Rhonda B. Friedman

Summation priming and coarse semantic coding in the right hemisphere

There are now numerous observations of subtle right hemisphere (RH) contributions to language comprehension. It has been suggested that these contributions reflect coarse semantic coding in the RH. That is, the RH weakly activates large semantic fieldsincluding concepts distantly related to the input wordwhereas the left hemisphere (LH) strongly activates small semantic fieldslimited to concepts closely related to the input (Beeman, 1993a,b). This makes the RH less effective at interpreting single words, but more sensitive to semantic overlap of multiple words. To test this theory, subjects read target words preceded by either Summation primes (three words each weakly related to the target) or Unrelated primes (three unrelated words), and target exposure duration was manipulated so that subjects correctly named about half the target words in each hemifield. In Experiment 1, subjects benefited more from Summation primes when naming target words presented to the left visual field-RH (Ivf-RH) than when naming target words presented to the right visual field-LH (rvf-LH), suggesting a RH advantage in coarse semantic coding. In Experiment 2, with a low proportion of related prime-target trials, subjects benefited more from Direct primes (one strong associate flanked by two unrelated words) than from Summation primes for rvf-LH target words, indicating that the LH activates closely related information much more strongly than distantly related information. Subjects benefited equally from both prime types for Ivf-RH target words, indicating that the RH activates closely related information only slightly more strongly, at best, than distantly related information. This suggests that the RH processes words with relatively coarser coding than the LH, a conclusion consistent with a recent suggestion that the RH coarsely codes visual input (Kosslyn, Chabris, Mar-solek, & Koenig, 1992).

A Parametric Approach to Orthographic Processing in the Brain: An fMRI Study

Brain activation studies of orthographic stimuli typically start with the premise that different types of orthographic strings (e.g., words, pseudowords) differ from each other in discrete ways, which should be reflected in separate and distinct areas of brain activation. The present study starts from a different premise: Words, pseudowords, letterstrings, and false fonts vary systematically across a continuous dimension of familiarity to English readers. Using a one-back matching task to force encoding of the stimuli, the four types of stimuli were visually presented to healthy adult subjects while fMRI activations were obtained. Data analysis focused on parametric comparisons of fMRI activation sites. We did not find any region that was exclusively activated for real words. Rather, differences among these string types were mainly expressed as graded changes in the balance of activations among the regions. Our results suggests that there is a widespread network of brain regions that form a common network for the processing of all orthographic string types.

Functional interactions of the inferior frontal cortex during the processing of words and word-like stimuli.

The hypothesis that ventral/anterior left inferior frontal gyrus (LIFG) subserves semantic processing and dorsal/posterior LIFG subserves phonological processing was tested by determining the pattern of functional connectivity of these regions with regions in left occipital and temporal cortex during the processing of words and word-like stimuli. In accordance with the hypothesis, we found strong functional connectivity between activity in ventral LIFG and activity in occipital and temporal cortex only for words, and strong functional connectivity between activity in dorsal LIFG and activity in occipital and temporal cortex for words, pseudowords, and letter strings, but not for false font strings. These results demonstrate a task-dependent functional fractionation of the LIFG in terms of its functional links with posterior brain areas.

Recovery from Deep Alexia to Phonological Alexia: Points on a Continuum

Reports of five patients whose deep alexic reading all evolved into phonological alexia in a similar fashion point to the hypothesis that deep alexia and phonological alexia represent different points on the same continuum. This hypothesis is explored further through an examination of previously published case reports of eleven patients with phonological alexia. Data from these patients suggest that there is a predictable succession of symptoms which form a continuum of severity of phonological alexia, with deep alexia as its endpoint. An account of the recovery from deep to phonological alexia, based upon a lexical (no-rules) model of reading, is provided (Glosser & Friedman, 1990), and the implications for therapy are considered. The significance of the notion of a continuum of phonological/deep alexia is discussed.

Comparison of a new mineral based hemostatic agent to a commercially available granular zeolite agent for hemostasis in a swine model of lethal extremity arterial hemorrhage

