Spectral and phase-coherence correlates of impaired auditory mismatch negativity (MMN) in schizophrenia: A MEG study.

BACKGROUND: Reduced auditory mismatch negativity (MMN) is robustly impaired in schizophrenia. However, mechanisms underlying dysfunctional MMN generation remain incompletely understood. This study aimed to examine the role of evoked spectral power and phase-coherence towards deviance detection and its impairments in schizophrenia. METHODS: Magnetoencephalography data was collected in 16 male schizophrenia patients and 16 male control participants during an auditory MMN paradigm. Analyses of event-related fields (ERF), spectral power and inter-trial phase-coherence (ITPC) focused on Heschl's gyrus, superior temporal gyrus, inferior/medial frontal gyrus and thalamus. RESULTS: MMNm ERF amplitudes were reduced in patients in temporal, frontal and subcortical regions, accompanied by decreased theta-band responses, as well as by a diminished gamma-band response in auditory cortex. At theta/alpha frequencies, ITPC to deviant tones was reduced in patients in frontal cortex and thalamus. Patients were also characterized by aberrant responses to standard tones as indexed by reduced theta-/alpha-band power and ITPC in temporal and frontal regions. Moreover, stimulus-specific adaptation was decreased at theta/alpha frequencies in left temporal regions, which correlated with reduced MMNm spectral power and ERF amplitude. Finally, phase-reset of alpha-oscillations after deviant tones in left thalamus was impaired, which correlated with impaired MMNm generation in auditory cortex. Importantly, both non-rhythmic and rhythmic components of spectral activity contributed to the MMNm response. CONCLUSIONS: Our data indicate that deficits in theta-/alpha- and gamma-band activity in cortical and subcortical regions as well as impaired spectral responses to standard sounds could constitute potential mechanisms for dysfunctional MMN generation in schizophrenia, providing a novel perspective towards MMN deficits in the disorder.

Ostracism and sharing in an intergroup context.

Previous research suggests that social exclusion is linked to a decrease in individuals' prosocial behavior. However, this effect has not been examined in an intergroup context. We manipulated social acceptance (using the Cyberball game) to examine participants' sharing with ingroup or outgroup members in a minimal group paradigm. Results revealed that when the prospective recipient was a group member who rejected them, socially excluded participants shared less than their socially accepted counterparts. However, when faced with members of an outgroup, socially excluded participants showed similar levels of prosocial behavior as their socially accepted counterparts. Further results suggest that the tendency of socially excluded participants to act in a less prosocial manner toward members of a group that had rejected them was generalized to the group as a whole (including group members with whom there had been no previous interaction). We discuss the theoretical and practical implications of these findings.

Investigating default mode network connectivity disruption in children of mothers with depression.

BACKGROUND: Exposure to maternal major depressive disorder (MDD) bears long-term negative consequences for children's well-being; to date, no research has examined how exposure at different stages of development differentially affects brain functioning. AIMS: Utilising a unique cohort followed from birth to preadolescence, we examined the effects of early versus later maternal MDD on default mode network (DMN) connectivity. METHOD: Maternal depression was assessed at birth and ages 6 months, 9 months, 6 years and 10 years, to form three groups: children of mothers with consistent depression from birth to 6 years of age, which resolved by 10 years of age; children of mothers without depression; and children of mothers who were diagnosed with MDD in late childhood. In preadolescence, we used magnetoencephalography and focused on theta rhythms, which characterise the developing brain. RESULTS: Maternal MDD was associated with disrupted DMN connectivity in an exposure-specific manner. Early maternal MDD decreased child connectivity, presenting a profile typical of early trauma or chronic adversity. In contrast, later maternal MDD was linked with tighter connectivity, a pattern characteristic of adult depression. Aberrant DMN connectivity was predicted by intrusive mothering in infancy and lower mother-child reciprocity and child empathy in late childhood, highlighting the role of deficient caregiving and compromised socio-emotional competencies in DMN dysfunction. CONCLUSIONS: The findings pinpoint the distinct effects of early versus later maternal MDD on the DMN, a core network sustaining self-related processes. Results emphasise that research on the influence of early adversity on the developing brain should consider the developmental stage in which the adversity occured.

