PROJECTS:
BRAIN STRUCTURES FOR LANGUAGE
RIGHT HEMISPHERE ROLE IN WORD PRODUCTION AND RETRIEVAL
RIGHT
HEMISPHERE ROLE IN SEMANTIC PROCESSING
SENTENCE
PROCESSING
NOUN/VERB
PROCESSING
Cortical anatomy is quite variable across individuals. Some cortical areas are typically larger in one hemisphere as compared to the other. However, for any given asymmetrical region, not every person shows the typical pattern of asymmetry. The functional significance of these individual differences is unknown. Similarly, on a given behavioral language laterality measure, the typical outcome is a right visual field (RVF)/left hemisphere advantage, yet only about 75% of right-handed individuals will obtain this result.
In a preliminary study (Chiarello, et al., 2004) we examined whether individuals who show inconsistent cortical asymmetries (favoring the left hemisphere for some structures, and the right hemisphere for others) are the same individuals who show inconsistent behavioral asymmetries (obtaining a RVF advantage on some language tasks, but not others). Participants in this research were tested on several lateralized language tasks (lexical decision, word and nonword naming, semantic priming, verb generation) and also underwent a structural MRI scan. Three posterior cortical areas were measured: the planum temporale (typically larger in the left hemisphere), Heschl's gyrus (typically larger in the left hemisphere) and the planum parietale (typically larger in the right hemisphere).
Two major findings were obtained. First, the asymmetry of the planum temporale was correlated with a composite behavioral asymmetry based on our five lexical tasks (r = +.50 for reaction time, r = +.42 for accuracy). This suggests that individual differences in visual lexical laterality tasks reflect, at least in part, variations in the efficiency and computational capacity of left vs right hemisphere cortical substrates for language. Second, there was a reliable association of the consistency of behavioral asymmetries (across tasks) and anatomical asymmetries (across regions), as examined by calculating standard deviations for the z-scored asymmetries across tasks, and across brain regions. We observed a positive correlation between the behavioral and neuroanatomical standard deviations for RT, r = +.52. Participants who showed large discrepancies in their behavioral asymmetries across tasks, also tended to show large discrepancies in their anatomical asymmetries across regions. These data provide support for the idea that, when typical anatomical asymmetries fail to co-occur, the distribution of language function across hemispheres may be less strictly regulated.
We are now exploring these issues in a much larger project, funded by NIH. We are testing 200 individuals on a variety of lateralized and non-lateralized language tasks, and measuring asymmetries in a variety of posterior and anterior cortical regions using structural MRI. Several hypotheses are being examined regarding individual differences in epigenetic control of brain development. In particular, we hypothesize that, for some individuals, brain development is relatively buffered from outside influences, and that such persons will evidence consistent, moderate asymmetries for language favoring the left hemisphere. In other individuals with less regulated brain development, asymmetries are more inconsistent and determined by random influences.
This research is being conducted in collaboration with Dr. Christiana Leonard (University of Florida, Gainesville) and Dr. Ronald Otto (Computerized Diagnostic Imaging Center, Riverside), and is supported by UCR Committee on Academic Research, NSF BCS-0079456, and NIDCD 006957-01.
Publications:
Chiarello, C., Kacinik, N., Manowitz, B., Otto, R., & Leonard, C. (2004). Cerebral asymmetries for language: Evidence for structural-behavioral correlations. Neuropsychology, 18, 219-231. - Abstract
Chiarello, C., Kacinik, N., Manowitz, B., Otto, R., Leonard, C. (2002). Individual differences in cerebral asymmetries for language: Behavioral anatomical correlations. Presented at Cognitive Neuroscience Society, 9th Annual Meeting.
Chiarello, C., Lombardino, L., Kacinik, N.A., Otto, R., & Leonard, C. Neuroanatomical and behavioral asymmetry in an adult compensated dyslexic. . Presented at Cognitive Neuroscience Society, 11th Annual Meeting, San Francisco, April 19, 2004.
