Sensitivity to lexical denotation and connotation in brain-damaged patients: a double dissociation?

Affective Prosody and Its Impact on the Neurology of Language, Depression, Memory and Emotions

Based on the seminal publications of Paul Broca and Carl Wernicke who established that aphasic syndromes (disorders of the verbal-linguistic aspects of communication) were predominantly the result of focal left-hemisphere lesions, "language" is traditionally viewed as a lateralized function of the left hemisphere. This, in turn, has diminished and delayed the acceptance that the right hemisphere also has a vital role in language, specifically in modulating affective prosody, which is essential for communication competency and psychosocial well-being. Focal lesions of the right hemisphere may result in disorders of affective prosody (aprosodic syndromes) that are functionally and anatomically analogous to the aphasic syndromes that occur following focal left-hemisphere lesions. This paper will review the deductive research published over the last four decades that has elucidated the neurology of affective prosody which, in turn, has led to a more complete and nuanced understanding of the neurology of language, depression, emotions and memory. In addition, the paper will also present the serendipitous clinical observations (inductive research) and fortuitous inter-disciplinary collaborations that were crucial in guiding and developing the deductive research processes that culminated in the concept that primary emotions and related display behaviors are a lateralized function of the right hemisphere and social emotions, and related display behaviors are a lateralized function of the left hemisphere.

Exploring Pragmatic Deficits in Relation to Theory of Mind and Executive Functions: Evidence from Individuals with Right Hemisphere Stroke

Research investigating pragmatic deficits in individuals with right hemisphere damage focuses on identifying the potential mechanisms responsible for the nature of these impairments. Nonetheless, the presumed shared cognitive mechanisms that could account for these deficits have not yet been established through data-based evidence from lesion studies. This study aimed to examine the co-occurrence of pragmatic language deficits, Theory of Mind impairments, and executive functions while also exploring their associations with brain lesion sites. Twenty-five patients suffering from unilateral right hemisphere stroke and thirty-seven healthy participants were recruited for this study. The two groups were tested in pragmatics, Theory of Mind, and executive function tasks. Structural imaging data were also obtained for the identification of the lesion sites. The findings of this study suggest a potential convergence among the three aforementioned cognitive mechanisms. Moreover, we postulate a hypothesis for a neural circuitry for communication impairments observed in individuals with right hemisphere damage.

Preliminary study of higher-order language and extralinguistic impairments in individuals with high clinical risk of psychosis and first episode of schizophrenia

AIM

Higher-order language functions are associated with understanding indirect speech acts, lexical-semantic processes, the understanding and production of prosody, discourse production and comprehension. Only a few studies imply that language abnormalities may be present in individuals at ultra-high risk for psychosis (UHR) and first-episode of schizophrenia (FE). The purpose of this study was to test the presence of higher-order language dysfunctions in UHR and FE subjects using a standardized comprehensive test battery.

METHODS

Twenty patients experiencing FE schizophrenia, 33 UHR individuals and 20 healthy controls (HC) took part in the study. Higher-order language and extralinguistic abilities were evaluated using the Right Hemisphere Language Battery (RHLB-PL). The battery consisted of tests covering the comprehension of implicit information, lexico-semantic processing, understanding humour, making inappropriate remarks and comments, understanding and explaining metaphors, understanding prosody and appropriateness of behaviour in communication settings.

RESULTS

The UHR patients scored lower than HC when comprehending implicit information, discourse and in areas associated with the effectiveness of interpersonal communication; however, they scored higher than the FE participants in explanation of metaphors and processing language information in the context of general knowledge. The FE participants scored lower than healthy controls in comprehension of implicit information, explanation of metaphors, discourse understanding, processing language information in the context of general knowledge and effectiveness of interpersonal communication.

CONCLUSIONS

The higher-order language dysfunctions mediated by the right hemisphere appear to be present in subjects at UHR of schizophrenia and those experiencing their FE. The results may play a crucial role in diagnostic processes.

Selective Metaphor Impairments After Left, Not Right, Hemisphere Injury

The relative contributions of the left and right hemispheres to the processing of metaphoric language remains unresolved. Neuropsychological studies of brain-injured patients have motivated the hypothesis that the right hemisphere plays a critical role in understanding metaphors. However, the data are inconsistent and the hypothesis is not well-supported by neuroimaging research. To address this ambiguity about the right hemisphere's role, we administered a metaphor sentence comprehension task to 20 left-hemisphere injured patients, 20 right hemisphere injured patients, and 20 healthy controls. Stimuli consisted of metaphors of three different types: predicate metaphors based on action verbs, nominal metaphors based on event nouns, and nominal metaphors based on entity nouns. For each metaphor (n = 60), a closely matched literal sentence with the same source term was also generated. Each sentence was followed by four adjective-noun answer choices (target + three foil types) and participants were instructed to select the phrase that best matched the meaning of the sentence. As a group, both left and right hemisphere patients performed worse on metaphoric than literal sentences, and the degree of this difficulty varied for the different types of metaphor - but there was no difference between the two patient groups. Tests for literal-metaphor dissociations at the level of single cases revealed two types of impairments: general comprehension deficits affecting metaphors and literal sentences equally, and selective metaphor impairments that were specific to different types of metaphor. All cases with selective metaphor deficits had injury to the left hemisphere, and no known comprehension difficulties with literal language. Our results argue against the hypothesis of a specific or necessary contribution of the right hemisphere for understanding metaphoric language. Further, they reveal deficits in metaphoric language comprehension not captured by traditional language assessments, suggesting overlooked communication difficulties in left hemisphere patients.

