Biomedical subjects

Kathleen Baynes

Publications and source records attributed to Kathleen Baynes.

8 recordsLinked to original sources

PubMed2006

The representation of discourse in the two hemispheres: an individual differences investigation.

Two experiments were conducted to investigate discourse representation in the two cerebral hemispheres as a function of reading skill. We used a lateralized visual-field procedure to compare left hemisphere (LH) and right hemisphere (RH) sensitivity to different discourse relations in readers with varying skill levels. In Experiment 1, we investigated two levels of discourse representation in memory: (a) the propositional representation and (b) the discourse model. We found that all readers were sensitive to propositional relations in the LH. In contrast, sensitivity to propositional relations in the RH increased as a function of reading skill. In addition, reading skill was positively related to topic relations in the LH, whereas it was negatively in the RH. In Experiment 2, we investigated propositional relations of different distances and again found that all readers were sensitive to propositional relations in the LH, whereas sensitivity to propositional relations in the RH was negatively related to reading skill. In general, reading skill appears to be associated with left-lateralized discourse representations.

Brain↗

PubMed2006

Hemispheric differences in the activation of perceptual information during sentence comprehension.

Previous research has suggested that perceptual information about objects is activated during sentence comprehension [Zwaan, R. A., Stanfield, R. A., & Yaxley, R. H. (2002). Language comprehenders mentally represent the shapes of objects. Psychological Science, 13(2), 168-171]. The goal in the current study was to examine the role of the two hemispheres in the activation of such information. Participants read sentences that conveyed information about the shape of an object (e.g., the egg was in the pan versus the egg was in the carton) and then received a picture of the object that was either consistent or inconsistent with the shape implied by the sentence (e.g., a fried egg versus a whole egg). In Experiment 1, pictures were presented briefly in either the left-visual field or the right-visual field. Participants showed a mismatch effect, slower responses when the picture was inconsistent with the shape of the object implied by the sentence than when it was consistent, but only when the pictures appeared in the right-visual field (left hemisphere). In Experiment 2, the sentences were revised such that the shape of the object was described explicitly. Participants showed a mismatch effect in both visual fields. These findings suggest that the right hemisphere activates shape information during sentence comprehension when a shape description is explicit, whereas the left hemisphere activates such information both when the shape is described explicitly and when it is implied.

Adolescent↗

PubMed2005

The propositional structure of discourse in the two cerebral hemispheres.

Readers construct at least two interrelated representations when they comprehend a text: (a) a representation of the explicit ideas in a text and the relations among them (i.e., a propositional representation) and (b) a representation of the context or situation to which a text refers (i.e., a discourse model). In a recent study, found evidence that readers' representations were structured according to propositional relations, but only in the left hemisphere. Both hemispheres, however, appeared to represent contextually relevant semantic information. The goal in the current study was to examine further the organization of explicit text concepts in the two hemispheres. We used an item-priming-in-recognition paradigm in combination with a lateralized visual-field manipulation. We found evidence for a propositionally structured representation in the left hemisphere, that is, priming effects that reflected the linear distance between primes and targets in the propositional structure of passages. We also found that the right hemisphere represented explicit text concepts, but we found no evidence that these concepts were organized structurally. In a second experiment, we found our item priming effects reflected the representation of text information in memory and did not reflect lexical-semantic priming at test.

Adolescent↗

PubMed2005

Auditory perceptual grouping and attention in dyslexia.

Despite dyslexia affecting a large number of people, the mechanisms underlying the disorder remain undetermined. There are numerous theories about the origins of dyslexia. Many of these relate dyslexia to low-level, sensory temporal processing deficits. Another group of theories attributes dyslexia to language-specific impairments. Here, we show that dyslexics perform worse than controls on an auditory perceptual grouping task. The results show differences in performance between the groups that depend on sound frequency and not solely on parameters related to temporal processing. Performance on this task suggests that dyslexics' deficits may result from impaired attentional control mechanisms. Such deficits are neither modality nor language-specific and may help to reconcile differences between theories of dyslexia.

Acoustic Stimulation↗

PubMed2004

Right hemisphere reading mechanisms in a global alexic patient.

