Chia-Lin Lee

Imaging cortical dynamics of language processing with the event-related optical signal

Language processing involves the rapid interaction of multiple brain regions. The study of its neurophysiological bases would therefore benefit from neuroimaging techniques combining both good spatial and good temporal resolution. Here we use the event-related optical signal (EROS), a recently developed imaging method, to reveal rapid interactions between left superior/middle temporal cortices (S/MTC) and inferior frontal cortices (IFC) during the processing of semantically or syntactically anomalous sentences. Participants were presented with sentences of these types intermixed with nonanomalous control sentences and were required to judge their acceptability. ERPs were recorded simultaneously with EROS and showed the typical activities that are elicited when processing anomalous stimuli: the N400 and the P600 for semantic and syntactic anomalies, respectively. The EROS response to semantically anomalous words showed increased activity in the S/MTC (corresponding in time with the N400), followed by IFC activity. Syntactically anomalous words evoked a similar sequence, with a temporal-lobe EROS response (corresponding in time with the P600), followed by frontal activity. However, the S/MTC activity corresponding to a semantic anomaly was more ventral than that corresponding to a syntactic anomaly. These data suggest that activation related to anomaly processing in sentences proceeds from temporal to frontal brain regions for both semantic and syntactic anomalies. This first EROS study investigating language processing shows that EROS can be used to image rapid interactions across cortical areas.

To watch, to see, and to differ: An event-related potential study of concreteness effects as a function of word class and lexical ambiguity

Electrophysiological techniques were used to assess the generalizability of concreteness effects on word processing across word class (nouns and verbs) and different types of lexical ambiguity (syntactic only and combined syntactic/semantic). The results replicated prior work in showing an enhanced N400 response and a sustained frontal negativity to concrete as compared with abstract nouns. The effect of concreteness on the N400 generalized to all word class and ambiguity conditions, whereas the frontal effect was present for all word types except for the syntactically and semantically ambiguous items when these were used as verbs. The seemingly dissociable ERP effects of concreteness at frontal and central/posterior electrode sites revealed by these data suggest that concreteness may impact multiple aspects of neurocognitive processing.

It’s All in the Family Brain Asymmetry and Syntactic Processing of Word Class

Although left-hemisphere (LH) specialization for language is often viewed as a key example of functional lateralization, there is increasing evidence that the right hemisphere (RH) can also extract meaning from words and sentences. However, the right hemisphere’s ability to appreciate syntactic aspects of language remains poorly understood. In the current study, we used separable, functionally well-characterized electrophysiological indices of lexico-semantic and syntactic processes to demonstrate RH sensitivity to syntactic violations among right-handers with a strong manual preference. Critically, however, the nature of this RH sensitivity to structural information was modulated by a genetically determined factor—familial sinistrality. The right hemisphere in right-handers without left-handed family members processed syntactic violations via the words’ accompanying lexico-semantic unexpectedness. In contrast, the right hemisphere in right-handers with left-handed family members could process syntactic information in a manner qualitatively similar to that of the left hemisphere.

Revisiting the incremental effects of context on word processing: Evidence from single-word event-related brain potentials.

The amplitude of the N400-an event-related potential (ERP) component linked to meaning processing and initial access to semantic memory-is inversely related to the incremental buildup of semantic context over the course of a sentence. We revisited the nature and scope of this incremental context effect, adopting a word-level linear mixed-effects modeling approach, with the goal of probing the continuous and incremental effects of semantic and syntactic context on multiple aspects of lexical processing during sentence comprehension (i.e., effects of word frequency and orthographic neighborhood). First, we replicated the classic word-position effect at the single-word level: Open-class words showed reductions in N400 amplitude with increasing word position in semantically congruent sentences only. Importantly, we found that accruing sentence context had separable influences on the effects of frequency and neighborhood on the N400. Word frequency effects were reduced with accumulating semantic context. However, orthographic neighborhood was unaffected by accumulating context, showing robust effects on the N400 across all words, even within congruent sentences. Additionally, we found that N400 amplitudes to closed-class words were reduced with incrementally constraining syntactic context in sentences that provided only syntactic constraints. Taken together, our findings indicate that modeling word-level variability in ERPs reveals mechanisms by which different sources of information simultaneously contribute to the unfolding neural dynamics of comprehension.

Differential age effects on lexical ambiguity resolution mechanisms

Multiple neurocognitive subsystems are involved in resolving lexical ambiguity under different circumstances. We examined how processing in these subsystems changes with normal aging by comparing ERP responses to homographs and unambiguous words completing congruent sentences (with both semantic and syntactic contextual information) or syntactic prose (syntactic information only). Like young adults in prior work, older adults elicited more negative N400s to homographs in congruent sentences, suggesting mismatch between the context and residual activation of the contextually irrelevant sense. However, the frontal negativity seen in young adults to homographs in syntactically well-defined but semantically neutral contexts was absent in older adults as a group, suggesting a decline in recruiting additional neural resources to aid difficult semantic selection. A subset of older adults with high verbal fluency maintained a young-like effect pattern.