Schizophrenia patients have higher-order language and extralinguistic impairments

INTRODUCTION

The extralinguistic and paralinguistic aspects of the language refer to higher-order language functions such as lexical-semantic processes, prosody, indirect speech acts or discourse comprehension and production. Studies suggest that these processes are mediated by the Right Hemisphere (RH) and there is also some evidence of RH dysfunctions in schizophrenia. The aim of the paper is to investigate the extralinguistic and paralinguistic processing mediated by Right Hemisphere in schizophrenia patients using a validated and standardized battery of tests.

METHODS

Two groups of participants were examined: a schizophrenia sample (40 participants) and a control group (39 participants). Extralinguistic and paralinguistic processing was assessed in all subjects by the Polish version of the Right Hemisphere Language Battery (RHLB-PL), which measures comprehension of implicit information, naming, understanding humor, inappropriate remarks and comments, explanation and understanding of metaphors, understanding emotional and language prosody and discourse understanding.

RESULTS

Schizophrenia patients scored significantly lower than controls in subtests measuring comprehension of implicit information, interpretation of humor, explanation of metaphors, inappropriate remarks and comments, discernment of emotional and language prosody and comprehension of discourse. No differences were observed in naming, understanding metaphors or in processing visuo-spatial information.

CONCLUSIONS

Extralinguistic and paralinguistic dysfunctions appear to be present in schizophrenia patients and they suggest that RH processing may be disturbed in that group of patients. As the disturbances of higher-order language processes mediated by the RH may cause serious impairments in the social communication of patients, it is worth evaluating them during clinical examination.

Getting the Right Idea: Semantic Activation in the Right Hemisphere May Help Solve Insight Problems

Two experiments examined hemispheric differences in information processing that may contribute to solving insight problems. We propose that right-hemisphere (RH) coarse semantic coding is more likely than left-hemisphere (LH) fine semantic coding to activate distantly related information or unusual interpretations of words, and thus more likely to activate solution-relevant information for insight problems. In Experiment 1, after trying to solve insight problems, participants read aloud solution or unrelated target words presented to the left visual field (lvf) or right visual field (rvf). Participants showed greater lvf-RH than rvf-LH priming for solutions for solved problems and priming only in the lvf-RH for unsolved problems. In Experiment 2, participants showed an lvf-RH advantage for recognizing solutions to unsolved problems. These results demonstrate that in a problem-solving context, there was greater activation of solution-relevant information in the RH than in the LH. This activation is useful for recognizing, and perhaps producing, solutions to insight problems.

Lower- and higher-level models of right hemisphere language. A selective survey

The models advanced to explain right hemisphere (RH) language function can be divided into two main types. According to the older (lower-level) models, RH language reflects the ontogenesis of conceptual and semantic-lexical development; the more recent models, on the other hand, suggest that the RH plays an important role in the use of higher-level language functions, such as metaphors, to convey complex, abstract concepts. The hypothesis that the RH may be preferentially involved in processing the semantic-lexical components of language was advanced by Zaidel in splitbrain patients and his model was confirmed by neuropsychological investigations, proving that right brain-damaged patients show selective semanticlexical disorders. The possible links between lower and higher levels of RH language are discussed, as is the hypothesis that the RH may have privileged access to the figurative aspects of novel metaphorical expressions, whereas conventionalization of metaphorical meaning could be a bilaterally-mediated process involving abstract semantic-lexical codes.

Flying under the radar: figurative language impairments in focal lesion patients

Despite the prevalent and natural use of metaphor in everyday language, the neural basis of this powerful communication device remains poorly understood. Early studies of brain-injured patients suggested the right hemisphere plays a critical role in metaphor comprehension, but more recent patient and neuroimaging studies do not consistently support this hypothesis. One explanation for this discrepancy is the challenge in designing optimal tasks for brain-injured populations. As traditional aphasia assessments do not assess figurative language comprehension, we designed a new metaphor comprehension task to consider whether impaired metaphor processing is missed by standard clinical assessments. Stimuli consisted of 60 pairs of moderately familiar metaphors and closely matched literal sentences. Sentences were presented visually in a randomized order, followed by four adjective-noun answer choices (target + three foil types). Participants were instructed to select the phrase that best matched the meaning of the sentence. We report the performance of three focal lesion patients and a group of 12 healthy, older controls. Controls performed near ceiling in both conditions, with slightly more accurate performance on literal than metaphoric sentences. While the Western Aphasia Battery (Kertesz, 1982) and the objects and actions naming battery (Druks and Masterson, 2000) indicated minimal to no language difficulty, our metaphor comprehension task indicated three different profiles of metaphor comprehension impairment in the patients’ performance. Single case statistics revealed comparable impairment on metaphoric and literal sentences, disproportionately greater impairment on metaphors than literal sentences, and selective impairment on metaphors. We conclude our task reveals that patients can have selective metaphor comprehension deficits. These deficits are not captured by traditional neuropsychological language assessments, suggesting overlooked communication difficulties.

Pathways to lexical ambiguity: fMRI evidence for bilateral fronto-parietal involvement in language processing

Numerous functional neuroimaging studies reported increased activity in the pars opercularis and the pars triangularis (Brodmann's areas 44 and 45) of the left hemisphere during the performance of linguistic tasks. The role of these areas in the right hemisphere in language processing is not understood and, although there is evidence from lesion studies that the right hemisphere is involved in the appreciation of semantic relations, no specific anatomical substrate has yet been identified. This event-related functional magnetic resonance imaging study compared brain activity during the performance of language processing trials in which either dominant or subordinate meaning activation of ambiguous words was required. The results show that the ventral part of the pars opercularis both in the left and the right hemisphere is centrally involved in language processing. In addition, they highlight the bilateral co-activation of this region with the supramarginal gyrus of the inferior parietal lobule during the processing of this type of linguistic material. This study, thus, provides the first evidence of co-activation of Broca's region and the inferior parietal lobule, succeeding in further specifying the relative contribution of these cortical areas to language processing.

