Handedness, hemispheric asymmetries, and joke comprehension

Strong Prediction: Language Model Surprisal Explains Multiple N400 Effects

Theoretical accounts of the N400 are divided as to whether the amplitude of the N400 response to a stimulus reflects the extent to which the stimulus was predicted, the extent to which the stimulus is semantically similar to its preceding context, or both. We use state-of-the-art machine learning tools to investigate which of these three accounts is best supported by the evidence. GPT-3, a neural language model trained to compute the conditional probability of any word based on the words that precede it, was used to operationalize contextual predictability. In particular, we used an information-theoretic construct known as surprisal (the negative logarithm of the conditional probability). Contextual semantic similarity was operationalized by using two high-quality co-occurrence-derived vector-based meaning representations for words: GloVe and fastText. The cosine between the vector representation of the sentence frame and final word was used to derive contextual cosine similarity estimates. A series of regression models were constructed, where these variables, along with cloze probability and plausibility ratings, were used to predict single trial N400 amplitudes recorded from healthy adults as they read sentences whose final word varied in its predictability, plausibility, and semantic relationship to the likeliest sentence completion. Statistical model comparison indicated GPT-3 surprisal provided the best account of N400 amplitude and suggested that apparently disparate N400 effects of expectancy, plausibility, and contextual semantic similarity can be reduced to variation in the predictability of words. The results are argued to support predictive coding in the human language network.

Language and reading impairments are associated with increased prevalence of non-right-handedness

Handedness has been studied for association with language-related disorders because of its link with language hemispheric dominance. No clear pattern has emerged, possibly because of small samples, publication bias, and heterogeneous criteria across studies. Non-right-handedness (NRH) frequency was assessed in N = 2503 cases with reading and/or language impairment and N = 4316 sex-matched controls identified from 10 distinct cohorts (age range 6-19 years old; European ethnicity) using a priori set criteria. A meta-analysis (Ncases  = 1994) showed elevated NRH % in individuals with language/reading impairment compared with controls (OR = 1.21, CI = 1.06-1.39, p = .01). The association between reading/language impairments and NRH could result from shared pathways underlying brain lateralization, handedness, and cognitive functions.

The influence of semantic relevance on the discernment of product appearance and function

Background

This study investigated the impact of semantic relevance on the ability to comprehend the appearance and function of a product, as presented in images.

Methods

The images used the constructs of Simile, Metaphor and Analogy to correspond to congruent, related and incongruent semantic structures, and measured the amplitude of Event-Related Potentials (ERPs) to compare these images with Landscape images. Sixteen participants with design-related educational backgrounds were invited to join in the ERP experiment.

Results

The results found that the image depicting the Metaphor showed a stronger N600 amplitude in the right anterior region of the brain than the Landscape image and the Analogy image induced a stronger N600 effect in the left anterior and right anterior part of the brain than the Landscape image. However, the Simile image did not trigger the N600. The N600 was triggered when the meaning of the Metaphor and Analogy being presented could not be understood. This indicates that a greater processing effort to comprehend them than was required for Simile. Analogy has a wider N600 distribution than Metaphor in the anterior area, suggesting that Analogy would require higher-level thinking processes and more complex semantic processing mechanisms than Metaphor.

Conclusions

The N600 implicated that an assessment method to detect the semantic relationship between appearance and function of a product would assist in determining whether a symbol was suitable to be associated with a product.

Scalar implicature is not a default process: An ERP study of the scalar implicature processing under the effect of focus factor

This study explored the processing mechanism of scalar implicatures under different focus conditions by the picture-sentence verification paradigm. Through the guidance of different types of incorrect sentences, scalar terms were controlled to adjust whether they were at the focus position and divided the focused and non-focused conditions. The behavioural results showed that when the content of the picture was "all squares have…", more participants under the focused condition could judge that the underinformative sentence "some squares have…" was not appropriate. Moreover, according to whether participants could stably determine that the underinformative sentences were inappropriate, they were divided into pragmatic and semantic responders. The ERP results showed that pragmatic responders evoked a P200 effect, an N400 effect and a sustained negativity effect according to the scalar terms, and a P200 effect and a sustained positivity effect according to the sentence-final words. In contrast, semantic responders did not elicit any ERP effect. These results indicate that the generation of scalar implicatures is not completely determined by the scalar terms and that the focus factor plays an important role in the scalar implicatures inference.

