No abstract

When faced with situations where many people talk at once, individuals can employ different listening strategies to deal with the cacophony of speech sounds and to achieve different goals. In this fMRI study, we investigated how the pattern of neural activity is affected by the type of attention applied to speech in a simulated “cocktail party.” Specifically, we compared brain activation patterns when listeners “attended selectively” to only one speaker and ignored all others, versus when they “distributed their attention” and followed several concurrent speakers. Conjunction analysis revealed a highly overlapping network of regions activated for both types of attention, including auditory association cortex (bilateral STG/STS) and frontoparietal regions related to speech processing and attention (bilateral IFG/insula, right MFG, left IPS). Activity within nodes of this network, though, was modulated by the type of attention required as well as the number of competing speakers. Auditory and speech-processing regions exhibited higher activity during distributed attention, whereas frontoparietal regions were activated more strongly during selective attention. These results suggest a common “attention to speech” network, which provides the computational infrastructure to deal effectively with multi-speaker input, but with sufficient flexibility to implement different prioritization strategies and to adapt to different listener goals.

Managing attention in multispeaker environments is a challenging feat that is critical for human performance. However, why some people are better than others in allocating attention appropriately remains highly unknown. Here, we investigated the contribution of two factors-working memory capacity (WMC) and professional experience-to performance on two different types of attention task: selective attention to one speaker and distributed attention among multiple concurrent speakers. We compared performance across three groups: individuals with low (n = 20) and high (n = 25) WMC, and aircraft pilots (n = 24), whose profession poses extremely high demands for both selective and distributed attention to speech. Results suggests that selective attention is highly effective, with good performance maintained under increasingly adverse conditions, whereas performance decreases substantially with the requirement to distribute attention among a larger number of speakers. Importantly, both types of attention benefit from higher WMC, suggesting reliance on some common capacity-limited resources. However, only selective attention was further improved in the pilots, pointing to its flexible and trainable nature, whereas distributed attention seems to suffer from more fixed and severe processing bottlenecks.

Our goal in this study was to behaviorally characterize the property (or properties) that render negative quantifiers more complex in processing compared to their positive counterparts (e.g. the pair few/many). We examined two sources: (i) negative polarity; (ii) entailment reversal (aka downward monotonicity). While negative polarity can be found in other pairs in language such as dimensional adjectives (e.g. the pair small/large), only in quantifiers does negative polarity also reverse the entailment pattern of the sentence. By comparing the processing traits of negative quantifiers with those of non-monotone expressions that contain negative adjectives, using a verification task and measuring reaction times, we found that negative polarity is cognitively costly, but in downward monotone quantifiers it is even more so. We therefore conclude that both negative polarity and downward monotonicity contribute to the processing complexity of negative quantifiers.

High-level cognitive capacities that serve communication, reasoning, and calculation are essential for finding our way in the world. But whether and to what extent these complex behaviors share the same neuronal substrate are still unresolved questions. The present study separated the aspects of logic from language and numerosity-mental faculties whose distinctness has been debated for centuries-and identified a new cytoarchitectonic area as correlate for an operation involving logical negation. A novel experimental paradigm that was implemented here in an RT/fMRI study showed a single cluster of activity that pertains to logical negation. It was distinct from clusters that were activated by numerical comparison and from the traditional language regions. The localization of this cluster was described by a newly identified cytoarchitectonic area in the left anterior insula, ventro-medial to Broca's region. We provide evidence for the congruence between the histologically and functionally defined regions on multiple measures. Its position in the left anterior insula suggests that it functions as a mediator between language and reasoning areas.

Managing attention in multi-speaker environments is a challenging feat that is critical for human performance. However, why some people are better than others in allocating attention appropriately, remains highly unknown. Here we investigated the contribution of two factors -Cognitive Capacity and Acquired Experience -to performance on two different types of Attention task: Selective Attention to one speaker and Distributed Attention among multiple concurrent speakers. We compared performance across three groups: Individuals with low (n=20) and high cognitive capacity (n=26), and Aircraft Pilots (n=25), who have gained extensive experience on both Selective and Distributed attention to speech through their training and profession. Results indicate that both types of Attention benefit from higher Cognitive Capacity, suggesting reliance on common capacity-limited resources. However, only Selective Attention was further improved in the Pilots, pointing to its flexible and trainable nature, whereas Distributed Attention seems to suffer from more fixed and hard-wired processing-bottlenecks.

Spontaneous real-life speech is imperfect in many ways. It contains disfluencies and ill-formed utterances and has a highly variable rate. When listening to spontaneous speech, the brain needs to contend with these features in order to extract the speaker’s meaning. Here, we studied how the neural response is affected by four specific factors that are prevalent in spontaneous colloquial speech: (1) the presence of fillers, (2) the need to detect syntactic boundaries in disfluent speech, and (3) variability in speech rate. Neural activity (EEG) was recorded from individuals as they listened to an unscripted, spontaneous narrative, which was analyzed in a time-resolved fashion to identify fillers and detect syntactic boundaries. When considering these factors in a speech-tracking analysis, which estimates a temporal response function (TRF) to describe the relationship between the stimulus and the neural response it generates, we found that the TRF was affected by all of them. This response was observed for lexical words but not for fillers, and it had an earlier onset for opening words vs. closing words of a clause and for clauses with slower speech rates. These findings broaden ongoing efforts to understand neural processing of speech under increasingly realistic conditions. They highlight the importance of considering the imperfect nature of real-life spoken language, linking past research on linguistically well-formed and meticulously controlled speech to the type of speech that the brain actually deals with on a daily basis.

No abstract