Activating the Right Hemisphere Through Left-Hand Muscle Contraction Improves Novel Metaphor Comprehension.

The neurotypical brain is characterized by left hemisphere lateralization for most language processing. However, the right hemisphere plays a crucial part when it is required to bring together seemingly unrelated concepts into meaningful expressions, such as in the case of novel metaphors (unfamiliar figurative expressions). The aim of the current study was to test whether it is possible to enhance novel metaphor comprehension through an easy, efficient, and non-invasive method - intentional contraction of the left hand's muscles, to activate the motor and sensory areas in the contralateral hemisphere. One hundred eighteen neurotypical participants were asked to perform a semantic judgment task involving two-word expressions of four types: literal, conventional metaphors, novel metaphors, or unrelated, while squeezing a rubber ball with their right hand, left hand, or not at all. Results demonstrated that left-hand contraction improved novel metaphor comprehension, as participants were more accurate and quicker in judging them to be meaningful. The findings of the present work provide a simple and efficient method for boosting right hemisphere activation, which can be used to improve metaphoric language comprehension. This method can aid several populations in which right hemisphere function is not fully established, and who struggle with processing figurative language, such as adolescents and individuals on the autistic spectrum.

High-gamma oscillations as neurocorrelates of ADHD: A MEG crossover placebo-controlled study.

Attention Deficit Hyperactive Disorder (ADHD) is a common neurobehavioral disorder with a significant and pervasive impact on patients' lives. Identifying neurophysiological correlates of ADHD is important for understanding its underlying mechanisms, as well as for improving clinical accuracy beyond cognitive and emotional factors. The present study focuses on finding a diagnostic stable neural correlate based on evaluating MEG resting state frequency bands. Twenty-two ADHD patients and 23 controls adults were blindly randomized to two methylphenidate/placebo evaluation days. On each evaluation day state anxiety was assessed, a 2N-back executive function task was performed, and resting state MEG brain activity was recorded at three timepoints. A frequency-based cluster analysis yielded higher high-gamma power for ADHD over posterior sensors and lower high-gamma power for ADHD over frontal-central sensors. These results were shown to be stable over three measurements, unaffected by methylphenidate treatment, and linked to cognitive accuracy and state anxiety. Furthermore, the differential high-gamma activity evidenced substantial ADHD diagnostic efficacy, comparable to the cognitive and emotional factors. These results indicate that resting state high-gamma activity is a promising, stable, valid and diagnostically-relevant neurocorrelate of ADHD. Due to the evolving understanding both in the cellular and network level of high-gamma oscillations, focusing future studies on this frequency band bears the potential for a better understanding of ADHD, thus advancing the specificity of the evaluation of the disorder and developing new tools for therapy.

Cumulative Risk on Oxytocin-Pathway Genes Impairs Default Mode Network Connectivity in Trauma-Exposed Youth.

Background: Although the default mode network (DMN) is a core network essential for brain functioning, little is known about its developmental trajectory, particularly on factors associated with its coherence into a functional network. In light of adult studies indicating DMN's susceptibility to stress-related conditions, we examined links between variability on oxytocin-pathway genes and DMN connectivity in youth exposed to chronic war-related trauma Methods: Following a cohort of war-exposed children from early childhood, we imaged the brains of 74 preadolescents (age 11-13 years; 39 war-exposed) during rest using magnetoencephalography (MEG). A cumulative risk index on oxytocin-pathway genes was constructed by combining single nucleotide polymorphisms on five genes previously linked with social deficits and psychopathology; OXTR rs1042778, OXTR rs2254298, OXTRrs53576, CD38 rs3796863, and AVPR1A RS3. Avoidant response to trauma reminders in early childhood and anxiety disorders in late childhood were assessed as predictors of disruptions to DMN theta connectivity. Results: Higher vulnerability on oxytocin-pathway genes predicted greater disruptions to DMN theta connectivity. Avoidant symptoms in early childhood and generalized anxiety disorder in later childhood were related to impaired DMN connectivity. In combination, stress exposure, oxytocin-pathway genes, and stress-related symptoms explained 24.6% of the variance in DMN connectivity, highlighting the significant effect of stress on the maturing brain. Conclusions: Findings are the first to link the oxytocin system and maturation of the DMN, a core system sustaining autobiographical memories, alteration of intrinsic and extrinsic attention, mentalization, and sense of self. Results suggest that oxytocin may buffer the effects of chronic early stress on the DMN, particularly theta rhythms that typify the developing brain.