Humor drawings evoked temporal and spectral EEG processes

The study aimed to explore the humor processing elicited through the manipulation of artistic drawings. Using the Comprehension-Elaboration Theory of humor as the main research background, the experiment manipulated the head portraits of celebrities based on the independent variables of facial deformation (large/small) and addition of affective features (positive/negative). A 64-channel electroencephalography was recorded in 30 participants while viewing the incongruous drawings of celebrities. The electroencephalography temporal and spectral responses were measured during the three stages of humor which included incongruity detection, incongruity comprehension and elaboration of humor. Analysis of event-related potentials indicated that for humorous vs non-humorous drawings, facial deformation and the addition of affective features significantly affected the degree of humor elicited, specifically: large > small deformation; negative > positive affective features. The N170, N270, N400, N600-800 and N900-1200 components showed significant differences, particularly in the right prefrontal and frontal regions. Analysis of event-related spectral perturbation showed significant differences in the theta band evoked in the anterior cingulate cortex, parietal region and posterior cingulate cortex; and in the alpha and beta bands in the motor areas. These regions are involved in emotional processing, memory retrieval, and laughter and feelings of amusement induced by elaboration of the situation.

Handedness in man: The energy availability hypothesis

More than 90% of the human species are right handed. Although outwardly our body appears symmetrical, a 50/50% lateralization in handedness never occurs. Neither have we seen more than 50% left handedness in any subset of the human population. By 12-15weeks of intrauterine life, as many as 6 times more fetuses are noted by ultrasound studies to be sucking on their right thumbs. Distinct difference in oxygenation leading to dissimilar energy availability between right and left subclavian arteries in place by week 9 of life may hold the clue to the lateralization of hand function and eventually, the same in the brain. We know there is a higher incidence of left handedness in males, twins, premature babies and those born to mothers who smoke. They may represent a subset with less distinct difference in oxygenation between the 2 subclavian arteries during the fetal stage. This hypothesis if correct not only closes the gap in understanding human handedness and lateralization but also opens a vista for new research to focus on in utero tissue energy availability and its impact on outcome in life.

From incoherence to mirth: neuro-cognitive processing of garden-path jokes

In so-called garden-path jokes, an initial semantic representation is violated, and semantic revision reestablishes a coherent representation. 48 jokes were manipulated in three conditions: (i) a coherent ending, (ii) a joke ending, and (iii) a discourse-incoherent ending. A reading times study (N = 24) and three studies with recordings of ERP and pupil changes (N = 21, 24, and 24, respectively) supported the hypothesized cognitive processes. Jokes showed increased reading times of the final word compared to coherent endings. ERP data mainly indicated semantic integration difficulties (N400). Larger pupil diameters to joke endings presumably reflect emotional responses. ERP evidence for increased discourse processing efforts and emotional responses, as assumed to be reflected in modulations of the late left anterior negativity (LLAN) and in an enhanced late frontal positivity (fP600), respectively, remains however incomplete. Processing of incoherent endings was also accompanied by increased reading times, a stronger and sustained N400, and context-sensitive P600 effects. Together, these findings provide evidence for a sequential, non-monotonic, and incremental discourse comprehension of garden-path jokes.

Cognitive benefits of right-handedness: a meta-analysis

Hand preference - which is related to cerebral dominance - is thought to be associated with cognitive skills; however, findings on this association are inconsistent and there is no consensus whether left- or right-handers have an advantage in either spatial or verbal abilities. In addition, it is not clear whether an interaction between sex and hand preference exists in relation to these cognitive abilities. As these matters are relevant from a neurodevelopmental perspective we performed a meta-analysis of the available literature. We searched PubMed and Embase, and included 14 studies (359,890 subjects) in the verbal ability meta-analysis and 16 studies (218,351 subjects) in the spatial ability meta-analysis. There was no difference between the full sample of left and right-handers for verbal ability, nor was there a hand preference-by-sex interaction. Subgroup analysis of children showed a small right-hand benefit. Our results further revealed a modest but significant effect favouring right-handedness for overall spatial ability, which was more pronounced when analysis was restricted to studies applying the mental rotation test. We could not identify a specific interaction with sex. Our results indicate that there is a small but significant cognitive advantage of right-handedness on spatial ability. In the verbal domain, this advantage is only significant in children. An interaction effect with sex is not confirmed.

