A rubric for extracting idea density from oral language samples.

While past research has demonstrated that low idea density (ID) scores from natural language samples correlate with late life risk for cognitive decline and Alzheimer's disease pathology, there are no published rubrics for collecting and analyzing language samples for idea density to verify or extend these findings into new settings. This unit outlines the history of ID research and findings, discusses issues with past rubrics, and then presents an operationalized method for the systematic measurement of ID in language samples, with an extensive manual available as a supplement to this unit (Analysis of Idea Density, AID). Finally, reliability statistics for this rubric in the context of dementia research on aging populations and verification that AID can replicate the significant association between ID and late-life cognition are presented.

Hemispheric asymmetries and prosodic emotion recognition deficits in Parkinson's disease.

While Parkinson's disease (PD) has traditionally been described as a movement disorder, there is growing evidence of cognitive and social deficits associated with the disease. However, few studies have looked at multi-modal social cognitive deficits in patients with PD. We studied lateralization of both prosodic and facial emotion recognition (the ability to recognize emotional valence from either tone of voice or from facial expressions) in PD. The Comprehensive Affect Testing System (CATS) is a well-validated test of human emotion processing that has been used to study emotion recognition in several major clinical populations, but never before in PD. We administered an abbreviated version of CATS (CATS-A) to 24 medicated PD participants and 12 age-matched controls. PD participants were divided into two groups, based on side of symptom onset and unilateral motor symptom severity: left-affected (N = 12) or right-affected PD participants (N = 12). CATS-A is a computer-based button press task with eight subtests relevant to prosodic and facial emotion recognition. Left-affected PD participants with inferred predominant right-hemisphere pathology were expected to have difficulty with prosodic emotion recognition since there is evidence that the processing of prosodic information is right-hemisphere dominant. We found that facial emotion recognition was preserved in the PD group, however, left-affected PD participants had specific impairment in prosodic emotion recognition, especially for sadness. Selective deficits in prosodic emotion recognition suggests that (1) hemispheric effects in emotion recognition may contribute to the impairment of emotional communication in a subset of people with PD and (2) the coordination of neural networks needed to decipher temporally complex social cues may be specifically disrupted in PD.

Idea density measured in late life predicts subsequent cognitive trajectories: implications for the measurement of cognitive reserve.

OBJECTIVE: The Nun Study showed that lower linguistic ability in young adulthood, measured by idea density (ID), increased the risk of dementia in late life. The present study examined whether ID measured in late life continues to predict the trajectory of cognitive change. METHOD: ID was measured in 81 older adults who were followed longitudinally for an average of 4.3 years. Changes in global cognition and 4 specific neuropsychological domains (episodic memory, semantic memory, spatial abilities, and executive function) were examined as outcomes. Separate random effects models tested the effect of ID on longitudinal change in outcomes, adjusted for age and education. RESULTS: Lower ID was associated with greater subsequent decline in global cognition, semantic memory, episodic memory, and spatial abilities. When analysis was restricted to only participants without dementia at the time ID was collected, results were similar. DISCUSSION: Linguistic ability in young adulthood, as measured by ID, has been previously proposed as an index of neurocognitive development and/or cognitive reserve. The present study provides evidence that even when ID is measured in old age, it continues to be associated with subsequent cognitive decline and as such may continue to provide a marker of cognitive reserve.

The measurement of everyday cognition (ECog): scale development and psychometric properties.

This article describes the development and validation of an instrument to assess cognitively mediated functional abilities in older adults, Everyday Cognition (ECog). The ECog is an informant-rated questionnaire comprised of multiple subscales. Confirmatory factor analysis (CFA) was used to examine its factor structure. Convergent validity was evaluated by comparing it to established measures of everyday function. External validity was evaluated by comparing ECog results across different clinical groups [cognitively normal, mild cognitive impairment (MCI), dementia]. CFA supported a seven-factor model including one global factor and six domain-specific factors (Everyday Memory, Language, Visuospatial Abilities, Planning, Organization, and Divided attention). The ECog correlated with established measures of functional status and global cognition, but only weakly with age and education. The clinical groups performed differently in each domain. In addition to the global factor, the Everyday Memory factor independently differentiated MCI from Normal, while the Everyday Language domain differentiated Dementia from MCI. Different subtypes of MCI also showed different patterns. Results suggest the ECog shows promise as a useful tool for the measurement of general and domain-specific everyday functions in the elderly.

Hemispheric asymmetries in the perceptual representations of words.

The representation of words in sentences can involve the activation and integration of perceptual information. For example, readers who are asked to view pictures of objects relating to a word in a sentence are influenced by perceptual information in the sentence context-readers are faster to respond to a picture of a whole apple after reading, "There is an apple in the bag," than after reading, "There is an apple in the salad." The purpose of this study was to examine how the two cerebral hemispheres use perceptual information about words as a function of sentence context. Patients who had damage to the left or right hemisphere and age-matched control participants read sentences that described, but did not entail, the shape or state of an object. They then made recognition judgments to pictures that either matched or mismatched the perceptual form implied by the sentence. Responses and latencies were examined for a match effect -- faster and more accurate responses to pictures in the match than mismatch condition -- controlling for comprehension ability and lesion size. When comprehension ability and lesion size are properly controlled, left-hemisphere-damaged patients and control participants exhibited the expected match effect, whereas right-hemisphere-damaged participants showed no effect of match condition. These results are consistent with research implicating the right hemisphere in the representation of contextually relevant perceptual information.

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.

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.

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.

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.

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.

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.

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.

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.