Phase-encoded fMRI tracks down brainstorms of natural language processing with subsecond precision.

Natural language processing unfolds information overtime as spatially separated, multimodal, and interconnected neural processes. Existing noninvasive subtraction-based neuroimaging techniques cannot simultaneously achieve the spatial and temporal resolutions required to visualize ongoing information flows across the whole brain. Here we have developed rapid phase-encoded designs to fully exploit the temporal information latent in functional magnetic resonance imaging data, as well as overcoming scanner noise and head-motion challenges during overt language tasks. We captured real-time information flows as coherent hemodynamic waves traveling over the cortical surface during listening, reading aloud, reciting, and oral cross-language interpreting tasks. We were able to observe the timing, location, direction, and surge of traveling waves in all language tasks, which were visualized as "brainstorms" on brain "weather" maps. The paths of hemodynamic traveling waves provide direct evidence for dual-stream models of the visual and auditory systems as well as logistics models for crossmodal and cross-language processing. Specifically, we have tracked down the step-by-step processing of written or spoken sentences first being received and processed by the visual or auditory streams, carried across language and domain-general cognitive regions, and finally delivered as overt speeches monitored through the auditory cortex, which gives a complete picture of information flows across the brain during natural language functioning. PRACTITIONER POINTS: Phase-encoded fMRI enables simultaneous imaging of high spatial and temporal resolution, capturing continuous spatiotemporal dynamics of the entire brain during real-time overt natural language tasks. Spatiotemporal traveling wave patterns provide direct evidence for constructing comprehensive and explicit models of human information processing. This study unlocks the potential of applying rapid phase-encoded fMRI to indirectly track the underlying neural information flows of sequential sensory, motor, and high-order cognitive processes.

Phase-encoded fMRI tracks down brainstorms of natural language processing with sub-second precision.

The human language system interacts with cognitive and sensorimotor regions during natural language processing. However, where, when, and how these processes occur remain unclear. Existing noninvasive subtraction-based neuroimaging techniques cannot simultaneously achieve the spatial and temporal resolutions required to visualize ongoing information flows across the whole brain. Here we have developed phase-encoded designs to fully exploit the temporal information latent in functional magnetic resonance imaging (fMRI) data, as well as overcoming scanner noise and head-motion challenges during overt language tasks. We captured neural information flows as coherent waves traveling over the cortical surface during listening, reciting, and oral cross-language interpreting. The timing, location, direction, and surge of traveling waves, visualized as 'brainstorms' on brain 'weather' maps, reveal the functional and effective connectivity of the brain in action. These maps uncover the functional neuroanatomy of language perception and production and motivate the construction of finer-grained models of human information processing.

Lexico-semantic Activation of Translation Equivalents During the Attentional Blink.

The attentional blink (AB) refers to the impaired identification of the second target (T2) when presented within approximately 500ms after the first target (T1). Although the AB is eliminated when two targets can be integrated into a single compound word, it remains unclear whether the lexico-semantic organization of translation equivalents modulates the magnitude of the AB. In the present study, we examined consecutive targets' processing in a rapid serial visual presentation (RSVP) paradigm using Chinese-English translation equivalents and non-translation equivalents. The results demonstrated that an overall presence of the AB effect was observed when T1 and T2 were non-translation equivalents. However, the AB effect disappeared completely when the two target words were translation equivalents. Taken together, these findings suggest that Chinese-English bilinguals are translating intentionally between Mandarin and English, which facilitates lexical access to word meaning from the two languages at the initial stages of visual word processing. Furthermore, such lexico-semantic activation of translation equivalents attributes to the elimination of the AB.

Electrophysiological Correlates of Character Transposition in the Left and Right Visual Fields.

This study examined the brain activity elicited by the hemispheric asymmetries and morpheme transposition of two-character Chinese words (canonical and transposed word) and pseudowords using event-related potentials (ERPs) with a dual-target rapid serial visual presentation (RSVP) task. Electrophysiological results showed facilitation effects for canonical words with centrally presented visual field (CVF) and right visual field (RVF) presentations but not with left visual field (LVF) presentations, as reflected by less negative N400 amplitudes. Moreover, more positive late positive component (LPC) amplitudes were observed for both canonical words and transposed words irrespective of the visual fields. More importantly, transposed words elicited a more negative N400 amplitude and a less positive LPC amplitude compared with the amplitudes elicited by canonical words for CVF and RVF presentations. For LVF presentations, transposed words elicited a less negative N250 amplitude compared with canonical words, and there was no significant difference between canonical words and transposed words in the N400 effect. Taken together, we concluded that character transposition facilitated the mapping of whole-word orthographic representation to semantic information in the LVF, as reflected by the N250 component, and such morpheme transposition influenced whole-word semantic processing in CVF and RVF presentations, as reflected by N400 and LPC components.

Which is more costly in Chinese to English simultaneous interpreting, "pairing" or "transphrasing"? Evidence from an fNIRS neuroimaging study.

This study examined the neural mechanism underlying two translation strategies associated with Chinese to English simultaneous interpreting (SI) targeting the left prefrontal cortex (PFC), which is generally involved in the control of interference and conflict resolution and has been identified as the brain area that plays a pivotal role in SI. Brain activation associated with the two strategies including "pairing" and "transphrasing" were compared with that from "nontranslation," which keeps the source language item unchanged in the target language production and is considered as a tactic that does not require complex cognitive operation associated with bilingual processing effort. Our findings revealed that "pairing" elicited the strongest and almost immediate brain activation in the Broca's area, and "transphrasing" resulted in the most extensive and strongest activation overall in the left PFC. By contrast, "nontranslation" induced very little brain activation in these regions. This work, which represents one of the first efforts in investigating brain activation related to translation strategies involving different levels of cognitive control, will not only pave a new avenue for better understanding of the cognitive mechanism underlying SI but also provide further insight into the role that the Broca's region plays in domain-general cognitive control.