Virtually all of the research done in our laboratory attempts to understand how language is processed in the human brain. One of the most prominent characteristics of the human brain is its bilateral, but asymmetrical, organization. As demonstrated by the study of split-brain patients, the left and right sides of the cortex can function as at least partially separable information processing systems. Our research investigates the consequences of this bilateral organization in the normal brain for many different aspects of language comprehension, such as noun and verb retrieval , word class effects , word meaning access , and sentence processing . We are also beginning to investigate how individual differences in cortical organization may relate to the consistency of cerebral asymmetries observed in various language tasks. In all of this research we seek to elucidate basic mechanisms of language comprehension by exploring the constraints and potentialities imposed by the bilateral organization of our brains.
In a typical experiment, participants view words presented to the left or right sides of the visual field (LVF, RVF). Due to the anatomy of the visual system, information presented in the LVF is directly transmitted to the right cerebral hemisphere, while information presented in the RVF is directly transmitted to the left cerebral hemisphere. Quantitative and qualitative differences in performance based on visual field of presentation allow us to infer the manner in which each cerebral hemisphere understands language.
We gratefully acknowledge the support of the National Science Foundation (grants 97-29009, BCS-0079456) for this work.
Reviews of this approach to language processing:
Chiarello, C. (1991). Interpretation of word meanings by the cerebral hemispheres: One is not enough. In: P. Schwanenflugel (Ed.), The psychology of word meanings, (pp. 251-278). Hillsdale: Erlbaum.
Beeman, M.J., & Chiarello, C. (1998). Complementary left and right hemisphere language comprehension. Current Directions in Psychological Science, 7, 2-8.
Chiarello, C. (1998). On codes of meaning and the meaning of codes: Semantic access and retrieval within and between hemispheres. In M. Beeman & C. Chiarello (Eds.), Right hemisphere language comprehension: Perspectives from cognitive neuroscience, (pp. 141-160). Mahwah, N.J.: Lawrence Erlbaum Associates.
Chiarello, C. (In press). Parallel systems for processing language: Hemispheric complementarity in the normal brain. To appear in Banich, M.T., & Mack, M. (Eds.), Mind, Brain, & Language: Multidisciplinary Perspectives. Mahwah, N.J.: Lawrence Erlbaum Associates.
RIGHT HEMISPHERE ROLE IN WORD PRODUCTION AND RETRIEVAL
Studies in our lab and others have indicated that the right hemisphere has access to a surprisingly rich semantic system supporting a variety of comprehension processes. We suggest that the same semantic system that supports comprehension within the RH can contribute to some components of word retrieval and generation, even if the RH processing system cannot output the final articulatory response. We have begun to explore this possibility by investigating potential right hemisphere involvement in verb generation. In this task, individuals are given a concrete noun and asked to retrieve a verb that is semantically related to it. Seven divided visual field experiments explored cerebral asymmetries for word retrieval in the verb generation task, as well as in rhyme generation, and immediate and delayed word pronunciation. The typical right visual field (RVF)/left hemisphere advantage was observed for pronunciation and rhyme generation. For verb generation, the RVF/left hemisphere advantage was obtained only when stimulus items had a single prepotent response, and not when there were multiple response alternatives. A semantic priming experiment suggested that activation for less common related verbs was maintained for a longer time course within the right, than within the left, hemisphere. The right hemisphere may play a role in continued activation of semantically related response alternatives in word generation.
This research is funded by the National Science Foundation (grant BCS-0079456).
Relevant papers:
Chiarello, C., Kacinik, N.A., Shears, C., Arambel, S., Halderman, L.K., & Robinson, C.S.(submitted). Exploring cerebral asymmetries for the verb generation task.
Chiarello, C., Liu, S., Shears, C., Kacinik, N., Robinson, C., & Halderman, L. Verb generation: Component processes and cerebral asymmetries. Presented at Psychonomic Society, 43rd Annual Meeting, Kansas City, November 23, 2002.