Testing the magnocellular-pathway advantage in facial expressions processing for consistency over time.

The ability to identify facial expressions rapidly and accurately is central to human evolution. Previous studies have demonstrated that this ability relies to a large extent on the magnocellular, rather than parvocellular, visual pathway, which is biased toward processing low spatial frequencies. Despite the generally consistent finding, no study to date has investigated the reliability of this effect over time. In the present study, 40 participants completed a facial emotion identification task (fearful, happy, or neutral faces) using facial images presented at three different spatial frequencies (low, high, or broad spatial frequency), at two time points separated by one year. Bayesian statistics revealed an advantage for the magnocellular pathway in processing facial expressions; however, no effect for time was found. Furthermore, participants' RT patterns of results were highly stable over time. Our replication, together with the consistency of our measurements within subjects, underscores the robustness of this effect. This capacity, therefore, may be considered in a trait-like manner, suggesting that individuals may possess various ability levels for processing facial expressions that can be captured in behavioral measurements.

Maternal depression impairs child emotion understanding and executive functions: The role of dysregulated maternal care across the first decade of life.

The long-term negative effects of maternal depression on child outcome are thought to be mediated in part by deficits in caregiving; yet, few studies utilized longitudinal cohorts and repeated observations to specify these links. We tested the impact of deficits in maternal regulatory caregiving across the first decade of life on children's emotional, social, and cognitive outcomes at 10 years. A community birth cohort was repeatedly assessed for maternal depression across the first year and again at 6 and 10 years. At 9 months, 6 years, and 10 years patterns of regulatory caregiving were assessed during mother-child interactions; at 6 and 10 years children underwent psychiatric diagnosis; and at 10 years children's emotion recognition (ERc), executive functions (EF), and social collaboration (SC) were evaluated. Depressed mothers displayed deficits to regulatory caregiving across development and their children exhibited more psychiatric disorders, lower SC, and impaired ERc. Structural equation modeling demonstrated both direct paths from dysregulated caregiving at 6 and 10 years to impaired child EF and ERc and mediated paths via child psychiatric disorder on all 3 outcomes. Effects of 9-month caregiving were only indirect, via child disorder, differentiating infants on risk versus resilient trajectories. Patterns of maternal caregiving were individually stable over time. Our findings demonstrate disruptions to core regulation-based abilities in children of depressed mothers beyond infancy, contribute to discussion on risk and resilience in the context of a distinct early life stress condition, and underscore late childhood as a period of specific vulnerabilities that should become a focus of targeted interventions. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Exposure to early and persistent maternal depression impairs the neural basis of attachment in preadolescence.

