Sandra Virtue

Neural activity of inferences during story comprehension

In this event-related functional magnetic resonance imaging (fMRI) study, participants listened to and comprehended short stories implying or explicitly stating inference events. The aim of this study was to examine the neural mechanisms that underlie inference generation, a process essential to successful comprehension. We observed distinct patterns of increased fMRI signal for implied over explicit events at two critical points during the stories: (1) within the right superior temporal gyrus when a verb in the text implied the inference; and (2) within the left superior temporal gyrus at the coherence break or when participants need to generate an inference to understand the story. To find the most compelling evidence of neural activity during inference generation, we examined fMRI signal at these two critical points separately for people with high working memory capacity (i.e., those individuals who are most likely to draw inferences during text comprehension). Interestingly, high working memory individuals showed greater fMRI signal for implied than explicit events in the left inferior frontal gyrus at the coherence break compared to low working memory individuals. This present study provides evidence that areas within the superior temporal gyrus and inferior frontal gyrus are heavily recruited when individuals generate inferences, even during ongoing comprehension that demands many cognitive processes. In addition, the data suggest that the right hemisphere superior temporal gyrus is particularly involved during early inferential processing, whereas the left hemisphere superior temporal gyrus is particularly involved during later inferential processing in story comprehension.

Fluctuations in the Availability of Information During Reading: Capturing Cognitive Processes Using the Landscape Model

In this investigation, we examine the availability of text elements over the course of reading a text. We describe the Landscape model (van den Broek, Young, Tzeng, & Linderholm, 1999) that captures, in one theoretical framework, multiple cognitive processes during reading and the resulting fluctuating activations of text elements. To demonstrate the applicability of the Landscape model, we simulate the availability of text elements in two reading situations. First, the Landscape model is shown to incorporate readers� specific purpose for reading, affecting the availability of text elements as a function of different standards of coherence. Second, the Landscape model is shown to incorporate readers� background knowledge during reading, allowing readers to detect inconsistencies in a text. Theoretical accounts such as the Landscape model extend our understanding of—and to investigate—the process of reading by providing information about the availability of text elements in a unified theoretical framework, thereby extending and complementing behavioral data.

Inferences during story comprehension: Cortical recruitment affected by predictability of events and working memory capacity

Although it has been consistently shown that readers generate bridging inferences during story comprehension, little is currently known about the neural substrates involved when people generate inferences and how these substrates shift with factors that facilitate or impede inferences, such as whether inferences are highly predictable or unpredictable. In the current study, functional magnetic resonance imaging (fMRI) signal increased for highly predictable inferences (relative to events that were previously explicitly stated) bilaterally in both the superior temporal gyri and the inferior frontal gyri. Interestingly, high working memory capacity comprehenders, who are most likely to generate inferences during story comprehension, showed greater signal increases than did low working memory capacity comprehenders in the right superior temporal gyrus and right inferior frontal gyrus. When comprehenders needed to draw unpredictable inferences in a story, fMRI signal increased relative to explicitly stated events in the left inferior gyrus and in the middle frontal gyrus, irrespective of working memory capacity. These results suggest that the predictability of a text (i.e., the causal constraint) and the working memory capacity of the comprehender influence the different neural substrates involved during the generation of bridging inferences.

Hemispheric processing of inferences: The effects of textual constraint and working memory capacity

In this study, we investigated hemispheric differences in the generation of bridging and predictive inferences. Participants read texts that provided either strong or weak causal constraints for a particular bridging (Experiment 1) or predictive (Experiment 2) inference and performed a lexical decision task to inference-related targets presented to the left or the right hemisphere. Facilitation for strongly constrained bridging and predictive inferences was found in both hemispheres. In contrast, facilitation for weakly constrained inferences was stronger in the right than in the left hemisphere for both bridging and predictive inferences, although for the latter there was some facilitation in the left hemisphere as well. We also considered whether these effects differ as a function of the working memory capacity of the reader. High working memory capacity readers showed greater facilitation for strongly constrained inferences than for weakly constrained inferences in both hemispheres, whereas low working memory capacity readers showed this same pattern in the left hemisphere but showed equal facilitation for strongly and weakly constrained inferences in the right hemisphere. These results suggest that hemispheric processing, textual constraint, and working memory capacity interact to affect how readers generate causal inferences.

Processing Causality in Narrative Events: Temporal Order Matters

To successfully comprehend narrative text, readers often make inferences about different causes and effects that occur in a text. In this study, participants read texts in which events related to a cause were presented before an effect (i.e., the forward causal condition), texts in which an effect was presented before the events related to a cause (i.e., the backward causal condition), or control (i.e., the non-causal) texts. Lexical decision response times to cause-relevant words were faster in the forward causal condition than in the control condition and were faster in the backward causal condition than in the control condition. Importantly, response times were faster in the forward causal condition than in the backward causal condition. These effects were unrelated to individual differences in reading ability. These results suggest that readers process causal relations regardless of temporal order but that causal events presented in backward temporal order may be processed more slowly compared to causal events presented in forward temporal order.