Differential effects of semantic and identity priming in patients with left and right hemisphere lesions

Abstract Patients with single brain lesions in the anterior or posterior left and right hemispheres and a group of controls were studied in two priming experiments. The first experiment employed associative pairs (DOCTOR-NURSE) and the second employed identical pairs (NURSE-nurse). Short and long prime-target stimulus onset asynchronies (SOAs) (i.e., 250 and 1850 msec) were manipulated within block in both experiments. In the first experiment, patients with left hemisphere injury showed a deficient priming effect while patients with right hemisphere injury and controls showed a normal pattern. In contrast, all groups showed an identity priming effect in the second experiment. These results indicate that while entries in the mental lexicon are available for the groups of patients studied, the spread of activation to related concepts in this lexicon is disrupted in the left hemisphere-damaged group.

Positively valenced stimuli facilitate creative novel metaphoric processes by enhancing medial prefrontal cortical activation

A metaphor is a figure of speech in which a subject is symbolic of another unrelated object. In the present study, we examined neural patterns associated with both novel unfamiliar and conventional familiar metaphoric processing, and how these patterns are modulated by affective valence. Prior to fMRI scanning, participants received a list of word pairs (novel unfamiliar metaphors as well as conventional familiar metaphors) and were asked to denote the valence (positive, negative, or neutral) of each word pair. During scanning, participants had to decide whether the word pairs formed meaningful or meaningless expressions. Results indicate that participants were faster and more accurate at deciding that positively valenced metaphors were meaningful compared to neutral metaphors. These behavioral findings were accompanied by increased activation in the medial prefrontal cortex (mPFC), posterior cingulate cortex (PCC), and the right inferior parietal lobe (RIPL). Specifically, positively valenced novel unfamiliar metaphors elicited activation in these brain regions in addition to the left superior temporal gyrus when compared to neutral novel metaphors. We also found that the mPFC and PCC mediated the processing of positively valenced metaphors when compared to negatively valenced metaphors. Positively valenced conventional metaphors, however, elicited different neural signatures when contrasted with either neutral or negatively valenced conventional metaphors. Together, our results indicate that positively valenced stimuli facilitate creative metaphoric processes (specifically novel metaphoric processes) by mediating attention and cognitive control processes required for the access, integration, and selection of semantic associations via modulation of the mPFC. The present study is important for the development of neural accounts of emotion-cognition interactions required for creativity, language, and successful social functioning in general.

The role of the right hemisphere in metaphor comprehension: a meta-analysis of functional magnetic resonance imaging studies

The role of the right hemisphere (RH) in metaphor comprehension is still controversial. Numerous neuroimaging studies have found that conventionality, sentential context, and task demand can influence the involvement of the RH in metaphor processing. The current meta-analysis used foci from 17 original functional magnetic resonance imaging studies to identify what factors modulate the involvement of the RH in metaphor processing. Activation likelihood estimation was used for quantification. We focused on the contrast of metaphorical meaning processing versus literal meaning processing and calculated the meta-analysis effects when (1) metaphorical meaning is conventional, (2) metaphorical meaning is novel, (3) metaphorical and literal meaning are presented in words, (4) metaphorical and literal meaning are presented in sentential context, (5) task is valence judgment, and (6) task is semantic relatedness judgment. The results indicated that the RH only showed significant effects in metaphor processing when the metaphorical meaning is novel, when metaphorical meaning is presented in sentential context, and when the task is semantic relatedness judgment. The effects were located in right fronto-temporal regions, including inferior frontal gyrus, middle frontal gyrus, insula, superior temporal gyrus, and middle temporal gyrus. These results suggest that conventionality, contextual complexity, and task demand can modulate the effect of figurativeness and influence the involvement of RH in metaphor comprehension. The main role of the RH in metaphor processing is related with activating broad semantic fields and integrating concepts that may have distant semantic relations, and hence provide support for the view that the RH is responsible for processing coarse semantic information in language comprehension.

Alogia and formal thought disorder: differential patterns of verbal fluency task performance

BACKGROUND

There is evidence that alogia and formal thought disorder (FTD), two prominent speech symptoms in schizophrenia, are associated with different patterns of verbal fluency task deficits. Verbal fluency is thought to involve several cognitive mechanisms, including controlled retrieval, semantic memory, and context processing.

METHODS

The current research examined whether alogia and FTD were associated with different patterns of verbal fluency performance and whether these patterns of verbal fluency performance would implicate deficits in controlled retrieval, semantic memory, or context processing. In the current research, 34 people with schizophrenia completed letter and category fluency tasks and detailed ratings of alogia and FTD symptoms were made from typed transcripts.

RESULTS

Overall, alogia was associated with increased response latency between each word on the category fluency task, suggesting an association between alogia and poor controlled retrieval. In contrast, FTD was associated with a decreased proportion of semantically-related words on letter fluency, suggesting an association between FTD and poor context processing.

CONCLUSIONS

Alogia and FTD appear to be associated with unique patterns of fluency performance, implicating separate cognitive mechanisms.