Maternal depression increases child vulnerability to psychopathology, loneliness, and social maladjustment; yet, its long-term effects on the social brain are unknown. In this prospective longitudinal study we examined the impact of early and persistent maternal depression on the neural basis of attachment in preadolescence. A community cohort was followed in two groups; children exposed to maternal depression from birth to 6 years and healthy controls. At 9 months and 6 years, mother-child interactions were coded for maternal sensitivity and affect synchrony and salivary oxytocin levels were assessed at 6 years. At preadolescence (11-13 years), children underwent magnetoencephalography (MEG) while exposed to own versus unfamiliar mother-child interaction. Own interaction elicited greater response in beta- and gamma-band oscillations across a wide cluster in temporal and insular cortices, including the Superior Temporal Sulcus, Superior Temporal Gyrus, Inferior Temporal Gyrus, and insula. Beta activations were predicted by maternal sensitivity across early childhood and gamma by affect synchrony. Oxytocin was related to beta response to social cues. Maternal depression impacted child's brain response in two ways. First, maternal depression significantly increased the prevalence of child affective disorder and such children showed no neural differentiation between attachment and non-attachment stimuli. Second, maternal depression decreased maternal sensitivity, affect synchrony, and child oxytocin across early childhood and these were longitudinally associated with aberrant neural response to attachment-specific and social-general cues in preadolescence. Our findings are the first to describe mechanisms by which maternal depression impairs the neural basis of attachment at the transition to adolescence and advocate the need for relationship-focused early interventions.

Brain responses to other people's pain in fibromyalgia: a magnetoencephalography study.

OBJECTIVES: We investigated whether the central pain symptoms in fibromyalgia syndrome (FM) are related to defective top-down sensorimotor regulation. The pain matrix was activated in a top-down manner by presenting pictures of painful situations while recording brain activity using magnetoencephalography (MEG). We investigated alpha desynchronisation in FM patients and healthy controls in response to pictures depicting pain. METHODS: 19 FM patients and 14 age-matched healthy controls (age 20-60) were recruited. Participants were shown photographs of right hands and feet in situations depicting pain or of control situations with no depiction of pain. MEG was recorded in a whole-head 248-sensor system as subjects laid supine. RESULTS: In healthy controls exposure to pictures depicting painful situations elicited a decrease in alpha activity (10Hz) at 100-500ms post-stimulus, which was significantly more pronounced than the one elicited by non-painful content mostly on sensors above the right sensorimotor cortex. However, FM patients did not show significant differences in alpha activity between responses to pain and no-pain pictures. CONCLUSIONS: Consistent with previous findings, healthy participants displayed stronger alpha desynchronisation for pain pictures, indicating automatic disinhibition of the sensorimotor cortices in response to the observation of pain in others. We found evidence for a deficient modulation of sensorimotor cortex in FM patients. The lack of differential response suggests that they perceived relatively neutral pictures as potentially painful, at least in this setting. Our findings suggest that defective top-down regulation may play a role in the pathogenesis of FM.

Chronic Early Stress Impairs Default Mode Network Connectivity in Preadolescents and Their Mothers.

BACKGROUND: Early life stress (ELS) bears long-term negative consequences throughout life. Yet ELS effect is mostly unknown, and no study has followed children to test its impact on the default mode network (DMN) in relation to maternal behavior across childhood. Focusing on brain oscillations, we utilized a unique cohort of war-exposed preadolescent children (11-13 years of age) and their mothers followed from early childhood to examine the effects of ELS combined with observed parenting on DMN connectivity and power in mother and child. METHODS: Participants included 161 mothers and children (children: 39 exposed/36 control subjects; mothers: 44 exposed/42 control subjects) who underwent magnetoencephalography scanning during rest. RESULTS: Stress exposure reduced DMN connectivity in mother and child; however, in mothers, the impaired connectivity occurred in the alpha band, whereas among children it occurred in the theta band, a biomarker of the developing brain. Maternal anxiety, depression, and posttraumatic symptoms in early childhood predicted lower maternal DMN connectivity. Among children, the experience of intrusive, anxious, and uncontained parenting across the first decade and greater cortisol production in late childhood predicted reduced DMN connectivity in preadolescence. Impairments to theta DMN connectivity increased in children with posttraumatic stress disorder. CONCLUSIONS: Findings indicate that ELS disrupts the synchronous coordination of distinct brain areas into coherent functioning of the DMN network, a core network implicated in self-relevant processes. Results suggest that one pathway for the lifelong effects of ELS on psychopathology and physical illness relate to impaired coherence of the DMN and its role in maintaining quiescence, alternating internal and external attention, and supporting the sense of self.

