Right hemisphere metaphor processing? Characterizing the lateralization of semantic processes

[A review of metaphor research]

The study of the metaphor is interdisciplinary and focuses mostly on three points in cognitive psychology: (a) the cognition of metaphoricity, (b) metaphor comprehension processes, and (c) the reason why one concept is represented by another concept as a metaphor. This article reviews the history of research on the metaphor from these three perspectives. Most recent studies support the following viewpoints. Metaphor comprehension is as quick and automatic as literal comprehension. Metaphor comprehension entails the processes of comparison and abstraction. The reason why one concept is compared with another concept is strongly related with the motivation process of combination between different concepts such as embodied cognition.

Age-related changes in the appreciation of novel metaphoric semantic relations

In the present study we tested the possibility that older adults differ from younger adults in their appreciation of metaphoric semantic relations, and that age-related changes occur due to the perception of novel metaphors. In the first experiment 35 younger (mean age?=?23.1) and 35 older adults (mean age?=?75.3) were asked to rate the plausibility of metaphoric, literal, and unrelated word pairs. Relative to young participants, older participants rated fewer expressions as metaphorically plausible. The second experiment was conducted to examine whether the findings of the first experiment could be accounted for by an age-associated difference in the appreciation of metaphors with different levels of familiarity. In the second experiment, 25 younger (mean age?=?24.4) and 25 older adults (mean age?=?77.5) were asked to rate the familiarity level of the plausible metaphoric expressions. Relative to young participants, older participants rated fewer expressions as novel and more expressions as familiar. The results suggest that novelty plays an important role in appreciating the plausibility of semantic relationships, and age-related changes are associated with the appreciation of the novelty of expressions.

Nonliteral language in Alzheimer dementia: a review

The use of nonliteral language in clinical assessment, especially testing the patients' ability to interpret proverbs, has a long tradition in psychiatry. However, its diagnostic sensitivity and specificity in dementias is not yet clear. The aim of this review article is to examine the current evidence on nonliteral/figurative language (proverb, metaphor, metonymy, idiom, irony, sarcasm) comprehension in Alzheimer's disease and related disorders. A comprehensive literature search identified 25 studies (16 proverb, 3 metaphor, 0 metonymy, 5 idiom, 3 sarcasm) on nonliteral language comprehension in dementia. Studies predominantly indicate a deficit. Most studies investigated Alzheimer's dementia. Applied correctly, nonliteral language is a worthwhile diagnostic tool to evaluate language and abstract thinking in dementias. During assessment, familiarity testing (e.g., by asking "are you familiar with the proverb XY") is obligatory. Still, future research is needed in several areas: evidence on decline of nonliteral language over the course of the illness is limited. So far, almost no studies delineated proverb comprehension in high risk populations such as patients with mild cognitive impairment. Currently, there is a lack of studies addressing performance in direct comparison to relevant differential diagnosis like older-age depression, delirium, brain lesion, or other psychiatric conditions.

Modulation of BOLD response in motion-sensitive lateral temporal cortex by real and fictive motion sentences

Can linguistic semantics affect neural processing in feature-specific visual regions? Specifically, when we hear a sentence describing a situation that includes motion, do we engage neural processes that are part of the visual perception of motion? How about if a motion verb was used figuratively, not literally? We used fMRI to investigate whether semantic content can "penetrate" and modulate neural populations that are selective to specific visual properties during natural language comprehension. Participants were presented audiovisually with three kinds of sentences: motion sentences ("The wild horse crossed the barren field."), static sentences, ("The black horse stood in the barren field."), and fictive motion sentences ("The hiking trail crossed the barren field."). Motion-sensitive visual areas (MT+) were localized individually in each participant as well as face-selective visual regions (fusiform face area; FFA). MT+ was activated significantly more for motion sentences than the other sentence types. Fictive motion sentences also activated MT+ more than the static sentences. Importantly, no modulation of neural responses was found in FFA. Our findings suggest that the neural substrates of linguistic semantics include early visual areas specifically related to the represented semantics and that figurative uses of motion verbs also engage these neural systems, but to a lesser extent. These data are consistent with a view of language comprehension as an embodied process, with neural substrates as far reaching as early sensory brain areas that are specifically related to the represented semantics.