The neuromechanism underlying verbal analogical reasoning of metaphorical relations: an event-related potentials study

Using event-related potentials (ERPs), this study investigated the neuromechanism underlying verbal analogical reasoning of two different metaphorical relations: attributive metaphor and relational metaphor. The analogical reasoning of attributive metaphor (AM-AR) involves a superficial similarity between analogues, while the analogical reasoning of relational metaphor (RM-AR) requires a structural similarity. Subjects were asked to judge whether one word pair was semantically analogous to another word pair. Results showed that the schema induction stage elicited a greater N400 component at the right anterior scalp for the AM-AR and RM-AR tasks, possibly attributable to semantic processing of metaphorical word pairs. The N400 was then followed by a widely distributed P300 and a late negative component (LNC1) at the left anterior scalp. The P300 was possibly related to the formation of a relational category, while the LNC1 was possibly related to the maintenance of a reasoning cue in working memory. The analogy mapping stage elicited broadly distributed N400 and LNC2, which might indicate the presence of semantic retrieval and analogical transfer. In the answer production stage, all conditions elicited the P2 component due to early stimulus encoding. The largest P2 amplitude was in the RM-AR task. The RM-AR elicited a larger LPC than did the AM-AR, even though the baseline correction was taken as a control for the differential P2 effect. The LPC effect might suggest that relational metaphors involved more integration processing than attributive metaphors.

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.

Treating Metaphor Interpretation Deficits Subsequent to Right Hemisphere Brain Damage: Preliminary Results

PURPOSE: This investigation sought to determine whether a structured intervention focused on improving use of semantic associations could improve patients' ability to provide oral interpretations of metaphors following Right Hemisphere Damage (RHD). METHODS: Principles of single subject experimental design provided the basis for the study. Five patients received either 10 or 20 baseline assessments of oral metaphor interpretation and, as a control, assessments of line orientation skill. They then received approximately 10 one-hour sessions of structured intervention to improve oral metaphor interpretation followed by post-training assessments and a 3 month follow up. RESULTS: Patients' performances revealed evidence of good response to training as shown by patients' ability to reach criterion on all intervention tasks and by their significant improvement on oral metaphor interpretation. There was relatively little improvement on the line orientation task. DISCUSSION: The results of this study support the clinical usefulness of this new approach to treating communication deficits associated with RHD due to stroke, even years post-onset. There are, however, questions that remain unanswered. For example, additional data will be needed to gauge how a patient's severity of impairment relates to the potential for improvement, to chart the durability and scope of improvement associated with the training, and to determine the type of visuospatial ability needed for using this type of pictorial material.

Stimulus design is an obstacle course: 560 matched literal and metaphorical sentences for testing neural hypotheses about metaphor

Despite the ubiquity and importance of metaphor in thought and communication, its neural mediation remains elusive. We suggest that this uncertainty reflects, in part, stimuli that have not been designed with recent conceptual frameworks in mind or that have been hampered by inadvertent differences between metaphoric and literal conditions. In this article, we begin addressing these shortcomings by developing a large, flexible, extensively normed, and theoretically motivated set of metaphoric and literal sentences. On the basis of the results of three norming studies, we provide 280 pairs of closely matched metaphoric and literal sentences that are characterized along 10 dimensions: length, frequency, concreteness, familiarity, naturalness, imageability, figurativeness, interpretability, valence, and valence judgment reaction time. In addition to allowing for control of these potentially confounding lexical and sentential factors, these stimuli are designed to address questions about the role of novelty, metaphor type, and sensory-motor grounding in determining the neural basis of metaphor comprehension. Supplemental data for this article may be downloaded from http://brm.psychonomic-journals.org/content/supplemental.

Automatic and controlled aspects of lexical associative processing in the two cerebral hemispheres

Associative processing in the cerebral hemispheres was examined using ERPs and visual half-field (VF) methods. Associative strength was manipulated using asymmetrically associated pairs: viewed in one order (forward), there was a strong prime-to-target association, but in the backward order, predictability was weak. N400 priming was greater for forward than backward pairs in both VFs and not different across VF, suggesting similar semantic representations and automatic meaning activation in the two hemispheres. However, a frontal P2 enhancement for forward pairs restricted to the LH suggests that it uses context to predict likely upcoming words. Also, greater late positive complex priming for backward pairs in the LH than the RH reveals a LH advantage for strategically reshaping meaning activation for weakly related and/or non-canonically ordered pairs. The results link asymmetries in word processing with those observed at the sentence level.

Cerebral localization of functions and the neurology of language: fact versus fiction or is it something else?

Over the last 15 years there has been a burgeoning number of publications using functional brain imaging (>40,000 articles based on an ISI/Web of Science search) to localize behavioral and cognitive processes to specific areas in the human brain that are often not confirmed by traditional, lesion-based studies. Thus, there is a need to reassess what cerebral localization of functions is and is not. Otherwise, there is no rational way to interpret the escalating claims of localization in the functional imaging literature that is taking on the appearance of neurophysiologic "phrenology". This article will present arguments to suggest that functional localization in the brain is a robust but very dynamic, four-dimensional process. It is a learned phenomenon driven over time by large-scale, spatially distributed, neural networks seeking to efficiently maximize the processing, storage, and manipulation of information for cognitive and behavioral operations. Because of historical considerations and space limitations, the main focus will be on localization of language-related functions whose theoretical neurological basis can be generalized for any complex cognitive-behavioral function.

Differences in task demands influence the hemispheric lateralization and neural correlates of metaphor

This study investigated metaphor comprehension in the broader context of task-difference effects and manipulation of processing difficulty. We predicted that right hemisphere recruitment would show greater specificity to processing difficulty rather than metaphor comprehension. Previous metaphor processing studies have established that the left inferior frontal gyrus strongly correlates with metaphor comprehension but there has been controversy about whether right hemisphere (RH) involvement is specific for metaphor comprehension. Functional MRI data were recorded from healthy subjects who read novel metaphors, conventional metaphors, definition-like sentences, or literal sentences. We investigated metaphor processing in contexts where semantic judgment or imagery modulates linguistic judgment. Our findings support the position that the type of task rather than figurative language processing per se modulates the left inferior gyrus (LIFG). RH involvement was more influenced by processing difficulty and less by the novelty or figurativity of linguistic expressions. Our results suggest that figurative language processing depends upon the effects of task-type and processing difficulty on imaging results.