MEG resting-state oscillations and their relationship to clinical symptoms in schizophrenia.

Neuroimaging studies suggest that schizophrenia is characterized by disturbances in oscillatory activity, although at present it remains unclear whether these neural abnormalities are driven by dimensions of symptomatology. Examining different subgroups of patients based on their symptomatology is thus very informative in understanding the role of neural oscillation patterns in schizophrenia. In the present study we examined whether neural oscillations in the delta, theta, alpha, beta and gamma bands correlate with positive and negative symptoms in individuals with schizophrenia (SZ) during rest. Resting-state brain activity of 39 SZ and 25 neurotypical controls was recorded using magnetoencephalography. Patients were categorized based on the severity of their positive and negative symptoms. Spectral analyses of beamformer data revealed that patients high in positive symptoms showed widespread low alpha power, and alpha power was negatively correlated with positive symptoms. In contrast, patients high in negative symptoms showed greater beta power in left hemisphere regions than those low in negative symptoms, and beta power was positively correlated with negative symptoms. We further discuss these findings and suggest that different neural mechanisms may underlie positive and negative symptoms in schizophrenia.

Evidence for a differential visual M300 brain response in gamblers.

OBJECTIVE: Gambling disorder is the first behavioral addiction recognized in the DSM-5. This marks the growing realization that both behavioral and substance-related addictions are manifestations of an 'addicted brain', displaying similar altered neurophysiological mechanisms. A decreased electrophysiological visual P300 is considered a hallmark effect of substance-related addictions, but has not yet been shown in behavioral addictions. METHODS: Magnetoencephalographic recordings of 15 gamblers and 17 controls were taken as they performed a cue-reactivity paradigm in which they passively viewed addiction- and non-addiction-related cues. RESULTS: The main finding of the study is a reduction in the magnetic counterpart of P300 (M300) for gamblers beyond cue condition over frontal regions. Additionally, we found a significant group by cue-type interaction. Gamblers exhibited heightened sensitivity to addiction-related cues in regions corresponding to the frontoparietal attentional network, whereas controls exhibited an opposite effect localized to the right insula. CONCLUSIONS: The results suggest that a reduced P300 characterizes addictions in general, not just substance-related addictions, thus providing important neurophysiological support for the inclusion of behavioral addictions in the DSM-5 and in the incentive-sensitization theory. SIGNIFICANCE: The study offers important insights into neural mechanisms underlying behavioral addictions, and may assist in developing better prevention and intervention strategies.

Oscillatory brain mechanisms of the hypnotically-induced out-of-body experience.

One of the most challenging questions regarding the nature and neural basis of consciousness is the embodied dimension of the phenomenon, that is, feeling located within the body and viewing the world from that spatial perspective. Current theories in neurophysiology highlight the active role of multisensory and sensorimotor integration in supporting self-location and self-perspective, and propose the right temporal-parietal-junction (rTPJ) as a key area for such function. These theories are based mainly on findings from two experimental paradigms: manipulation of bottom-up multisensory information integration regarding one's body location (full-body illusion), or direct and invasive manipulation disrupting brain activity at the rTPJ. In this study we take a different approach by using hypnotic suggestion - a non-invasive top-down technique - to manipulate the subjective experience of self-location. The brain activity of 18 right-handed participants was recorded using magnetoencephalography (MEG) while their subjective experience of self-location was hypnotically manipulated. Spectral analyses were conducted on the spontaneous MEG data before and during an induction of an out-of-body experience (OBE) by a trained psychiatrist. The results indicate high correlations between power at alpha and high-gamma frequency-bands and the degree of perceived change in self-location. Regions exhibiting such correlations include temporal-occipital regions, the rTPJ, as well as frontal and midline regions. These findings are in line with an oscillatory-based predictive coding framework.

