Dr. M. Z. (Monika) Zempléni
Supervisor: Dr. L. A. Stowe
Period of employment: January 2002 - January 2006
Download the dissertation from the University Library website.
Theoretical Background
Although language areas were traditionally located in the left hemisphere (LH) there are numerous data to indicate that several language processes, which belong mainly to the semantic and pragmatic domains, require bihemispheric cooperation and are characterized by predominant right hemisphere (RH) involvement. Figurative language comprehension and semantic ambiguity resolution processes are inter alia predominantly RH related processes.
Patients with schizophrenia, especially those with thought disorder, are frequently characterized by abnormal linguistic performance both with regard to comprehension and production (DeLisi, 2001). Although phonological and syntactic abnormalities are also reported in schizophrenia, the most prominent deviance belongs to the semantic and pragmatic domains. Moreover those linguistic phenomena (e.g. meaning selection) that seem to be the most disturbed in schizophrenia were found to be bihemispherically distributed with marked RH participation in healthy subjects. Data suggest that interhemispheric connections are abnormal and language areas are not appropriately lateralized in schizophrenia (Sommer et al., 2001). Some authors ascribe a crucial role to these factors in the pathogenesis of the disorder (Nasrallah,1985; Crow, 1997).
Since meaning selection is a language process which strongly relies on appropriate bihemispheric cooperation (implicating normal brain lateralization as well), meaning selection tasks appear to be good tools for evaluating the hypothesized abnormal lateral distribution of language areas in schizophrenia.
Ph.D. Project
The aim of the project is to evaluate the neural substrate of meaning selection in healthy subjects and patients with schizophrenia, using functional magnetic resonance imaging (fMRI) and behavioral methods. The study will focus on homograph and idiom comprehension in sentence context.
Test materials will be sentences containing either a homograph or an idiom. The homographs will be disambiguated either to the dominant or to the subordinate meaning in the sentence; while idioms will be biased toward their literal or idiomatic meaning. Non-ambiguous sentences will serve as controls.
The primary method of the project will be functional fMRI in order to identify the neural activation patterns during the carrying out of the homograph and idiom comprehension tasks. Behavioral methods will complement the fMRI sessions. fMRI data will be analyzed by the SPM-99 statistical package. The lateral distribution of the activation pattern (Laterality Index) will be calculated on both the group and on the individual levels. The brain activation patterns will be compared to the behavioral data (idiom and homograph comprehension tasks).
The main hypothesis of the project can be summarized as the following:
The right hemisphere (RH) plays a role in meaning selection, therefore RH activation is expected to be found using fMRI in healthy subjects. Patients with schizophrenia are expected to show deviant neural activity during the meaning selection tasks.
References
Crow, T. J. (1997).
Is schizophrenia the price that Homo Sapiens pays for language?
Schizophrenia Research, 28, 127-141.
DeLisi, L. E. (2001).
Speech disorder in Schizophrenia: Review of the Literature and
Exploration of its Relation to the Uniquely human Capacity for Language.
Schizophrenia Bulletin, 27(3), 481-496.
Nasrallah, H. A. (1985).
The Unintegrated Right Cerebral Hemispheric Consciousness as Alien Intruder:
A Possible Mechanism for Schneiderian Delusions in Schizophrenia.
Comprehensive Psychiatry, 26(3), 273-280.
Sommer, I. E. C., Ramsey, N. F. & Kahn, R. S. (2001).
Language lateralization in schizophrenia, an fMRI study.
Schizophrenia Research, 52, 56-67.