BACKGROUND Gaining hemostatic control of vascular injuries sustained in combat using topical agents remains a challenge. We previously developed a new hemostatic agent consisting of a granular combination of a smectite mineral and a superabsorbent polymer (WoundStattrade mark; WS) which demonstrated the ability to stop high pressure bleeding. We have since modified WS to contain only the smectite mineral and compared the performance of WS to QuikClotstrade mark zeolite granules (QCG) in a lethal vascular injury model. METHODS Fourteen (seven per group) anesthetized swine (35-44kg) had a lethal femoral artery injury produced by creating a 6mm arteriotomy in the vessel. After 45s of hemorrhage, animals were randomized to be treated with either WS or QCG for 3min. A second application was provided if hemostasis failed. Fluid resuscitation was begun at the time of application to achieve a mean arterial blood pressure of 65mmHg. Animals were observed for 120min or until death. Primary endpoints were survival, survival time, post-treatment blood loss, and resuscitation fluid volume. RESULTS WS resulted in 100% survival to 120min. No animal in the QCG group survived (p=0.0005). Survival times for WS animals were significantly greater compared to QCG (p=0.0001). Post-treatment blood loss (p=0.0043) and post-resuscitation fluid volume (p=0.0043) was significantly less for animals treated with WS compared to QCG. CONCLUSION WS consisting of just the smectite mineral was superior to QCG tested in this model. Additional study is warranted to determine its potential for use in combat and civilian trauma.

Left hemisphere pathways in reading: Inferences from pure alexia without hemianopia

In pure alexia, reading is impaired despite almost normal speech, spelling, and writing. We studied a righthanded man with pure alexia, but no hemianopia. He had more difficulty reading longer words (word-length effect), but had no selective reading impairment in phonologic or semantic analysis. Clinical-CT correlation suggests that (1) left hemisphere visual pathways crucial for reading arise from or pass close to the left occipitotemporal or inferior temporal gyrus, and (2) relevant transcallosal fibers from the right hemisphere course inferior to the posterior horn of the left lateral ventricle before ascending to left hemisphere language areas.

Two Types of Phonological Alexia

It is hypothesized, on the basis of a lexical model of reading, that there are two different underlying causes of phonological alexia. It is predicted that these two types of phonological alexia will be accompanied by different sets of symptoms. Published cases of phonological alexia are examined for evidence in support of these predictions. Two distinct groups of phonological alexic patients are observed. These results support the notion of two types of phonological alexia. The failure to find any phonological alexic patients who do not fall into one of these two categories provides evidence against non-lexical reading models.

Lexical semantic and associative priming in Alzheimer's disease.

Semantic memory impairment was investigated in patients with probable Alzheimers disease (AD) using a threshold oral word reading task to assess priming of different lexical relationships. Healthy elderly controls showed significant priming for associatively related nouns (tempest-teapot) and also for nouns semantically related either because both designate basic-level exemplars of a common superordinate category (cousin-nephew) or because the target names the superordinate category of the prime (daughter-relative). AD patients, in contrast, showed preserved priming of lexical associates but impaired priming of certain semantic relationships. They showed no priming between words designating coordinate exemplars within a category, despite preserved priming of the superordinate category label. Findings are consistent with the view that at least part of the semantic deficit in AD is due to disruption of semantic knowledge that affects relationships among basic-level concepts, more than the relationships between these concepts and their corresponding superordinate category of membership.

Rationale and efficacy of a tactile—kinaesthetic treatment for alexia

Abstract Patients with pure alexia typically read words by first naming each letter of the word, either aloud or silently. These patients do not show signs of phonological alexia (poor pseudoword and functor reading). Patient T.L., a pure alexic patient with poor letter-naming abilities, had marked difficulty reading functors and pseudowords, but not spelling them or identifying them when they were spelled to him, a pattern which has been called ‘modality-specific phonological alexia’. We used a multiple-baseline design to evaluate a tactile-kinaesthetic treatment programme designed to improve T.L.s letter-naming, thus enabling him to read in letter-by-letter fashion. Results showed that the treatment was efficacious, with a 51% improvement achieved in trained word reading and a 40% increase in untrained word reading. Furthermore, the part-of-speech effect was no longer significant following treatment, a result that our hypothesis of T.L.s underlying impairment predicted.

Impaired spelling in Alzheimers disease: a linguisticdeficit?

Abstract Different kinds of real words and pronounceable pseudowords (PWs) were presentedfor writing to dictation to patients with the diagnosis of probable Alzheimers disease (AD) and toage- and education-matched healthy controls. Though spelling less accurately on all tasks, ADpatients responded in a manner generally qualitatively similar to controls. Except for a slightlyenhanced effect of spelling regularity in real word writing accuracy, AD patients showed thesame sensitivity to various lexical, orthographic and phonological variables as controls. Bothgroups showed no difference in spelling accuracy for words and PWs with regular vs ambiguousspelling patterns, and groups also showed similar orthographic preferences when spelling PWshaving several different acceptable pronunciations. Finally, AD patients and controls producedsimilar types of errors when spelling real words. Dementia severity was related to the overallaccuracy, but not to the pattern, of spelling responses. It is suggested that the decline in responseaccuracy in cognitively demanding writing tasks in patients with more advanced dementia ismost likely due to semantic impairment and impairments of nonlinguistic functions of attention,executive control and praxis, rather than to a disturbance within language specific processes.