Hemispheric differences in the recruitment of semantic processing mechanisms

This study examined how the two cerebral hemispheres recruit semantic processing mechanisms by combining event-related potential measures and visual half-field methods in a word priming paradigm in which semantic strength and predictability were manipulated using lexically associated word pairs. Activation patterns on the late positive complex (LPC), linked to controlled aspects of processing, showed that previously documented left hemisphere (LH) processing benefits for word pairs with a weak forward but strong backward association stem from the ability to appreciate meaning relations in an order-independent fashion and/or strategically reorder them. Whereas there is a LH benefit for such strategic processing during comprehension in passive tasks, the present study further showed that the right hemisphere (RH) is also able to make use of these mechanisms when explicit semantic judgments are required. In both hemispheres, N400 responses, linked to initial semantic activation, were largely graded by association strength, with more amplitude reduction for forward associates and strong, symmetrically associated pairs compared to backward associates and matched weak, symmetrically associated pairs. However, responses to moderately associated pairs were more facilitated after initial presentation to the LH than to the RH. This pattern converges with sentence-processing findings that point to LH advantages for using context information to predict features of likely upcoming words. Together, the results suggest that an important basis for hemispheric asymmetries in language comprehension arises from when and how each uses top-down semantic mechanisms to shape initial semantic activation over time.

Metaphor processing in high and low schizotypal individuals

Two hypotheses were considered regarding the relationship between positive schizotypy and metaphor processing. On the basis of continuity between schizophrenia and schizotypy, high schizotypal individuals would be expected to be impaired at metaphor processing. However, given the right hemisphere processing bias that has been associated with positive schizotypy, they would be expected to be superior at metaphor processing. A story completion task in which participants judged the appropriateness of literal and metaphoric statements was administered to 30 high and 29 low schizotypal individuals. Contrary to both hypotheses, groups did not differ in their ability to discriminate between appropriate and inappropriate statements, whether literal or metaphoric. However, the high schizotypal group demonstrated a less conservative response bias; they were more likely than the low schizotypal group to identify a statement as appropriate, whether it was or was not. Implications of these results for our understanding of language processing in schizophrenia and schizotypy are discussed.

Electrophysiological insights into the processing of nominal metaphors

We used event-related potentials (ERPs) to examine the time-course of processing metaphorical and literal sentences in the brain. ERPs were measured to sentence-final (Experiment 1) and mid-sentence (Experiment 2) critical words (CWs) as participants read and made plausibility judgments about familiar nominal metaphors ("A is a B") as well as literal and semantically anomalous sentences of the same form. Unlike the anomalous words, which evoked a robust N400 effect (on the CW in experiments 1 and 2 as well as on the sentence-final word in experiment 2), CWs in the metaphorical, relative to the literal, sentences only evoked an early, localized N400 effect that was over by 400ms after CW onset, suggesting that, by this time, their metaphorical meaning had been accessed. CWs in the metaphorical sentences also evoked a significantly larger LPC (Late Positive Component) than in the literal sentences. We suggest that this LPC reflected additional analysis that resolved a conflict between the implausibility of the literal sentence interpretation and the match between the metaphorical meaning of the CW, the context and stored information within semantic memory, resulting from early access to both literal and figurative meanings of the CWs.

Beyond laterality: a critical assessment of research on the neural basis of metaphor

Metaphors are a fundamental aspect of human cognition. The major neuropsychological hypothesis that metaphoric processing relies primarily on the right hemisphere is not confirmed consistently. We propose ways to advance our understanding of the neuropsychology of metaphor that go beyond simple laterality. Neuropsychological studies need to more carefully control confounding lexical and sentential factors, and consider the role of different parts of speech as they are extended metaphorically. They need to incorporate recent theoretical frameworks such as the career of metaphor theory, and address factors such as novelty. We also advocate the use of new methods such as voxel-based lesion-symptom mapping, which permits precise and formal tests of hypotheses correlating behavior with lesions sites. Finally, we outline a plausible model for the neural basis of metaphor. (JINS, 2009, 16, 1-5.).