Are scalar implicatures automatically processed and different for each individual? A mismatch negativity (MMN) study

Scalar implicatures are ordinarily activated in human communication when the speaker uses a weak expression (e.g., some) from a set of stronger alternatives (e.g., many, all). It has been debated whether scalar inferences are generated by default. To clarify this issue and examine whether individual pragmatic ability will affect the mechanism of scalar inference processing, we performed experiment with an MMN paradigm to capture the neurophysiological indicators of automatic processing of spoken sentences and divided participants into high and low pragmatic ability groups. Experimental results showed that compared with the condition that an informative sentence ("Some animals have tails") is the deviant stimuli, when an underinformative sentence ("Some tigers have tails") is the deviant stimuli, the high pragmatic ability group induced mismatch negativity (MMN) and sustained negativity, while the low pragmatic ability group had no ERP effects. These results indicated that at least some people can automatically activate the scalar implicatures when encountering scalar trigger words, even in the inattentive status.

How vertical hand movements impact brain activity elicited by literally and metaphorically related words: an ERP study of embodied metaphor

Embodied metaphor theory suggests abstract concepts are metaphorically linked to more experientially basic ones and recruit sensorimotor cortex for their comprehension. To test whether words associated with spatial attributes reactivate traces in sensorimotor cortex, we recorded EEG from the scalp of healthy adults as they read words while performing a concurrent task involving either upward- or downward- directed arm movements. ERPs were time-locked to words associated with vertical space—either literally (ascend, descend) or metaphorically (inspire, defeat)—as participants made vertical movements that were either congruent or incongruent with the words. Congruency effects emerged 200–300 ms after word onset for literal words, but not until after 500 ms post-onset for metaphorically related words. Results argue against a strong version of embodied metaphor theory, but support a role for sensorimotor simulation in concrete language.

So that's what you meant! Event-related potentials reveal multiple aspects of context use during construction of message-level meaning

Factors that modulate the influence of contextual information on semantic processing in language comprehension have been thoroughly investigated with the N400 component of the event-related potential (ERP), a direct measure of initial contact with semantic memory. Although context has a strong and immediate impact on processing, multiple mechanisms contribute to the construction of message-level representations during normal comprehension. Some of these may be engaged after or concurrent with the formation of an initial meaning representation, and can then serve to revise or reshape meaning. In this study, ERPs were recorded while participants read plausible sentences that continuously varied in the amount of contextual constraint for the sentence-final word, defined via extensive norming data including the range of possible alternative completions for the contexts. Consistent with numerous past studies, the amplitude of the N400 was graded with expectancy, as amplitudes decreased with increasing constraint. Additionally, a left-lateralized, broad, slow negativity onsetting around 400-500 ms was largest for sentences with moderately strong constraint. Within this range of constraint, the negativity was larger for sentences with fewer alternative completions compared to those with many different ones. The timing and scalp distribution of the effect resemble brain responses linked to engagement of working memory resources, ambiguity resolution, and comprehension of jokes. Similar to cases of "frame-shifting" in non-literal language, this effect may reflect processing associated with reinterpretation or reconsideration of contextual material when multiple interpretations of a sentence were likely.