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.

Processing of metaphors in transcortical motor aphasia

Great emphasis has been placed on the right hemisphere, due to its possible selective contribution, in the processing of metaphorical statements.

OBJECTIVES

To describe the processing of metaphors in the case of a patient with transcortical motor aphasia, using specific tests for patients with encephalic injuries of the right hemisphere, and to contribute to the discussion on the inter-hemispheric relationships associated with this function.

METHODS

A 54 year-old man with transcortical motor aphasia was evaluated three years after a left hemisphere stroke. The tasks of comprehension of metaphors were based on the subtest Metaphor Comprehension Task of the Montreal Evaluation of Communications Scale (MEC). Two metaphor comprehension tests were applied, in 45-minute sessions with a 48 hour interval between each. Test 1 involved comprehension of the metaphors according to the options offered, and Test 2 the comprehension of metaphors measured by response time and visual field.

RESULTS

Although the right hemisphere was not affected by the stroke in this case, difficulties were observed in the processing of metaphors.

CONCLUSIONS

This study suggests that the left hemisphere participates in the processing of figurative meanings. The adaptability of the brain can also re-accommodate the uninjured areas of the brain, causing the dynamic of the brain to be modified. As a result, deducing cerebral functions based on clinical data can be problematic. The value of this study is that it can contribute to clinical aspects of language rehabilitation.

Neurology of affective prosody and its functional-anatomic organization in right hemisphere

Unlike the aphasic syndromes, the organization of affective prosody in brain has remained controversial because affective-prosodic deficits may occur after left or right brain damage. However, different patterns of deficits are observed following left and right brain damage that suggest affective prosody is a dominant and lateralized function of the right hemisphere. Using the Aprosodia Battery, which was developed to differentiate left and right hemisphere patterns of affective-prosodic deficits, functional-anatomic evidence is presented in patients with focal ischemic strokes to support the concepts that (1) affective prosody is a dominant and lateralized function of the right hemisphere, (2) the intrahemispheric organization of affective prosody in the right hemisphere, with the partial exception of Repetition, is analogous to the organization of propositional language in the left hemisphere and (3) the aprosodic syndromes are cortically based as part of evolutionary adaptations underlying human language and communication.

Comprehension of implicit meanings in social situations involving irony: A functional MRI study

To understand implicit social meanings, the interaction of literal meanings and relevant information in a situational context is important. However, previous studies have not investigated such contextual interactions. Using functional magnetic resonance imaging (fMRI), we investigated cortical mechanisms underlying the processing of implicit meanings, particularly irony, in realistic social situations, focusing on contextual interactions. Healthy subjects were shown pictures depicting daily communicative situations during judgment tasks involving situational appropriateness and literal correctness. The left medial prefrontal cortex showed significantly greater activation during tasks involving situational judgments than during literal judgments. The right temporal pole was activated task-independently during irony-specific processing. The medial orbitofrontal cortex was activated task-dependently during irony processing in situational judgment tasks. These regions have been reported to be involved in theory of mind, and have not been implicated in previous studies on the linguistic processing of implicit meanings. This suggests that the intentional assessment of situational appropriateness for task execution is carried out in the left medial prefrontal cortex, whereas irony is processed in the right temporal pole by assessing situational context automatically, and is judged based on the situational context in the medial orbitofrontal cortex. Our results show that the processing of implicit meanings and irony in contextually rich situations depends on brain mechanisms involved in the "theory of mind," based on processing relevant information in a situational context, and suggest different functions in each region.

Social regulation of affective experience of humor

The element of surprise, a necessary condition for the experience of humor, often derives from the fact that the alternative interpretation/resolution offered by the punch line of a joke is physically or socially forbidden. Children's humor typifies violation of physical norms, whereas adult humor typically pushes the boundaries of social norms. Excess norm violation, to the point of offending, can attenuate the experience of humor/mirth. To examine the neural basis of regulation of affective experience of humor by social norms, we scanned 16 normal subjects while they viewed a series of cartoons that varied in funniness and social acceptability. Behavioral results indicated two separate groups of subjects, those who found the cartoons less offensive and those who found them more offensive. In the group that found the jokes more offensive, there was a negative correlation between funniness and social inappropriateness. In this group, the corresponding Humor by Social inappropriateness interaction during functional magnetic resonance imaging revealed enhanced activation in the right hippocampus along with relative deactivation in the ventral medial prefrontal cortex (VMPFC). By contrast, the Funniness by Social appropriateness interaction resulted in activation in the VMPFC and relative deactivation in the right hippocampus. These results suggest that the regulation of humor by social norms involves reciprocal response patterns between VMPFC and hippocampus regions implicated in contextual regulation of behavior and memory, respectively.

Metaphor explanation attenuates the right-hand preference for depictive co-speech gestures that imitate actions

Differential activation levels of the two hemispheres due to hemispheric specialization for various linguistic processes might determine hand choice for co-speech gestures. To test this hypothesis, we compared hand choices for gesturing in 20 healthy right-handed participants during explanation of metaphorical vs. non-metaphorical meanings, on the assumption that metaphor explanation enhances the right hemisphere contribution to speech production. Hand choices were analyzed separately for: depictive gestures that imitate action ("character viewpoint gestures," [McNeill, D. (1992). Hand and mind. What gestures reveal about thought. Chicago: University of Chicago Press.]), depictive gestures that express motion, relative locations, and shape ("observer viewpoint gestures"), and "abstract deictic gestures." It was found that the right-hand over left-hand preference was significantly weaker in the metaphor condition than in the non-metaphor conditions for depictive gestures that imitated action. Findings suggest that the activation of the right hemisphere in the metaphor condition reduces the likelihood of left hemisphere generation of gestures that imitate action, thus attenuating the right-hand preference.