When Elephants Fly: Differential Sensitivity of Right and Left Inferior Frontal Gyri to Discourse and World Knowledge

Both local discourse and world knowledge are known to influence sentence processing. We investigated how these two sources of information conspire in language comprehension. Two types of critical sentences, correct and world knowledge anomalies, were preceded by either a neutral or a local context. The latter made the world knowledge anomalies more acceptable or plausible. We predicted that the effect of world knowledge anomalies would be weaker for the local context. World knowledge effects have previously been observed in the left inferior frontal region (Brodmann's area 45/47). In the current study, an effect of world knowledge was present in this region in the neutral context. We also observed an effect in the right inferior frontal gyrus, which was more sensitive to the discourse manipulation than the left inferior frontal gyrus. In addition, the left angular gyrus reacted strongly to the degree of discourse coherence between the context and critical sentence. Overall, both world knowledge and the discourse context affect the process of meaning unification, but do so by recruiting partly different sets of brain areas.

Spatial asymmetries in viewing and remembering scenes: consequences of an attentional bias?

Given a single fixation, memory for scenes containing salient objects near both the left and right view boundaries exhibited a rightward bias in boundary extension (Experiment 1). On each trial, a 500-msec picture and 2.5-sec mask were followed by a boundary adjustment task. Observers extended boundaries 5% more on the right than on the left. Might this reflect an asymmetric distribution of attention? In Experiments 2A and 2B, free viewing of pictures revealed that first saccades were more often leftward (62%) than rightward (38%). In Experiment 3, 500-msec pictures were interspersed with 2.5-sec masks. A subsequent object recognition memory test revealed better memory for left-side objects. Scenes were always mirror reversed for half the observers, thus ruling out idiosyncratic scene compositions as the cause of these asymmetries. Results suggest an unexpected leftward bias of attention that selectively enhanced the representations, causing a smaller boundary extension error and better object memory on the views' left sides.

Neural correlates of metaphor processing: the roles of figurativeness, familiarity and difficulty

There is currently much interest in investigating the neural substrates of metaphor processing. In particular, it has been suggested that the right hemisphere plays a special role in the comprehension of figurative (non-literal) language, and in particular metaphors. However, some studies find no evidence of right hemisphere involvement in metaphor comprehension (e.g. [Lee, S. S., & Dapretto, M. (2006). Metaphorical vs. literal word meanings: fMRI evidence against a selective role of the right hemisphere. NeuroImage, 29, 536-544; Rapp, A. M., Leube, D. T., Erb, M., Grodd, W., & Kircher, T. T. J. (2004). Neural correlates of metaphor processing. Cognitive Brain Research, 20, 395-402]). We suggest that lateralization differences between literal and metaphorical language may be due to factors such as differences in familiarity ([Schmidt, G. L., DeBuse, C. J., & Seger, C. A. (2007). Right hemisphere metaphor processing? Characterizing the lateralization of semantic processes. Brain and Language, 100, 127-141]), or difficulty ([Bookheimer, S. (2002). Functional MRI of language: New approaches to understanding the cortical organization of semantic processing. Annual Review of Neuroscience, 25, 151-188; Rapp, A. M., Leube, D. T., Erb, M., Grodd, W., & Kircher, T. T. J. (2004). Neural correlates of metaphor processing. Cognitive Brain Research, 20, 395-402]) in addition to figurativeness. The purpose of this study was to separate the effects of figurativeness, familiarity, and difficulty on the recruitment of neural systems involved in language, in particular right hemisphere mechanisms. This was achieved by comparing neural activation using functional magnetic resonance imaging (fMRI) between four conditions: literal sentences, familiar and easy to understand metaphors, unfamiliar and easy to understand metaphors, and unfamiliar and difficult to understand metaphors. Metaphors recruited the right insula, left temporal pole and right inferior frontal gyrus in comparison with literal sentences. Familiar metaphors recruited the right middle frontal gyrus when contrasted with unfamiliar metaphors. Easy metaphors showed higher activation in the left middle frontal gyrus as compared to difficult metaphors, while difficult metaphors showed selective activation in the left inferior frontal gyrus as compared to easy metaphors. We conclude that the right hemisphere is involved in metaphor processing and that the factors of figurativeness, familiarity and difficulty are important in determining neural recruitment of semantic processing.