RIGHT HEMISPHERE ROLE IN SEMANTIC PROCESSING
One critical component of language comprehension involves accessing word meanings in memory. As part of this process, the meanings of other related words are rendered temporarily accessible. Our research indicates that this process takes place within each hemisphere, but in a different manner. In particular, the right hemisphere appears to be important for maintaining the accessibility of both close and distantly related word meanings, while the left hemisphere maintains just the most closely related word meanings (Chiarello, et al., 1990; Chiarello & Richards, 1992; Chiarello, et al., 2003). We think that the left hemisphere narrows meaning activation to those concepts likely to be relevant in a particular language context, while the right hemisphere maintains a range of alternative meanings, some of which may not "fit" with the immediate context. The latter process may be particularly important for understanding figurative language (e.g., metaphors, idioms, indirect speech) and for drawing inferences during text processing.
We are also currently investigating the role of the right hemisphere in language production using semantic generation tasks (Chiarello, et al., 2001b), where it appears the right hemisphere may play a role in the activation of multiple potential responses.
Representative and Recent Publications:
Chiarello, C., Burgess, C., Richards, L., and Pollock, A. (1990). Semantic and associative priming in the cerebral hemispheres: Some words do, some words don't, .... sometimes, some places. Brain and Language, 38, 75-104. - Abstract
Chiarello, C. (1991). Interpretation of word meanings by the cerebral hemispheres: One is not enough. In: P. Schwanenflugel (Ed.), The psychology of word meanings, (pp. 251-278). Hillsdale: Erlbaum.
Chiarello, C., and Richards, L. (1992). Another look at categorical priming in the cerebral hemispheres. Neuropsychologia, 30, 381-392. - Abstract
Burgess, C., and Chiarello, C. (1996). Neurocognitive mechanisms underlying metaphor comprehension and other figurative language. Metaphor & Symbolic Activity, 11, 67-84. - Abstract
Chiarello, C. (1998). On codes of meaning and the meaning of codes: Semantic access and retrieval within and between hemispheres. In M. Beeman & C. Chiarello (Eds.), Right hemisphere language comprehension: Perspectives from cognitive neuroscience, (pp. 141-160). Mahwah, N.J.: Lawrence Erlbaum Associates.
Chiarello, C., Maxfield, L., Liu, S., & Kacinik, N. (2001a). Categorical processing in the left and right hemispheres: The effect of category repetition. Brain and Cognition, 43, 66-69. - Abstract
Chiarello, C., Liu, S., Kacinik, N., & Shears, C. (2001b). Cerebral asymmetries for verb generation. Presented at Cognitive Neuroscience Society, 8th Annual Meeting, New York.
Chiarello, C., Liu, S., Shears, C., Quan, N., & Kacinik, N. (2003). Priming of strong semantic relations in the left and right visual fields: A time course investigation. Neuropsychologia, 41, 721-732.
Shears, C., & Chiarello, C. (2003). No go on neutrals? An interhemispheric account of semantic category priming. Laterality, 8, 1-24. - Abstract
Understanding sentences involves using both the meanings of individual words and the grammatical and syntactic cues provided by the sentence to construct a representation of the sentence’s meaning. The resulting sentence-level meaning is sometimes referred to as a "message level" representation. Prior research had suggested that the left, but not the right, cerebral hemisphere could construct message-level meanings for sentences. However, more recent research in our laboratory has questioned this conclusion. In one study, we showed that both hemispheres benefited from number agreement in noun phrases, which is one grammatical mechanism used in sentence construction (Liu, Chiarello, & Quan, 1999). We have also shown that the right, as well as the left, hemisphere is sensitive to sentence-final anomaly (e.g., The weak lad lifted up the store - Chiarello, et al., 2001; Faust, et al., 2003). These data suggest that, while the left hemisphere is more adept at many aspects of sentence comprehension, the right hemisphere also is constructing sentence-level meaning. Current experiments are seeking to identify the grammatical and semantic mechanisms used by each hemisphere to understand sentences.