A special role for the right hemisphere in metaphor comprehension?

It has been suggested that the right hemisphere (RH) has a privileged role in the processing of figurative language, including metaphors, idioms, and verbal humor. Previous experiments using hemifield visual presentation combined with human electrophysiology support the idea that the RH plays a special role in joke comprehension. The current study examines metaphoric language. Event-related potentials (ERPs) were recorded as healthy adults read English sentences that ended predictably (High-cloze Literals), or with a plausible but unexpected word (Low-cloze Literals and Low-cloze Metaphoricals). Sentence final words were presented in either the left or the right visual hemifield. Relative to High-cloze Literals, Low-cloze Literals elicited a larger N400 component after presentation to both the left and the right hemifield. Low-cloze Literals also elicited a larger frontal positivity following the N400, but only with presentation to the right hemifield (left hemisphere). These data suggest both cerebral hemispheres can benefit from supportive sentence context, but may suggest an important role for anterior regions of the left hemisphere in the selection of semantic information in the face of competing alternatives. Relative to Low-cloze Literals, Low-cloze Metaphoricals elicited more negative ERPs during the timeframe of the N400 and afterwards. However, ERP metaphoricity effects were very similar across hemifields, suggesting that the integration of metaphoric meanings was similarly taxing for the two hemispheres, contrary to the predictions of the right hemisphere theory of metaphor.

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.

Right hemisphere metaphor processing? Characterizing the lateralization of semantic processes

Previous laterality studies have implicated the right hemisphere in the processing of metaphors, however it is not clear if this result is due to metaphoricity per se or another aspect of semantic processing. Three divided visual field experiments varied metaphorical and literal sentence familiarity. We found a right hemisphere advantage for unfamiliar sentences containing distant semantic relationships, and a left hemisphere advantage for familiar sentences containing close semantic relationships, regardless of whether sentences were metaphorical or literal. This pattern of results is consistent with theories postulating predominantly left hemisphere processing of close semantic relationships and predominantly right hemisphere processing of distant semantic relationships.

Functional MRI of conventional and anomalous metaphors in Mandarin Chinese

This study looks at whether conventional and anomalous metaphors are processed in different locations in the brain while being read when compared with a literal condition in Mandarin Chinese. We find that conventional metaphors differ from the literal condition with a slight amount of increased activation in the right inferior temporal gyrus. In addition, when the anomalous metaphor condition is compared with the literal condition, increased activation occurs bilaterally in the frontal and temporal gyri. Lastly, the comparison between the anomalous and conventional metaphor conditions shows bilateral activation in the middle frontal gyrus and the precentral gyrus, and right-hemisphere activation in the superior frontal gyrus. Left hemisphere activation is found in the inferior frontal gyrus and fusiform gyrus. The left hemisphere activation in the frontal and temporal gyri point to the recruitment of traditional language-based areas for anomalous metaphor sentences, while the right-hemisphere activation found suggests that remote associations are being formed. In short, our study supports the idea that metaphors are not a homogenous type of figurative language and that distinguishing between different types of metaphors will advance theories of language comprehension.

Insight and frontal cortical function in schizophrenia: a review

Insight into illness has been identified as a clinically important phenomenon, in no small part due to an association with treatment-adherence. An increasing number of studies, but not all, have observed poor insight to be a reflection of cognitive dysfunction in schizophrenia. A review of 34 published English-language studies found a significant number (i.e., 21) reporting a relationship between insight deficits and impaired performance on cognitive tasks primarily mediated by frontal cortex. A significant number of reviewed studies examined insight function in more than one psychiatric population, including bipolar and schizoaffective disorder. The most replicated findings from these studies were the correlations between insight deficits and impaired performance on the Wisconsin Card Sorting Test (WCST). More specifically, WCST perseverative errors correlated positively and the number of categories completed correlated negatively with poor insight, suggesting that impaired insight may be mediated by deficiencies in conceptual organization and flexibility in abstract thinking. Since the WCST requires the ability to demonstrate conceptual flexibility through the generation, maintenance and switching of mental sets along with the capacity to use verbal feedback to correct errors, it would appear that such 'executive' functions are most related to insight. In addition, recently identified structural correlates of poor insight in schizophrenia show some association with anosognosia in neurological patients. This review will discuss the implications of these findings and directions for future research.

Brain correlates of discourse processing: an fMRI investigation of irony and conventional metaphor comprehension

Higher levels of discourse processing evoke patterns of cognition and brain activation that extend beyond the literal comprehension of sentences. We used fMRI to examine brain activation patterns while 16 healthy participants read brief three-sentence stories that concluded with either a literal, metaphoric, or ironic sentence. The fMRI images acquired during the reading of the critical sentence revealed a selective response of the brain to the two types of nonliteral utterances. Metaphoric utterances resulted in significantly higher levels of activation in the left inferior frontal gyrus and in bilateral inferior temporal cortex than the literal and ironic utterances. Ironic statements resulted in significantly higher activation levels than literal statements in the right superior and middle temporal gyri, with metaphoric statements resulting in intermediate levels in these regions. The findings show differential hemispheric sensitivity to these aspects of figurative language, and are relevant to models of the functional cortical architecture of language processing in connected discourse.