Responses on a lateralized lexical decision task relate to both reading times and comprehension

Research over the last few years has shown that the dominance of the left hemisphere in language processing is less complete than previously thought [Beeman, M. (1993). Semantic processing in the right hemisphere may contribute to drawing inferences from discourse. Brain and Language, 44, 80-120; Faust, M., & Chiarello, C. (1998). Sentence context and lexical ambiguity resolution by the two hemispheres. Neuropsychologia, 36(9), 827-835; Weems, S. A., & Zaidel, E. (2004). The relationship between reading ability and lateralized lexical decision. Brain and Cognition, 55(3), 507-515]. Engaging the right brain in language processing is required for processing speaker/writer intention, particularly in those subtle interpretive processes that help in deciphering humor, irony, and emotional inference. In two experiments employing a divided field or lateralized lexical decision task (LLDT), accuracy and reaction times (RTs) were related to reading times and comprehension on sentence reading. Differences seen in RTs and error rates by visual fields were found to relate to performance. Smaller differences in performance between fields tended to be related to better performance on the LLDT in both experiments and, in Experiment 1, to reading measures. Readers who can exploit both hemispheres for language processing equally appear to be at an advantage in lexical access and possibly also in reading performance.

"Aha!": The neural correlates of verbal insight solutions

What are the neural correlates of insight solutions? To explore this question we asked participants to perform an anagram task while in the fMRI scanner. Previous research indicates that anagrams are unique in that they can yield both insight and search solutions in expert subjects. Using a single-trial fMRI paradigm, we utilized the anagram methodology to explore the neural correlates of insight versus search solutions. We used both reaction time measures and subjective reports to classify each trial as a search or insight solution. Data indicate that verbal insight solutions activate a distributed neural network that includes bilateral activation in the insula, the right prefrontal cortex, and the anterior cingulate. These areas are discussed with their possible role in evaluation and metacognition of insight solutions, as well as attention and monitoring during insight.

Say it with flowers! An fMRI study of object mediated communication

Human communicational interaction can be mediated by a host of expressive means from words in a natural language to gestures and material symbols. Given the proper contextual setting even an everyday object can gain a mediating function in a communicational situation. In this study we used event-related fMRI to study the brain activity caused by everyday material objects when they are perceived as signals. We found that comprehension of material signals activates bilaterally areas of the ventral stream and pars triangularis of the inferior frontal cortex, that is, areas traditionally associated with verbal language and semantics. In addition, we found that right-hemisphere inferior frontal cortex is recruited as a function of the increasing unconventionality of communicative objects. Together these findings support an interpretation of the traditional language areas as playing a more general role across modalities in relation to communicational mediation of social semantic meaning.

Discourse Impairments Following Right Hemisphere Brain Damage: A Critical Review

Right hemisphere brain damage (RHD) rarely causes aphasias marked by clear and widespread failures of comprehension or extreme difficulty producing fluent speech. Nonetheless, subtle language comprehension deficits can occur following unilateral RHD. In this article, we review the empirical record on discourse function following right hemisphere damage, as well as relevant work on non-brain damaged individuals that focuses on right hemisphere function. The review is divided into four sections that focus on discourse processing, inferencing, humor, and non-literal language. While the exact role that the right hemisphere plays in language processing, and the exact way that the two cerebral hemispheres coordinate their linguistic processes are still open to debate, our review suggests that the right hemisphere plays a critical role in managing inferred or implied information by maintaining relevant information and/or suppressing irrelevant information. Deficits in one or both of these mechanisms may account for discourse deficits following RHD.

Metaphor comprehension in Alzheimer's disease: novelty matters

The comprehension of non-literal language was investigated in 20 probable Alzheimer's disease (pAD) patients by comparing their performance to that of 20 matched control subjects. pAD patients were unimpaired in the comprehension of conventional metaphors and idioms. However, their performance was significantly lower in the case of non-conventional (novel) metaphor comprehension. This ability was not related to global cognitive deterioration or to deficits in the cognitive domains of attention, memory and language comprehension. On the other hand, the impairment in verbal reasoning appeared to be relevant for both novel and conventional metaphor comprehension. The relationship between novel metaphor comprehension and performance in the visual-spatial planning task of the Behavioral Assessment of the Dysexecutive Syndrome (BADS) suggests that executive impairment, possibly related to prefrontal dysfunction, may be responsible for the pAD patients' poor performance in novel metaphor comprehension. The present findings suggest a role of the prefrontal cortex in novel metaphor comprehension.