This research has been done in collaboration with Dr. Miriam Faust ( Bar-Ilan University) and Stella Arambel, and has been supported in part by the U.S.-Israel Binational Science Foundation (94-00112).
Representative and Recent Publications:
Faust, M., and Chiarello, C. (1998). Constraints on sentence priming in the cerebral hemispheres: Effects of intervening words in sentences and lists. Brain and Language, 63, 219-236. - Abstract
Faust, M., & Chiarello, C. (1998). Sentence context and lexical ambiguity resolution by the two hemispheres. Neuropsychologia, 36, 827-836. - Abstract
Chiarello, C., Liu, S., & Faust, M. (2001). Bihemispheric sensitivity to sentence anomaly. Neuropsychologia, 39, 1451-1463. - Abstract
Faust, M., Bar-lev, A., & Chiarello, C. (2003). Sentence priming effects in the two cerebral hemispheres: Influences of lexical relatedness, word order, and sentence anomaly. Neuropsychologia, 41, 480-492. - Abstract
Faust, M., Barak, O., & Chiarello, C. (In press). The effects of multiple script priming on word recognition by the two cerebral hemispheres: Implications for discourse processing. Brain and Language.
Arambel, S., & Chiarello, C. (In press). Priming nouns and verbs: Differential influences of semantic and grammatical cues in the two cerebral hemispheres. Brain and Language.
Nouns and verbs appear to be processed differently in the brain, as indicated by data from brain-injured patients, from functional neuroimaging, and also from cerebral laterality experiments. However, we know very little about why these differences occur. Are there neurologically separable systems for processing nouns and verbs, or are nouns and verbs processed differently because of some dimension of meaning that tends to covary with word class? To address these questions, we first collected normative data for approximately 1200 English nouns and verbs (Chiarello, Shears, & Lund, 1999 - an electronic version of these norms is available upon request). Our norms include imageability ratings for each word, as well as a computational index of noun-verb typicality (the extent to which a word tends to occur in typical noun or verb contexts). We are currently exploring the processing of verbs across a range of tasks (lexical decision, pronunciation, noun/verb decision, verb generation, and sentence completion) in order to determine: (1) whether different variables predict noun vs verb response times; (2) the conditions under which noun and verb processing dissociates across hemispheres.
Our preliminary findings thus far indicate that:
- there are somewhat different predictors for noun vs verb lexical decision latencies (Kacinik, Shears, & Chiarello, 2000)
- noun-verb typicality has a greater influence in some word tasks than in others
- when nouns and verbs are equated for imageability, the left hemisphere advantage is obtained for both word classes (Chiarello, Liu, Shears, & Kacinik, 2002). This implies that some noun/verb dissociations may be attributable to semantic differences that tend to covary with word class.
This research is funded by the National Science Foundation (grants 97-29009, BCS-0079456).
Relevant papers:
Chiarello, C., Shears, C., & Lund, K. (1999). Imageability and distributional typicality measures of nouns and verbs in contemporary English. Behavior Research Methods, Instruments, & Computers, 31, 603-637. - Abstract
Kacinik, N., Shears, C., & Chiarello, C. (2000). Familiarity for nouns and verbs: Not the same as, but better than, frequency. Proceedings of the Twenty-second Annual Cognitive Science Society, 1035. Mahwah, NJ: Lawrence Erlbaum Associates. - Abstract
Chiarello, C., Liu, S., Shears, C., & Kacinik, N. (2002). Differential asymmetries for recognizing nouns and verbs: Where are they? Neuropsychology, 16, 35-48. - Abstract
Kacinik, N., & Chiarello, C. (2002). Predicting noun and verb latencies: Influential variables and task effects. In W.D. Gray & C.D. Schunn (Eds.), Proceedings of the Cognitive Science Society, 24th Annual Meeting, pp. 524-529. Mahwah, NJ: Lawrence Erlbaum Associates.