Stop laughing! Humor perception with and without expressive suppression

The neurophysiological study of emotion regulation focused on the strategy of reappraisal-i.e., the cognitive reinterpretation of a stimulus. Reappraisal reduces emotional expression, the experience of both negative and positive feelings, and the amplitude of an event-related potential (ERP)-the late positive potential (LPP). In contrast, the strategy of expressive suppression (ES), being the inhibition of emotional expression, has been reported to reduce subjective feelings of positive, but not negative emotion, and has not yet been investigated with ERPs. We focused on the LPP to assess the correlates of ES in the context of humor perception. Twenty-two female participants rated sequences of humorous (H) and non-humorous (NH) pictures, while their zygomaticus muscle was recorded. A spontaneous (SP) condition, in which participants attended naturally to the pictures, resulted in higher ratings of funniness, increased smiling, and increased LPP amplitude for H compared to NH stimuli. An ES condition, in which participants suppressed their facial reactions, resulted in reduced smiling, without affecting subjective ratings. LPP amplitude did not differ between H and NH stimuli during ES, suggesting equal allocation of processing resources to both stimuli. These results suggest that, similarly to reappraisal, ES modifies the way the brain processes positive emotional stimuli.

Similar Neural Correlates for Language and Sequential Learning: Evidence from Event-Related Brain Potentials

We used event-related potentials (ERPs) to investigate the time course and distribution of brain activity while adults performed (a) a sequential learning task involving complex structured sequences, and (b) a language processing task. The same positive ERP deflection, the P600 effect, typically linked to difficult or ungrammatical syntactic processing, was found for structural incongruencies in both sequential learning as well as natural language, and with similar topographical distributions. Additionally, a left anterior negativity (LAN) was observed for language but not for sequential learning. These results are interpreted as an indication that the P600 provides an index of violations and the cost of integration of expectations for upcoming material when processing complex sequential structure. We conclude that the same neural mechanisms may be recruited for both syntactic processing of linguistic stimuli and sequential learning of structured sequence patterns more generally.

Sex hormone activity in alcohol addiction: integrating organizational and activational effects

There are well-known sex differences in the epidemiology and etiopathology of alcohol dependence. Male gender is a crucial risk factor for the onset of alcohol addiction. A directly modifying role of testosterone in alcohol addiction-related behavior is well established. Sex hormones exert both permanent (organizational) and transient (activational) effects on the human brain. The sensitive period for these effects lasts throughout life. In this article, we present a novel early sex hormone activity model of alcohol addiction. We propose that early exposure to sex hormones triggers structural (organizational) neuroadaptations. These neuroadaptations affect cellular and behavioral responses to adult sex hormones, sensitize the brain's reward system to the reinforcing properties of alcohol and modulate alcohol addictive behavior later in life. This review outlines clinical findings related to the early sex hormone activity model of alcohol addiction (handedness, the second-to-fourth-finger length ratio, and the androgen receptor and aromatase) and includes clinical and preclinical literature regarding the activational effects of sex hormones in alcohol drinking behavior. Furthermore, we discuss the role of the hypothalamic-pituitary-adrenal and -gonadal axes and the opioid system in mediating the relationship between sex hormone activity and alcohol dependence. We conclude that a combination of exposure to sex hormones in utero and during early development contributes to the risk of alcohol addiction later in life. The early sex hormone activity model of alcohol addiction may prove to be a valuable tool in the development of preventive and therapeutic strategies.

Predictability and novelty in literal language comprehension: an ERP study

Linguists have suggested that one mechanism for the creative extension of meaning in language involves mapping, or constructing correspondences between conceptual domains. For example, the sentence, "The clever boys used a cardboard box as a boat," sets up a novel mapping between the concepts cardboard box and boat, while "His main method of transportation is a boat," relies on a more conventional mapping between method of transportation and boat. To examine the electrophysiological signature of this mapping process, electroencephalogram (EEG) was recorded from the scalp as healthy adults read three sorts of sentences: low-cloze (unpredictable) conventional ("His main method of transportation is a boat,"), low-cloze novel mapp'ing ("The clever boys used a cardboard box as a boat,"), and high-cloze (predictable) conventional ("The only way to get around Venice is to navigate the canals in a boat,"). Event-related brain potentials (ERPs) were time-locked to sentence final words. The novel and conventional conditions were matched for cloze probability (a measure of predictability based on the sentence context), lexical association between the sentence frame and the final word (using latent semantic analysis), and other factors known to influence ERPs to language stimuli. The high-cloze conventional control condition was included to compare the effects of mapping conventionality to those of predictability. The N400 component of the ERPs was affected by predictability but not by conventionality. By contrast, a late positivity was affected both by the predictability of sentence final words, being larger for words in low-cloze contexts that made target words difficult to predict, and by novelty, as words in the novel condition elicited a larger positivity 700-900ms than the same words in the (cloze-matched) conventional condition.