Exploring cognitive effects of self reported mild stroke in older adults: selective but robust effects on story memory

Relatively little systematic information is available regarding patterns of cognitive effects of mild stroke in older adults. We explored this problem with a series of two independent samples from the Victoria Longitudinal Study data archives. In Study 1, self-reported mild stroke and neurologically intact matched controls were (a) confirmed as similar on a set of neurocognitive speed, basic cognition, and awareness indicators, and (b) compared for differences on a set of episodic, semantic, and working memory tasks. The mild stroke group was selectively worse on the language intensive story memory task. This effect was partially attributable to a deficit in remembering the most thematic information. Study 2 closely replicated these procedures and results. In addition, Study 2 follow-up analyses, comparing provisional right-hemisphere damaged and left-hemisphere damaged (LHD) participants, revealed that the thematic story memory deficit for mild stroke participants could be due to the selective impairment of LHD participants.

Embodied semantics for actions: findings from functional brain imaging

The theory of embodied semantics for actions specifies that the sensory-motor areas used for producing an action are also used for the conceptual representation of the same action. Here we review the functional imaging literature that has explored this theory and consider both supporting as well as challenging fMRI findings. In particular we address the representation of actions and concepts as well as literal and metaphorical phrases in the premotor cortex.

The Role of the Right Cerebral Hemisphere in Processing Novel Metaphoric Expressions: A Transcranial Magnetic Stimulation Study

Previous research suggests that the right hemisphere (RH) may contribute uniquely to the processing of metaphoric language. However, causal relationships between local brain activity in the RH and metaphors comprehension were never established. In addition, most studies have focused on familiar metaphoric expressions which might be processed similarly to any conventional word combination. The present study was designed to overcome these two problems by employing repetitive transcranial magnetic stimulation (rTMS) to examine the role of the RH in processing novel metaphoric expressions taken from poetry. Right-handed participants were presented with four types of word pairs, literal, conventional metaphoric and novel metaphoric expressions, and unrelated word pairs, and were asked to perform a semantic judgment task. rTMS of the right posterior superior temporal sulcus disrupted processing of novel but not conventional metaphors, whereas rTMS over the left inferior frontal gyrus selectively impaired processing of literal word pairs and conventional but not novel metaphors (Experiment 1). In a further experiment, we showed that these effects were due to right-left asymmetries rather than posterior-anterior differences (Experiment 2). This is the first demonstration of TMS-induced impairment in processing novel metaphoric expressions, and as such, confirms the specialization of the RH in the activation of a broader range of related meanings than the left hemisphere, including novel, nonsalient meanings. The findings thus suggest that the RH may be critically involved in at least one important component of novel metaphor comprehension, the integration of the individual meanings of two seemingly unrelated concepts into a meaningful metaphoric expression.

Dynamics of hemispheric activity during metaphor comprehension: Electrophysiological measures

Brain imaging studies have lead to conflicting findings regarding the involvement of the right hemisphere (RH) in metaphor comprehension. Some report more relative RH activation when processing figurative expressions but others have shown just the opposite. The inconsistencies might be a result of the low temporal resolution related to current brain imaging techniques which is insufficient to uncover patterns of hemispheric interaction that change over time. Event-related potentials and a source estimation technique (LORETA) were used to investigate such temporal interactions when processing two-word expressions denoting literal, conventional metaphoric, and novel metaphoric meaning, as well as unrelated word pairs. Participants performed a semantic judgment task in which they decided whether each word pair conveyed a meaningful expression. Our findings indicate that during comprehension of novel metaphors there are some stages of considerable RH involvement, mainly of the temporal and superior frontal areas. Although the processing mechanisms used for all types of expressions were similar and require both hemispheres, the relative contribution of each hemisphere at specific processing stages depended on stimulus type. Those stages correspond roughly to the N400 and LPC components which reflect semantic and contextual integration, respectively. The present study demonstrates that RH mechanisms are necessary, but not sufficient, for understanding metaphoric expressions. Both hemispheres work in concert in a complex dynamical pattern during literal and figurative language comprehension. Electrophysiological recordings together with source localization algorithms such as LORETA are a viable tool for measuring this type of activity patterns.

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.