Ambiguity's aftermath: How age differences in resolving lexical ambiguity affect subsequent comprehension

When ambiguity resolution is difficult, younger adults recruit selection-related neural resources that older adults do not. To elucidate the nature of those resources and the consequences of their recruitment for subsequent comprehension, we embedded noun/verb homographs and matched unambiguous words in syntactically well-specified but semantically neutral sentences. Target words were followed by a prepositional phrase whose head noun was plausible for only one meaning of the homograph. Replicating past findings, younger but not older adults elicited sustained frontal negativity to homographs compared to unambiguous words. On the subsequent head nouns, younger adults showed plausibility effects in all conditions, attesting to successful meaning selection through suppression. In contrast, older adults showed smaller plausibility effects following ambiguous words and failed to show plausibility effects when the context picked out the homographs non-dominant meaning (i.e., they did not suppress the contextually-irrelevant dominant meaning). Meaning suppression processes, reflected in the frontal negativity, thus become less available with age, with consequences for subsequent comprehension.

Effects of semantic constraint and cloze probability on Chinese classifier-noun agreement

This study aims to examine when and how readers make use of top-down information to predict or integrate upcoming words by utilizing the characteristics of Chinese classifier-noun agreement, as measured by event-related potentials (ERPs). Constraint strength of classifiers (strong and weak) and cloze probability of the pairing noun (high, low, implausible) was manipulated. Weakly constrained classifiers elicited a less positive P200 and an enhanced frontal negativity than strongly constrained classifiers, suggesting that readers used the preceding classifier to predict the upcoming noun, even before the pairing noun appeared. For ERPs elicited by the pairing nouns, there was a significant interaction between semantic constraint and cloze probability for the N400. For nouns following the weakly constrained classifiers, there was a graded cloze probability effect on the N400 (High < Low < Imp). For nouns following the strongly constrained classifiers, both low cloze and implausible nouns elicited larger N400s than high cloze nouns; however, there was no difference between low cloze and implausible nouns. The critical comparison for the constraint effect of low cloze nouns was found for the N400 but not for frontal

Dynamic analog testing via ATE digital test channels

A dynamic analog test methodology using digital tester is proposed. A simple triangular waveform is built on the device interface board for the stimulus generation. The response waveform is quantized by the dual comparators in a digital pin electronic circuit. Statistical analysis is conducted to enhance the quantization resolution and minimize the noise effect. The experimental results using an ATE show that the error is less than 2%. It confirms the feasibility of the proposed methodology.

Word meanings survive visual crowding: evidence from ERPs

ABSTRACT Conscious identification of an object in the periphery is drastically impaired when it is surrounded by flankers as opposed to when presented in isolation; this is known as visual crowding. However, one previous behavioural study has shown that semantic priming can actually occur from a crowded stimulus [Yeh, He, & Cavanagh, 2012. Semantic priming from crowded words. Psychological Science, 23(6), 608–616. doi:10.1177/0956797611434746]. Based on this finding, the current study used event-related potentials (ERPs; N400 component) to verify that the response facilitation seen in Yeh et al. [2012. Semantic priming from crowded words. Psychological Science, 23(6), 608–616. doi:10.1177/0956797611434746] indeed occurs at the semantic level. We confirmed that the crowded words do produce semantic-level priming. That is, crowded words led to N400 reduction on subsequent targets: the semantically related target elicited a smaller N400 component than did the unrelated targets. And both crowded and isolated primes elicited the same amount of N400 reduction, consistent with the previous behavioural result. Several models on crowding and word processing are discussed and an alternative word processing theory is proposed to explain our results.

Sensory and semantic activations evoked by action attributes of manipulable objects: Evidence from ERPs

&NA; “Two route” theories of object‐related action processing posit different temporal activation profiles of grasp‐to‐move actions (rapidly evoked based on object structure) versus skilled use actions (more slowly activated based on semantic knowledge). We capitalized on the exquisite temporal resolution and multidimensionality of Event‐Related Potentials (ERPs) to directly test this hypothesis. Participants viewed manipulable objects (e.g., calculator) preceded by objects sharing either “grasp”, “use”, or no action attributes (e.g., bar of soap, keyboard, earring, respectively), as well as by action‐unrelated but taxonomically‐related objects (e.g., abacus); participants judged whether the two objects were related. The results showed more positive responses to “grasp‐to‐move” primed objects than “skilled use” primed objects or unprimed objects starting in the P1 (0–150 ms) time window and continuing onto the subsequent N1 and P2 components (150–300 ms), suggesting that only “grasp‐to‐move”, but not “skilled use”, actions may facilitate visual attention to object attributes. Furthermore, reliably reduced N400s (300–500 ms), an index of semantic processing, were observed to taxonomically primed and “skilled use” primed objects relative to unprimed objects, suggesting that “skilled use” action attributes are a component of distributed, multimodal semantic representations of objects. Together, our findings provide evidence supporting two‐route theories by demonstrating that “grasp‐to‐move” and “skilled use” actions impact different aspects of object processing and highlight the relationship of “skilled use” information to other aspects of semantic memory. Highlights“Grasp‐to‐move” and “skilled use” actions impact object processing differently.Early visual attention‐based priming was found for “grasp‐to‐move” actions.Anterior N400 effects were found for “skilled use” actions.The “two route” hypothesis of object‐related action processing is supported.