Christine Chiarello

Right hemisphere language comprehension : perspectives from cognitive neuroscience

Contents: C. Chiarello, M. Beeman, Introduction to the Cognitive Neuroscience of Right Hemisphere Language Comprehension. Part I:Decoding Speech Sounds and Individual Words. R. Ivry, P.C. Lebby, The Neurology of Consonant Perception: Specialized Module or Distributed Processors? J.M. Clarke, C.M. McCann, E. Zaidel, The Corpus Callosum and Language: Anatomical-Behavioral Relationships. M.T. Banich, C.D. Nicholas, Integration of Processing Between the Hemispheres in Word Recognition. K. Baynes, J.C. Eliassen, The Visual Lexicon: Its Access and Organization in Commissurotomy Patients. H.B. Coslett, E.M. Saffran, Reading and the Right Hemisphere: Evidence From Acquired Dyslexia. C. Chiarello, M. Beeman, Commentary: Right Hemisphere Linguistic Decoding--More Than Meets the Eye and Ear? Part II:Lexical and Sentence-Level Semantics. C. Chiarello, On Codes of Meaning and the Meaning of Codes: Semantic Access and Retrieval Within and Between Hemispheres. M. Faust, Obtaining Evidence of Language Comprehension From Sentence Priming. J.W. King, G.G. Ganis, M. Kutas, Potential Asymmetries in Language Comprehension: In Search of the Electrical Right. C. Burgess, K. Lund, Modeling Cerebral Asymmetries in High-Dimensional Space. C. Chiarello, M. Beeman, Commentary: Getting the Right Meaning From Words and Sentences. Part III:Discourse Processing and Problem Solving. M. Beeman, Coarse Semantic Coding and Discourse Comprehension. J.C. Borod, R.L. Bloom, C. Santschi-Haywood, Verbal Aspects of Emotional Communication. H. Brownell, G. Martino, Deficits in Inference and Social Cognition: The Effects of Right Hemisphere Brain Damage on Discourse. B. Stemmer, Y. Joanette, The Interpretation of Narrative Discourse of Brain-Damaged Individuals Within the Framework of a Multilevel Discourse Model. S.M. Fiore, J.W. Schooler, Right Hemisphere Contributions to Creative Problem Solving: Converging Evidence for Divergent Thinking. M. Beeman, C. Chiarello, Commentary: Getting the Right Meaning From Discourse. M. Beeman, C. Chiarello, Concluding Remarks: Getting the Whole Story Right.

Size Matters: Cerebral Volume Influences Sex Differences in Neuroanatomy

Biological and behavioral differences between the sexes range from obvious to subtle or nonexistent. Neuroanatomical differences are particularly controversial, perhaps due to the implication that they might account for behavioral differences. In this sample of 200 men and women, large effect sizes (Cohens d > 0.8) were found for sex differences in total cerebral gray and white matter, cerebellum, and gray matter proportion (women had a higher proportion of gray matter). The only one of these sex differences that survived adjustment for the effect of cerebral volume was gray matter proportion. Individual differences in cerebral volume accounted for 21% of the difference in gray matter proportion, while sex accounted for an additional 4%. The relative size of the corpus callosum was 5% larger in women, but this difference was completely explained by a negative relationship between relative callosal size and cerebral volume. In agreement with Jancke et al., individuals with higher cerebral volume tended to have smaller corpora callosa. There were few sex differences in the size of structures in Brocas and Wernickes area. We conclude that individual differences in brain volume, in both men and women, account for apparent sex differences in relative size.

Sentence context and lexical ambiguity resolution by the two hemispheres

A lexical decision experiment investigated hemisphere asymmetries in resolving lexical ambiguity within a sentence context. Sentences that biased a single meaning (either dominant or subordinate) of sentence-final ambiguous words were followed by a lateralized target related to the sentence-congruent or -incongruent meaning of the ambiguous word, or an unrelated word. In the RVF sentence-congruent targets were facilitated, while incongruent targets were not primed. In contrast, related targets were facilitated in the LVF, regardless of sentence context. This suggests that selecting the contextually appropriate word meaning requires the left hemisphere, and supports a right hemisphere role in maintaining alternate word senses.

Varieties of Interhemispheric Inhibition, or How to Keep a Good Hemisphere Down

Recent views of cerebral laterality suggest that both hemispheres contribute to the performance of most cognitive tasks. This would appear to require regulatory mechanisms to coordinate, select, and integrate the processes subserved by each hemisphere. In this paper we consider whether interhemispheric inhibition is used to achieve unified performance from a bilateral system capable of producing simultaneous and potentially conflicting, outputs. We examine the theoretical bases and empirical support offered for three varieties of interhemispheric inhibition. Interhemispheric suppression refers to mechanisms that may permit one hemisphere to halt or prevent concurrent processing by the opposite hemisphere. Such inhibition may operate either in a reciprocal, or in a unidirectional, fashion. Interhemispheric isolation may require an inhibitory process that suspends information transfer to prevent potentially harmful interhemispheric intrusions. Finally, one hemisphere could impede processing within the other via interference, that is, by providing irrelevant or detrimental information. It is argued that, while such mechanisms are plausible, evidence supportive of each is not convincing. We consider why it has been difficult to obtain clear-cut support for interhemispheric inhibition and suggest some avenues for further research.

Understanding Metaphors: Is the Right Hemisphere Uniquely Involved?.