Laterality in metaphor processing: lack of evidence from functional magnetic resonance imaging for the right hemisphere theory

We investigated processing of metaphoric sentences using event-related functional magnetic resonance imaging (fMRI). Seventeen healthy subjects (6 female, 11 male) read 60 novel short German sentence pairs with either metaphoric or literal meaning and performed two different tasks: judging the metaphoric content and judging whether the sentence has a positive or negative connotation. Laterality indices for 8 regions of interest were calculated: Inferior frontal gyrus (opercular part and triangular part), superior, middle, and inferior temporal gyrus, precuneus, temporal pole, and hippocampus. A left lateralised network was activated with no significant differences in laterality between the two tasks. The lowest degree of laterality was found in the temporal pole. Other factors than metaphoricity per se might trigger right hemisphere recruitment. Results are discussed in the context of lesion and hemifield studies.

Hemispheric asymmetry and pun comprehension: when cowboys have sore calves

Event-related potentials (ERPs) were recorded as healthy participants listened to puns such as "During branding, cowboys have sore calves." To assess hemispheric differences in pun comprehension, visually presented probes that were either highly related (COW), moderately related (LEG), or unrelated, were presented in either the left or right visual half field (LVF/RVF). The sensitivity of each hemisphere to the different meanings evoked by the pun was assessed by ERP relatedness effects with presentation to the LVF and the RVF. In Experiment 1, the inter-stimulus interval between the pun and the onset of the visual probe was 0 ms; in Experiment 2, this value was 500 ms. In Experiment 1, both highly and moderately related probes elicited similar priming effects with RVF presentation. Relative to their unrelated counterparts, related probes elicited less negative ERPs in the N400 interval (300-600 ms post-onset), and more positive ERPs 600-900 ms post-onset, suggesting both meanings of the pun were equally active in the left hemisphere. LVF presentation yielded similar priming effects (less negative N400 and a larger positivity thereafter) for the highly related probes, but no effects for moderately related probes. In Experiment 2, similar N400 priming effects were observed for highly and moderately related probes presented to both visual fields. Compared to unrelated probes 600-900 ms post-onset, related probes elicited a centro-parietal positivity with RVF presentation, but a fronto-polar positivity with LVF presentation. Results suggest that initially, the different meanings evoked by a pun are both active in the left hemisphere, but only the most highly related meaning is active in the right hemisphere. By 500 ms, both meanings are active in both hemispheres.

An fMRI investigation of the neural correlates underlying the processing of novel metaphoric expressions

The neural networks associated with processing related pairs of words forming literal, novel, and conventional metaphorical expressions and unrelated pairs of words were studied in a group of 15 normal adults using fMRI. Subjects read the four types of linguistic expressions and decided which relation exists between the two words (metaphoric, literal, or unrelated). According to the Graded Salience Hypothesis (GSH, ), which predicts a selective RH involvement in the processing of novel, nonsalient meanings, it is primarily the degree of meaning salience of a linguistic expression rather than literality or nonliterality, which modulates the degree of left hemisphere (LH) and right hemisphere (RH) processing of metaphors. In the present study, novel metaphorical expressions represented the nonsalient interpretations, whereas conventional metaphors and literal expressions represented the salient interpretations. A direct comparison of the novel metaphors vs. the conventional metaphors revealed significantly stronger activity in right posterior superior temporal sulcus, right inferior frontal gyrus, and left middle frontal gyrus. These results support the GSH and suggest a special role for the RH in processing novel metaphors. Furthermore, the right PSTS may be selectively involved in verbal creativity.

Bilateral brain processes for comprehending natural language

Comprehension of natural language--stories, conversations, text--is very simple for those doing the comprehending and very complex for cognitive neuroscientists. It also presents a paradox: the advantage of the left hemisphere (LH) for most language tasks is one of the best-established facts about the brain; yet, when it comes to comprehending complex, natural language, the right hemisphere (RH) might play an important role. Accumulated evidence from neuropsychology, neuroimaging, and neuroanatomy suggests at least three roughly separable (but highly interactive) components of semantic processing. Each process in turn has bilateral components, with the RH component performing coarser computations for the same general process. Examining asymmetrical brain and cognitive functions provides a unique opportunity for understanding the neural basis of complex cognition.