Right hemisphere has the last laugh: neural dynamics of joke appreciation

Understanding a joke relies on semantic, mnemonic, inferential, and emotional contributions from multiple brain areas. Anatomically constrained magnetoencephalography (aMEG) combining high-density whole-head MEG with anatomical magnetic resonance imaging allowed us to estimate where the humor-specific brain activations occur and to understand their temporal sequence. Punch lines provided either funny, not funny (semantically congruent), or nonsensical (incongruent) replies to joke questions. Healthy subjects rated them as being funny or not funny. As expected, incongruous endings evoke the largest N400m in left-dominant temporo-prefrontal areas, due to integration difficulty. In contrast, funny punch lines evoke the smallest N400m during this initial lexical–semantic stage, consistent with their primed “surface congruity” with the setup question. In line with its sensitivity to ambiguity, the anteromedial prefrontal cortex may contribute to the subsequent “second take” processing, which, for jokes, presumably reflects detection of a clever “twist” contained in the funny punch lines. Joke-selective activity simultaneously emerges in the right prefrontal cortex, which may lead an extended bilateral temporo-frontal network in establishing the distant unexpected creative coherence between the punch line and the setup. This progression from an initially promising but misleading integration from left frontotemporal associations, to medial prefrontal ambiguity evaluation and right prefrontal reprocessing, may reflect the essential tension and resolution underlying humor.

Isn't It Ironic? An Electrophysiological Exploration of Figurative Language Processing

Although the neurocognitive processes underlying the comprehension of figurative language, especially metaphors and idioms, have been studied extensively, less is known about the processing of irony. In two experiments using event-related brain potentials (ERPs), we examined the types of cognitive processes involved in the comprehension of ironic and literal sentences and their relative time course. The experiments varied in modality (auditory, visual), task demands (comprehension task vs. passive reading), and probability of stimulus occurrence. ERPs consistently revealed a large late positivity (i.e., P600 component) in the absence of an N400 component for irony compared to equivalent literal sentences independent of modality. This P600 was shown to be unaffected by the factors task demands and probability of occurrence. Taken together, the findings suggest that the observed P600 is related to irony processing, and might be a reflection of pragmatic interpretation processes. During the comprehension of irony, no semantic integration difficulty arises (absence of N400), but late inferential processes appear to be necessary for understanding ironic meanings (presence of P600). This finding calls for a revision of current models of figurative language processing.

Effect of initiation-inhibition and handedness on the patterns of the P50 event-related potential component: a low resolution electromagnetic tomography study

BACKGROUND

Recent research recognizes the association between handedness, linguistic processes and cerebral networks subserving executive functioning, but the nature of this association remains unclear. Since the P50 event related potential (ERP) is considered to reflect thalamocortical processes in association with working memory (WM) operation the present study focuses on P50 patterns elicited during the performance of a linguistic related executive functioning test in right- and left-handers.

METHODS

In 64 young adults with a high educational level (33 left-handed) the P50 event-related potential was recorded while performing the initiation and inhibition condition of a modified version of the Hayling Sentence Completion test adjusted to induce WM. The manual preference of the participants was evaluated with the use of the Edinburgh Handedness Inventory (EHI).

RESULTS

P50 showed greater amplitudes in left- than in right-handers, mainly in frontal leads, in the initiation condition. Reduced amplitudes in inhibition compared to initiation condition were observed in left-handers. Low Resolution Electromagnetic Tomography (LORETA) analysis showed lower frontal lobe activation in the inhibition than in the initiation condition in both right- and left-handers. Also, LORETA yielded that right-handers exhibited greater activation in the inhibition condition than left-handers. Additionally, LORETA showed assymetrical hemispheric activation patterns in right-handers, in contrast to symmetrical patterns observed in left-handers. Higher P50 amplitudes were recorded in right-hemisphere of right-handers in the initiation condition.

CONCLUSION

Brain activation, especially the one closely related to thalamocortical function, elicited during WM operation involving initiation and inhibition processes appears to be related to handedness.