Simulating the pattern of right-hemisphere-damaged patients for the processing of the alternative metaphorical meanings of words: evidence in favor of a cognitive resources hypothesis

Lately, many studies have suggested that communication impairments in brain-damaged individuals might be explained--at least in part--in terms of cognitive resource allocation. Reproducing a clinical pattern in normal subjects by using a dual-task treatment might be a way of evaluating the role of cognitive resources in the right hemisphere's contribution to verbal communication. This study suggests that the RH's presumed specific contribution to the processing of the alternative metaphorical meanings of words is, at least to some extent, the expression of the RH's complementary, and necessary, contribution to the pool of attentional resources needed for the most effortful processing.

Metaphorical vs. literal word meanings: fMRI evidence against a selective role of the right hemisphere

The neural networks associated with processing metaphorical word meanings were investigated in normal adults using fMRI. Subjects listened to sets of three adjectives and decided whether the last two had a similar meaning. One condition required accessing the literal meaning of the middle word (e.g., hot-cold-chilly), whereas the other condition required accessing its nonliteral, or metaphorical, meaning (e.g., hot-cold-unfriendly). Direct comparison of the nonliteral vs. literal condition showed reliable activity only in left prefrontal and temporo-parietal regions. These results argue against a selective role of the right hemisphere (RH) in accessing metaphorical word meanings. In line with a growing literature, these findings suggest that prior reports of greater RH involvement for metaphorical language might reflect the increased complexity of figurative language rather than an RH specialization for understanding metaphors.

Processing homonymy and polysemy: effects of sentential context and time-course following unilateral brain damage

The present study investigated the abilities of left-hemisphere-damaged (LHD) non-fluent aphasic, right-hemisphere-damaged (RHD), and normal control individuals to access, in sentential biasing contexts, the multiple meanings of three types of ambiguous words, namely homonyms (e.g., "punch"), metonymies (e.g., "rabbit"), and metaphors (e.g., "star"). Furthermore, the predictions of the "suppression deficit" and "coarse semantic coding" hypotheses, which have been proposed to account for RH language function/dysfunction, were tested. Using an auditory semantic priming paradigm, ambiguous words were incorporated in dominant- or subordinate-biasing sentence-primes followed after a short (100 ms) or long (1,000 ms) interstimulus interval (ISI) by dominant-meaning-related, subordinate-meaning-related or unrelated target words. For all three types of ambiguous words, both the effects of context and ISI were obvious in the performance of normal control subjects, who showed multiple meaning activation at the short ISI, but eventually, at the long ISI, contextually appropriate meaning selection. Largely similar performance was exhibited by the LHD non-fluent aphasic patients as well. In contrast, RHD patients showed limited effects of context, and no effects of the time-course of processing. In addition, although homonymous and metonymous words showed similar patterns of activation (i.e., both meanings were activated at both ISIs), RHD patients had difficulties activating the subordinate meanings of metaphors, suggesting a selective problem with figurative meanings. Although the present findings do not provide strong support for either the "coarse semantic coding" or the "suppression deficit" hypotheses, they are viewed as being more consistent with the latter, according to which RH damage leads to deficits suppressing alternative meanings of ambiguous words that become incompatible with the context.

The role of the right hemisphere in processing nonsalient metaphorical meanings: Application of Principal Components Analysis to fMRI data

Some researches indicate that the right hemisphere (RH) has a unique role in comprehending the figurative meaning of metaphors whereas the results of other studies do not support the notion of a selective role for the RH in accessing metaphorical meanings. The present research used fMRI technology to test a theoretical explanation of the above conflicting findings. This theoretical account is derived from the Graded Salience Hypothesis (GSH) [Giora, R. (1997). Understanding figurative and literal language: the Graded Salience Hypothesis. Cognitive Linguistics, 7, 183-206; Giora, R. (2003). On our mind: Salience, context and figurative language. New York: Oxford University Press], according to which the degree of meaning salience, rather than literality or nonliterality primarily affects differences between the LH and RH in linguistic processing. Thus, the GSH predicts a selective RH involvement in comprehension of novel, nonsalient metaphoric meanings and LH involvement in the comprehension of conventional, salient metaphoric meanings. Fifteen normal adults participated in a block designed fMRI experiment that compared the patterns of brain activation induced by processing the meanings of literal, conventional metaphoric, novel metaphoric and unrelated word pairs. The subjects performed a semantic judgment task. We applied the Principal Components Analysis (PCA) technique in order to find different functional networks corresponding to the different stimuli. Our results, obtained from PCA of the fMRI data indicate that the right homologue of Wernicke's area has a special role in processing novel metaphors. We suggest that a unique network, consisting of the right homologue of Wernicke's area, right and left premotor areas, right and left insula and Broca's area, is recruited for the processing of novel metaphors but not for the processing of conventional metaphors.

Metaphor Comprehension in Right Brain-Damaged Patients with Visuo-Verbal and Verbal Material: A Dissociation (RE)Considered

Metaphor comprehension was investigated in 50 right-hemisphere damaged (RHD) patients and 38 control subjects in two experimental conditions: a visuo-verbal and a verbal test. In the visuo-verbal test, subjects had to match a metaphorical sentence with one of four pictures representing the correct metaphorical meaning, the literal meaning, a control metaphor and a control literal meaning. In the verbal test, a metaphorical sentence had to be matched to a correct written metaphorical interpretation, a literal or a control interpretation. On both tests, the number of correct metaphorical responses in the RHD group was lower than in the control group. However, RHD patients performed more poorly in the visuo-verbal than in the verbal condition. Interestingly, when they selected the wrong response, the RHD patients tended to select the literal one only in the visuo-verbal condition. Context does not seem to be responsible for the dissociation between the two tests. The influence of the RHD patients' major visuo-spatial deficits was also checked, to exclude their role in the tendency to be literal with visuo-verbal material. Results are discussed in the perspective of an integration deficit.

