Which Way to Integration? Examining Directional Association in Word-to-Text Integration Using ERPs

Skilled reading proceeds in a largely incremental manner, with readers attempting to integrate linguistic information from each word as it is encountered. The degree to which prospective and retrospective integration processes are functional in driving incrementally remains an open area of inquiry. In this study, event-related potentials (ERPs) were used to explore on-line lexico-semantic integration in conditions in which prospective and retrospective processing was more or less likely to occur, through the manipulation of the direction of lexical association between word in isolation and embedded in two-sentence texts. The N400 ERP component, an index of lexico-semantic processing, was examined across forward and backward association conditions. In both a word relatedness judgment (RJ) task and text comprehension (TC) task, reduced N400 amplitudes were seen over central scalp electrodes in conditions in which word pairs were either forward associated or backward associated, relative to conditions in which word pairs were unrelated (RJ) or lacking one word of the pair (TC). Additionally, a reduced negativity was found for forward associated pairs over right parietal electrodes in RJ, and an increased positivity was found for the backward associated condition over left parietal electrodes in TC. The evidence from central electrodes suggests that retrospective integration processes, and not simply prospective expectancy processes, modulate the N400 in incremental text processing. Additionally, the results suggest an enhanced role for expectancy in modulating ERPs at right parietal sites, and, potentially, an engagement of memory resonance processes in text processing over left parietal sites

Impact of discourse on incremental comprehension processes: Event-related potential studies of word-by-word reading

The studies in this Dissertation used EEG/ERP to examine readers’ incremental, on-line reading comprehension. Study 1 tested the ability of words - as the closing elements of propositions - to trigger outdated mental representations. Participants read text passages in 3 conditions - Consistent, Inconsistent, and Causal. The Inconsistent condition differed from the Consistent condition due to protagonist inconsistencies. Additionally, the Causal condition differed from the Inconsistent condition by the addition of single-sentence causal justifications for the inconsistencies. Electrophysiological results indicated that readers were sensitive to inconsistencies from quite early in word processing, suggesting the functioning of semantically related attentional processes drawn to the meaning features of the input. At later time windows, both words in inconsistent passages and words in causal passages differed from those in consistent passages, with effects varying by scalp location, suggesting related but somewhat functionally distinct memorial processes. Overall, the responses are interpreted as reflecting on-line attentional and memorial mechanisms involved in detecting when a word “doesn’t fit” in a text or discourse, as well those involved when there is more than one available “interpretation” of a text. Study 2 tested the potential effects of contextually-guided referential semantics. Participants read two-sentence texts created to influence a representation that specified one conceptual feature in the first sentence. The second sentence contained a word that was either Consistent or Inconsistent with that feature. The results from Study 2 diverged from predictions in two ways. First, no N400 differences were found between conditions. This was similar to what was found in Study 1 and provides support for a connection between semantic binding and the N400 in connected text. Second, a frontal P600 was found, but in the opposite direction as predicted, with related words eliciting more positive responses than unrelated words. Potentially, this reflects the ability of words in the Feature Consistent texts to act as retrieval cues for related features in the first sentence. In both studies in this Dissertation, effects across levels of linguistic representation were observed, albeit to a lesser extent in Study 2. These findings provide on-line evidence of word-level processing during text comprehension

Early stage visual-orthographic processes predict long-term retention of word form and meaning: A visual encoding training study

Adult learners of Chinese learned new characters through writing, visual chunking or reading-only. Following training, ERPs were recorded during character recognition tasks, first shortly after the training and then three months later. We hypothesized that the character training effects would be seen in ERP components associated with word recognition and episodic memory. Results confirmed a larger N170 for visual chunking training than other training and a larger P600 for learned characters than novel characters. Another result was a training effect on the amplitude of the P100, which was greater following writing training than other training, suggesting that writing training temporarily lead to increased visual attention to the orthographic forms. Furthermore, P100 amplitude at the first post-test was positively correlated with character recall 3 months later. Thus the marker of early visual attention (P100) was predictive of retention of orthographic knowledge acquired in training

Learning new meanings for known words: biphasic effects of prior knowledge

<p>Long after knowing the meaning of roller-“skate”, one may learn that “skate” is also a kind of fish. Such learning of new meanings for familiar words involves two potentially contrasting processes: form-based familiarity may facilitate the learning, and meaning-based interference may be inhibitory. We had native speakers learn new meanings for familiar and less familiar words, as well as for unfamiliar (novel) words. Tracking learning at several points revealed a biphasic pattern: higher learning rates and greater learning efficiency for familiar words relative to novel words early in learning and a reversal of this pattern later. After meaning learning, lexical access to familiar, but not to less familiar, words became faster than exposure controls. Overall, the results suggest that form-based familiarity facilitates learning earlier, while meaning-based interference becomes more influential later. The co-activation of new and old meanings during learning may play a role in lexicalisation of new meanings.</p

ERP Indicators of local and global text influences on word-to-text integration

<p>In two ERP experiments we examined local (recent text) and global (centrality) text influences on word-to-text integration. Participants read words that appeared across a sentence boundary or in text-final position. In both cases, the word was either related (central) or unrelated (non-central) to the central theme of the passage. Additionally, words across a sentence boundary had an antecedent in the preceding sentence (local binding) or did not (baseline). Results indicate local-binding processes influence sentence-initial words with no additional effect of centrality, evidenced by a reduced N400 for central and non-central words with a local-binding opportunity relative to baseline. At text-final words, we observed a reduced P600 (Experiment 1) as well as an N400 (Experiment 2) for central relative to non-central words. This pattern suggests that integration across a sentence boundary is supported by local context and that over the course of continued reading, integration begins to reflect global text meaning.</p