Two divided visual field priming experiments examined cerebral asymmetries for understanding metaphors varying in sentence constraint. Experiment 1 investigated ambiguous words (e.g., SWEET and BRIGHT) with literal and metaphoric meanings in ambiguous and unambiguous sentence contexts, while Experiment 2 involved standard metaphors (e.g., The drink you gave me was a meteor) with sententially consistent and inconsistent targets (i.e., POTENT vs COMET). Similar literal and metaphor priming effects were found in both visual fields across most experimental conditions. However, RH processes also maintained activation of sententially inconsistent literal meanings following metaphoric expressions. These results do not strongly support the RH as the preferred substrate for metaphor comprehension (e.g., ), and suggest that processes in both hemispheres can support metaphor comprehension, although not via identical mechanisms. The LH may utilize sentence constraint to select and integrate only contextually relevant literal and metaphoric meanings, whereas the RH may be less sensitive to sentence context and can maintain the activation of some alternative interpretations. This may be potentially useful in situations where an initial understanding must be revised.

Priming of strong semantic relations in the left and right visual fields: a time-course investigation

Prior time-course investigations of cerebral asymmetries in word processing have sometimes reported hemisphere differences in the onset and duration of semantic priming. In the current study, very strongly related word pairs (categorical associates such as arm-leg) were employed in a low relatedness proportion lexical decision priming paradigm. A range of prime-target stimulus onset asynchronies (SOAs: 150-800 ms) was included. Only very weak evidence was obtained for a LVF priming lag at the briefest SOA, while priming was bilateral at moderately long SOAs. We consider these data in the context of previous time-course studies and suggest that, when highly semantically similar word pairs are used, a right hemisphere priming lag is, at best, a very small effect.

Imageability and distributional typicality measures of nouns and verbs in contemporary English

Dissociations between noun and verb processing are not uncommon after brain injury; yet, precise psycholinguistic comparisons of nouns and verbs are hampered by the underrepresentation of verbs in published semantic word norms and by the absence of contemporary estimates for part-of-speech usage. We report herein imageability ratings and rating response times (RTs) for 1,197 words previously categorized as pure nouns, pure verbs, or words of balanced noun-verb usage on the basis of the Francis and Kučera (1982) norms. Nouns and verbs differed in rated imageability, and there was a stronger correspondence between imageability rating and RT for nouns than for verbs. For all word types, the image-rating-RT function implied that subjects employed an image generation process to assign ratings. We also report a new measure of noun-verbtypicality that used the Hyperspace Analog to Language (HAL; Lund & Burgess, 1996) context vectors (derived from a large sample of Usenet text) to compute the mean context distance between each word and all of thepure nouns andpure verbs. For a subset of the items, the resulting HAL noun-verb difference score was compared with part-of-speech usage in a representative sample of the Usenet corpus. It is concluded that this score can be used to estimate the extent to which a given word occurs in typical noun or verb sentence contexts in informal contemporary English discourse. The item statistics given in Appendix B will enable experimenters to select representative examples of nouns and verbs or to compare typical with atypical nouns (or verbs), while holding constant or covarying rated imageability.

Bihemispheric processing of redundant bilateral lexical information.

Cerebral asymmetries in lexical ambiguity resolution were studied. In 2 experiments, targets related to the dominant and subordinate meanings of ambiguous word primes were presented for lexical decision after a 750-ms stimulus onset asynchrony. Experiment 1 compared presentation of target words to the left visual field/right-hemisphere (LVF/RH), to the right visual field/left-hemisphere (RVF/LH), or after redundant bilateral visual field (BVF) presentation. Experiment 2 examined unilateral priming in the absence of a BVF condition. On unilateral trials, priming was observed for dominant meanings in both the LVF/RH and RVF/LH, whereas subordinate priming was obtained only in the RVF/LH. These results suggest a possible role of hemispheric interaction in the availability of ambiguous word meanings. BVF performance evidenced a bilateral redundancy gain and priming that resembled that obtained on RVF/LH trials. Additional BVF analyses were not consistent with a strict race model interpretation and appear to implicate hemispheric cooperation in the bihemisperic processing of lexical information.

Cerebral asymmetries for language: evidence for structural-behavioral correlations.

The current investigation tested 20 male right-handers in 5 divided visual field lexical tasks. Asymmetries in Heschls gyrus, planum temporale, and planum parietale were measured using structural magnetic resonance imaging. Composite task asymmetries were positively correlated with asymmetry of the planum temporale only. There was also an association between the consistency of anatomical and behavioral asymmetries: Individuals who departed the most from the modal pattern of cortical asymmetry across regions also tended to show the greatest variability in asymmetry across tasks. Hence, individual differences in language laterality tasks may be affected by variation in asymmetry of posterior language structures. Additionally, when typical anatomical asymmetries fail to co-occur, there may be a less strictly regulated distribution of function across hemispheres.

A Large-Scale Investigation of Lateralization in Cortical Anatomy and Word Reading: Are There Sex Differences?

The authors report findings of a large-scale, multitask investigation of sex differences in both structural asymmetries and lateralization of word reading. Two hundred participants were tested in eight divided visual field lexical tasks, and each received a structural magnetic resonance imaging scan. The authors examined whether there was evidence for sex differences in overall measures of neuroanatomical and behavioral lateralization, in specific language tasks and brain regions, and in variation in asymmetry within and across tasks and brain regions. There was very little evidence for sex differences on any behavioral measure. The few indications of sex differences in the current report accounted for 2% or less of the individual variation in asymmetry and could not be replicated in independent subsamples. No sex differences were observed in the asymmetry of structures in Brocas and Wernickes areas such as pars triangularis, pars opercularis, the planum temporale, planum parietale, or Heschls gyrus. There were also no sex differences in the variability of neuroanatomical asymmetries within or between brain regions. However, a significant relationship between planum temporale and behavioral asymmetry was restricted to men.