We investigated the implicit, or covert, reading ability of a global alexic patient (EA) to help determine the contribution of the right hemisphere to reading. Previous studies of alexic patients with left hemisphere damage have suggested that the ability to derive meaning from printed words that cannot be read out loud may reflect right hemisphere reading mechanisms. Other investigators have argued that residual left hemisphere abilities are sufficient to account for implicit reading and moreover do not require the postulation of a right hemisphere system that has no role in normal reading processes. However, few studies have assessed covert reading in patients with lesions as extensive as the one in EA, which affected left medial, inferior temporal-occipital cortex, hippocampus, splenium, and dorsal white matter. EA was presented with lexical decision, semantic categorization, phonemic categorization, and letter matching tasks. Although EA was unable to access phonology and could not overtly name words or letters, she was nevertheless capable of making lexical and semantic decisions at above chance levels, with an advantage for concrete versus abstract words. Her oral and written spelling were relatively intact, suggesting that orthographic knowledge is retained, although inaccessible through the visual modality. Based on her ability to access lexical and semantic information without contacting phonological representations, we propose that EA's implicit reading emerges from, and is supported, by the right hemisphere. Finally, we conclude that her spelling and writing abilities are supported by left hemisphere mechanisms.

Anomia↗

PubMed2003

Pyridoxine-dependent seizures and cognition in adulthood.

A case report of neonatal onset pyridoxine-dependent seizures in a male patient with early diagnosis and treatment is presented. The patient's epilepsy was recognized and treated with pyridoxine (vitamin B6) within 8 hours of birth. Treatment has been nearly continuous since that time. This paper reports the results of a full neuropsychological evaluation at age 37 years and MRI completed at age 31 years. Consistent with other case reports in the literature, there was a significant Performance IQ (PIQ) advantage with decreased Verbal IQ (VIQ) and expressive language skills (Full-Scale IQ 71, VIQ 64, PIQ 85). MRI demonstrated characteristic thinning of the posterior corpus callosum. This report provides an example of early treatment that nonetheless results in a mild mental retardation. The similarity of the structural changes on MRI and the cognitive profile of this patient to those of others reported in the literature suggest that the underlying mechanism for both may be the same.

Adult↗

PubMed2002

Discourse representation in the two cerebral hemispheres.

Readers construct at least two interrelated representations when they comprehend a text: (a) a propositional representation containing the individual ideas that are derived from each sentence and the relations among them and (b) a discourse model, a representation of the context or situation to which the text refers. We used a paradigm called "item priming in recognition" to examine how these representations are stored in the cerebral hemispheres. In Experiment 1, the priming paradigm was used in combination with a lateralized visual field (VF) procedure. We found evidence that readers' representations were structured according to propositional relations, but only in the left hemisphere. Item recognition was facilitated when a concept was preceded by another concept from the same proposition when targets were presented to the left, but not to the right, hemisphere. We found priming in both hemispheres, however, when targets were context-appropriate senses of ambiguous words or topics of passages. In Experiment 2, we replicated the priming effects in three callosotomy patients. We argue that the distinction between a propositional representation and a discourse model is important with respect to how discourse is represented in the brain. The propositional representation appears to reside in the left hemisphere, whereas aspects of the discourse model appear to be represented in both hemispheres.

Adult↗

PubMed2002

Separable effects of priming and imageability on word processing: an ERP study.

Concrete, highly imageable words (e.g. banana) are easier to understand than abstract words for which it is difficult to generate an image (e.g. justice). This effect of concreteness or imageability has been taken by some as evidence for the existence of separable verbal- and image-based semantic systems. Instead, however, effects of concreteness may result from better associations to relevant contextual representations for concrete than for abstract words within a single semantic system. In this study, target words of high and low imageability were preceded by supportive (related) or non-supportive (unrelated) context words. The influence of contextual support on the imageability effect was measured by recording event-related brain potentials (ERPs) to the high and low imageable target words in both context conditions. The topographic distributions of the ERPs elicited by the high versus low imageable target words were found to be different, and this effect was independent of contextual support. These data are consistent with the idea that distinct verbal- and image-based semantic codes exist for word representations, and that as a result, concrete words that are highly imageable can be understood more easily.

Adult↗