A Longitudinal Analysis of Criminal and Aggressive Behaviors Among a National Sample of Adults in Mutual-Help Recovery Homes

Criminal and aggressive behaviors are frequently observed among those recovering from substance abuse problems. In the present one-year longitudinal study, a national sample of residents from self-governed, communal-living recovery homes for substance abuse completed baseline and follow-up measures of criminal and aggressive behavior. Results indicated that a length of stay of 6 months or longer was associated with lower levels of self-reported criminal and aggressive behaviors at the one-year follow-up. Environmental mechanisms proposed as influences for these outcomes, as well as treatment implications, are discussed.

Hemispheric processing of inferences during text comprehension: the role of consistency and task difficulty.

Although the hemispheres likely carry out different processes during reading, currently little is known about how the consistency effect and the difficulty of the task influences hemispheric processing during text comprehension. In the current study participants read texts promoting an inference, and performed a lexical decision task to inference-related targets presented to the left visual field–right hemisphere or the right visual field–left hemisphere. To manipulate the consistency of information targets were either consistent or inconsistent with the inference. To manipulate difficulty the antecedent and its referent were either separated by two sentences (i.e., the less-difficult condition) or four sentences (i.e., the more-difficult condition). In the consistent condition facilitation was greater in the left hemisphere than the right hemisphere. In the inconsistent condition facilitation was greater in the right hemisphere than the left hemisphere. When analyses were combined across conditions, consistent targets showed greater facilitation in the left hemisphere than in the right hemisphere. Interestingly the level of difficulty did not mediate how the hemispheres process inferences. The current findings suggest that the consistency of information, rather than the difficulty of a task, primarily influences inference generation in the cerebral hemispheres.

Hemispheric processing of idioms: The influence of familiarity and ambiguity

Abstract Recent findings suggest that the right hemisphere plays a key role when readers comprehend figurative language. However, it is currently unclear how specific types of figurative language, such as idioms (e.g., “to bury the hatchet”), are processed in the right and left cerebral hemispheres. Prior research suggests that a readers previous exposure to an idiomatic phrase (i.e., the level of familiarity) and the plausibility of an idiom (i.e., the level of ambiguity) influence how idioms are processed. To investigate how familiarity influences the hemispheric processing of idioms (Experiment 1), participants read texts containing familiar or less familiar idioms and made lexical decisions to related target words presented to the left visual field-right hemisphere or to the right visual field-left hemisphere. To investigate how ambiguity influences the hemispheric processing of idioms (Experiment 2), participants read texts containing high or low ambiguity idioms and completed a lexical decision task to related target words presented to each visual field-hemisphere. For both familiar and less familiar idioms, greater facilitation was evident in the left hemisphere than in the right hemisphere. Additionally, greater facilitation was evident in the left hemisphere for low ambiguity idioms than for high ambiguity idioms, and greater facilitation was evident in the right hemisphere for high ambiguity idioms than for low ambiguity idioms. These findings suggest that the right hemisphere has an advantage when readers process ambiguous idioms, whereas the left hemisphere has an advantage when readers process low ambiguity idioms, and both familiar and less familiar idioms.

Hemispheric processing in bilinguals: The role of shared meanings across languages and sentential constraint

In monolinguals, the right hemisphere plays a key role when readers process multiple meanings of ambiguous words and when text weakly leads to a specific outcome (i.e., is weakly constrained). However, currently little is known about the influence of word meanings and sentential constraint in the hemispheres of bilinguals. Using a divided visual field paradigm, we investigated how cognates, interlingual homographs, and control words (within strongly and weakly constrained sentences) influence hemispheric processing in bilinguals. In the current study, both languages showed facilitation in the right hemisphere, whereas only the language currently in use showed facilitation in the left hemisphere. In addition, bilinguals (unlike monolinguals) processed strongly constrained targets more quickly than weakly constrained targets in both hemispheres. Thus, bilinguals and monolinguals process shared meanings of words similarly in the right hemisphere, but process sentential constraint differently in the hemispheres.

Hemispheric processing of semantic information: The effects of the semantic priming task and working memory capacity

In a classic semantic priming study (Beeman et al., 1994), participants showed a naming advantage for strongly related targets compared to weakly related targets in the left hemisphere, whereas no difference in naming advantage was found between strongly and weakly related targets in the right hemisphere. However, it is unclear how the type of task and individual differences influence this hemispheric activation. In the current study participants completed a lexical decision task when presented with strongly, weakly, and unrelated words in each visual field-hemisphere. A left hemisphere advantage was evident for strongly and weakly related words compared to unrelated words and a right hemisphere advantage was evident for strongly related words compared to weakly related and unrelated words. Additionally, high working memory capacity participants responded more accurately to strongly related words than weakly or unrelated words in the right hemisphere, whereas low working memory capacity participants showed no difference between these conditions in the right hemisphere. Thus, the type of semantic priming task and working memory capacity seem to influence the hemispheric processing of strongly and weakly related information.