Impairment in predictive processes during auditory mismatch negativity in ScZ: Evidence from event-related fields.

Patients with schizophrenia (ScZ) show pronounced dysfunctions in auditory perception but the underlying mechanisms as well as the localization of the deficit remain unclear. To examine these questions, the current study examined whether alterations in the neuromagnetic mismatch negativity (MMNm) in ScZ-patients could involve an impairment in sensory predictions in local sensory and higher auditory areas. Using a whole-head MEG-approach, we investigated the MMNm as well as P300m and N100m amplitudes during a hierarchical auditory novelty paradigm in 16 medicated ScZ-patients and 16 controls. In addition, responses to omitted sounds were investigated, allowing for a critical test of the predictive coding hypothesis. Source-localization was performed to identify the generators of the MMNm, omission responses as well as the P300m. Clinical symptoms were examined with the positive and negative syndrome scale. Event-related fields (ERFs) to standard sounds were intact in ScZ-patients. However, the ScZ-group showed a reduction in the amplitude of the MMNm during both local (within trials) and global (across trials) conditions as well as an absent P300m at the global level. Importantly, responses to sound omissions were reduced in ScZ-patients which overlapped both in latency and generators with the MMNm sources. Thus, our data suggest that auditory dysfunctions in ScZ involve impaired predictive processes that involve deficits in both automatic and conscious detection of auditory regularities. Hum Brain Mapp 38:5082-5093, 2017. © 2017 Wiley Periodicals, Inc.

Brain responses to regular and octave-scrambled melodies: A case of predictive-coding?

Melody recognition is an online process of evaluating incoming information and comparing this information to an existing internal corpus, thereby reducing prediction error. The predictive-coding model postulates top-down control on sensory processing accompanying reduction in prediction error. To investigate the relevancy of this model to melody processing, the current study examined early magnetoencephalogram (MEG) auditory responses to familiar and unfamiliar melodies in 25 participants. The familiar melodies followed and primed an octave-scrambled version of the same melody. The retrograde version of theses melodies served as the unfamiliar control condition. Octave-transposed melodies were included to examine the influence of pitch representation (pitch-height/pitch-chroma representation) on brain responses to melody recognition. Results demonstrate a reduction of the M100 auditory response to familiar, as compared with unfamiliar, melodies regardless of their form of presentation (condensed vs. octave-scrambled). This trend appeared to begin after the third tone of the melody. An additional behavioral study with the same melody corpus showed a similar trend-namely, a significant difference between familiarity rating for familiar and unfamiliar melodies, beginning with the third tone of the melody. These results may indicate a top-down inhibition of early auditory responses to melodies that is influenced by pitch representation. (PsycINFO Database Record

Source localization scale correction for Beamformer analysis.

BACKGROUND: Magnetoencephalography measurements are often processed by using imaging algorithms such as beamforming. The estimated source magnitude tends to suffer from unbalanced scaling across different brain locations. Hence, when examining current estimates for source activity it is vital to rescale the estimated source magnitude, in order to obtain a uniformly scaled image. NEW METHOD: We present a generalized scale correction method (Nempty) that uses empty room MEG measurements to evaluate the noise level. RESULTS: The location bias and spatial resolution of the estimated signal indicated that some scaling correction needs to be applied. Of all the scale correction methods that were tested, the best correction was achieved when using Nempty. COMPARISON WITH EXISTING METHODS: We show that a diagonal matrix does not reflect the true nature of the noise covariance matrix. Hence, diagonal matrix based methods are sub-optimal. CONCLUSION: We recommend adding empty room MEG measurements to each experimental recording session, for purposes of both scale correction and beamformer performance verification.

Hypnotically induced somatosensory alterations: Toward a neurophysiological understanding of hypnotic anaesthesia.