Processing of metaphoric and non-metaphoric alternative meanings of words after right- and left-hemispheric lesion

This study examines the specificity of the contribution of the right hemisphere to the processing of metaphoric meaning of words. Ten right- and 10 left-hemisphere-damaged subjects, and 20 normal control subjects were submitted to: (1) a word-triad task where they had to associate alternative metaphoric and non-metaphoric words to a target word, and to (2) a word-dyad task where they had to decide whether or not there was a semantic relationship between two words. The two tasks aimed at differentiating between the subjects' preference for a given semantic meaning versus a genuine semantic deficit for a particular meaning. Results revealed that both right- and left-hemisphere-damaged groups presented a genuine semantic deficit for the processing of metaphoric meaning. The absence of a double dissociation between the two brain-damaged groups does not support the hypothesis of a specific contribution of the right-hemisphere to the processing of metaphoric meaning of words.

Aha! Insight experience correlates with solution activation in the right hemisphere

In one experiment, we tested for an association between semantic activation in the right hemisphere (RH) and left hemisphere (LH) and the Aha! experience when people recognize solutions to insight-like problems. The compound remote associate problems used in this experiment sometimes evoke an Aha! experience and sometimes do not. On each trial, participants (N = 44) attempted to solve these problems and, after 7 sec, named a target word, made a solution decision, and rated their insight experience of recognizing the solution. As in prior studies, the participants demonstrated more solution priming for solutions presented to the left visual field-RH (lvf-RH) than for solutions presented to the right visual field-LH (rvf-LH). As was predicted, following unsolved problems the participants showed greater priming for solutions that they rated as evoking an insight experience on the subsequent solution decision than for solutions that did not evoke an insight experience. This association was stronger for solutions presented to the lvf-RH than for those presented to the rvf-LH. These results tie the subjective experience of insight to an objective measure--semantic priming--and suggest that people have an Aha! experience in part because they already had semantic activation that could lead them to recognize the solution quickly. We believe semantic activation in both hemispheres cooperatively contributes to problem solving, but weak solution activation that contributes to the Aha! experience is more likely to occur in the RH than in the LH.

An ERP study of sensory mismatch expressions in Japanese

Combinations of different sensory words produce mismatch expressions like smooth color and red touch in contrast to normal expressions like red color and smooth touch. Concerning these sensory mismatch expressions, results of three experiments are reported. Experiment 1 revealed that (i) mismatch expressions were less comprehensible than normal expressions, and that (ii) there were two patterns among mismatch expressions: the high-comprehensible mismatch expression (HighCME, e.g., smooth color) and the low-comprehensible mismatch expression (LowCME, e.g., red touch). Experiment 2 revealed that the mismatch expressions produced a significantly greater N400 amplitude than the normal expressions. Experiment 3 implied that the difference between High/LowCME was reflected in a later latency band or in a topographical difference of N400, although the statistical significance was marginal. It is argued that the processes to integrate linguistic elements (e.g., combining adjectives and nouns) are not homogeneous.

Insight and neurocognition in schizophrenia

The relationship between neurocognitive impairments in schizophrenia remains unclear. Recent literature was reviewed and the most consistent finding was an association between perseverative errors on the Wisconsin Card Sort Test (WCST) and poor insight. The aim was to confirm and extend this finding using a range of assessments relevant to perseveration, and different dimensions of insight, in a sample of 33 acutely psychotic subjects within 5 years of onset of schizophrenia and related disorders. Results showed a correlation (r=-0.59) between insight and perseverative errors, rather than more general measures of abstraction. A factor representing relabelling symptoms, derived from insight scale items, correlated even more strongly; however, other insight factors correlated more weakly, suggesting they are less dependent on neuropsychological deficits. The ability to monitor output and correct errors appears to be closely related to the core features of insight in psychosis.

Sensitivity to local sentence context information in lexical ambiguity resolution: evidence from left- and right-hemisphere-damaged individuals

Using a cross-modal semantic priming paradigm, the present study investigated the ability of left-hemisphere-damaged (LHD) nonfluent aphasic, right-hemisphere-damaged (RHD) and non-brain-damaged (NBD) control subjects to use local sentence context information to resolve lexically ambiguous words. Critical sentences were manipulated such that they were either unbiased, or biased toward one of two meanings of sentence-final equibiased ambiguous words. Sentence primes were presented auditorily, followed after a short (0 ms) or long (750 ms) interstimulus interval (ISI) by the presentation of a first- or second-meaning related visual target, on which subjects made a lexical decision. At the short ISI, neither patient group appeared to be influenced by context, in sharp contrast to the performance of the NBD control subjects. LHD nonfluent aphasic subjects activated both meanings of ambiguous words regardless of context, whereas RHD subjects activated only the first meaning in unbiased and second-meaning biased contexts. At the long ISI, LHD nonfluent aphasic subjects failed to show evidence of activation of either meaning, while RHD individuals activated first meanings in unbiased contexts and contextually appropriate meanings in second-meaning biased contexts. These findings suggest that both left (LH) and right hemisphere (RH) damage lead to deficits in using local contextual information to complete the process of ambiguity resolution. LH damage seems to spare initial access to word meanings, but initially impairs the ability to use context and results in a faster than normal decay of lexical activation. RH damage appears to initially disrupt access to context, resulting in an over-reliance on frequency in the activation of ambiguous word meanings.