The communicative style of a speaker can affect language comprehension? ERP evidence from the comprehension of irony

An important issue in irony comprehension concerns when and how listeners integrate extra-linguistic and linguistic information to compute the speaker's intended meaning. To assess whether knowledge about the speaker's communicative style impacts the brain response to irony, ERPs were recorded as participants read short passages that ended either with literal or ironic statements made by one of two speakers. The experiment was carried out in two sessions in which each speaker's use of irony was manipulated. In Session 1, 70% of ironic statements were made by the ironic speaker, while the non-ironic speaker expressed 30% of them. For irony by the non-ironic speaker, an increased P600 was observed relative to literal utterances. By contrast, both ironic and literal statements made by the ironic speaker elicited similar P600 amplitudes. In Session 2, conducted 1 day later, both speakers' use of irony was balanced (i.e. 50% ironic, 50% literal). ERPs for Session 2 showed an irony-related P600 for the ironic speaker but not for the non-ironic speaker. Moreover, P200 amplitude was larger for sentences congruent with each speaker's communicative style (i.e. for irony made by the ironic speaker, and for literal statements made by the non-ironic speaker). These findings indicate that pragmatic knowledge about speakers can affect language comprehension 200 ms after the onset of a critical word, as well as neurocognitive processes underlying the later stages of comprehension (500-900 ms post-onset). Thus perceived speakers' characteristics dynamically impact the construction of appropriate interpretations of ironic utterances.

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.

In your right mind: right hemisphere contributions to language processing and production

The verbal/nonverbal account of left and right hemisphere functionality is the prevailing dichotomy describing the cerebral lateralization of function. Yet the fact that the left hemisphere is the superior language processor does not necessarily imply that the right hemisphere is completely lacking linguistic ability. This paper reviews the growing body of research demonstrating that, far from being nonverbal, the right hemisphere has significant language processing strength. From prosodic and paralinguistic aspects of speech production, reception, and interpretation, to prelexical, lexical and postlexical components of visual word recognition; strong involvement of the right hemisphere is implicated. The evidence reviewed challenges the notion that language is solely a function of the "verbal" left hemisphere, indicating that the right cerebral hemisphere makes significant and meaningful contributions to normal language processing as well.

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.

Lateralization of repetition effects in event-related potentials to words in left- and right-handed women

In our previous event-related potential (ERP) study [A. Nowicka, I. Szatkowska, Memory-induced modulation of event-related potentials in frontal cortex of human subjects: a divided visual field study, Neurosci. Lett. 359 (2004) 171-174], word repetition effects in right-handed males were observed only in case of the direct stimulation of the left (competent) hemisphere. Since the left-handedness and the factor of female gender may determine the lateralization of verbal functions, the goal of the present study was to test the sensitivity of the ERP repetition effects to the visual field of word presentation in the group of left- and right-handed women. ERPs were recorded from symmetrical sites over the left and right hemisphere. Target words were presented in the left (LVF) or right (RVF) visual hemifield. Subjects' were instructed to recognize the target word on a response card. A substantial portion of words was repeated twice. Words elicited different ERPs at frontal sites when presented the first and second times: ERPs were more positive to the repeated stimulus than to its first occurrence. However, in right-handed participants, repetition effects were only observed when target words were presented to the RVF whereas in left-handed participants, repetition effects were only observed when target words were presented to the LVF. These findings are indicative of the asymmetrical involvement of the two hemispheres in memory-induced modulation of brain activity related to verbal processing in left- and right-handed women.

Sex differences in brain activation elicited by humor

With recent investigation beginning to reveal the cortical and subcortical neuroanatomical correlates of humor appreciation, the present event-related functional MRI (fMRI) study was designed to elucidate sex-specific recruitment of these humor related networks. Twenty healthy subjects (10 females) underwent fMRI scanning while subjectively rating 70 verbal and nonverbal achromatic cartoons as funny or unfunny. Data were analyzed by comparing blood oxygenation-level-dependent signal activation during funny and unfunny stimuli. Males and females share an extensive humor-response strategy as indicated by recruitment of similar brain regions: both activate the temporal-occipital junction and temporal pole, structures implicated in semantic knowledge and juxtaposition, and the inferior frontal gyrus, likely to be involved in language processing. Females, however, activate the left prefrontal cortex more than males, suggesting a greater degree of executive processing and language-based decoding. Females also exhibit greater activation of mesolimbic regions, including the nucleus accumbens, implying greater reward network response and possibly less reward expectation. These results indicate sex-specific differences in neural response to humor with implications for sex-based disparities in the integration of cognition and emotion.