Whereas numerous studies have investigated hypnotic analgesia, few have investigated hypnotic anaesthesia. Using magnetoencephalography (MEG) we investigated and localized brain responses (event-related fields and oscillatory activity) during sensory processing under hypnotic anaesthesia. Nineteen right handed neurotypical individuals with moderate-to-high hypnotizability received 100 vibrotactile stimuli to right and left index fingers in a random sequence. Thereafter a hypnotic state was induced, in which anaesthetic suggestion was applied to the left hand only. Once anaesthetic suggestion was achieved, a second, identical, session of vibrotactile stimuli was commenced. We found greater brain activity in response to the stimuli delivered to the left (attenuated) hand before hypnotic anaesthesia, than under hypnotic anaesthesia, in both the beta and alpha bands. In the beta band, the reduction of activity under hypnotic anaesthesia was found around 214-413ms post-stimuli and was located mainly in the right insula. In the alpha band, it was found around 253-500ms post-stimuli and was located mainly in the left inferior frontal gyrus. In a second experiment, attention modulation per se was ruled out as the underlying cause of the effects found. These findings may suggest that the brain mechanism underlying hypnotic anaesthesia involves top-down somatosensory inhibition and, therefore, a reduction of somatosensory awareness. The result of this mechanism is a mental state in which individuals lose bodily sensation.

Magnetoencephalographic evidence of early right hemisphere overactivation during metaphor comprehension in schizophrenia.

Whereas language processing in neurotypical brains is left lateralized, individuals with schizophrenia (SZ) display a bilateral or reversed pattern of lateralization. We used MEG to investigate the implications of this atypicality on fine (left hemisphere) versus coarse (right hemisphere) semantic processing. Ten SZ and 14 controls were presented with fine (conventional metaphor, literal, and unrelated expressions) and coarse (novel metaphor) linguistic stimuli. Results showed greater activation of the right hemisphere for novel metaphors and greater bilateral activation for unrelated expressions at the M170 window in SZ. Moreover, at the M350, SZ showed reduced bilateral activation. We conclude that SZ are overreliant on early-stage coarse semantic processing. As a result, they jump too quickly to remote conclusions, with limited control over the meanings they form. This may explain one of the core symptoms of the disorder-loose associations.

Fine-coarse semantic processing in schizophrenia: a reversed pattern of hemispheric dominance.

Left lateralization for language processing is a feature of neurotypical brains. In individuals with schizophrenia, lack of left lateralization is associated with the language impairments manifested in this population. Beeman׳s fine-coarse semantic coding model asserts left hemisphere specialization in fine (i.e., conventionalized) semantic coding and right hemisphere specialization in coarse (i.e., non-conventionalized) semantic coding. Applying this model to schizophrenia would suggest that language impairments in this population are a result of greater reliance on coarse semantic coding. We investigated this hypothesis and examined whether a reversed pattern of hemispheric involvement in fine-coarse semantic coding along the time course of activation could be detected in individuals with schizophrenia. Seventeen individuals with schizophrenia and 30 neurotypical participants were presented with two word expressions of four types: literal, conventional metaphoric, unrelated (exemplars of fine semantic coding) and novel metaphoric (an exemplar of coarse semantic coding). Expressions were separated by either a short (250 ms) or long (750 ms) delay. Findings indicate that whereas during novel metaphor processing, controls displayed a left hemisphere advantage at 250 ms delay and right hemisphere advantage at 750 ms, individuals with schizophrenia displayed the opposite. For conventional metaphoric and unrelated expressions, controls showed left hemisphere advantage across times, while individuals with schizophrenia showed a right hemisphere advantage. Furthermore, whereas individuals with schizophrenia were less accurate than control at judging literal, conventional metaphoric and unrelated expressions they were more accurate when judging novel metaphors. Results suggest that individuals with schizophrenia display a reversed pattern of lateralization for semantic coding which causes them to rely more heavily on coarse semantic coding. Thus, for individuals with schizophrenia, speech situation are always non-conventional, compelling them to constantly seek for meanings and prejudicing them toward novel or atypical speech acts. This, in turn, may disadvantage them in conventionalized communication and result in language impairment.