Rita Berndt - US grants

A project is proposed to obtain systematic evaluation of the course of recovery from aphasia in a population of stroke patients. The study has three specific goals: First, this project will provide extensive information on the demographic, neuroanatomical, medical and neurolinguistic correlates of the recovery of specific language functions in aphasia. This information about prognostic factors can be used as a data base for the development of on-liner, computer assisted decision aids that would be of use to the neurologist in deciding questions of patient management. Second, the proposed study will evaluate the hypothesis that some language functions recover better than others. Experimental tests will be administered that allow relatively selective evaluation of distinct aspects of language comprehension (such as phoneme discrimination) and of speech production (such as syntactic complexity).. Scores obtained on these measures will be used to evaluate the possibility that there are different recovery rates for particulaar aspects of gross language functions such as comprehension and production. In addition to their considerable theoretical importance, the results of such an evaluation would have significant implications for the design of therapies and communication aids for the aphasic patient. Third, the study proposed here will furnish data for testing hypothesis concerning the functional components that underlie the major aphasic syndromes. Specific issues to be addressed include the incidence of linguistically-defined symptoms (e.g., agrammatism) within the classical syndromes (e.g., Broca's aphasia), and the extent to which the phenomenon of evolution of syndromes during recovery reflects substantive changes in language capacities. This third goal reflects an attempt to join the theories and methods developed in recent neurolinguistic studies of language impairment with the more traditional approach to the study of recovery from aphasia.

Two related projects are proposed as part of an application for a Research Career Development Award. First, it is suggested that information about the evolution of patients' symptoms during recovery from aphasia will provide an important source of constraint on the postulation of explanatory models to account for particular aphasis syndromes. Three separate experimental batteries are developed to investigate the nature of the underlying deficit in agrammatic Broca's aphasia, conduction aphasia and anomic aphasia. Specific hypotheses are developed concerning the possible relationships among co-occuring symptoms and their underlying basis. Patients meeting the selection criteria will be tested at several intervals over the course of the first year post-onset using one of the experimental batteries. A second project is proposed to develop a computer-based system for the simulation and classification of reading and writing errors produced by dyslexic and dysgraphic patients. This system will focus on the classification of errors involving the translation between graphemes and phonemes, and is intended to investigate the incidence of errors that are related to grapheme-to-phoneme or phoneme-to-grapheme conversion.

Language disorders resulting from focal brain damage can take a variety of forms, and there is evidence that some aphasic deficits are specific to the comprehension and interpretation of sentences. This project investigates the nature and causes of sentence processing disorders that occur in aphasia. The long-term goal is to develop a detailed model of sentence comprehension and production that can provide a functional explanation for the symptoms found in aphasia. Such a model would have a variety of applications. If specific aphasic symptoms can be interpreted as arising from identifiable processing deficits within a testable model, then attempts to remediate symptoms can be more defini- tively focused on the responsible representation or process. Moreover, discrete components of language processing that are identified through studies of aphasic patients would be likely to be the components that will, ultimately, prove to be localizable in the brain. The specific aims for the next project period test the hypothesis that two separable levels of structural representation are exploited during sentence processing. In separate tests of comprehension and production, the capacity to construct a constituent representation of sentence surface structures is distinguished from the ability to interpret the thematic roles of sentence nouns. The predicates to be used in these studies involve verbs and prepositions, with the goal of comparing the "mapping" between two levels of representation for each of these two predicate types. A series of "targeted intervention studies" is proposed in which specific deficits in the construction of each of these levels of representation is addressed in a treatment study, with the goal of measuring the effect of the intervention on hypothetically related, but untreated, components. In addition, development continues of a quantificational system for the analysis of sentence production deficits that expands the domain of application of the existing system to a wider range of aphasic deficits.

A program of research is proposed on the topic of reading disorders that occur in premorbidly-literate adults who have suffered focal brain damage. These disorders (acquired dyslexias) frequently accompany other language symptoms (aphasia), but sometimes occur as isolated deficits. Acquired dyslexias are common sequelae of left hemisphere cortical insult from cerebrovascular accident and traumatic head injury. The symptoms exhibited by individual dyslexic patients are interpreted as resulting from deficits to specific processing components within a model of normal reading. Information about the functional sub-systems that are implicated in a particular symptom provide a rational basis to approach two of the long-term goals of the project: the localization in the brain of the cognitive processes involved in reading and the development of treatment techniques for addressing specific symptoms. The project is focused on that aspect of the reading system that is required to "sound out" (or assemble) sound segments (phonology) from print. The inability to perform this operation has been described in several types of patients with deficits to each of these three have been reported. Evidence is reviewed here that these three sub-components of the phonological assembly operation require intact cognitive/linguistic abilities in domains that are not specific to reading: 1) in the processes required to analyze and manipulate sub-lexical phonological segments; and 2) in phonological short-term (working) memory. Three methods are proposed to test the separability of the three hypothesized components and these cognitive/linguistic processes, and to investigate the processing links between them. 1. A battery of tasks addressing each of the hypothesized components and related processes has been developed and will be administered to patients with acquired dyslexia, using the traditional method of testing for dissociations among symptoms: 2. A series of "intervention" studies is planned to investigate the causal direction of co-occurrence relationships by bringing about a change in one hypothesized component and observing its effect on the patient's symptoms: and hypothesized component and observing its effect on the patient's symptoms: and 3> A large-scale connectionist computer model of print-to-sound transformation, developed earlier, will be further refined with the specific goal of determining the optimal size of the sub-lexical unit that participates in print-to-sound mapping.