Right hemisphere activation of joke-related information: an event-related brain potential study

Two studies tested the hypothesis that the right hemisphere engages in relatively coarse semantic coding that aids high-level language tasks such as joke comprehension. Scalprecorded event-related brain potentials (ERPs) were collected as healthy adults read probe words (CRAZY) preceded either by jokes or nonfunny controls ("Everyone had so much fun jumping into the swimming pool, we decided to put in a little water/platform"). Probes were related to the meaning of the jokes, but not the controls. In Experiment 1a, with central presentation, probes following jokes (related) elicited less negative ERPs 300-700 msec postonset (N400) than did probes following nonfunny controls (unrelated). This finding suggests related probes were primed by the jokes. In addition, unrelated probes elicited a larger anterior positivity 700-900 msec than did related, as irrelevant stimuli impacted control processes invoked by task demands. In Experiment 1b, probes (CRAZY) were preceded only by sentence-final words from jokes (water) or controls (platform). No ERP effects were observed in Experiment 1b, suggesting the N400 priming effect and the anterior positivity observed in Experiment 1a ref lect semantic activations at the discourse level. To assess hemispheric differences in semantic activations, in Experiment 2, ERPs were recorded as participants read probe words presented in their left and right visual fields (LVF and RVF, respectively). Probes elicited a smaller N400 component when preceded by jokes than controls. This N400 priming effect was larger with presentation to the LVF, suggesting joke-relevant information was more active in the right hemisphere. The anterior positivity was observed with RVF but not LVF presentation, suggesting an important role for the left hemisphere in controlled retrieval in language comprehension.

Long-range temporal correlations in electroencephalographic oscillations: Relation to topography, frequency band, age and gender

Presence of long-range temporal correlations in neuronal oscillations is thought to be beneficial for a reliable transfer of information in neuronal networks. In the present study long-range temporal correlations in electroencephalographic (EEG) neuronal oscillations were characterized with respect to their topography, frequency-band specificity (alpha and beta oscillations), gender and age. EEG was recorded in 91 normal subjects (age 20-65 years) in a resting condition. The amplitude of ongoing alpha and beta oscillations was extracted with band-pass filtering and Hilbert transform, and long-range temporal correlations were analyzed with detrended fluctuation analysis. The topography of long-range temporal correlations was comparable for alpha and beta oscillations, showing largest scaling exponents in the occipital and parietal areas. This topography was partially similar to that of the power distribution and a weak positive correlation was observed between long-range temporal correlations and power of neuronal oscillations. Long-range temporal correlations were stronger in alpha than beta oscillations, but only in a few electrode locations in the left hemisphere. In both frequency bands long-range temporal correlations were stronger in males than in females and were largely unaffected by the age of the subjects. It is hypothesized that the idling state of the occipital areas in the closed-eyes condition may explain both large power values and pronounced long-range temporal correlations in this region.

Hemispheric asymmetries and joke comprehension

Joke comprehension deficits in patients with right hemisphere (RH) damage raise the question of the role of the intact RH in understanding jokes. One suggestion is that semantic, or meaning, activations are different in the RH and LH, and RH meanings are particularly important for joke comprehension. To assess whether hypothesized differences in semantic activation in the two hemispheres were relevant to joke comprehension, we recorded event-related brain potentials (ERPs) as healthy adults read laterally presented "punch words" to one-line jokes and nonjoke controls. Jokes presented to the RVF/LH elicited larger amplitude N400 than the nonjoke endings; when presented to the LVF/RH, the joke and nonjoke endings elicited N400s of equal amplitude. This finding suggests that semantic activations in the two hemispheres do differ, with RH semantic activation facilitating joke comprehension.