no longer exerted a semantic influence. In a final set of experiments, we demonstrated that the semantic bias is robust and appears even in the presence of more predictive cues (spatial probability). These results suggest that as long as an object is attended, its semantic properties bias attention, even if it is irrelevant to an ongoing task and if more predictive factors are available.

Controlled processing during sequencing.

Longstanding evidence has identified a role for the frontal cortex in sequencing within both linguistic and non-linguistic domains. More recently, neuropsychological studies have suggested a specific role for the left premotor-prefrontal junction (BA 44/6) in selection between competing alternatives during sequencing. In this study, we used neuroimaging with healthy adults to confirm and extend knowledge about the neural correlates of sequencing. Participants reproduced visually presented sequences of syllables and words using manual button presses. Items in the sequence were presented either consecutively or concurrently. Concurrent presentation is known to trigger the planning of multiple responses, which might compete with one another. Therefore, we hypothesized that regions involved in controlled processing would show greater recruitment during the concurrent than the consecutive condition. Whole-brain analysis showed concurrent > consecutive activation in sensory, motor and somatosensory cortices and notably also in rostral-dorsal anterior cingulate cortex. Region of interest analyses showed increased activation within left BA 44/6 and correlation between this region's activation and behavioral response times. Functional connectivity analysis revealed increased connectivity between left BA 44/6 and the posterior lobe of the cerebellum during the concurrent than the consecutive condition. These results corroborate recent evidence and demonstrate the involvement of BA 44/6 and other control regions when ordering co-activated representations.