DESCRIPTION (Adapted from the Investigator's Abstract): Language disorders resulting from focal brain damage can take a variety of forms, and there is evidence that some aphasic deficits selectively affect the comprehension and interpretation of sentences. This project investigates the functional bases of the sentence processing disorders that occur in aphasia. The specific aims for the next project period involve continued investigation of the contribution of impairments of lexical/semantic representations and/or processes to symptoms involving sentence production and comprehension. Aphasic patients and normal control subjects will participate in a variety of different types of experiments: (1) The contribution of various types of information to lexical retrieval in sentence production will be investigated using tasks combining semantic, syntactic, visual/pictorial, or phonological cues to trigger word retrieval in timed production tasks. These studies will evaluate the relative contribution of these information sources to retrieval of nouns and verbs that are high and low in imageability, and will assess the degree to which competing responses interfere with retrieval. (2) New techniques will be designed to elicit sentences of different structural types from patients by exploiting the factors believed to affect lexical and structural decisions in normal sentence production; the relative effectiveness of these factors will be assessed in a separate set of experiments. (3) The contribution of semantic factors to impairment in the comprehension of reversible sentences will be studied using standard sentence/picture matching and speeded verification. The consequences of verb meanings for thematic role assignment are hypothesized to have specific and measurable effects on patients' comprehension performance. (4) Patients' sensitivity to violations of sentence meaning that are caused by illegal combinations of lexical semantic and structural information will be evaluated using the word monitoring task. Sentence complexity (passive v. active) is expected to attenuate violation detection for patients with poor sentence comprehension. The long-term goal is to develop a model sentence comprehension and production that can provide a functional explanation for the symptoms found in aphasia. Such a model would have a variety of applications. If specific aphasic symptoms can be interpreted as arising from identifiable processing deficits within a testable model, then attempts to remediate symptoms can be more definitely focused on the responsible representation or process. Moreover, discrete components of language processing that are identified through studies of aphasic patients are likely to be the components that will, ultimately, prove to be localizable in the brain.

The goal of the Training Program is to provide an environment that will encourage the pursuit of research that applies emerging methods for the study of brain/behavior relationships to the topic of language and language disorders Theoretical and technical advances in the last decade have encouraged the development of the field of Cognitive Neuroscience- the study of how cognitive processes are carried out in the development of the field of Cognitive Neuroscience-the study of how cognitive processes are carried out in the brain. This program is conceived as a part of that general effort, with special emphasis on the cognitive processes that are related to language. The faculty members contributing to this proposal represent the academic disciplines of Cognitive Psychology and Neuropsychology, Computer Science, Physiology, Linguistics, Neurology and Neuroanatomy, yet all of them are engaged in research investigating language/brain relationships. These faculty members will serve as mentors for post-doctoral trainees from clinical fields such as Speech/Language Pathology or Clinical Neuropsychology, or from basic science disciplines such as Computer Science, Neuroscience, Linguistics or Psychology. The training program emphasizes hands/on research training with a primary mentor, supplemented by measures that assure a breadth of contact with other faculty and experience in related disciplines. Available training facilities support techniques employing computational (neural network) modeling, cognitive neuropsychological investigation of normal subjects and aphasic patients, functional neuroimaging of language activities using fMRI, study of Event Related Potentials recorded from scalp during cognitive tasks, and neuroanatomical study of the effects of brain lesions. Tow first-year and second-year Fellows will be supported after the first year of the program, and trainees will typically complete the program within two years. The long-term goal of training is to produce independent investigators who will pursue a career of scientific research on topics related to language and language disorders using techniques available from the field of cognitive neuroscience.

DESCRIPTION (provided by applicant): Aphasia strikes approximately one in 250 Americans. The reduced ability to communicate with language represents, in most cases, a catastrophic loss of self-sufficiency and a source of profound social isolation. No treatment for aphasia reported to date has reliably brought about changes in language production that migrate from highly constrained laboratory tasks such as single picture description to more challenging and socially functional tasks such as the production of entire narratives. The current climate in health care limits access to speech therapy, and thus it is imperative to develop approaches to treatment which allow patients to supplement 1:1 clinical treatment with intensive independent home practice. We have developed two computer programs to address the need for effective aphasia treatments that can be used semi-independently. One is a communication system (CS), which allows aphasic users to record spoken sentences a single word or phrase at a time, to replay these words or phrases, and to build them into sentences and narratives by manipulating visual icons on a computer screen. The other program is a language therapy system (TS) incorporating speech recognition and natural language understanding technology, which allows the computer to 'understand' the patient's spoken sentence and to provide feedback about whether it correctly describes a picture on the screen. This allows independent home practice of spoken language. The goals of this project are: (1) to replicate pilot results showing measurably more structured language production by aphasic patients using the CS, and to link these effects to characteristics of subjects' language processing impairments (Exp. 1); (2) to assess the impact of enhancing the CS with word-finding support for more severely impaired patients (Exp. 2); (3) to replicate the positive outcomes in pilot studies which used the TS and CS to improve aphasic patients' spoken language production, and to use the TS to train subjects on grammatical structures that provide tests of specific hypotheses about the impact of impaired short term memory on aphasic production (Exp. 3); and (4) to use data automatically collected by the CS to investigate the nature of the underlying disruption and to motivate the most effective approaches to remediation (Exp. 4). Information obtained from these studies will provide a basis for the further development of novel, theoretically motivated approaches to aphasia treatment.